[
    {
        "text": "Finite-size scaling of the random-field Ising model above the upper\n  critical dimension: Finite-size scaling above the upper critical dimension is a long-standing\npuzzle in the field of Statistical Physics. Even for pure systems various\nscaling theories have been suggested, partially corroborated by numerical\nsimulations. In the present manuscript we address this problem in the even more\ncomplicated case of disordered systems. In particular, we investigate the\nscaling behavior of the random-field Ising model at dimension $D = 7$, i.e.,\nabove its upper critical dimension $D_{\\rm u} = 6$, by employing extensive\nground-state numerical simulations. Our results confirm the hypothesis that at\ndimensions $D > D_{\\rm u}$, linear length scale $L$ should be replaced in\nfinite-size scaling expressions by the effective scale $L_{\\rm eff} = L^{D /\nD_{\\rm u}}$. Via a fitted version of the quotients method that takes this\nmodification, but also subleading scaling corrections into account, we compute\nthe critical point of the transition for Gaussian random fields and provide\nestimates for the full set of critical exponents. Thus, our analysis indicates\nthat this modified version of finite-size scaling is successful also in the\ncontext of the random-field problem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase Separation Transition in a Nonconserved Two Species Model: A one dimensional stochastic exclusion process with two species of particles,\n$+$ and $-$, is studied where density of each species can fluctuate but the\ntotal particle density is conserved. From the exact stationary state weights we\nshow that, in the limiting case where density of negative particles vanishes,\nthe system undergoes a phase separation transition where a macroscopic domain\nof vacancies form in front of a single surviving negative particle. We also\nshow that the phase separated state is associated with a diverging correlation\nlength for any density and the critical exponents characterizing the behaviour\nin this region are different from those at the transition line. The static and\nthe dynamical critical exponents are obtained from the exact solution and\nnumerical simulations, respectively.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Duality between random trap and barrier models: We discuss the physical consequences of a duality between two models with\nquenched disorder, in which particles propagate in one dimension among random\ntraps or across random barriers. We derive an exact relation between their\ndiffusion fronts at fixed disorder, and deduce from this that their\ndisorder-averaged diffusion fronts are exactly equal. We use effective dynamics\nschemes to isolate the different physical processes by which particles\npropagate in the models and discuss how the duality arises from a\ncorrespondence between the rates for these different processes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Marginal and Conditional Second Laws of Thermodynamics: We consider the entropy production of a strongly coupled bipartite system.\nThe total entropy production can be partitioned into various components, which\nwe use to define local versions of the Second Law that are valid without the\nusual idealization of weak coupling. The key insight is that causal\nintervention offers a way to identify those parts of the entropy production\nthat result from feedback between the sub-systems. From this the central\nrelations describing the thermodynamics of strongly coupled systems follow in a\nfew lines.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Screening of an electrically charged particle in a two-dimensional\n  two-component plasma at $\u0393=2$: We consider the thermodynamic effects of an electrically charged impurity\nimmersed in a two-dimensional two-component plasma, composed by particles with\ncharges $\\pm e$, at temperature $T$, at coupling $\\Gamma=e^2/(k_B T)=2$,\nconfined in a large disk of radius $R$. Particularly, we focus on the analysis\nof the charge density, the correlation functions, and the grand potential. Our\nanalytical results show how the charges are redistributed in the circular\ngeometry considered here. When we consider a positively charged impurity, the\nnegative ions accumulate close to the impurity leaving an excess of positive\ncharge that accumulates at the boundary of the disk. Due to the symmetry under\ncharge exchange, the opposite effect takes place when we place a negative\nimpurity. Both the cases in which the impurity charge is an integer multiple of\nthe particle charges in the plasma, $\\pm e$, and a fraction of them are\nconsidered; both situations require a slightly different mathematical\ntreatments, showing the effect of the quantization of plasma charges. The bulk\nand tension effects in the plasma described by the grand potential are not\nmodified by the introduction of the charged particle. Besides the effects due\nto the collapse coming from the attraction between oppositely charged ions, an\nadditional topological term appears in the grand potential, proportional to\n$-n^2\\ln(mR)$, with $n$ the dimensionless charge of the particle. This term\nmodifies the central charge of the system, from $c=1$ to $c=1-6n^2$, when\nconsidered in the context of conformal field theories.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fractional differential and integral operations and cumulative processes: In this study the general formula for differential and integral operations of\nfractional calculus via fractal operators by the method of cumulative\ndiminution and cumulative growth is obtained. The under lying mechanism in the\nsuccess of traditional fractional calculus for describing complex systems is\nuncovered. The connection between complex physics with fractional\ndifferentiation and integration operations is established.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Trapping of an active Brownian particle at a partially absorbing wall: Active matter concerns the self-organization of energy consuming elements\nsuch as motile bacteria or self-propelled colloids. A canonical example is an\nactive Brownian particle (ABP) that moves at constant speed while its direction\nof motion undergoes rotational diffusion. When ABPs are confined within a\nchannel, they tend to accumulate at the channel walls, even when inter-particle\ninteractions are ignored. Each particle pushes on the boundary until a tumble\nevent reverses its direction. The wall thus acts as a sticky boundary. In this\npaper we consider a natural extension of sticky boundaries that allows for a\nparticle to be permanently killed (absorbed) whilst attached to a wall. In\nparticular, we investigate the first passage time (FPT) problem for an ABP in a\ntwo-dimensional channel where one of the walls is partially absorbing.\nCalculating the exact FPT statistics requires solving a non-trivial two-way\ndiffusion boundary value problem (BVP). We follow a different approach by\nseparating out the dynamics away from the absorbing wall from the dynamics of\nabsorption and escape whilst attached to the wall. Using probabilistic methods,\nwe derive an explicit expression for the MFPT of absorption, assuming that the\narrival statistics of particles at the wall are known. Our method also allows\nus to incorporate a more general encounter-based model of absorption.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of Eulerian walkers: We investigate the dynamics of Eulerian walkers as a model of self-organized\ncriticality. The evolution of the system is subdivided into characteristic\nperiods which can be seen as avalanches. The structure of avalanches is\ndescribed and the critical exponent in the distribution of first avalanches\n$\\tau=2$ is determined. We also study a mean square displacement of Eulerian\nwalkers and obtain a simple diffusion law in the critical state. The evolution\nof underlying medium from a random state to the critical one is also described.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Long-wavelength instabilities in a system of interacting active\n  particles: Based on a microscopic model, we develop a continuum description for a\nsuspension of microscopic self propelled particles. With this continuum\ndescription we study the role of long-range interactions in destabilizing\nmacroscopic ordered phases that are developed by short-range interactions.\nLong-wavelength fluctuations can destabilize both isotropic and also symmetry\nbroken polar phase in a suspension of dipolar particles. The instabilities in a\nsuspension of pullers (pushers) arise from splay (bend) fluctuations. Such\ninstabilities are not seen in a suspension of quadrupolar particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Robustness of a perturbed topological phase: We investigate the stability of the topological phase of the toric code model\nin the presence of a uniform magnetic field by means of variational and\nhigh-order series expansion approaches. We find that when this perturbation is\nstrong enough, the system undergoes a topological phase transition whose first-\nor second-order nature depends on the field orientation. When this transition\nis of second order, it is in the Ising universality class except for a special\nline on which the critical exponent driving the closure of the gap varies\ncontinuously, unveiling a new topological universality class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Disorder Driven Roughening Transitions of Elastic Manifolds and Periodic\n  Elastic Media: The simultaneous effect of both disorder and crystal-lattice pinning on the\nequilibrium behavior of oriented elastic objects is studied using scaling\narguments and a functional renormalization group technique. Our analysis\napplies to elastic manifolds, e.g., interfaces, as well as to periodic elastic\nmedia, e.g., charge-density waves or flux-line lattices. The competition\nbetween both pinning mechanisms leads to a continuous, disorder driven\nroughening transition between a flat state where the mean relative displacement\nsaturates on large scales and a rough state with diverging relative\ndisplacement. The transition can be approached by changing the impurity\nconcentration or, indirectly, by tuning the temperature since the pinning\nstrengths of the random and crystal potential have in general a different\ntemperature dependence. For D dimensional elastic manifolds interacting with\neither random-field or random-bond disorder a transition exists for 2<D<4, and\nthe critical exponents are obtained to lowest order in \\epsilon=4-D. At the\ntransition, the manifolds show a superuniversal logarithmic roughness. Dipolar\ninteractions render lattice effects relevant also in the physical case of D=2.\nFor periodic elastic media, a roughening transition exists only if the ratio p\nof the periodicities of the medium and the crystal lattice exceeds the critical\nvalue p_c=6/\\pi\\sqrt{\\epsilon}. For p<p_c the medium is always flat. Critical\nexponents are calculated in a double expansion in \\mu=p^2/p_c^2-1 and\n\\epsilon=4-D and fulfill the scaling relations of random field models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The quantum (non-Abelian) Potts model and its exact solution: We generalize the classical one dimensional Potts model to the case where the\nsymmetry group is a non-Abelian finite group. It turns out that this new model\nhas a quantum nature in that its spectrum of energy eigenstates consists of\nentangled states. We determine the complete energy spectrum, i.e. the ground\nstates and all the excited states with their degeneracy structure. We calculate\nthe partition function by two different algebraic and combinatorial methods. We\nalso determine the entanglement properties of its ground states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A memory-induced diffusive-superdiffusive transition: ensemble and\n  time-averaged observables: The ensemble properties and time-averaged observables of a memory-induced\ndiffusive-superdiffusive transition are studied. The model consists in a random\nwalker whose transitions in a given direction depend on a weighted linear\ncombination of the number of both right and left previous transitions. The\ndiffusion process is nonstationary and its probability develops the phenomenon\nof aging. Depending on the characteristic memory parameters, the ensemble\nbehavior may be normal, superdiffusive, or ballistic. In contrast, the\ntime-averaged mean squared displacement is equal to that of a normal undriven\nrandom walk, which renders the process non-ergodic. In addition, and similarly\nto Levy walks [Godec and Metzler, Phys. Rev. Lett. 110, 020603 (2013)], for\ntrajectories of finite duration the time-averaged displacement apparently\nbecome random with properties that depend on the measurement time and also on\nthe memory properties. These features are related to the non-stationary\npower-law decay of the transition probabilities to their stationary values.\nTime-averaged response to a bias is also calculated. In contrast with Levy\nwalks [Froemberg and Barkai, Phys. Rev. E 87, 030104(R) (2013)], the response\nalways vanishes asymptotically.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hierarchy Bloch Equations for the Reduced Statistical Density Operators\n  in Canonical and Grand canonical Ensembles: Starting from Bloch equation for a canonical ensemble, we deduce a set of\nhierarchy equations for the reduced statistical density operator for an\nidentical many-body system with two-body interaction. They provide a law\naccording to which the reduced density operator varies in temperature. By\ndefinition of the reduced density operator in Fock space for a grand canonical\nensemble, we also obtain the analogous Bloch equation and the corresponding\nhierarchy reduced equations for the identical interacting many-body system. We\ndiscuss their possible solutions and applications.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "String Method for Generalized Gradient Flows: Computation of Rare Events\n  in Reversible Stochastic Processes: Rare transitions in stochastic processes can often be rigorously described\nvia an underlying large deviation principle. Recent breakthroughs in the\nclassification of reversible stochastic processes as gradient flows have led to\na connection of large deviation principles to a generalized gradient structure.\nHere, we show that, as a consequence, metastable transitions in these\nreversible processes can be interpreted as heteroclinic orbits of the\ngeneralized gradient flow. This in turn suggests a numerical algorithm to\ncompute the transition trajectories in configuration space efficiently, based\non the string method traditionally restricted only to gradient diffusions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Distribution of extremes in the fluctuations of two-dimensional\n  equilibrium interfaces: We investigate the statistics of the maximal fluctuation of two-dimensional\nGaussian interfaces. Its relation to the entropic repulsion between rigid walls\nand a confined interface is used to derive the average maximal fluctuation $<m>\n\\sim \\sqrt{2/(\\pi K)} \\ln N$ and the asymptotic behavior of the whole\ndistribution $P(m) \\sim N^2 e^{-{\\rm (const)} N^2 e^{-\\sqrt{2\\pi K} m} -\n\\sqrt{2\\pi K} m}$ for $m$ finite with $N^2$ and $K$ the interface size and\ntension, respectively. The standardized form of $P(m)$ does not depend on $N$\nor $K$, but shows a good agreement with Gumbel's first asymptote distribution\nwith a particular non-integer parameter. The effects of the correlations among\nindividual fluctuations on the extreme value statistics are discussed in our\nfindings.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Symmetry decomposition of negativity of massless free fermions: We consider the problem of symmetry decomposition of the entanglement\nnegativity in free fermionic systems. Rather than performing the standard\npartial transpose, we use the partial time-reversal transformation which\nnaturally encodes the fermionic statistics. The negativity admits a resolution\nin terms of the charge imbalance between the two subsystems. We introduce a\nnormalised version of the imbalance resolved negativity which has the advantage\nto be an entanglement proxy for each symmetry sector, but may diverge in the\nlimit of pure states for some sectors. Our main focus is then the resolution of\nthe negativity for a free Dirac field at finite temperature and size. We\nconsider both bipartite and tripartite geometries and exploit conformal field\ntheory to derive universal results for the charge imbalance resolved\nnegativity. To this end, we use a geometrical construction in terms of an\nAharonov-Bohm-like flux inserted in the Riemann surface defining the\nentanglement. We interestingly find that the entanglement negativity is always\nequally distributed among the different imbalance sectors at leading order. Our\nanalytical findings are tested against exact numerical calculations for free\nfermions on a lattice.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-universal dynamics of dimer growing interfaces: A finite temperature version of body-centered solid-on-solid growth models\ninvolving attachment and detachment of dimers is discussed in 1+1 dimensions.\nThe dynamic exponent of the growing interface is studied numerically via the\nspectrum gap of the underlying evolution operator. The finite size scaling of\nthe latter is found to be affected by a standard surface tension term on which\nthe growth rates depend. This non-universal aspect is also corroborated by the\ngrowth behavior observed in large scale simulations. By contrast, the\nroughening exponent remains robust over wide temperature ranges.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non Commutative Geometry of Tilings and Gap Labelling: To a given tiling a non commutative space and the corresponding C*-algebra\nare constructed. This includes the definition of a topology on the groupoid\ninduced by translations of the tiling. The algebra is also the algebra of\nobservables for discrete models of one or many particle systems on the tiling\nor its periodic identification. Its scaled ordered K_0-group furnishes the gap\nlabelling of Schroedinger operators. The group is computed for one dimensional\ntilings and Cartesian products thereof. Its image under a state is investigated\nfor tilings which are invariant under a substitution. Part of this image is\ngiven by an invariant measure on the hull of the tiling which is determined.\nThe results from the Cartesian products of one dimensional tilings point out\nthat the gap labelling by means of the values of the integrated density of\nstates is already fully determined by this measure.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Blind calibration for compressed sensing: State evolution and an online\n  algorithm: Compressed sensing, allows to acquire compressible signals with a small\nnumber of measurements. In applications, a hardware implementation often\nrequires a calibration as the sensing process is not perfectly known. Blind\ncalibration, that is performing at the same time calibration and compressed\nsensing is thus particularly appealing. A potential approach was suggested by\nSch\\\"ulke and collaborators in Sch\\\"ulke et al. 2013 and 2015, using\napproximate message passing (AMP) for blind calibration (cal-AMP). Here, the\nalgorithm is extended from the already proposed offline case to the online\ncase, where the calibration is refined step by step as new measured samples are\nreceived. Furthermore, we show that the performance of both the offline and the\nonline algorithms can be theoretically studied via the State Evolution (SE)\nformalism. Through numerical simulations, the efficiency of cal-AMP and the\nconsistency of the theoretical predictions are confirmed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ageing of complex networks: Many real-world complex networks arise as a result of a competition between\ngrowth and rewiring processes. Usually the initial part of the evolution is\ndominated by growth while the later one rather by rewiring. The initial growth\nallows the network to reach a certain size while rewiring to optimise its\nfunction and topology. As a model example we consider tree networks which first\ngrow in a stochastic process of node attachment and then age in a stochastic\nprocess of local topology changes. The ageing is implemented as a Markov\nprocess that preserves the node-degree distribution. We quantify differences\nbetween the initial and aged network topologies and study the dynamics of the\nevolution. We implement two versions of the ageing dynamics. One is based on\nreshuffling of leaves and the other on reshuffling of branches. The latter one\ngenerates much faster ageing due to non-local nature of changes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous scaling in statistical models of passively advected vector\n  fields: The field theoretic renormalization group and the operator product expansion\nare applied to the stochastic model of passively advected vector field with the\nmost general form of the nonlinear term allowed by the Galilean symmetry. The\nadvecting turbulent velocity field is governed by the stochastic Navier--Stokes\nequation. It is shown that the correlation functions of the passive vector\nfield in the inertial range exhibit anomalous scaling behaviour. The\ncorresponding anomalous exponents are determined by the critical dimensions of\ntensor composite fields (operators) built solely of the passive vector field.\nThey are calculated (including the anisotropic sectors) in the leading order of\nthe expansion in $y$, the exponent entering the correlator of the stirring\nforce in the Navier--Stokes equation (one-loop approximation of the\nrenormalization group). The anomalous exponents exhibit an hierarchy related to\nthe degree of anisotropy: the less is the rank of the tensor operator, the less\nis its dimension. Thus the leading terms, determined by scalar operators, are\nthe same as in the isotropic case, in agreement with the Kolmogorov's\nhypothesis of the local isotropy restoration.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Some geometric critical exponents for percolation and the random-cluster\n  model: We introduce several infinite families of new critical exponents for the\nrandom-cluster model and present scaling arguments relating them to the k-arm\nexponents. We then present Monte Carlo simulations confirming these\npredictions. These new exponents provide a convenient way to determine k-arm\nexponents from Monte Carlo simulations. An understanding of these exponents\nalso leads to a radically improved implementation of the Sweeny Monte Carlo\nalgorithm. In addition, our Monte Carlo data allow us to conjecture an exact\nexpression for the shortest-path fractal dimension d_min in two dimensions:\nd_min = (g+2)(g+18)/(32g) where g is the Coulomb-gas coupling, related to the\ncluster fugacity q via q = 2 + 2 cos(g\\pi/2) with 2 \\le g \\le 4.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic Ising model in an oscillating field: Avrami theory for the\n  hysteretic response and finite-size scaling for the dynamic phase transition: Hysteresis is studied for a two-dimensional, spin-1/2, nearest-neighbor,\nkinetic Ising ferromagnet in an oscillating field, using Monte Carlo\nsimulations and analytical theory. Attention is focused on large systems and\nstrong field amplitudes at a temperature below T_c. In this parameter regime,\nthe magnetization switches through random nucleation and subsequent growth of\nmany droplets of spins aligned with the applied field. Using a time-dependent\nextension of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory of metastable\ndecay, we analyze the statistical properties of the hysteresis-loop area and\nthe correlation between the magnetization and the applied field. This analysis\nenables us to accurately predict the results of extensive Monte Carlo\nsimulations. The average loop area exhibits an extremely slow approach to an\nasymptotic, logarithmic dependence on the product of the amplitude and the\nfrequency of the applied field. This may explain the inconsistent exponent\nestimates reported in previous attempts to fit experimental and numerical data\nfor the low-frequency behavior of this quantity to a power law. At higher\nfrequencies we observe a dynamic phase transition. Applying standard\nfinite-size scaling techniques from the theory of second-order equilibrium\nphase transitions to this nonequilibrium phase transition, we obtain estimates\nfor the transition frequency and the critical exponents (beta/nu \\approx 0.11,\ngamma/nu \\approx 1.84 and nu \\approx 1.1). In addition to their significance\nfor the interpretation of recent experiments on switching in ferromagnetic and\nferroelectric nanoparticles and thin films, our results provide evidence for\nthe relevance of universality and finite-size scaling to dynamic phase\ntransitions in spatially extended nonstationary systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite temperature vortex dynamics in Bose Einstein condensates: We study the decay of vortices in Bose-Einstein condensates at finite\ntemperatures by means of the Zaremba Nikuni Griffin formalism, in which the\ncondensate is modelled by a Gross Pitaevskiiequation, which is coupled to a\nBoltzmann kinetic equation for the thermal cloud. At finite temperature, an\noff-centred vortex in a harmonically trapped pancake shaped condensate decays\nby spiralling out towards the edge of the condensate. This decay, which depends\nheavily on temperature and atomic collisions, agrees with that predicted by the\nHall Vinen phenomenological model of friction force, which is used to describe\nquantised vorticity in superfluid systems. Our result thus clarifies the\nmicroscopic origin of the friction and provides an ab initio determination of\nits value.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the transport of interacting particles in a chain of cavities:\n  Description through a modified Fick-Jacobs equation: We study the transport process of interacting Brownian particles in a tube of\nvarying cross section. To describe this process we introduce a modified\nFick-Jacobs equation, considering particles that interact through a hard-core\npotential. We were able to solve the equation with numerical methods for the\ncase of symmetric and asymmetric cavities. We focused in the concentration of\nparticles along the direction of the tube. We also preformed Monte Carlo\nsimulations to evaluate the accuracy of the results, obtaining good agreement\nbetween theory and simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low-rank Monte Carlo for Smoluchowski-class equations: The work discusses a new low-rank Monte Carlo technique to solve\nSmoluchowski-like kinetic equations. It drastically decreases the computational\ncomplexity of modeling of size-polydisperse systems. For the studied systems it\ncan outperform the existing methods by more than ten times; its superiority\nfurther grows with increasing system size. Application to the recently\ndeveloped temperature-dependent Smoluchowski equations is also demonstrated.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic roughening model with opposite Kardar-Parisi-Zhang\n  nonlinearities: We introduce a model that simulates a kinetic roughening process with two\nkinds of particles: one follows the ballistic deposition (BD) kinetic and, the\nother, the restricted solid-on-solid (KK) kinetic. Both of these kinetics are\nin the universality class of the nonlinear KPZ equation, but the BD kinetic has\na positive nonlinear constant while the KK kinetic has a negative one. In our\nmodel, called BD-KK model, we assign the probabilities p and (1-p) to the KK\nand BD kinetics, respectively. For a specific value of p, the system behaves as\na quasi linear model and the up-down symmetry is recuperated. We show that\nnonlinearities of odd-order are relevant in these low nonlinear limit.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical behavior of the planar magnet model in three dimensions: We use a hybrid Monte Carlo algorithm in which a single-cluster update is\ncombined with the over-relaxation and Metropolis spin re-orientation algorithm.\nPeriodic boundary conditions were applied in all directions. We have calculated\nthe fourth-order cumulant in finite size lattices using the single-histogram\nre-weighting method. Using finite-size scaling theory, we obtained the critical\ntemperature which is very different from that of the usual XY model. At the\ncritical temperature, we calculated the susceptibility and the magnetization on\nlattices of size up to $42^3$. Using finite-size scaling theory we accurately\ndetermine the critical exponents of the model and find that $\\nu$=0.670(7),\n$\\gamma/\\nu$=1.9696(37), and $\\beta/\\nu$=0.515(2). Thus, we conclude that the\nmodel belongs to the same universality class with the XY model, as expected.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cooperative Transport of Brownian Particles: We consider the collective motion of finite-sized, overdamped Brownian\nparticles (e.g., motor proteins) in a periodic potential. Simulations of our\nmodel have revealed a number of novel cooperative transport phenomena,\nincluding (i) the reversal of direction of the net current as the particle\ndensity is increased and (ii) a very strong and complex dependence of the\naverage velocity on both the size and the average distance of the particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spatial Particle Condensation for an Exclusion Process on a Ring: We study the stationary state of a simple exclusion process on a ring which\nwas recently introduced by Arndt {\\it et al} [J. Phys. A {\\bf 31} (1998)\nL45;cond-mat/9809123]. This model exhibits spatial condensation of particles.\nIt has been argued that the model has a phase transition from a ``mixed phase''\nto a ``disordered phase''. However, in this paper exact calculations are\npresented which, we believe, show that in the framework of a grand canonical\nensemble there is no such phase transition. An analysis of the fluctuations in\nthe particle density strongly suggests that the same result also holds for the\ncanonical ensemble.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random matrices applications to soft spectra: It recently has been found that methods of the statistical theories of\nspectra can be a useful tool in the analysis of spectra far from levels of\nHamiltonian systems. Several examples originate from areas, such as\nquantitative linguistics and polymers. The purpose of the present study is to\ndeepen this kind of approach by performing a more comprehensive spectral\nanalysis that measures both the local and long-range statistics. We have found\nthat, as a common feature, spectra of this kind can exhibit a situation in\nwhich local statistics are relatively quenched while the long range ones show\nlarge fluctuations. By combining extensions of the standard Random Matrix\nTheory (RMT) and considering long spectra, we demonstrate that this phenomenon\noccurs when weak disorder is introduced in a RMT spectrum or when strong\ndisorder acts in a Poisson regime. We show that the long-range statistics\nfollow the Taylor law, which suggests the presence of a fluctuation scaling\n(FS) mechanism in this kind of spectra.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reaction Diffusion and Ballistic Annihilation Near an Impenetrable\n  Boundary: The behavior of the single-species reaction process $A+A\\to O$ is examined\nnear an impenetrable boundary, representing the flask containing the reactants.\nTwo types of dynamics are considered for the reactants: diffusive and ballistic\npropagation. It is shown that the effect of the boundary is quite different in\nboth cases: diffusion-reaction leads to a density excess, whereas ballistic\nannihilation exhibits a density deficit, and in both cases the effect is not\nlocalized at the boundary but penetrates into the system. The field-theoretic\nrenormalization group is used to obtain the universal properties of the density\nexcess in two dimensions and below for the reaction-diffusion system. In one\ndimension the excess decays with the same exponent as the bulk and is found by\nan exact solution. In two dimensions the excess is marginally less relevant\nthan the bulk decay and the density profile is again found exactly for late\ntimes from the RG-improved field theory. The results obtained for the diffusive\ncase are relevant for Mg$^{2+}$ or Cd$^{2+}$ doping in the TMMC crystal's\nexciton coalescence process and also imply a surprising result for the dynamic\nmagnetization in the critical one-dimensional Ising model with a fixed spin.\nFor the case of ballistic reactants, a model is introduced and solved exactly\nin one dimension. The density-deficit profile is obtained, as is the density of\nleft and right moving reactants near the impenetrable boundary.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetics of Ring Formation: We study reversible polymerization of rings. In this stochastic process, two\nmonomers bond and as a consequence, two disjoint rings may merge into a\ncompound ring, or, a single ring may split into two fragment rings. This\naggregation-fragmentation process exhibits a percolation transition with a\nfinite-ring phase in which all rings have microscopic length and a giant-ring\nphase where macroscopic rings account for a finite fraction of the entire mass.\nInterestingly, while the total mass of the giant rings is a deterministic\nquantity, their total number and their sizes are stochastic quantities. The\nsize distribution of the macroscopic rings is universal, although the span of\nthis distribution increases with time. Moreover, the average number of giant\nrings scales logarithmically with system size. We introduce a card-shuffling\nalgorithm for efficient simulation of the ring formation process, and present\nnumerical verification of the theoretical predictions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Multicanonical Molecular Dynamics Study on a Simple Bead-Spring Model\n  for Protein Folding: We have performed a multicanonical molecular dynamics simulation on a simple\nmodel protein.We have studied a model protein composed of charged, hydrophobic,\nand neutral spherical bead monomers.Since the hydrophobic interaction is\nconsidered to significantly affect protein folding, we particularly focus on\nthe competition between effects of the Coulomb interaction and the hydrophobic\ninteraction. We found that the transition which occurs upon decreasing the\ntemperature is markedly affected by the change in both parameters and forms of\nthe hydrophobic potential function, and the transition changes from first order\nto second order, when the Coulomb interaction becomes weaker.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Simulating first-order phase transition with hierarchical autoregressive\n  networks: We apply the Hierarchical Autoregressive Neural (HAN) network sampling\nalgorithm to the two-dimensional $Q$-state Potts model and perform simulations\naround the phase transition at $Q=12$. We quantify the performance of the\napproach in the vicinity of the first-order phase transition and compare it\nwith that of the Wolff cluster algorithm. We find a significant improvement as\nfar as the statistical uncertainty is concerned at a similar numerical effort.\nIn order to efficiently train large neural networks we introduce the technique\nof pre-training. It allows to train some neural networks using smaller system\nsizes and then employing them as starting configurations for larger system\nsizes. This is possible due to the recursive construction of our hierarchical\napproach. Our results serve as a demonstration of the performance of the\nhierarchical approach for systems exhibiting bimodal distributions.\nAdditionally, we provide estimates of the free energy and entropy in the\nvicinity of the phase transition with statistical uncertainties of the order of\n$10^{-7}$ for the former and $10^{-3}$ for the latter based on a statistics of\n$10^6$ configurations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum fluctuation theorem for initial near-equilibrium system: Quantum work fluctuation theorem (FT) commonly requires the system initially\nprepared in an equilibrium state. Whether there exists universal exact quantum\nwork FT for initial state beyond equilibrium needs further discussions. Here, I\ninitialize the system in a near-equilibrium state, and derive the corresponding\nmodified Jarzynski equality by using the perturbation theory. The correction is\nnontrivial because it directly leads to the principle of maximum work or the\nsecond law of thermodynamics for near-equilibrium system and also gives a much\ntighter bound of work for a given process. I also verify my theoretical results\nby considering a concrete many-body system, and reveal a fundamental connection\nbetween quantum critical phenomenon and near-equilibrium state at really high\ntemperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetics of phase ordering on curved surfaces: An interface description and numerical simulations of model A kinetics are\nused for the first time to investigate the intra-surface kinetics of phase\nordering on corrugated surfaces. Geometrical dynamical equations are derived\nfor the domain interfaces. The dynamics is shown to depend strongly on the\nlocal Gaussian curvature of the surface, and can be fundamentally different\nfrom that in flat systems: dynamical scaling breaks down despite the\npersistence of the dominant interfacial undulation mode; growth laws are slower\nthan $t^{1/2}$ and even logarithmic; a new very-late-stage regime appears\ncharacterized by extremely slow interface motion; finally, the zero-temperature\nfixed point no longer exists, leading to metastable states. Criteria for the\nexistence of the latter are derived and discussed in the context of more\ncomplex systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The role of mobility in epidemics near criticality: The general epidemic process (GEP), also known as\nsusceptible-infected-recovered model (SIR), describes how an epidemic spreads\nwithin a population of susceptible individuals who acquire permanent\nimmunization upon recovery. This model exhibits a second-order absorbing state\nphase transition, commonly studied assuming immobile healthy individuals. We\ninvestigate the impact of mobility on disease spreading near the extinction\nthreshold by introducing two generalizations of GEP, where the mobility of\nsusceptible and recovered individuals is examined independently. In both cases,\nincluding mobility violates GEP's rapidity reversal symmetry and alters the\nnumber of absorbing states. The critical dynamics of the models are analyzed\nthrough a perturbative renormalization group approach and large-scale\nstochastic simulations using a Gillespie algorithm. The renormalization group\nanalysis predicts both models to belong to the same novel universality class\ndescribing the critical dynamics of epidemic spreading when the infected\nindividuals interact with a diffusive species and gain immunization upon\nrecovery. At the associated renormalization group fixed point, the immobile\nspecies decouples from the dynamics of the infected species, dominated by the\ncoupling with the diffusive species. Numerical simulations in two dimensions\naffirm our renormalization group results by identifying the same set of\ncritical exponents for both models. Violation of the rapidity reversal symmetry\nis confirmed by breaking the associated hyperscaling relation. Our study\nunderscores the significance of mobility in shaping population spreading\ndynamics near the extinction threshold.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Vibrations of closed-shell Lennard-Jones icosahedral and cuboctahedral\n  clusters and their effect on the cluster ground state energy: Vibrational spectra of closed shell Lennard-Jones icosahedral and\ncuboctahedral clusters are calculated for shell numbers between 2 and 9.\nEvolution of the vibrational density of states with the cluster shell number is\nexamined and differences between icosahedral and cuboctahedral clusters\ndescribed. This enabled a quantum calculation of quantum ground state energies\nof the clusters in the quasiharmonic approximation and a comparison of the\ndifferences between the two types of clusters. It is demonstrated that in the\nquantum treatment, the closed shell icosahedral clusters binding energies\ndiffer from those of cuboctahedral clusters more than is the case in classical\ntreatment.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exclusion Processes and boundary conditions: A family of boundary conditions corresponding to exclusion processes is\nintroduced. This family is a generalization of the boundary conditions\ncorresponding to the simple exclusion process, the drop-push model, and the\none-parameter solvable family of pushing processes with certain rates on the\ncontinuum [1-3]. The conditional probabilities are calculated using the Bethe\nansatz, and it is shown that at large times they behave like the corresponding\nconditional probabilities of the family of diffusion-pushing processes\nintroduced in [1-3].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extended Gibbs ensembles with flow: A statistical treatment of finite unbound systems in the presence of\ncollective motions is presented and applied to a classical Lennard-Jones\nHamiltonian, numerically simulated through molecular dynamics. In the ideal gas\nlimit, the flow dynamics can be exactly re-casted into effective time-dependent\nLagrange parameters acting on a standard Gibbs ensemble with an extra total\nenergy conservation constraint. Using this same ansatz for the low density\nfreeze-out configurations of an interacting expanding system, we show that the\npresence of flow can have a sizeable effect on the microstate distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Microcanonical Monte Carlo Study of One Dimensional Self-Gravitating\n  Lattice Gas Models: In this study we present a Microcanonical Monte Carlo investigation of one\ndimensional self-gravitating toy models. We study the effect of hard-core\npotentials and compare to those results obtained with softening parameters and\nalso the effect of the geometry of the models. In order to study the effect of\nthe geometry and the borders in the system we introduce a model with the\nsymmetry of motion in a line instead of a circle, which we denominate as $1/r$\nmodel. The hard-core particle potential introduces the effect of the size of\nparticles and, consequently, the effect of the density of the system that is\nredefined in terms of the packing fraction of the system. The latter plays a\nrole similar to the softening parameter $\\epsilon$ in the softened particles'\ncase. In the case of low packing fractions both models with hard-core particles\nshow a behavior that keeps the intrinsic properties of the three dimensional\ngravitational systems such as negative heat capacity. For higher values of the\npacking fraction the ring the system behaves as the Hamiltonian Mean Field\nmodel and while for the $1/r$ it is similar to the one-dimensional systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Empirical Traffic Data and Their Implications for Traffic Modeling: From single vehicle data a number of new empirical results about the temporal\nevolution, correlation, and density-dependence of macroscopic traffic\nquantities have been determined. These have relevant implications for traffic\nmodeling and allow to test existing traffic models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Two-dimensional scaling properties of experimental fracture surfaces: The morphology of fracture surfaces encodes the various complex damage and\nfracture processes occurring at the microstructure scale that have lead to the\nfailure of a given heterogeneous material. Understanding how to decipher this\nmorphology is therefore of fundamental interest. This has been extensively\ninvestigated over these two last decades. It has been established that 1D\nprofiles of these fracture surfaces exhibit properties of scaling invariance.\nIn this paper, we present deeper analysis and investigate the 2D scaling\nproperties of these fracture surfaces. We showed that the properties of scaling\ninvariance are anisotropic and evidenced the existence of two peculiar\ndirections on the post-mortem fracture surface caracterized by two different\nscaling exponents: the direction of the crack growth and the direction of the\ncrack front. These two exponents were found to be universal, independent of the\ncrack growth velocity, in both silica glass and aluminum alloy, archetype of\nbrittle and ductile material respectively. Moreover, the 2D structure function\nthat fully characterizes the scaling properties of the fracture surface was\nshown to take a peculiar form similar to the one predicted by some models\nissued from out-of-equilibrium statistical physics. This suggest some promising\nanalogies between dynamic phase transition models and the stability of a crack\nfront pinned/unpinned by the heterogenities of the material.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlated Percolation: Cluster concepts have been extremely useful in elucidating many problems in\nphysics. Percolation theory provides a generic framework to study the behavior\nof the cluster distribution. In most cases the theory predicts a geometrical\ntransition at the percolation threshold, characterized in the percolative phase\nby the presence of a spanning cluster, which becomes infinite in the\nthermodynamic limit. Standard percolation usually deals with the problem when\nthe constitutive elements of the clusters are randomly distributed. However\ncorrelations cannot always be neglected. In this case correlated percolation is\nthe appropriate theory to study such systems. The origin of correlated\npercolation could be dated back to 1937 when Mayer [1] proposed a theory to\ndescribe the condensation from a gas to a liquid in terms of mathematical\nclusters (for a review of cluster theory in simple fluids see [2]). The\nlocation for the divergence of the size of these clusters was interpreted as\nthe condensation transition from a gas to a liquid. One of the major drawback\nof the theory was that the cluster number for some values of thermodynamic\nparameters could become negative. As a consequence the clusters did not have\nany physical interpretation [3]. This theory was followed by Frenkel's\nphenomenological model [4], in which the fluid was considered as made of non\ninteracting physical clusters with a given free energy. This model was later\nimproved by Fisher [3], who proposed a different free energy for the clusters,\nnow called droplets, and consequently a different scaling form for the droplet\nsize distribution. This distribution, which depends on two geometrical\nparameters, has the nice feature that the mean droplet size exhibits a\ndivergence at the liquid-gas critical point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Strong Correlations and Fickian Water Diffusion in Narrow Carbon\n  Nanotubes: We have used atomistic molecular dynamics (MD) simulations to study the\nstructure and dynamics of water molecules inside an open ended carbon nanotube\nplaced in a bath of water molecules. The size of the nanotube allows only a\nsingle file of water molecules inside the nanotube. The water molecules inside\nthe nanotube show solid-like ordering at room temperature, which we quantify by\ncalculating the pair correlation function. It is shown that even for the\nlongest observation times, the mode of diffusion of the water molecules inside\nthe nanotube is Fickian and not sub-diffusive. We also propose a\none-dimensional random walk model for the diffusion of the water molecules\ninside the nanotube. We find good agreement between the mean-square\ndisplacements calculated from the random walk model and from MD simulations,\nthereby confirming that the water molecules undergo normal-mode diffusion\ninside the nanotube. We attribute this behavior to strong positional\ncorrelations that cause all the water molecules inside the nanotube to move\ncollectively as a single object. The average residence time of the water\nmolecules inside the nanotube is shown to scale quadratically with the nanotube\nlength.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Short range order in a steady state of irradiated Cu-Pd alloys:\n  Comparison with fluctuations at thermal equilibrium: The equilibrium short-range order (SRO) in Cu-Pd alloys is studied\ntheoretically. The evolution of the Fermi surface-related splitting of the\n(110) diffuse intensity peak with changing temperature is examined. The results\nare compared with experimental observations for electron-irradiated samples in\na steady state, for which the temperature dependence of the splitting was\npreviously found in the composition range from 20 to 28 at.% Pd. The\nequilibrium state is studied by analysing available experimental and\ntheoretical results and using a recently proposed alpha-expansion theory of SRO\nwhich is able to describe the temperature-dependent splitting. It is found that\nthe electronic-structure calculations in the framework of the\nKorringa-Kohn-Rostoker coherent potential approximation overestimate the\nexperimental peak splitting. This discrepancy is attributed to the shift of the\nintensity peaks with respect to the positions of the corresponding\nreciprocal-space minima of the effective interatomic interaction towards the\n(110) and equivalent positions. Combined with an assumption about monotonicity\nof the temperature behaviour of the splitting, such shift implies an increase\nof the splitting with increasing temperature for all compositions considered in\nthis study. The alpha-expansion calculations seem to confirm this conclusion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Conservation-laws-preserving algorithms for spin dynamics simulations: We propose new algorithms for numerical integration of the equations of\nmotion for classical spin systems with fixed spatial site positions. The\nalgorithms are derived on the basis of a mid-point scheme in conjunction with\nthe multiple time staging propagation. Contrary to existing predictor-corrector\nand decomposition approaches, the algorithms introduced preserve all the\nintegrals of motion inherent in the basic equations. As is demonstrated for a\nlattice ferromagnet model, the present approach appears to be more efficient\neven over the recently developed decomposition method.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the statistical arrow of time: What is the physical origin of the arrow of time? It is a commonly held\nbelief in the physics community that it relates to the increase of entropy as\nit appears in the statistical interpretation of the second law of\nthermodynamics. At the same time, the subjective information-theoretical\ninterpretation of probability, and hence entropy, is a standard viewpoint in\nthe foundations of statistical mechanics. In this article, it is argued that\nthe subjective interpretation is incompatible with the philosophical point of\nview that the arrow of time is a fundamental property of Nature. The\nsubjectivist can only uphold this philosophy if the role played by the second\nlaw of thermodynamics in defining time's arrow is abandoned.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Strongly-Coupled Coulomb Systems using finite-$T$ Density Functional\n  Theory: A review of studies on Strongly-Coupled Coulomb Systems since the\n  rise of DFT and SCCS-1977: The conferences on \"Strongly Coupled Coulomb Systems\" (SCCS) arose from the\n\"Strongly Coupled Plasmas\" meetings, inaugurated in 1977. The progress in SCCS\ntheory is reviewed in an `author-centered' frame to limit its scope. Our\nefforts, i.e., with Fran\\c{c}ois Perrot, sought to apply density functional\ntheory (DFT) to SCCS calculations. DFT was then poised to become the major\ncomputational scheme for condensed matter physics. The ion-sphere models of\nSalpeter and others evolved into useful average-atom models for finite-$T$\nCoulomb systems, as in Lieberman's Inferno code. We replaced these by\ncorrelation-sphere models that exploit the description of matter via density\nfunctionals linked to pair-distributions. These methods provided practical\ncomputational means for studying strongly interacting electron-ion Coulomb\nsystems like warm-dense matter (WDM). The staples of SCCS are wide-ranged,\nviz., equation of state, plasma spectroscopy, opacity (absorption, emission),\nscattering, level shifts, transport properties, e.g., electrical and heat\nconductivity, laser- and shock- created plasmas, their energy relaxation and\ntransient properties etc. These calculations need pseudopotentials and\nexchange-correlation functionals applicable to finite-$T$ Coulomb systems that\nmay be used in ab initio codes, molecular dynamics, etc. The search for simpler\ncomputational schemes has proceeded via proposals for orbital-free DFT,\nstatistical potentials, classical maps of quantum systems using classical\nschemes like HNC to include strong coupling effects (CHNC). Laughlin's\nclassical plasma map for the fractional quantum Hall effect (FQHE) is a seminal\nexample where we report new results for graphene.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Simple analytical model of a thermal diode: Recently there is a lot of attention given to manipulation of heat by\nconstructing thermal devices such as thermal diodes, transistors and logic\ngates. Many of the models proposed have an asymmetry which leads to the desired\neffect. Presence of non-linear interactions among the particles is also\nessential. But, such models lack analytical understanding. Here we propose a\nsimple, analytically solvable model of a thermal diode. Our model consists of\nclassical spins in contact with multiple heat baths and constant external\nmagnetic fields. Interestingly the magnetic field is the only parameter\nrequired to get the effect of heat rectification.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonequilibrium coupled Brownian phase oscillators: A model of globally coupled phase oscillators under equilibrium (driven by\nGaussian white noise) and nonequilibrium (driven by symmetric dichotomic\nfluctuations) is studied. For the equilibrium system, the mean-field state\nequation takes a simple form and the stability of its solution is examined in\nthe full space of order parameters. For the nonequilbrium system, various\nasymptotic regimes are obtained in a closed analytical form. In a general case,\nthe corresponding master equations are solved numerically. Moreover, the\nMonte-Carlo simulations of the coupled set of Langevin equations of motion is\nperformed. The phase diagram of the nonequilibrium system is presented. For the\nlong time limit, we have found four regimes. Three of them can be obtained from\nthe mean-field theory. One of them, the oscillating regime, cannot be predicted\nby the mean-field method and has been detected in the Monte-Carlo numerical\nexperiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Granular fluid thermostatted by a bath of elastic hard spheres: The homogeneous steady state of a fluid of inelastic hard spheres immersed in\na bath of elastic hard spheres kept at equilibrium is analyzed by means of the\nfirst Sonine approximation to the (spatially homogeneous) Enskog--Boltzmann\nequation. The temperature of the granular fluid relative to the bath\ntemperature and the kurtosis of the granular distribution function are obtained\nas functions of the coefficient of restitution, the mass ratio, and a\ndimensionless parameter $\\beta$ measuring the cooling rate relative to the\nfriction constant. Comparison with recent results obtained from an iterative\nnumerical solution of the Enskog--Boltzmann equation [Biben et al., Physica A\n310, 308 (202)] shows an excellent agreement. Several limiting cases are also\nconsidered. In particular, when the granular particles are much heavier than\nthe bath particles (but have a comparable size and number density), it is shown\nthat the bath acts as a white noise external driving. In the general case, the\nSonine approximation predicts the lack of a steady state if the control\nparameter $\\beta$ is larger than a certain critical value $\\beta_c$ that\ndepends on the coefficient of restitution and the mass ratio. However, this\nphenomenon appears outside the expected domain of applicability of the\napproximation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Floquet dynamical quantum phase transitions under synchronized periodic\n  driving: We study a generic class of fermionic two-band models under synchronized\nperiodic driving, i.e., with the different terms in a Hamiltonian subject to\nperiodic drives with the same frequency and phase. With all modes initially in\na maximally mixed state, the synchronized drive is found to produce nonperiodic\npatterns of dynamical quantum phase transitions, with their appearance\ndetermined by an interplay of the band structure and the frequency of the\ndrive. A case study of the anisotropic XY chain in a transverse magnetic field,\ntranscribed to an effective two-band model, shows that the modes come with\nquantized geometric phases, allowing for the construction of an effective\ndynamical order parameter. Numerical studies in the limit of a strong magnetic\nfield reveal distinct signals of precursors of dynamical quantum phase\ntransitions also when the initial state of the XY chain is perturbed slightly\naway from maximal mixing, suggesting that the transitions may be accessible\nexperimentally. A blueprint for an experiment built around laser-trapped\ncircular Rydberg atoms is proposed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Clusters in an epidemic model with long-range dispersal: In presence of long range dispersal, epidemics spread in spatially\ndisconnected regions known as clusters. Here, we characterize exactly their\nstatistical properties in a solvable model, in both the supercritical\n(outbreak) and critical regimes. We identify two diverging length scales,\ncorresponding to the bulk and the outskirt of the epidemic. We reveal a\nnontrivial critical exponent that governs the cluster number, the distribution\nof their sizes and of the distances between them. We also discuss applications\nto depinning avalanches with long range elasticity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interplay among helical order, surface effects and range of interacting\n  layers in ultrathin films: The properties of helical thin films have been thoroughly investigated by\nclassical Monte Carlo simulations. The employed model assumes classical planar\nspins in a body-centered tetragonal lattice, where the helical arrangement\nalong the film growth direction has been modeled by nearest neighbor and\nnext-nearest neighbor competing interactions, the minimal requirement to get\nhelical order. We obtain that, while the in-plane transition temperatures\nremain essentially unchanged with respect to the bulk ones, the helical/fan\narrangement is stabilized at more and more low temperature when the film\nthickness, n, decreases; in the ordered phase, increasing the temperature, a\nsoftening of the helix pitch wave-vector is also observed. Moreover, we show\nalso that the simulation data around both transition temperatures lead us to\nexclude the presence of a first order transition for all analyzed sizes.\nFinally, by comparing the results of the present work with those obtained for\nother models previously adopted in literature, we can get a deeper insight\nabout the entwined role played by the number (range) of interlayer interactions\nand surface effects in non-collinear thin films.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extreme boundary conditions and random tilings: Standard statistical mechanical or condensed matter arguments tell us that\nbulk properties of a physical system do not depend too much on boundary\nconditions. Random tilings of large regions provide counterexamples to such\nintuition, as illustrated by the famous 'arctic circle theorem' for dimer\ncoverings in two dimensions. In these notes, I discuss such examples in the\ncontext of critical phenomena, and their relation to 1+1d quantum particle\nmodels. All those turn out to share a common feature: they are inhomogeneous,\nin the sense that local densities now depend on position in the bulk. I explain\nhow such problems may be understood using variational (or hydrodynamic)\narguments, how to treat long range correlations, and how non trivial edge\nbehavior can occur. While all this is done on the example of the dimer model,\nthe results presented here have much greater generality. In that sense the\ndimer model serves as an opportunity to discuss broader methods and results.\n[These notes require only a basic knowledge of statistical mechanics.]",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universality of striped morphologies: We present a method for predicting the low-temperature behavior of spherical\nand Ising spin models with isotropic potentials. For the spherical model the\ncharacteristic length scales of the ground states are exactly determined but\nthe morphology is shown to be degenerate with checkerboard patterns, stripes\nand more complex morphologies having identical energy. For the Ising models we\nshow that the discretization breaks the degeneracy causing striped morphologies\nto be energetically favored and therefore they arise universally as ground\nstates to potentials whose Hankel transforms have nontrivial minima.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal entanglement entropy in 2D conformal quantum critical points: We study the scaling behavior of the entanglement entropy of two dimensional\nconformal quantum critical systems, i.e. systems with scale invariant wave\nfunctions. They include two-dimensional generalized quantum dimer models on\nbipartite lattices and quantum loop models, as well as the quantum Lifshitz\nmodel and related gauge theories. We show that, under quite general conditions,\nthe entanglement entropy of a large and simply connected sub-system of an\ninfinite system with a smooth boundary has a universal finite contribution, as\nwell as scale-invariant terms for special geometries. The universal finite\ncontribution to the entanglement entropy is computable in terms of the\nproperties of the conformal structure of the wave function of these quantum\ncritical systems. The calculation of the universal term reduces to a problem in\nboundary conformal field theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Collective oscillations in driven coagulation: We present a novel form of collective oscillatory behavior in the kinetics of\nirreversible coagulation with a constant input of monomers and removal of large\nclusters. For a broad class of collision rates, this system reaches a\nnon-equilibrium stationary state at large times and the cluster size\ndistribution tends to a universal form characterised by a constant flux of mass\nthrough the space of cluster sizes. Universality, in this context, means that\nthe stationary state becomes independent of the cut-off as the cut-off grows.\nThis universality is lost, however, if the aggregation rate between large and\nsmall clusters increases sufficiently steeply as a function of cluster sizes.\nWe identify a transition to a regime in which the stationary state vanishes as\nthe cut-off grows. This non-universal stationary state becomes unstable,\nhowever, as the cut-off is increased and undergoes a Hopf bifurcation. After\nthis bifurcation, the stationary kinetics are replaced by persistent and\nperiodic collective oscillations. These oscillations carry pulses of mass\nthrough the space of cluster sizes. As a result, the average mass flux remains\nconstant. Furthermore, universality is partially restored in the sense that the\nscaling of the period and amplitude of oscillation is inherited from the\ndynamical scaling exponents of the universal regime. The implications of this\nnew type of long-time asymptotic behaviour for other driven non-equilibrium\nsystems are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extrapolating the thermodynamic length with finite-time measurements: The excess work performed in a heat-engine process with given finite\noperation time \\tau is bounded by the thermodynamic length, which measures the\ndistance during the relaxation along a path in the space of the thermodynamic\nstate. Unfortunately, the thermodynamic length, as a guidance for the heat\nengine optimization, is beyond the experimental measurement. We propose to\nmeasure the thermodynamic length \\mathcal{L} through the extrapolation of\nfinite-time measurements\n\\mathcal{L}(\\tau)=\\int_{0}^{\\tau}[P_{\\mathrm{ex}}(t)]^{1/2}dt via the excess\npower P_{\\mathrm{ex}}(t). The current proposal allows to measure the\nthermodynamic length for a single control parameter without requiring extra\neffort to find the optimal control scheme. We illustrate the measurement\nstrategy via examples of the quantum harmonic oscillator with tuning frequency\nand the classical ideal gas with changing volume.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Monomer-Dimer Mixture on a Honeycomb Lattice: We study a monomer-dimer mixture defined on a honeycomb lattice as a toy\nmodel for the spin ice system in a magnetic field. In a low-doping region of\nmonomers, the effective description of this system is given by the dual\nsine-Gordon model. In intermediate- and strong-doping regions, the Potts\nlattice gas theory can be employed. Synthesizing these results, we construct a\nrenormalization-group flow diagram, which includes the stable and unstable\nfixed points corresponding to ${\\cal M}_5$ and ${\\cal M}_6$ in the minimal\nmodels of the conformal field theory. We perform numerical transfer-matrix\ncalculations to determine a global phase diagram and also to proffer evidence\nto check our prediction.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Will jams get worse when slow cars move over?: Motivated by an analogy with traffic, we simulate two species of particles\n(`vehicles'), moving stochastically in opposite directions on a two-lane ring\nroad. Each species prefers one lane over the other, controlled by a parameter\n$0 \\leq b \\leq 1$ such that $b=0$ corresponds to random lane choice and $b=1$\nto perfect `laning'. We find that the system displays one large cluster (`jam')\nwhose size increases with $b$, contrary to intuition. Even more remarkably, the\nlane `charge' (a measure for the number of particles in their preferred lane)\nexhibits a region of negative response: even though vehicles experience a\nstronger preference for the `right' lane, more of them find themselves in the\n`wrong' one! For $b$ very close to 1, a sharp transition restores a homogeneous\nstate. Various characteristics of the system are computed analytically, in good\nagreement with simulation data.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Multicomponent fluid of hard spheres near a wall: The rational function approximation method, density functional theory, and\nNVT Monte Carlo simulation are used to obtain the density profiles of\nmulticomponent hard-sphere mixtures near a planar hard wall. Binary mixtures\nwith a size ratio 1:3 in which both components occupy a similar volume are\nspecifically examined. The results indicate that the present version of density\nfunctional theory yields an excellent overall performance. A reasonably\naccurate behavior of the rational function approximation method is also\nobserved, except in the vicinity of the first minimum, where it may even\npredict unphysical negative values.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Functional renormalization group approach to the dynamics of first-order\n  phase transitions: We apply the functional renormalization group theory to the dynamics of\nfirst-order phase transitions and show that a potential with all odd-order\nterms can describe spinodal decomposition phenomena. We derive a\nmomentum-dependent dynamic flow equation which is decoupled from the static\nflow equation. We find the expected instability fixed points; and their\nassociated exponents agree remarkably with the existent theoretical and\nnumerical results. The complex renormalization group flows are found and their\nproperties are shown. Both the exponents and the complex flows show that the\nspinodal decomposition possesses singularity with consequent scaling and\nuniversality.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Survival of an evasive prey: We study the survival of a prey that is hunted by N predators. The predators\nperform independent random walks on a square lattice with V sites and start a\ndirect chase whenever the prey appears within their sighting range. The prey is\ncaught when a predator jumps to the site occupied by the prey. We analyze the\nefficacy of a lazy, minimal-effort evasion strategy according to which the prey\ntries to avoid encounters with the predators by making a hop only when any of\nthe predators appears within its sighting range; otherwise the prey stays\nstill. We show that if the sighting range of such a lazy prey is equal to 1\nlattice spacing, at least 3 predators are needed in order to catch the prey on\na square lattice. In this situation, we establish a simple asymptotic relation\nln(Pev)(t) \\sim (N/V)2ln(Pimm(t)) between the survival probabilities of an\nevasive and an immobile prey. Hence, when the density of the predators is low\nN/V<<1, the lazy evasion strategy leads to the spectacular increase of the\nsurvival probability. We also argue that a short-sighting prey (its sighting\nrange is smaller than the sighting range of the predators) undergoes an\neffective superdiffusive motion, as a result of its encounters with the\npredators, whereas a far-sighting prey performs a diffusive-type motion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Geometric magnetism in classical transport theory: The effective dynamics of a slow classical system coupled to a fast chaotic\nenvironment is described by means of a Master equation. We show how this\napproach permits a very simple derivation of geometric magnetism.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous scaling and large-scale anisotropy in magnetohydrodynamic\n  turbulence: Two-loop renormalization-group analysis of the\n  Kazantsev--Kraichnan kinematic model: The field theoretic renormalization group and operator product expansion are\napplied to the Kazantsev--Kraichnan kinematic model for the magnetohydrodynamic\nturbulence. The anomalous scaling emerges as a consequence of the existence of\ncertain composite fields (\"operators\") with negative dimensions. The anomalous\nexponents for the correlation functions of arbitrary order are calculated in\nthe two-loop approximation (second order of the renormalization-group\nexpansion), including the anisotropic sectors. The anomalous scaling and the\nhierarchy of anisotropic contributions become stronger due to those\nsecond-order contributions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The non-Landauer Bound for the Dissipation of Bit Writing Operation: We propose a novel bound on the mimimum dissipation required in any\ncircumstances to transfer a certain amount of charge through any resistive\ndevice. We illustrate it on the task of writing a logical 1 (encoded as a\nprescribed voltage) into a capacitance, through various linear or nonlinear\ndevices. We show that, even though the celebrated Landauer bound (which only\napplies to bit erasure) does not apply here, one can still formulate a \"non-\nLandauer\" lower bound on dissipation, that crucially depends on the time budget\nto perform the operation, as well as the average conductance of the driving\ndevice. We compare our bound with empirical results reported in the literature\nand realistic simulations of CMOS pass and transmission gates in decananometer\ntechnology. Our non-Landauer bound turns out to be a quantitative benchmark to\nassess the (non-)optimality of a writing operation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Emergent universal statistics in nonequilibrium systems with dynamical\n  scale selection: Pattern-forming nonequilibrium systems are ubiquitous in nature, from driven\nquantum matter and biological life forms to atmospheric and interstellar gases.\nIdentifying universal aspects of their far-from-equilibrium dynamics and\nstatistics poses major conceptual and practical challenges due to the absence\nof energy and momentum conservation laws. Here, we experimentally and\ntheoretically investigate the statistics of prototypical nonequilibrium systems\nin which inherent length-scale selection confines the dynamics near a mean\nenergy hypersurface. Guided by spectral analysis of the field modes and scaling\narguments, we derive a universal nonequilibrium distribution for kinetic field\nobservables. We confirm the predicted energy distributions in experimental\nobservations of Faraday surface waves, and in quantum chaos and active\nturbulence simulations. Our results indicate that pattern dynamics and\ntransport in driven physical and biological matter can often be described\nthrough monochromatic random fields, suggesting a path towards a unified\nstatistical field theory of nonequilibrium systems with length-scale selection.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of lengthscales and attractions on the collapse of hydrophobic\n  polymers in water: We present results from extensive molecular dynamics simulations of collapse\ntransitions of hydrophobic polymers in explicit water focused on understanding\neffects of lengthscale of the hydrophobic surface and of attractive\ninteractions on folding. Hydrophobic polymers display parabolic, protein-like,\ntemperature-dependent free energy of unfolding. Folded states of small\nattractive polymers are marginally stable at 300 K, and can be unfolded by\nheating or cooling. Increasing the lengthscale or decreasing the polymer-water\nattractions stabilizes folded states significantly, the former dominated by the\nhydration contribution. That hydration contribution can be described by the\nsurface tension model, $\\Delta G=\\gamma (T)\\Delta A$, where the surface\ntension, $\\gamma$, is lengthscale dependent and decreases monotonically with\ntemperature. The resulting variation of the hydration entropy with polymer\nlengthscale is consistent with theoretical predictions of Huang and Chandler\n(Proc. Natl. Acad. Sci.,97, 8324-8327, 2000) that explain the blurring of\nentropy convergence observed in protein folding thermodynamics. Analysis of\nwater structure shows that the polymer-water hydrophobic interface is soft and\nweakly dewetted, and is characterized by enhanced interfacial density\nfluctuations. Formation of this interface, which induces polymer folding, is\nstrongly opposed by enthalpy and favored by entropy, similar to the\nvapor-liquid interface.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Logarithmically slow onset of synchronization: Here we investigate specifically the transient of a synchronizing system,\nconsidering synchronization as a relaxation phenomenon. The stepwise\nestablishment of synchronization is studied in the system of dynamically\ncoupled maps introduced by Ito & Kaneko (Phys. Rev. Lett., 88, 028701, 2001 &\nPhys. Rev. E, 67, 046226, 2003), where the plasticity of dynamical couplings\nmight be relevant in the context of neuroscience. We show the occurrence of\nlogarithmically slow dynamics in the transient of a fully deterministic\ndynamical system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Growth of surfaces generated by a probabilistic cellular automaton: A one-dimensional cellular automaton with a probabilistic evolution rule can\ngenerate stochastic surface growth in $(1 + 1)$ dimensions. Two such discrete\nmodels of surface growth are constructed from a probabilistic cellular\nautomaton which is known to show a transition from a active phase to a\nabsorbing phase at a critical probability associated with two particular\ncomponents of the evolution rule. In one of these models, called model $A$ in\nthis paper, the surface growth is defined in terms of the evolving front of the\ncellular automaton on the space-time plane. In the other model, called model\n$B$, surface growth takes place by a solid-on-solid deposition process\ncontrolled by the cellular automaton configurations that appear in successive\ntime-steps. Both the models show a depinning transition at the critical point\nof the generating cellular automaton. In addition, model $B$ shows a kinetic\nroughening transition at this point. The characteristics of the surface width\nin these models are derived by scaling arguments from the critical properties\nof the generating cellular automaton and by Monte Carlo simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "What is liquid? Lyapunov instability reveals symmetry-breaking\n  irreversibilities hidden within Hamilton's many-body equations of motion: Typical Hamiltonian liquids display exponential \"Lyapunov instability\", also\ncalled \"sensitive dependence on initial conditions\". Although Hamilton's\nequations are thoroughly time-reversible, the forward and backward Lyapunov\ninstabilities can differ, qualitatively. In numerical work, the expected\nforward/backward pairing of Lyapunov exponents is also occasionally violated.\nTo illustrate, we consider many-body inelastic collisions in two space\ndimensions. Two mirror-image colliding crystallites can either bounce, or not,\ngiving rise to a single liquid drop, or to several smaller droplets, depending\nupon the initial kinetic energy and the interparticle forces. The difference\nbetween the forward and backward evolutionary instabilities of these problems\ncan be correlated with dissipation and with the Second Law of Thermodynamics.\nAccordingly, these asymmetric stabilities of Hamilton's equations can provide\nan \"Arrow of Time\". We illustrate these facts for two small crystallites\ncolliding so as to make a warm liquid. We use a specially-symmetrized form of\nLevesque and Verlet's bit-reversible Leapfrog integrator. We analyze\ntrajectories over millions of collisions with several equally-spaced time\nreversals.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mechanisms of Carrier-Induced Ferromagnetism in Diluted Magnetic\n  Semiconductors: Two different approaches to the problem of carrier-induced ferromagnetism in\nthe system of the disordered magnetic ions, one bases on self-consistent\nprocedure for the exchange mean fields, other one bases on the RKKY\ninteraction, used in present literature as the alternative approximations is\nanalyzed. Our calculations in the framework of exactly solvable model show that\ntwo different contributions to the magnetic characteristics of the system\nrepresent these approaches. One stems from the diagonal part of carrier-ion\nexchange interaction that corresponds to mean field approximation. Other one\nstems from the off-diagonal part that describes the interaction between ion\nspins via free carriers. These two contributions can be responsible for the\ndifferent magnetic properties, so aforementioned approaches are complementary,\nnot alternative. A general approach is proposed and compared with different\napproximations to the problem under consideration.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Corner transfer matrix renormalization group method for two-dimensional\n  self-avoiding walks and other O(n) models: We present an extension of the corner transfer matrix renormalisation group\n(CTMRG) method to O(n) invariant models, with particular interest in the\nself-avoiding walk class of models (O(n=0)). The method is illustrated using an\ninteracting self-avoiding walk model. Based on the efficiency and versatility\nwhen compared to other available numerical methods, we present CTMRG as the\nmethod of choice for two-dimensional self-avoiding walk problems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-hyperuniform metastable states around a disordered hyperuniform\n  state of densely packed spheres: stochastic density functional theory at\n  strong coupling: Disordered and hyperuniform structures of densely packed spheres near and at\njamming are characterized by vanishing of long-wavelength density fluctuations,\nor equivalently by long-range power-law decay of the direct correlation\nfunction (DCF). We focus on previous simulation results that exhibit\ndegradation of hyperuniformity in jammed structures while maintaining the\nlong-range nature of the DCF to a certain length scale. Here we demonstrate\nthat a field-theoretic formulation of the stochastic density functional theory\nis relevant to explore the degradation mechanism. The strong-coupling expansion\nmethod of the stochastic density functional theory is developed to obtain the\nmetastable chemical potential considering intermittent fluctuations in dense\npackings. The metastable chemical potential yields an analytical form of the\nmetastable DCF that has a short-range cutoff inside the sphere while retaining\nthe long-range power-law behavior. It is confirmed that the metastable DCF\nprovides zero-wavevector limit of structure factor in quantitative agreement\nwith the previous simulation results of degraded hyperuniformity. We can also\npredict the emergence of soft modes localized at the particle scale from\nplugging this metastable DCF into the linearized Dean-Kawasaki equation, a\nstochastic density functional equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Virtual potentials for feedback traps: The recently developed feedback trap can be used to create arbitrary virtual\npotentials, to explore the dynamics of small particles or large molecules in\ncomplex situations. Experimentally, feedback traps introduce several finite\ntime scales: there is a delay between the measurement of a particle's position\nand the feedback response; the feedback response is applied for a finite update\ntime; and a finite camera exposure integrates motion. We show how to\nincorporate such timing effects into the description of particle motion. For\nthe test case of a virtual quadratic potential, we give the first accurate\ndescription of particle dynamics, calculating the power spectrum and variance\nof fluctuations as a function of feedback gain, testing against simulations. We\nshow that for small feedback gains, the motion approximates that of a particle\nin an ordinary harmonic potential. Moreover, if the potential is varied in\ntime, for example by varying its stiffness, the work that is calculated\napproximates that done in an ordinary changing potential. The quality of the\napproximation is set by the ratio of the update time of the feedback loop to\nthe relaxation time of motion in the virtual potential.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entanglement transitions as a probe of quasiparticles and quantum\n  thermalization: We introduce a diagnostic for quantum thermalization based on mixed-state\nentanglement. Specifically, given a pure state on a tripartite system $ABC$, we\nstudy the scaling of entanglement negativity between $A$ and $B$. For\nrepresentative states of self-thermalizing systems, either eigenstates or\nstates obtained by a long-time evolution of product states, negativity shows a\nsharp transition from an area-law scaling to a volume-law scaling when the\nsubsystem volume fraction is tuned across a finite critical value. In contrast,\nfor a system with quasiparticles, it exhibits a volume-law scaling irrespective\nof the subsystem fraction. For many-body localized systems, the same quantity\nshows an area-law scaling for eigenstates, and volume-law scaling for long-time\nevolved product states, irrespective of the subsystem fraction. We provide a\ncombination of numerical observations and analytical arguments in support of\nour conjecture. Along the way, we prove and utilize a `continuity bound' for\nnegativity: we bound the difference in negativity for two density matrices in\nterms of the Hilbert-Schmidt norm of their difference.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic Turing Patterns for systems with one diffusing species: The problem of pattern formation in a generic two species reaction--diffusion\nmodel is studied, under the hypothesis that only one species can diffuse. For\nsuch a system, the classical Turing instability cannot take place. At variance,\nby working in the generalized setting of a stochastic formulation to the\ninspected problem, Turing like patterns can develop, seeded by finite size\ncorrections. General conditions are given for the stochastic Turing patterns to\noccur. The predictions of the theory are tested for a specific case study.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Obtaining pressure versus concentration phase diagrams in spin systems\n  from Monte Carlo simulations: We propose an efficient procedure for determining phase diagrams of systems\nthat are described by spin models. It consists of combining cluster algorithms\nwith the method proposed by Sauerwein and de Oliveira where the grand canonical\npotential is obtained directly from the Monte Carlo simulation, without the\nnecessity of performing numerical integrations. The cluster algorithm presented\nin this paper eliminates metastability in first order phase transitions\nallowing us to locate precisely the first-order transitions lines. We also\nproduce a different technique for calculating the thermodynamic limit of\nquantities such as the magnetization whose infinite volume limit is not\nstraightforward in first order phase transitions. As an application, we study\nthe Andelman model for Langmuir monolayers made of chiral molecules that is\nequivalent to the Blume-Emery-Griffiths spin-1 model. We have obtained the\nphase diagrams in the case where the intermolecular forces favor interactions\nbetween enantiomers of the same type (homochiral interactions). In particular,\nwe have determined diagrams in the surface pressure versus concentration plane\nwhich are more relevant from the experimental point of view and less usual in\nnumerical studies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Decoupling of self-diffusion and structural relaxation during a\n  fragile-to-strong crossover in a kinetically constrained lattice gas: We present an interpolated kinetically constrained lattice gas model which\nexhibits a transition from fragile to strong supercooled liquid behavior. We\nfind non-monotonic decoupling that is due to this crossover and is seen in\nexperiment.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universality Class of Discrete Solid-on-Solid Limited Mobility\n  Nonequilibrium Growth Models for Kinetic Surface Roughening: We investigate, using the noise reduction technique, the asymptotic\nuniversality class of the well-studied nonequilibrium limited mobility\natomistic solid-on-solid surface growth models introduced by Wolf and Villain\n(WV) and Das Sarma and Tamborenea (DT) in the context of kinetic surface\nroughening in ideal molecular beam epitaxy. We find essentially all the earlier\nconclusions regarding the universality class of DT and WV models to be severely\nhampered by slow crossover and extremely long lived transient effects. We\nidentify the correct asymptotic universality class(es) which differs from\nearlier conclusions in several instances.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hurst Exponents, Markov Processes, and Fractional Brownian motion: There is much confusion in the literature over Hurst exponents. Recently, we\ntook a step in the direction of eliminating some of the confusion. One purpose\nof this paper is to illustrate the difference between fBm on the one hand and\nGaussian Markov processes where H not equal to 1/2 on the other. The difference\nlies in the increments, which are stationary and correlated in one case and\nnonstationary and uncorrelated in the other. The two- and one-point densities\nof fBm are constructed explicitly. The two-point density doesn't scale. The\none-point density is identical with that for a Markov process with H not 1/2.\nWe conclude that both Hurst exponents and histograms for one point densities\nare inadequate for deducing an underlying stochastic dynamical system from\nempirical data.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Decision Making in the Arrow of Time: We show that the steady-state entropy production rate of a stochastic process\nis inversely proportional to the minimal time needed to decide on the direction\nof the arrow of time. Here we apply Wald's sequential probability ratio test to\noptimally decide on the direction of time's arrow in stationary Markov\nprocesses. Furthermore the steady state entropy production rate can be\nestimated using mean first-passage times of suitable physical variables. We\nderive a first-passage time fluctuation theorem which implies that the decision\ntime distributions for correct and wrong decisions are equal. Our results are\nillustrated by numerical simulations of two simple examples of nonequilibrium\nprocesses.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stretch diffusion and heat conduction in 1D nonlinear lattices: In the study of 1D nonlinear Hamiltonian lattices, the conserved quantities\nplay an important role in determining the actual behavior of heat conduction.\nBesides the total energy, total momentum and total stretch could also be\nconserved quantities. In microcanonical Hamiltonian dynamics, the total energy\nis always conserved. It was recently argued by Das and Dhar that whenever\nstretch (momentum) is not conserved in a 1D model, the momentum (stretch) and\nenergy fields exhibit normal diffusion. In this work, we will systematically\ninvestigate the stretch diffusions for typical 1D nonlinear lattices. No clear\nconnection between the conserved quantities and heat conduction can be\nestablished. The actual situation is more complicated than what Das and Dhar\nclaimed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic theory of discontinuous shear thickening for a dilute gas-solid\n  suspension: A kinetic theory for a dilute gas-solid suspension under a simple shear is\ndeveloped. With the aid of the corresponding Boltzmann equation, it is found\nthat the flow curve (stress-strain rate relation) has a S-shape as a crossover\nfrom the Newtonian to the Bagnoldian for a granular suspension or from the\nNewtonian to a fluid having a viscosity proportional to the square of the shear\nrate for a suspension consisting of elastic particles. The existence of the\nS-shape in the flow curve directly leads to a discontinuous shear thickening\n(DST). This DST corresponds to the discontinuous transition of the kinetic\ntemperature between a quenched state and an ignited state. The results of the\nevent-driven Langevin simulation of hard spheres perfectly agree with the\ntheoretical results without any fitting parameter. The simulation confirms that\nthe DST takes place in the linearly unstable region of the uniformly sheared\nstate.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low temperature thermodynamics of inverse square spin models in one\n  dimension: We present a field-theoretic renormalization group calculation in two loop\norder for classical O(N)-models with an inverse square interaction in the\nvicinity of their lower critical dimensionality one. The magnetic\nsusceptibility at low temperatures is shown to diverge like $T^{-a} \\exp(b/T)$\nwith $a=(N-2)/(N-1)$ and $b=2\\pi^2/(N-1)$. From a comparison with the exactly\nsolvable Haldane-Shastry model we find that the same temperature dependence\napplies also to ferromagnetic quantum spin chains.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Geometric magnetism in open quantum systems: An isolated classical chaotic system, when driven by the slow change of\nseveral parameters, responds with two reaction forces: geometric friction and\ngeometric magnetism. By using the theory of quantum fluctuation relations we\nshow that this holds true also for open quantum systems, and provide explicit\nexpressions for those forces in this case. This extends the concept of Berry\ncurvature to the realm of open quantum systems. We illustrate our findings by\ncalculating the geometric magnetism of a damped charged quantum harmonic\noscillator transported along a path in physical space in presence of a magnetic\nfield and a thermal environment. We find that in this case the geometric\nmagnetism is unaffected by the presence of the heat bath.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical curves in conformally invariant statistical systems: We consider critical curves -- conformally invariant curves that appear at\ncritical points of two-dimensional statistical mechanical systems. We show how\nto describe these curves in terms of the Coulomb gas formalism of conformal\nfield theory (CFT). We also provide links between this description and the\nstochastic (Schramm-) Loewner evolution (SLE). The connection appears in the\nlong-time limit of stochastic evolution of various SLE observables related to\nCFT primary fields. We show how the multifractal spectrum of harmonic measure\nand other fractal characteristics of critical curves can be obtained.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase Transitions and Scaling in Systems Far From Equilibrium: Scaling ideas and renormalization group approaches proved crucial for a deep\nunderstanding and classification of critical phenomena in thermal equilibrium.\nOver the past decades, these powerful conceptual and mathematical tools were\nextended to continuous phase transitions separating distinct non-equilibrium\nstationary states in driven classical and quantum systems. In concordance with\ndetailed numerical simulations and laboratory experiments, several prominent\ndynamical universality classes have emerged that govern large-scale, long-time\nscaling properties both near and far from thermal equilibrium. These pertain to\ngenuine specific critical points as well as entire parameter space regions for\nsteady states that display generic scale invariance. The exploration of\nnon-stationary relaxation properties and associated physical aging scaling\nconstitutes a complementary potent means to characterize cooperative dynamics\nin complex out-of-equilibrium systems. This article describes dynamic scaling\nfeatures through paradigmatic examples that include near-equilibrium critical\ndynamics, driven lattice gases and growing interfaces, correlation-dominated\nreaction-diffusion systems, and basic epidemic models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metastability in Markov processes: We present a formalism to describe slowly decaying systems in the context of\nfinite Markov chains obeying detailed balance. We show that phase space can be\npartitioned into approximately decoupled regions, in which one may introduce\nrestricted Markov chains which are close to the original process but do not\nleave these regions. Within this context, we identify the conditions under\nwhich the decaying system can be considered to be in a metastable state.\nFurthermore, we show that such metastable states can be described in\nthermodynamic terms and define their free energy. This is accomplished showing\nthat the probability distribution describing the metastable state is indeed\nproportional to the equilibrium distribution, as is commonly assumed. We test\nthe formalism numerically in the case of the two-dimensional kinetic Ising\nmodel, using the Wang--Landau algorithm to show this proportionality\nexplicitly, and confirm that the proportionality constant is as derived in the\ntheory. Finally, we extend the formalism to situations in which a system can\nhave several metastable states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact Large Deviations of the Current in the Asymmetric Simple Exclusion\n  Process with Open Boundaries: In this thesis, we consider one of the most popular models of non-equilibrium\nstatistical physics: the Asymmetric Simple Exclusion Process, in which\nparticles jump stochastically on a one-dimensional lattice, between two\nreservoirs at fixed densities, with the constraint that each site can hold at\nmost one particle at a given time. This model has the mathematical property of\nbeing integrable, which makes it a good candidate for exact calculations. What\ninterests us in particular is the current of particles that flows through the\nsystem (which is a sign of it being out of equilibrium), and how it fluctuates\nwith time. We present a method, based on the \"matrix Ansatz\" devised by\nDerrida, Evans, Hakim and Pasquier, that allows to access the exact cumulants\nof that current, for any finite size of the system and any value of its\nparameters. We also analyse the large size asymptotics of our result, and make\na conjecture for the phase diagram of the system in the so-called \"s-ensemble\".\nFinally, we show how our method relates to the algebraic Bethe Ansatz, which\nwas thought not to be applicable to this situation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical Casimir Forces for Films with Bulk Ordering Fields: The confinement of long-ranged critical fluctuations in the vicinity of\nsecond-order phase transitions in fluids generates critical Casimir forces\nacting on confining surfaces or among particles immersed in a critical solvent.\nThis is realized in binary liquid mixtures close to their consolute point\n$T_{c}$ which belong to the universality class of the Ising model. The\ndeviation of the difference of the chemical potentials of the two species of\nthe mixture from its value at criticality corresponds to the bulk magnetic\nfiled of the Ising model. By using Monte Carlo simulations for this latter\nrepresentative of the corresponding universality class we compute the critical\nCasimir force as a function of the bulk ordering field at the critical\ntemperature $T=T_{c}$. We use a coupling parameter scheme for the computation\nof the underlying free energy differences and an energy-magnetization\nintegration method for computing the bulk free energy density which is a\nnecessary ingredient. By taking into account finite-size corrections, for\nvarious types of boundary conditions we determine the universal Casimir force\nscaling function as a function of the scaling variable associated with the bulk\nfield. Our numerical data are compared with analytic results obtained from\nmean-field theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Point processes in arbitrary dimension from fermionic gases, random\n  matrix theory, and number theory: It is well known that one can map certain properties of random matrices,\nfermionic gases, and zeros of the Riemann zeta function to a unique point\nprocess on the real line. Here we analytically provide exact generalizations of\nsuch a point process in d-dimensional Euclidean space for any d, which are\nspecial cases of determinantal processes. In particular, we obtain the\nn-particle correlation functions for any n, which completely specify the point\nprocesses. We also demonstrate that spin-polarized fermionic systems have these\nsame n-particle correlation functions in each dimension. The point processes\nfor any d are shown to be hyperuniform. The latter result implies that the pair\ncorrelation function tends to unity for large pair distances with a decay rate\nthat is controlled by the power law r^[-(d+1)]. We graphically display one- and\ntwo-dimensional realizations of the point processes in order to vividly reveal\ntheir \"repulsive\" nature. Indeed, we show that the point processes can be\ncharacterized by an effective \"hard-core\" diameter that grows like the square\nroot of d. The nearest-neighbor distribution functions for these point\nprocesses are also evaluated and rigorously bounded. Among other results, this\nanalysis reveals that the probability of finding a large spherical cavity of\nradius r in dimension d behaves like a Poisson point process but in dimension\nd+1 for large r and finite d. We also show that as d increases, the point\nprocess behaves effectively like a sphere packing with a coverage fraction of\nspace that is no denser than 1/2^d.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Generalized thermodynamic uncertainty relations: We analyze ensemble in which energy (E), temperature (T) and multiplicity (N)\ncan all fluctuate and with the help of nonextensive statistics we propose a\nrelation connecting all fluctuating variables. It generalizes Lindhard's\nthermodynamic uncertainty relations known in literature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical Phenomena and Renormalization-Group Theory: We review results concerning the critical behavior of spin systems at\nequilibrium. We consider the Ising and the general O($N$)-symmetric\nuniversality classes, including the $N\\to 0$ limit that describes the critical\nbehavior of self-avoiding walks. For each of them, we review the estimates of\nthe critical exponents, of the equation of state, of several amplitude ratios,\nand of the two-point function of the order parameter. We report results in\nthree and two dimensions. We discuss the crossover phenomena that are observed\nin this class of systems. In particular, we review the field-theoretical and\nnumerical studies of systems with medium-range interactions. Moreover, we\nconsider several examples of magnetic and structural phase transitions, which\nare described by more complex Landau-Ginzburg-Wilson Hamiltonians, such as\n$N$-component systems with cubic anisotropy, O($N$)-symmetric systems in the\npresence of quenched disorder, frustrated spin systems with noncollinear or\ncanted order, and finally, a class of systems described by the tetragonal\nLandau-Ginzburg-Wilson Hamiltonian with three quartic couplings. The results\nfor the tetragonal Hamiltonian are original, in particular we present the\nsix-loop perturbative series for the $\\beta$-functions. Finally, we consider a\nHamiltonian with symmetry $O(n_1)\\oplus O(n_2)$ that is relevant for the\ndescription of multicritical phenomena.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Harnessing symmetry to control quantum transport: Controlling transport in quantum systems holds the key to many promising\nquantum technologies. Here we review the power of symmetry as a resource to\nmanipulate quantum transport, and apply these ideas to engineer novel quantum\ndevices. Using tools from open quantum systems and large deviation theory, we\nshow that symmetry-mediated control of transport is enabled by a pair of twin\ndynamic phase transitions in current statistics, accompanied by a coexistence\nof different transport channels. By playing with the symmetry decomposition of\nthe initial state, one can modulate the importance of the different transport\nchannels and hence control the flowing current. Motivated by the problem of\nenergy harvesting we illustrate these ideas in open quantum networks, an\nanalysis which leads to the design of a symmetry-controlled quantum thermal\nswitch. We review an experimental setup recently proposed for symmetry-mediated\nquantum control in the lab based on a linear array of atom-doped optical\ncavities, and the possibility of using transport as a probe to uncover hidden\nsymmetries, as recently demonstrated in molecular junctions, is also discussed.\nOther symmetry-mediated control mechanisms are also described. Overall, these\nresults demonstrate the importance of symmetry not only as an organizing\nprinciple in physics but also as a tool to control quantum systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Two dimensional XXZ-Ising model on square-hexagon lattice: We study a two dimensional XXZ-Ising on square-hexagon (4-6) lattice with\nspin-1/2. The phase diagram of the ground state energy is discussed, shown two\ndifferent ferrimagnetic states and two type of antiferromagnetic states, beside\nof a ferromagnetic state. To solve this model, it could be mapped into the\neight-vertex model with union jack interaction term. Imposing exact solution\ncondition we find the region where the XXZ-Ising model on 4-6 lattice have\nexact solutions with one free parameter, for symmetric eight-vertex model\ncondition. In this sense we explore the properties of the system and analyze\nthe competition of the interaction parameters providing the region where it has\nan exact solution. However the present model does not satisfy the \\textit{free\nfermion} condition, unless for a trivial situation. Even so we are able to\ndiscuss their critical points region, when the exactly solvable condition is\nignored.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ground state of the hard-core Bose gas on lattice I. Energy estimates: We investigate the properties of the ground state of a system of interacting\nbosons on regular lattices with coordination number $k\\geq 2$. The interaction\nis a pure, infinite, on-site repulsion. Our concern is to give an improved\nupper bound on the ground state energy per site. For a density $\\rho$ a trivial\nupper bound is known to be $-k\\rho(1-\\rho)$. We obtain a smaller variational\nbound within a reasonably large family of trial functions. The estimates make\nuse of a large deviation principle for the energy of the Ising model on the\nsame lattice.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Beyond quantum microcanonical statistics: Descriptions of molecular systems usually refer to two distinct theoretical\nframeworks. On the one hand the quantum pure state, i.e. the wavefunction, of\nan isolated system which is determined to calculate molecular properties and to\nconsider the time evolution according to the unitary Schr\\\"odinger equation. On\nthe other hand a mixed state, i.e. a statistical density matrix, is the\nstandard formalism to account for thermal equilibrium, as postulated in the\nmicrocanonical quantum statistics. In the present paper an alternative\ntreatment relying on a statistical analysis of the possible wavefunctions of an\nisolated system is presented. In analogy with the classical ergodic theory, the\ntime evolution of the wavefunction determines the probability distribution in\nthe phase space pertaining to an isolated system. However, this alone cannot\naccount for a well defined thermodynamical description of the system in the\nmacroscopic limit, unless a suitable probability distribution for the quantum\nconstants of motion is introduced. We present a workable formalism assuring the\nemergence of typical values of thermodynamic functions, such as the internal\nenergy and the entropy, in the large size limit of the system. This allows the\nidentification of macroscopic properties independently of the specific\nrealization of the quantum state. A description of material systems in\nagreement with equilibrium thermodynamics is then derived without constraints\non the physical constituents and interactions of the system. Furthermore, the\ncanonical statistics is recovered in all generality for the reduced density\nmatrix of a subsystem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Chains of Viscoelastic Spheres: Given a chain of viscoelastic spheres with fixed masses of the first and last\nparticles. We raise the question: How to chose the masses of the other\nparticles of the chain to assure maximal energy transfer? The results are\ncompared with a chain of particles for which a constant coefficient of\nrestitution is assumed. Our simple example shows that the assumption of\nviscoelastic particle properties has not only important consequences for very\nlarge systems (see [1]) but leads also to qualitative changes in small systems\nas compared with particles interacting via a constant restitution coefficient.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonequilibrium statistical mechanics and entropy production in a\n  classical infinite system of rotators: We analyze the dynamics of a simple but nontrivial classical Hamiltonian\nsystem of infinitely many coupled rotators. We assume that this infinite system\nis driven out of thermal equilibrium either because energy is injected by an\nexternal force (Case I), or because heat flows between two thermostats at\ndifferent temperatures (Case II). We discuss several possible definitions of\nthe entropy production associated with a finite or infinite region, or with a\npartition of the system into a finite number of pieces. We show that these\ndefinitions satisfy the expected bounds in terms of thermostat temperatures and\nenergy flow.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimized Monte Carlo Method for glasses: A new Monte Carlo algorithm is introduced for the simulation of supercooled\nliquids and glass formers, and tested in two model glasses. The algorithm is\nshown to thermalize well below the Mode Coupling temperature and to outperform\nother optimized Monte Carlo methods. Using the algorithm, we obtain finite size\neffects in the specific heat. This effect points to the existence of a large\ncorrelation length measurable in equal time correlation functions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Heat Transport in low-dimensional systems: Recent results on theoretical studies of heat conduction in low-dimensional\nsystems are presented. These studies are on simple, yet nontrivial, models.\nMost of these are classical systems, but some quantum-mechanical work is also\nreported. Much of the work has been on lattice models corresponding to phononic\nsystems, and some on hard particle and hard disc systems. A recently developed\napproach, using generalized Langevin equations and phonon Green's functions, is\nexplained and several applications to harmonic systems are given. For\ninteracting systems, various analytic approaches based on the Green-Kubo\nformula are described, and their predictions are compared with the latest\nresults from simulation. These results indicate that for momentum-conserving\nsystems, transport is anomalous in one and two dimensions, and the thermal\nconductivity kappa, diverges with system size L, as kappa ~ L^alpha. For one\ndimensional interacting systems there is strong numerical evidence for a\nuniversal exponent alpha =1/3, but there is no exact proof for this so far. A\nbrief discussion of some of the experiments on heat conduction in nanowires and\nnanotubes is also given.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spontaneous and induced dynamic correlations in glass-formers II: Model\n  calculations and comparison to numerical simulations: We study in detail the predictions of various theoretical approaches, in\nparticular mode-coupling theory (MCT) and kinetically constrained models\n(KCMs), concerning the time, temperature, and wavevector dependence of\nmulti-point correlation functions that quantify the strength of both induced\nand spontaneous dynamical fluctuations. We also discuss the precise predictions\nof MCT concerning the statistical ensemble and microscopic dynamics dependence\nof these multi-point correlation functions. These predictions are compared to\nsimulations of model fragile and strong glass-forming liquids. Overall, MCT\nfares quite well in the fragile case, in particular explaining the observed\ncrucial role of the statistical ensemble and microscopic dynamics, while MCT\npredictions do not seem to hold in the strong case. KCMs provide a simplified\nframework for understanding how these multi-point correlation functions may\nencode dynamic correlations in glassy materials. However, our analysis\nhighlights important unresolved questions concerning the application of KCMs to\nsupercooled liquids.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-equilibrium tube length fluctuations of entangled polymers: We investigate the nonequilibrium tube length fluctuations during the\nrelaxation of an initially stretched, entangled polymer chain. The\ntime-dependent variance $\\sigma^2$ of the tube length follows in the early-time\nregime a simple universal power law $\\sigma^2 = A \\sqrt{t}$ originating in the\ndiffusive motion of the polymer segments. The amplitude $A$ is calculated\nanalytically both from standard reptation theory and from an exactly solvable\nlattice gas model for reptation and its dependence on the initial and\nequilibrium tube length respectively is discussed. The non-universality\nsuggests the measurement of the fluctuations (e.g. using flourescence\nmicroscopy) as a test for reptation models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Leaf-excluded percolation in two and three dimensions: We introduce the \\emph{leaf-excluded} percolation model, which corresponds to\nindependent bond percolation conditioned on the absence of leaves (vertices of\ndegree one). We study the leaf-excluded model on the square and simple-cubic\nlattices via Monte Carlo simulation, using a worm-like algorithm. By studying\nwrapping probabilities, we precisely estimate the critical thresholds to be\n$0.355\\,247\\,5(8)$ (square) and $0.185\\,022(3)$ (simple-cubic). Our estimates\nfor the thermal and magnetic exponents are consistent with those for\npercolation, implying that the phase transition of the leaf-excluded model\nbelongs to the standard percolation universality class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Identifying Functional Thermodynamics in Autonomous Maxwellian Ratchets: We introduce a family of Maxwellian Demons for which correlations among\ninformation bearing degrees of freedom can be calculated exactly and in compact\nanalytical form. This allows one to precisely determine Demon functional\nthermodynamic operating regimes, when previous methods either misclassify or\nsimply fail due to approximations they invoke. This reveals that these Demons\nare more functional than previous candidates. They too behave either as\nengines, lifting a mass against gravity by extracting energy from a single heat\nreservoir, or as Landauer erasers, consuming external work to remove\ninformation from a sequence of binary symbols by decreasing their individual\nuncertainty. Going beyond these, our Demon exhibits a new functionality that\nerases bits not by simply decreasing individual-symbol uncertainty, but by\nincreasing inter-bit correlations (that is, by adding temporal order) while\nincreasing single-symbol uncertainty. In all cases, but especially in the new\nerasure regime, exactly accounting for informational correlations leads to\ntight bounds on Demon performance, expressed as a refined Second Law of\nThermodynamics that relies on the Kolmogorov-Sinai entropy for dynamical\nprocesses and not on changes purely in system configurational entropy, as\npreviously employed. We rigorously derive the refined Second Law under minimal\nassumptions and so it applies quite broadly---for Demons with and without\nmemory and input sequences that are correlated or not. We note that general\nMaxwellian Demons readily violate previously proposed, alternative such bounds,\nwhile the current bound still holds.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Work fluctuations of self-propelled particles in the phase separated\n  state: We study the large deviations of the distribution P(W_\\tau) of the work\nassociated with the propulsion of individual active brownian particles in a\ntime interval \\tau, in the region of the phase diagram where macroscopic phase\nseparation takes place. P(W_\\tau) is characterised by two peaks, associated to\nparticles in the gaseous and in the clusterised phases, and two separate\nnon-convex branches. Accordingly, the generating function of W_\\tau cumulants\ndisplays a double singularity. We discuss the origin of such non-convex\nbranches in terms of the peculiar dynamics of the system phases, and the\nrelation between the observation time \\tau and the typical persistence times of\nthe particles in the two phases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quenching along a gapless line: A different exponent for defect density: We use a new quenching scheme to study the dynamics of a one-dimensional\nanisotropic $XY$ spin-1/2 chain in the presence of a transverse field which\nalternates between the values $h+\\de$ and $h-\\de$ from site to site. In this\nquenching scheme, the parameter denoting the anisotropy of interaction ($\\ga$)\nis linearly quenched from $-\\infty$ to $ +\\infty$ as $\\ga = t/\\tau$, keeping\nthe total strength of interaction $J$ fixed. The system traverses through a\ngapless phase when $\\ga$ is quenched along the critical surface $h^2 = \\de^2 +\nJ^2$ in the parameter space spanned by $h$, $\\de$ and $\\ga$. By mapping to an\nequivalent two-level Landau-Zener problem, we show that the defect density in\nthe final state scales as $1/\\tau^{1/3}$, a behavior that has not been observed\nin previous studies of quenching through a gapless phase. We also generalize\nthe model incorporating additional alternations in the anisotropy or in the\nstrength of the interaction, and derive an identical result under a similar\nquenching. Based on the above results, we propose a general scaling of the\ndefect density with the quenching rate $\\tau$ for quenching along a gapless\ncritical line.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of Rod like Particles in Supercooled Liquids -- Probing Dynamic\n  Heterogeneity and Amorphous Order: Probing dynamic and static correlation in glass-forming supercooled liquids\nhas been a challenge for decades in spite of extensive research. Dynamic\ncorrelation which manifests itself as Dynamic Heterogeneity is ubiquitous in a\nvast variety of systems starting from molecular glass-forming liquids, dense\ncolloidal systems to collections of cells. On the other hand, the mere concept\nof static correlation in these dense disordered systems remain somewhat elusive\nand its existence is still actively debated. We propose a novel method to\nextract both dynamic and static correlations using rod-like particles as probe.\nThis method can be implemented in molecular glass-forming liquids in\nexperiments as well as in other soft matter systems including biologically\nrelevant systems. We also rationalize the observed log-normal like distribution\nof rotational decorrelation time of elongated probe molecules in reported\nexperimental studies along with a proposal of a novel methodology to extract\ndynamic and static correlation lengths in experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Iterated Conformal Dynamics and Laplacian Growth: The method of iterated conformal maps for the study of Diffusion Limited\nAggregates (DLA) is generalized to the study of Laplacian Growth Patterns and\nrelated processes. We emphasize the fundamental difference between these\nprocesses: DLA is grown serially with constant size particles, while Laplacian\npatterns are grown by advancing each boundary point in parallel, proportionally\nto the gradient of the Laplacian field. We introduce a 2-parameter family of\ngrowth patterns that interpolates between DLA and a discrete version of\nLaplacian growth. The ultraviolet putative finite-time singularities are\nregularized here by a minimal tip size, equivalently for all the models in this\nfamily. With this we stress that the difference between DLA and Laplacian\ngrowth is NOT in the manner of ultraviolet regularization, but rather in their\ndeeply different growth rules. The fractal dimensions of the asymptotic\npatterns depend continuously on the two parameters of the family, giving rise\nto a \"phase diagram\" in which DLA and discretized Laplacian growth are at the\nextreme ends. In particular we show that the fractal dimension of Laplacian\ngrowth patterns is much higher than the fractal dimension of DLA, with the\npossibility of dimension 2 for the former not excluded.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Path statistics, memory, and coarse-graining of continuous-time random\n  walks on networks: Continuous-time random walks (CTRWs) on discrete state spaces, ranging from\nregular lattices to complex networks, are ubiquitous across physics, chemistry,\nand biology. Models with coarse-grained states, for example those employed in\nstudies of molecular kinetics, and models with spatial disorder can give rise\nto memory and non-exponential distributions of waiting times and first-passage\nstatistics. However, existing methods for analyzing CTRWs on complex energy\nlandscapes do not address these effects. We therefore use statistical mechanics\nof the nonequilibrium path ensemble to characterize first-passage CTRWs on\nnetworks with arbitrary connectivity, energy landscape, and waiting time\ndistributions. Our approach is valuable for calculating higher moments (beyond\nthe mean) of path length, time, and action, as well as statistics of any\nconservative or non-conservative force along a path. For homogeneous networks\nwe derive exact relations between length and time moments, quantifying the\nvalidity of approximating a continuous-time process with its discrete-time\nprojection. For more general models we obtain recursion relations, reminiscent\nof transfer matrix and exact enumeration techniques, to efficiently calculate\npath statistics numerically. We have implemented our algorithm in PathMAN, a\nPython script that users can easily apply to their model of choice. We\ndemonstrate the algorithm on a few representative examples which underscore the\nimportance of non-exponential distributions, memory, and coarse-graining in\nCTRWs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A systematic $1/c$-expansion of form factor sums for dynamical\n  correlations in the Lieb-Liniger model: We introduce a framework for calculating dynamical correlations in the\nLieb-Liniger model in arbitrary energy eigenstates and for all space and time,\nthat combines a Lehmann representation with a $1/c$ expansion. The $n^{\\rm th}$\nterm of the expansion is of order $1/c^n$ and takes into account all $\\lfloor\n\\tfrac{n}{2}\\rfloor+1$ particle-hole excitations over the averaging eigenstate.\nImportantly, in contrast to a 'bare' $1/c$ expansion it is uniform in space and\ntime. The framework is based on a method for taking the thermodynamic limit of\nsums of form factors that exhibit non integrable singularities. We expect our\nframework to be applicable to any local operator.\n  We determine the first three terms of this expansion and obtain an explicit\nexpression for the density-density dynamical correlations and the dynamical\nstructure factor at order $1/c^2$. We apply these to finite-temperature\nequilibrium states and non-equilibrium steady states after quantum quenches. We\nrecover predictions of (nonlinear) Luttinger liquid theory and generalized\nhydrodynamics in the appropriate limits, and are able to compute sub-leading\ncorrections to these.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Folding transitions in three-dimensional space with defects: A model describing the three-dimensional folding of the triangular lattice on\nthe face-centered cubic lattice is generalized allowing the presence of defects\ncorresponding to cuts in the two-dimensional network. The model can be\nexpressed in terms of Ising-like variables with nearest-neighbor and plaquette\ninteractions in the hexagonal lattice; its phase diagram is determined by the\nCluster Variation Method. The results found by varying the curvature and defect\nenergy show that the introduction of defects turns the first-order crumpling\ntransitions of the model without defects into continuous transitions. New\nphases also appear by decreasing the energy cost of defects and the behavior of\ntheir densities has been analyzed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact Markovian kinetic equation for a quantum Brownian oscillator: We derive an exact Markovian kinetic equation for an oscillator linearly\ncoupled to a heat bath, describing quantum Brownian motion. Our work is based\non the subdynamics formulation developed by Prigogine and collaborators. The\nspace of distribution functions is decomposed into independent subspaces that\nremain invariant under Liouville dynamics. For integrable systems in\nPoincar\\'e's sense the invariant subspaces follow the dynamics of uncoupled,\nrenormalized particles. In contrast for non-integrable systems, the invariant\nsubspaces follow a dynamics with broken-time symmetry, involving generalized\nfunctions. This result indicates that irreversibility and stochasticity are\nexact properties of dynamics in generalized function spaces. We comment on the\nrelation between our Markovian kinetic equation and the Hu-Paz-Zhang equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical properties of the laser beam propagating in a turbulent\n  medium: We examine statistical properties of a laser beam propagating in a turbulent\nmedium. We prove that the intensity fluctuations at large propagation distances\npossess Gaussian probability density function and establish quantitative\ncriteria for realizing the Gaussian statistics depending on the laser\npropagation distance, the laser beam waist, the laser frequency and the\nturbulence strength. We calculate explicitly the laser envelope pair\ncorrelation function and corrections to its higher order correlation functions\nbreaking Gaussianity. We discuss also statistical properties of the brightest\nspots in the speckle pattern.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Preface: Long-range Interactions and Synchronization: Spontaneous synchronization is a general phenomenon in which a large\npopulation of coupled oscillators of diverse natural frequencies self-organize\nto operate in unison. The phenomenon occurs in physical and biological systems\nover a wide range of spatial and temporal scales, e.g., in electrochemical and\nelectronic oscillators, Josephson junctions, laser arrays, animal flocking,\npedestrians on footbridges, audience clapping, etc. Besides the obvious\nnecessity of the synchronous firings of cardiac cells to keep the heart\nbeating, synchrony is desired in many man-made systems such as parallel\ncomputing, electrical power-grids. On the contrary, synchrony could also be\nhazardous, e.g., in neurons, leading to impaired brain function in Parkinson's\ndisease and epilepsy. Due to this wide range of applications, collective\nsynchrony in networks of oscillators has attracted the attention of physicists,\napplied mathematicians and researchers from many other fields. An essential\naspect of synchronizing systems is that long-range order naturally appear in\nthese systems, which questions the fact whether long-range interactions may be\nparticular suitable to synchronization. In this context, it is interesting to\nremind that long-range interacting system required several adaptations from\nstatistical mechanics \\`a la Gibbs Boltzmann, in order to deal with the\npeculiarities of these systems: negative specific heat, breaking of ergodicity\nor lack of extensivity. As for synchrony, it is still lacking a theoretical\nframework to use the tools from statistical mechanics. The present issue\npresents a collection of exciting recent theoretical developments in the field\nof synchronization and long-range interactions, in order to highlight the\nmutual progresses of these twin areas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spontaneous cold-to-hot heat transfer in Knudsen gas: It is well known that, when in a thermal bath, a Knudsen gas may reach a\nnonequilibrium steady state; often, this is not treated as a thermodynamic\nproblem. Here, we show that if incorporated in a large-sized setup, such a\nphenomenon has nontrivial consequences and cannot circumvent thermodynamics:\ncold-to-hot heat transfer may spontaneously occur without an energetic penalty,\neither cyclically (with entropy barriers) or continuously (with an energy\nbarrier). As the system obeys the first law of thermodynamics, the second law\nof thermodynamics cannot be applied.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mean-Field Approximation for Spacing Distribution Functions in Classical\n  Systems: We propose a mean-field method to calculate approximately the spacing\ndistribution functions $p^{(n)}(s)$ in 1D classical many-particle systems. We\ncompare our method with two other commonly used methods, the independent\ninterval approximation (IIA) and the extended Wigner surmise (EWS). In our\nmean-field approach, $p^{(n)}(s)$ is calculated from a set Langevin equations\nwhich are decoupled by using a mean-field approximation. We found that in spite\nof its simplicity, the mean-field approximation provides good results in\nseveral systems. We offer many examples in which the three methods mentioned\npreviously give a reasonable description of the statistical behavior of the\nsystem. The physical interpretation of each method is also discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hyperuniformity of Quasicrystals: Hyperuniform systems, which include crystals, quasicrystals and special\ndisordered systems, have attracted considerable recent attention, but rigorous\nanalyses of the hyperuniformity of quasicrystals have been lacking because the\nsupport of the spectral intensity is dense and discontinuous. We employ the\nintegrated spectral intensity, $Z(k)$, to quantitatively characterize the\nhyperuniformity of quasicrystalline point sets generated by projection methods.\nThe scaling of $Z(k)$ as $k$ tends to zero is computed for one-dimensional\nquasicrystals and shown to be consistent with independent calculations of the\nvariance, $\\sigma^2(R)$, in the number of points contained in an interval of\nlength $2R$. We find that one-dimensional quasicrystals produced by projection\nfrom a two-dimensional lattice onto a line of slope $1/\\tau$ fall into distinct\nclasses determined by the width of the projection window. For a countable dense\nset of widths, $Z(k) \\sim k^4$; for all others, $Z(k)\\sim k^2$. This\ndistinction suggests that measures of hyperuniformity define new classes of\nquasicrystals in higher dimensions as well.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The effect of memory and active forces on transition path times\n  distributions: An analytical expression is derived for the transition path time distribution\nfor a one-dimensional particle crossing of a parabolic barrier. Two cases are\nanalyzed: (i) A non-Markovian process described by a generalized Langevin\nequation with a power-law memory kernel and (ii) a Markovian process with a\nnoise violating the fluctuation-dissipation theorem, modeling the stochastic\ndynamics generated by active forces. In the case (i) we show that the anomalous\ndynamics strongly affecting the short time behavior of the distributions, but\nthis happens only for very rare events not influencing the overall statistics.\nAt long times the decay is always exponential, in disagreement with a recent\nstudy suggesting a stretched exponential decay. In the case (ii) the active\nforces do not substantially modify the short time behavior of the distribution,\nbut lead to an overall decrease of the average transition path time. These\nfindings offer some novel insights, useful for the analysis of experiments of\ntransition path times in (bio)molecular systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-Debye relaxations: The characteristic exponent in the excess wings\n  model: The characteristic (Laplace or L\\'evy) exponents uniquely characterize\ninfinitely divisible probability distributions. Although of purely mathematical\norigin they appear to be uniquely associated with the memory functions present\nin evolution equations which govern the course of such physical phenomena like\nnon-Debye relaxations or anomalous diffusion. Commonly accepted procedure to\nmimic memory effects is to make basic equations time smeared, i.e., nonlocal in\ntime. This is modeled either through the convolution of memory functions with\nthose describing relaxation/diffusion or, alternatively, through the time\nsmearing of time derivatives. Intuitive expectations say that such introduced\ntime smearings should be physically equivalent. This leads to the conclusion\nthat both kinds of so far introduced memory functions form a \"twin\" structure\nfamiliar to mathematicians for a long time and known as the Sonine pair. As an\nillustration of the proposed scheme we consider the excess wings model of\nnon-Debye relaxations, determine its evolution equations and discuss properties\nof the solutions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random Deposition Model with a Constant Capture Length: We introduce a sequential model for the deposition and aggregation of\nparticles in the submonolayer regime. Once a particle has been randomly\ndeposited on the substrate, it sticks to the closest atom or island within a\ndistance \\ell, otherwise it sticks to the deposition site. We study this model\nboth numerically and analytically in one dimension. A clear comprehension of\nits statistical properties is provided, thanks to capture equations and to the\nanalysis of the island-island distance distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dimensionality effects in restricted bosonic and fermionic systems: The phenomenon of Bose-like condensation, the continuous change of the\ndimensionality of the particle distribution as a consequence of freezing out of\none or more degrees of freedom in the low particle density limit, is\ninvestigated theoretically in the case of closed systems of massive bosons and\nfermions, described by general single-particle hamiltonians. This phenomenon is\nsimilar for both types of particles and, for some energy spectra, exhibits\nfeatures specific to multiple-step Bose-Einstein condensation, for instance the\nappearance of maxima in the specific heat.\n  In the case of fermions, as the particle density increases, another\nphenomenon is also observed. For certain types of single particle hamiltonians,\nthe specific heat is approaching asymptotically a divergent behavior at zero\ntemperature, as the Fermi energy $\\epsilon_{\\rm F}$ is converging towards any\nvalue from an infinite discrete set of energies: ${\\epsilon_i}_{i\\ge 1}$. If\n$\\epsilon_{\\rm F}=\\epsilon_i$, for any i, the specific heat is divergent at T=0\njust in infinite systems, whereas for any finite system the specific heat\napproaches zero at low enough temperatures. The results are particularized for\nparticles trapped inside parallelepipedic boxes and harmonic potentials.\n  PACS numbers: 05.30.Ch, 64.90.+b, 05.30.Fk, 05.30.Jp",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical Casimir effects in 2D Ising model with curved defect lines: This work is aimed at studying the influence of critical Casimir effects on\nenergetic properties of curved defect lines in the frame of 2D Ising model. Two\ntypes of defect curves were investigated. We start with a simple task of\nglobule formation from four-defect line. It was proved that an exothermic\nreaction of collapse occurs and the dependence of energy release on temperature\nwas observed. Critical Casimir energy of extensive line of constant curvature\nwas also examined. It was shown that its critical Casimir energy is\nproportional to curvature that leads to the tendency to radius decreasing under\nCasimir forces. The results obtained can be applied to proteins folding problem\nin polarized liquid.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Velocity and Speed Correlations in Hamiltonian Flocks: We study a $2d$ Hamiltonian fluid made of particles carrying spins coupled to\ntheir velocities. At low temperatures and intermediate densities, this\nconservative system exhibits phase coexistence between a collectively moving\ndroplet and a still gas. The particle displacements within the droplet have\nremarkably similar correlations to those of birds flocks. The center of mass\nbehaves as an effective self-propelled particle, driven by the droplet's total\nmagnetization. The conservation of a generalized angular momentum leads to\nrigid rotations, opposite to the fluctuations of the magnetization orientation\nthat, however small, are responsible for the shape and scaling of the\ncorrelations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal dimensional crossover of domain wall dynamics in ferromagnetic\n  films: The magnetic domain wall motion driven by a magnetic field is studied in\n(Ga,Mn)As and (Ga,Mn)(As,P) films of different thicknesses. In the thermally\nactivated creep regime, a kink in the velocity curves and a jump of the\nroughness exponent evidence a dimensional crossover in the domain wall\ndynamics. The measured values of the roughness exponent zeta_{1d} = 0.62 +/-\n0.02 and zeta_{2d} = 0.45 +/- 0.04 are compatible with theoretical predictions\nfor the motion of elastic line (d = 1) and surface (d = 2) in two and three\ndimensional media, respectively.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Master equation approach to the stochastic accumulation dynamics of\n  bacterial cell cycle: The mechanism of bacterial cell size control has been a mystery for decades,\nwhich involves the well-coordinated growth and division in the cell cycle. The\nrevolutionary modern techniques of microfluidics and the advanced live imaging\nanalysis techniques allow long term observations and high-throughput analysis\nof bacterial growth on single cell level, promoting a new wave of quantitative\ninvestigations on this puzzle. Taking the opportunity, this theoretical study\naims to clarify the stochastic nature of bacterial cell size control under the\nassumption of the accumulation mechanism, which is favoured by recent\nexperiments on species of bacteria. Via the master equation approach with\nproperly chosen boundary conditions, the distributions concerned in cell size\ncontrol are estimated and are confirmed by experiments. In this analysis, the\ninter-generation Green's function is analytically evaluated as the key to\nbridge two kinds of statistics used in batch-culture and mother machine\nexperiments. This framework allows us to quantify the noise level in growth and\naccumulation according to experimental data. As a consequence of non-Gaussian\nnoises of the added sizes, the non-equilibrium nature of bacterial cell size\nhomeostasis is predicted, of which the biological meaning requires further\ninvestigation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The asymptotic Bethe ansatz solution for one-dimensional SU(2) spinor\n  bosons with finite range Gaussian interactions: We propose a one-dimensional model of spinor bosons with SU(2) symmetry and a\ntwo-body finite range Gaussian interaction potential. We show that the model is\nexactly solvable when the width of the interaction potential is much smaller\ncompared to the inter-particle separation. This model is then solved via the\nasymptotic Bethe ansatz technique. The ferromagnetic ground state energy and\nchemical potential are derived analytically. We also investigate the effects of\na finite range potential on the density profiles through local density\napproximation. Finite range potentials are more likely to lead to quasi\nBose-Einstein condensation than zero range potentials.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical behavior of the Coulomb-glass model in the zero-disorder limit:\n  Ising universality in a system with long-range interactions: The ordering of charges on half-filled hypercubic lattices is investigated\nnumerically, where electroneutrality is ensured by background charges. This\nsystem is equivalent to the $s = 1/2$ Ising lattice model with\nantiferromagnetic $1/r$ interaction. The temperature dependences of specific\nheat, mean staggered occupation, and of a generalized susceptibility indicate\ncontinuous order-disorder phase transitions at finite temperatures in two- and\nthree-dimensional systems. In contrast, the susceptibility of the\none-dimensional system exhibits singular behavior at vanishing temperature. For\nthe two- and three-dimensional cases, the critical exponents are obtained by\nmeans of a finite-size scaling analysis. Their values are consistent with those\nof the Ising model with short-range interaction, and they imply that the\nstudied model cannot belong to any other known universality class. Samples of\nup to 1400, $112^2$, and $22^3$ sites are considered for dimensions 1 to 3,\nrespectively.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reply to Comment on Effect of polydispersity on the ordering transition\n  of adsorbed self-assembled rigid rods: We comment on the nature of the ordering transition of a model of equilibrium\npolydisperse rigid rods, on the square lattice, which is reported by Lopez et\nal. to exhibit random percolation criticality in the canonical ensemble, in\nsharp contrast to (i) our results of Ising criticality for the same model in\nthe grand canonical ensemble [Phys. Rev. E 82, 061117 (2010)] and (ii) the\nabsence of exponent(s) renormalization for constrained systems with logarithmic\nspecific heat anomalies predicted on very general grounds by Fisher [M.E.\nFisher, Phys. Rev. 176, 257 (1968)].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Percolation of sticks: effect of stick alignment and length dispersity: Using Monte Carlo simulation, we studied the percolation of sticks, i.e.\nzero-width rods, on a plane paying special attention to the effects of stick\nalignment and their length dispersity. The stick lengths were distributed in\naccordance with log-normal distributions, providing a constant mean length with\ndifferent widths of distribution. Scaling analysis was performed to obtain the\npercolation thresholds in the thermodynamic limits for all values of the\nparameters. Greater alignment of the sticks led to increases in the percolation\nthreshold while an increase in length dispersity decreased the percolation\nthreshold. A fitting formula has been proposed for the dependency of the\npercolation threshold both on stick alignment and on length dispersity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Supercooled liquids are Fickian yet non-Gaussian: Reply to \"Comment on 'Fickian non-Gaussian diffusion in glass-forming\nliquids' \".\n  In [ArXiv:2210.07119v1], Berthier et al. questioned the findings of our\nletter [Phys. Rev. Lett. 128, 168001 (2022)], concerning the existence and the\nfeatures of Fickian non-Gaussian diffusion in glass-forming liquids. Here we\ndemonstrate that their arguments are either wrong, or not meaningful to our\nscope. Thus, we fully confirm the validity and novelty of our results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Velocity Distributions in Homogeneously Cooling and Heated Granular\n  Fluids: We study the single particle velocity distribution for a granular fluid of\ninelastic hard spheres or disks, using the Enskog-Boltzmann equation, both for\nthe homogeneous cooling of a freely evolving system and for the stationary\nstate of a uniformly heated system, and explicitly calculate the fourth\ncumulant of the distribution. For the undriven case, our result agrees well\nwith computer simulations of Brey et al. \\cite{brey}. Corrections due to\nnon-Gaussian behavior on cooling rate and stationary temperature are found to\nbe small at all inelasticities. The velocity distribution in the uniformly\nheated steady state exhibits a high energy tail $\\sim \\exp(-A c^{3/2})$, where\n$c$ is the velocity scaled by the thermal velocity and $A\\sim 1/\\sqrt{\\eps}$\nwith $\\eps$ the inelasticity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Modified Thirring model beyond the excluded-volume approximation: Long-range interacting systems may exhibit ensemble inequivalence and can\npossibly attain equilibrium states under completely open conditions, for which\nenergy, volume and number of particles simultaneously fluctuate. Here we\nconsider a modified version of the Thirring model for self-gravitating systems\nwith attractive and repulsive long-range interactions in which particles are\ntreated as hard spheres in dimension d=1,2,3. Equilibrium states of the model\nare studied under completely open conditions, in the unconstrained ensemble, by\nmeans of both Monte Carlo simulations and analytical methods and are compared\nwith the corresponding states at fixed number of particles, in the\nisothermal-isobaric ensemble. Our theoretical description is performed for an\narbitrary local equation of state, which allows us to examine the system beyond\nthe excluded-volume approximation. The simulations confirm the theoretical\nprediction of the possible occurrence of first-order phase transitions in the\nunconstrained ensemble. This work contributes to the understanding of\nlong-range interacting systems exchanging heat, work and matter with the\nenvironment.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Microscopic View on Short-Range Wetting at the Free Surface of the\n  Binary Metallic Liquid Gallium-Bismuth: An X-ray Reflectivity and Square\n  Gradient Theory Study: We present an x-ray reflectivity study of wetting at the free surface of the\nbinary liquid metal gallium-bismuth (Ga-Bi) in the region where the bulk phase\nseparates into Bi-rich and Ga-rich liquid phases. The measurements reveal the\nevolution of the microscopic structure of wetting films of the Bi-rich,\nlow-surface-tension phase along different paths in the bulk phase diagram. A\nbalance between the surface potential preferring the Bi-rich phase and the\ngravitational potential which favors the Ga-rich phase at the surface pins the\ninterface of the two demixed liquid metallic phases close to the free surface.\nThis enables us to resolve it on an Angstrom level and to apply a mean-field,\nsquare gradient model extended by thermally activated capillary waves as\ndominant thermal fluctuations. The sole free parameter of the gradient model,\ni.e. the so-called influence parameter, $\\kappa$, is determined from our\nmeasurements. Relying on a calculation of the liquid/liquid interfacial tension\nthat makes it possible to distinguish between intrinsic and capillary wave\ncontributions to the interfacial structure we estimate that fluctuations affect\nthe observed short-range, complete wetting phenomena only marginally. A\ncritical wetting transition that should be sensitive to thermal fluctuations\nseems to be absent in this binary metallic alloy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Learning nonequilibrium control forces to characterize dynamical phase\n  transitions: Sampling the collective, dynamical fluctuations that lead to nonequilibrium\npattern formation requires probing rare regions of trajectory space. Recent\napproaches to this problem based on importance sampling, cloning, and spectral\napproximations, have yielded significant insight into nonequilibrium systems,\nbut tend to scale poorly with the size of the system, especially near dynamical\nphase transitions. Here we propose a machine learning algorithm that samples\nrare trajectories and estimates the associated large deviation functions using\na many-body control force by leveraging the flexible function representation\nprovided by deep neural networks, importance sampling in trajectory space, and\nstochastic optimal control theory. We show that this approach scales to\nhundreds of interacting particles and remains robust at dynamical phase\ntransitions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stationary State Skewness in Two Dimensional KPZ Type Growth: We present numerical Monte Carlo results for the stationary state properties\nof KPZ type growth in two dimensional surfaces, by evaluating the finite size\nscaling (FSS) behaviour of the 2nd and 4th moments, $W_2$ and $W_4$, and the\nskewness, $W_3$, in the Kim-Kosterlitz (KK) and BCSOS model. Our results agree\nwith the stationary state proposed by L\\\"assig. The roughness exponents\n$W_n\\sim L^{\\alpha_n}$ obey power counting, $\\alpha_n= n \\alpha$, and the\namplitude ratio's of the moments are universal. They have the same values in\nboth models: $W_3/W_2^{1.5}= -0.27(1)$ and $W_4/W_2^{2}= +3.15(2)$. Unlike in\none dimension, the stationary state skewness is not tunable, but a universal\nproperty of the stationary state distribution. The FSS corrections to scaling\nin the KK model are weak and $\\alpha$ converges well to the\nKim-Kosterlitz-L\\\"assig value $\\alpha={2/5} $. The FSS corrections to scaling\nin the BCSOS model are strong. Naive extrapolations yield an smaller value,\n$\\alpha\\simeq 0.38(1)$, but are still consistent with $\\alpha={2/5}$ if the\nleading irrelevant corrections to FSS scaling exponent is of order\n$y_{ir}\\simeq -0.6(2)$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Properties of Higher-Order Phase Transitions: Experimental evidence for the existence of strictly higher-order phase\ntransitions (of order three or above in the Ehrenfest sense) is tenuous at\nbest. However, there is no known physical reason why such transitions should\nnot exist in nature. Here, higher-order transitions characterized by both\ndiscontinuities and divergences are analysed through the medium of partition\nfunction zeros. Properties of the distributions of zeros are derived, certain\nscaling relations are recovered, and new ones are presented.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Percolation in random environment: We consider bond percolation on the square lattice with perfectly correlated\nrandom probabilities. According to scaling considerations, mapping to a random\nwalk problem and the results of Monte Carlo simulations the critical behavior\nof the system with varying degree of disorder is governed by new, random fixed\npoints with anisotropic scaling properties. For weaker disorder both the\nmagnetization and the anisotropy exponents are non-universal, whereas for\nstrong enough disorder the system scales into an {\\it infinite randomness fixed\npoint} in which the critical exponents are exactly known.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical systems on large networks with predator-prey interactions are\n  stable and exhibit oscillations: We analyse the stability of linear dynamical systems defined on sparse,\nrandom graphs with predator-prey, competitive, and mutualistic interactions.\nThese systems are aimed at modelling the stability of fixed points in large\nsystems defined on complex networks, such as, ecosystems consisting of a large\nnumber of species that interact through a food-web. We develop an exact theory\nfor the spectral distribution and the leading eigenvalue of the corresponding\nsparse Jacobian matrices. This theory reveals that the nature of local\ninteractions have a strong influence on system's stability. We show that, in\ngeneral, linear dynamical systems defined on random graphs with a prescribed\ndegree distribution of unbounded support are unstable if they are large enough,\nimplying a tradeoff between stability and diversity. Remarkably, in contrast to\nthe generic case, antagonistic systems that only contain interactions of the\npredator-prey type can be stable in the infinite size limit. This qualitatively\nfeature for antagonistic systems is accompanied by a peculiar oscillatory\nbehaviour of the dynamical response of the system after a perturbation, when\nthe mean degree of the graph is small enough. Moreover, for antagonistic\nsystems we also find that there exist a dynamical phase transition and critical\nmean degree above which the response becomes non-oscillatory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Domino effect for world market fluctuations: In order to emphasize cross-correlations for fluctuations in major market\nplaces, series of up and down spins are built from financial data. Patterns\nfrequencies are measured, and statistical tests performed. Strong\ncross-correlations are emphasized, proving that market moves are collective\nbehaviors.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Physics-informed Bayesian inference of external potentials in classical\n  density-functional theory: The swift progression of machine learning (ML) has not gone unnoticed in the\nrealm of statistical mechanics. ML techniques have attracted attention by the\nclassical density-functional theory (DFT) community, as they enable discovery\nof free-energy functionals to determine the equilibrium-density profile of a\nmany-particle system. Within DFT, the external potential accounts for the\ninteraction of the many-particle system with an external field, thus, affecting\nthe density distribution. In this context, we introduce a statistical-learning\nframework to infer the external potential exerted on a many-particle system. We\ncombine a Bayesian inference approach with the classical DFT apparatus to\nreconstruct the external potential, yielding a probabilistic description of the\nexternal potential functional form with inherent uncertainty quantification.\nOur framework is exemplified with a grand-canonical one-dimensional particle\nensemble with excluded volume interactions in a confined geometry. The required\ntraining dataset is generated using a Monte Carlo (MC) simulation where the\nexternal potential is applied to the grand-canonical ensemble. The resulting\nparticle coordinates from the MC simulation are fed into the learning framework\nto uncover the external potential. This eventually allows us to compute the\nequilibrium density profile of the system by using the tools of DFT. Our\napproach benchmarks the inferred density against the exact one calculated\nthrough the DFT formulation with the true external potential. The proposed\nBayesian procedure accurately infers the external potential and the density\nprofile. We also highlight the external-potential uncertainty quantification\nconditioned on the amount of available simulated data. The seemingly simple\ncase study introduced in this work might serve as a prototype for studying a\nwide variety of applications, including adsorption and capillarity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Simulation of heat transport in low-dimensional oscillator lattices: The study of heat transport in low-dimensional oscillator lattices presents a\nformidable challenge. Theoretical efforts have been made trying to reveal the\nunderlying mechanism of diversified heat transport behaviors. In lack of a\nunified rigorous treatment, approximate theories often may embody controversial\npredictions. It is therefore of ultimate importance that one can rely on\nnumerical simulations in the investigation of heat transfer processes in\nlow-dimensional lattices. The simulation of heat transport using the\nnon-equilibrium heat bath method and the Green-Kubo method will be introduced.\nIt is found that one-dimensional (1D), two-dimensional (2D) and\nthree-dimensional (3D) momentum-conserving nonlinear lattices display power-law\ndivergent, logarithmic divergent and constant thermal conductivities,\nrespectively. Next, a novel diffusion method is also introduced. The heat\ndiffusion theory connects the energy diffusion and heat conduction in a\nstraightforward manner. This enables one to use the diffusion method to\ninvestigate the objective of heat transport. In addition, it contains\nfundamental information about the heat transport process which cannot readily\nbe gathered otherwise.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagrams and critical behavior of the quantum spin-1/2 XXZ model\n  on diamond-type hierarchical lattices: In this paper, the phase diagrams and the critical behavior of the spin-1/2\nanisotropic XXZ ferromagnetic model (the anisotropic parameter\n{\\Delta}\\in(-\\infty,1]) on two kinds of diamond-type hierarchical (DH) lattices\nwith fractal dimensions d_{f}=2.58 and 3, respectively, are studied via the\nreal-space renormalization group method. It is found that in the isotropic\nHeisenberg limit ({\\Delta}=0), there exist finite temperature phase transitions\nfor the two kinds of DH lattices above. The systems are also investigated in\nthe range of -\\infty<{\\Delta}<0 and it is found that they exhibit XY-like fixed\npoints. Meanwhile, the critical exponents of the above two systems are also\ncalculated. The results show that for the lattice with d_{f}=2.58, the value of\nthe Ising critical exponent {\\nu}_{I} is the same as that of classical Ising\nmodel and the isotropic Heisenberg critical exponent {\\nu}_{H} is a finite\nvalue, and for the lattice with d_{f}=3, the values of {\\nu}_{I} and {\\nu}_{H}\nagree well with those obtained on the simple cubic lattice. We also discuss the\nquantum fluctuation at all temperatures and find the fluctuation of XY-like\nmodel is stronger than the anistropic Heisenberg model at the low-temperature\nregion. By analyzing the fluctuation, we conclude that there will be remarkable\neffect of neglecting terms on the final results of the XY-like model. However,\nwe can obtain approximate result at bigger temperatures and give qualitatively\ncorrect picture of the phase diagram.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hybrid soft-mode and off-center Ti model of barium titanate: It has been recently established by NMR techniques that in the high\ntemperature cubic phase of BaTiO$_3$ the Ti ions are not confined to the high\nsymmetry cubic sites, but rather occupy one of the eight off-center positions\nalong the $[111]$ directions. The off-center Ti picture is in apparent contrast\nwith most soft-mode type theoretical descriptions of this classical perovskite\nferroelectric. Here we apply a mesoscopic model of BaTiO$_3$, assuming that the\nsymmetrized occupation operators for the Ti off-center sites are linearly\ncoupled to the normal coordinates for lattice vibrations. On the time scale of\nTi intersite jumps, most phonon modes are fast and thus merely contribute to an\neffective static Ti-Ti interaction. Close to the stability limit for the soft\nTO optic modes, however, the phonon time scale becomes comparable to the\nrelaxation time for the Ti occupational states of $T_{1u}$ symmetry, and a\nhybrid vibrational-orientational soft mode appears. The frequency of the hybrid\nsoft mode is calculated as a function of temperature and coupling strength, and\nits its role in the ferroelectric phase transition is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Unequal Intra-layer Coupling in a Bilayer Driven Lattice Gas: The system under study is a twin-layered square lattice gas at half-filling,\nbeing driven to non-equilibrium steady states by a large, finite `electric'\nfield. By making intra-layer couplings unequal we were able to extend the phase\ndiagram obtained by Hill, Zia and Schmittmann (1996) and found that the\ntri-critical point, which separates the phase regions of the stripped (S) phase\n(stable at positive interlayer interactions J_3), the filled-empty (FE) phase\n(stable at negative J_3) and disorder (D), is shifted even further into the\nnegative J_3 region as the coupling traverse to the driving field increases.\nMany transient phases to the S phase at the S-FE boundary were found to be\nlong-lived. We also attempted to test whether the universality class of D-FE\ntransitions under a drive is still Ising. Simulation results suggest a value of\n1.75 for the exponent gamma but a value close to 2.0 for the ratio gamma/nu. We\nspeculate that the D-FE second order transition is different from Ising near\ncriticality, where observed first-order-like transitions between FE and its\n\"local minimum\" cousin occur during each simulation run.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effect of Elastic Deformations on the Critical Behavior of Disordered\n  Systems with Long-Range Interactions: A field-theoretic approach is applied to describe behavior of\nthree-dimensional, weakly disordered, elastically isotropic, compressible\nsystems with long-range interactions at various values of a long-range\ninteraction parameter. Renormalization-group equations are analyzed in the\ntwo-loop approximation by using the Pade-Borel summation technique. The fixed\npoints corresponding to critical and tricritical behavior of the systems are\ndetermined. Elastic deformations are shown to changes in critical and\ntricritical behavior of disordered compressible systems with long-range\ninteractions. The critical exponents characterizing a system in the critical\nand tricritical regions are determined.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on \"Fluctuation Theorem Uncertainty Relation\" and \"Thermodynamic\n  Uncertainty Relations from Exchange Fluctuation Theorems\": In recent letter [Phys.~Rev.~Lett {\\bf 123}, 110602 (2019)], Y.~Hasegawa and\nT.~V.~Vu derived a thermodynamic uncertainty relation. But the bound of their\nrelation is loose. In this comment, through minor changes, an improved bound is\nobtained. This improved bound is the same as the one obtained in\n[Phys.~Rev.~Lett {\\bf 123}, 090604 (2019)] by A.~M.~Timpanaro {\\it et. al.},\nbut the derivation here is straightforward.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Screening of an electrically charged particle in a two-dimensional\n  two-component plasma at $\u0393=2$: We consider the thermodynamic effects of an electrically charged impurity\nimmersed in a two-dimensional two-component plasma, composed by particles with\ncharges $\\pm e$, at temperature $T$, at coupling $\\Gamma=e^2/(k_B T)=2$,\nconfined in a large disk of radius $R$. Particularly, we focus on the analysis\nof the charge density, the correlation functions, and the grand potential. Our\nanalytical results show how the charges are redistributed in the circular\ngeometry considered here. When we consider a positively charged impurity, the\nnegative ions accumulate close to the impurity leaving an excess of positive\ncharge that accumulates at the boundary of the disk. Due to the symmetry under\ncharge exchange, the opposite effect takes place when we place a negative\nimpurity. Both the cases in which the impurity charge is an integer multiple of\nthe particle charges in the plasma, $\\pm e$, and a fraction of them are\nconsidered; both situations require a slightly different mathematical\ntreatments, showing the effect of the quantization of plasma charges. The bulk\nand tension effects in the plasma described by the grand potential are not\nmodified by the introduction of the charged particle. Besides the effects due\nto the collapse coming from the attraction between oppositely charged ions, an\nadditional topological term appears in the grand potential, proportional to\n$-n^2\\ln(mR)$, with $n$ the dimensionless charge of the particle. This term\nmodifies the central charge of the system, from $c=1$ to $c=1-6n^2$, when\nconsidered in the context of conformal field theories.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Emergent non-Hermitian physics in generalized Lotka-Volterra model: In this paper, we study the non-Hermitian physics emerging from a\npredator-prey ecological model described by a generalized Lotka-Volterra\nequation. In the phase space, this nonlinear equation exhibits both chaotic and\nlocalized dynamics, which are separated by a critical point. These distinct\ndynamics originate from the interplay between the periodicity and\nnon-Hermiticity of the effective Hamiltonian in the linearized equation of\nmotion. Moreover, the dynamics at the critical point, such as algebraic\ndivergence, can be understood as an exceptional point in the context of\nnon-Hermitian physics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Identification of a polymer growth process with an equilibrium\n  multi-critical collapse phase transition: the meeting point of swollen,\n  collapsed and crystalline polymers: We have investigated a polymer growth process on the triangular lattice where\nthe configurations produced are self-avoiding trails. We show that the scaling\nbehaviour of this process is similar to the analogous process on the square\nlattice. However, while the square lattice process maps to the collapse\ntransition of the canonical interacting self-avoiding trail model (ISAT) on\nthat lattice, the process on the triangular lattice model does not map to the\ncanonical equilibrium model. On the other hand, we show that the collapse\ntransition of the canonical ISAT model on the triangular lattice behaves in a\nway reminiscent of the $\\theta$-point of the interacting self-avoiding walk\nmodel (ISAW), which is the standard model of polymer collapse. This implies an\nunusual lattice dependency of the ISAT collapse transition in two dimensions.\n  By studying an extended ISAT model, we demonstrate that the growth process\nmaps to a multi-critical point in a larger parameter space. In this extended\nparameter space the collapse phase transition may be either $\\theta$-point-like\n(second-order) or first-order, and these two are separated by a multi-critical\npoint. It is this multi-critical point to which the growth process maps.\nFurthermore, we provide evidence that in addition to the high-temperature\ngas-like swollen polymer phase (coil) and the low-temperature liquid drop-like\ncollapse phase (globule) there is also a maximally dense crystal-like phase\n(crystal) at low temperatures dependent on the parameter values. The\nmulti-critical point is the meeting point of these three phases. Our\nhypothesised phase diagram resolves the mystery of the seemingly differing\nbehaviours of the ISAW and ISAT models in two dimensions as well as the\nbehaviour of the trail growth process.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Inequalities generalizing the second law of thermodynamics for\n  transitions between non-stationary states: We discuss the consequences of a variant of the Hatano-Sasa relation in which\na non-stationary distribution is used in place of the usual stationary one. We\nfirst show that this non-stationary distribution is related to a difference of\ntraffic between the direct and dual dynamics. With this formalism, we extend\nthe definition of the adiabatic and non-adiabatic entropies introduced by M.\nEsposito and C. Van den Broeck in Phys. Rev. Lett. 104, 090601 (2010) for the\nstationary case. We also obtain interesting second-law like inequalities for\ntransitions between non-stationary states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interaction-disorder competition in a spin system evaluated through the\n  Loschmidt Echo: The interplay between interactions and disorder in closed quantum many-body\nsystems is relevant for thermalization phenomenon. In this article, we address\nthis competition in an infinite temperature spin system, by means of the\nLoschmidt echo (LE), which is based on a time reversal procedure. This quantity\nhas been formerly employed to connect quantum and classical chaos, and in the\npresent many-body scenario we use it as a dynamical witness. We assess the LE\ntime scales as a function of disorder and interaction strengths. The strategy\nenables a qualitative phase diagram that shows the regions of ergodic and\nnonergodic behavior of the polarization under the echo dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A field-theoretic approach to nonequilibrium work identities: We study nonequilibrium work relations for a space-dependent field with\nstochastic dynamics (Model A). Jarzynski's equality is obtained through\nsymmetries of the dynamical action in the path integral representation. We\nderive a set of exact identities that generalize the fluctuation-dissipation\nrelations to non-stationary and far-from-equilibrium situations. These\nidentities are prone to experimental verification. Furthermore, we show that a\nwell-studied invariance of the Langevin equation under supersymmetry, which is\nknown to be broken when the external potential is time-dependent, can be\npartially restored by adding to the action a term which is precisely\nJarzynski's work. The work identities can then be retrieved as consequences of\nthe associated Ward-Takahashi identities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite temperature theory of the trapped two dimensional Bose gas: We present a Hartree-Fock-Bogoliubov (HFB) theoretical treatment of the\ntwo-dimensional trapped Bose gas and indicate how semiclassical approximations\nto this and other formalisms have lead to confusion. We numerically obtain\nresults for the fully quantum mechanical HFB theory within the Popov\napproximation and show that the presence of the trap stabilizes the condensate\nagainst long wavelength fluctuations. These results are used to show where\nphase fluctuations lead to the formation of a quasicondensate.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Criticality of natural absorbing states: We study a recently introduced ladder model which undergoes a transition\nbetween an active and an infinitely degenerate absorbing phase. In some cases\nthe critical behaviour of the model is the same as that of the branching\nannihilating random walk with $N\\geq 2$ species both with and without hard-core\ninteraction. We show that certain static characteristics of the so-called\nnatural absorbing states develop power law singularities which signal the\napproach of the critical point. These results are also explained using random\nwalk arguments. In addition to that we show that when dynamics of our model is\nconsidered as a minimum finding procedure, it has the best efficiency very\nclose to the critical point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Uncovering the secrets of the 2d random-bond Blume-Capel model: The effects of bond randomness on the ground-state structure, phase diagram\nand critical behavior of the square lattice ferromagnetic Blume-Capel (BC)\nmodel are discussed. The calculation of ground states at strong disorder and\nlarge values of the crystal field is carried out by mapping the system onto a\nnetwork and we search for a minimum cut by a maximum flow method. In finite\ntemperatures the system is studied by an efficient two-stage Wang-Landau (WL)\nmethod for several values of the crystal field, including both the first- and\nsecond-order phase transition regimes of the pure model. We attempt to explain\nthe enhancement of ferromagnetic order and we discuss the critical behavior of\nthe random-bond model. Our results provide evidence for a strong violation of\nuniversality along the second-order phase transition line of the random-bond\nversion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A generalized thermodynamics for power-law statistics: We show that there exists a natural way to define a condition of generalized\nthermal equilibrium between systems governed by Tsallis thermostatistics, under\nthe hypotheses that i) the coupling between the systems is weak, ii) the\nstructure functions of the systems have a power-law dependence on the energy.\nIt is found that the q values of two such systems at equilibrium must satisfy a\nrelationship involving the respective numbers of degrees of freedom. The\nphysical properties of a Tsallis distribution can be conveniently characterized\nby a new parameter eta which can vary between 0 and + infinite, these limits\ncorresponding respectively to the two opposite situations of a microcanonical\ndistribution and of a distribution with a predominant power-tail at high\nenergies. We prove that the statistical expression of the thermodynamic\nfunctions is univocally determined by the requirements that a) systems at\nthermal equilibrium have the same temperature, b) the definitions of\ntemperature and entropy are consistent with the second law of thermodynamics.\nWe find that, for systems satisfying the hypotheses i) and ii) specified above,\nthe thermodynamic entropy is given by Renyi entropy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Directed transport in equilibrium : analysis of the dimer model with\n  inertial terms: We have previously shown an analysis of our dimer model in the over-damped\nregime to show directed transport in equilibrium. Here we analyze the full\nmodel with inertial terms present to establish the same result. First we derive\nthe Fokker-Planck equation for the system following a Galilean transformation\nto show that a uniformly translating equilibrium distribution is possible.\nThen, we find out the velocity selection for the centre of mass motion using\nthat distribution on our model. We suggest generalization of our calculations\nfor soft collision potentials and indicate to interesting situation with\npossibility of oscillatory non-equilibrium state within equilibrium.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite-temperature properties of quasi-2D Bose-Einstein condensates: Using the finite-temperature path integral Monte Carlo method, we investigate\ndilute, trapped Bose gases in a quasi-two dimensional geometry. The quantum\nparticles have short-range, s-wave interactions described by a hard-sphere\npotential whose core radius equals its corresponding scattering length. The\neffect of both the temperature and the interparticle interaction on the\nequilibrium properties such as the total energy, the density profile, and the\nsuperfluid fraction is discussed. We compare our accurate results with both the\nsemi-classical approximation and the exact results of an ideal Bose gas. Our\nresults show that for repulsive interactions, (i) the minimum value of the\naspect ratio, where the system starts to behave quasi-two dimensionally,\nincreases as the two-body interaction strength increases, (ii) the superfluid\nfraction for a quasi-2D Bose gas is distinctly different from that for both a\nquasi-1D Bose gas and a true 3D system, i.e., the superfluid fraction for a\nquasi-2D Bose gas decreases faster than that for a quasi-1D system and a true\n3D system with increasing temperature, and shows a stronger dependence on the\ninteraction strength, (iii) the superfluid fraction for a quasi-2D Bose gas\nlies well below the values calculated from the semi-classical approximation,\nand (iv) the Kosterlitz-Thouless transition temperature decreases as the\nstrength of the interaction increases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite size induced phenomena in 2D classical spin models: We make a short overview of the recent analytic and numerical studies of the\nclassical two-dimensional XY and Heisenberg models at low temperatures. Special\nattention is being paid to an influence of finite system size L on the\npeculiarities of the low-temperature phase. In accordance with the\nMermin-Wagner-Hohenberg theorem, spontaneous magnetisation does not appear in\nthe above models at infinite L. However it emerges for the finite system sizes\nand leads to new features of the low-temperature behaviour.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quench dynamics and scaling laws in topological nodal loop semimetals: We employ quench dynamics as an effective tool to probe different\nuniversality classes of topological phase transitions. Specifically, we study a\nmodel encompassing both Dirac-like and nodal loop criticalities. Examining the\nKibble-Zurek scaling of topological defect density, we discover that the\nscaling exponent is reduced in the presence of extended nodal loop gap\nclosures. For a quench through a multicritical point, we also unveil a\npath-dependent crossover between two sets of critical exponents. Bloch state\ntomography finally reveals additional differences in the defect trajectories\nfor sudden quenches. While the Dirac transition permits a static trajectory\nunder specific initial conditions, we find that the underlying nodal loop leads\nto complex time-dependent trajectories in general. In the presence of a nodal\nloop, we find, generically, a mismatch between the momentum modes where\ntopological defects are generated and where dynamical quantum phase transitions\noccur. We also find notable exceptions where this correspondence breaks down\ncompletely.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Zero temperature coarsening in Ising model with asymmetric second\n  neighbour interaction in two dimensions: We consider the zero temperature coarsening in the Ising model in two\ndimensions where the spins interact within the Moore neighbourhood. The\nHamiltonian is given by $H = - \\sum_{<i,j>}{S_iS_j} - \\kappa\n\\sum_{<i,j'>}{S_iS_{j'}}$ where the two terms are for the first neighbours and\nsecond neighbours respectively and $\\kappa \\geq 0$. The freezing phenomena,\nalready noted in two dimensions for $\\kappa=0$, is seen to be present for any\n$\\kappa$. However, the frozen states show more complicated structure as\n$\\kappa$ is increased; e.g. local anti-ferromagnetic motifs can exist for\n$\\kappa>2$. Finite sized systems also show the existence of an iso-energetic\nactive phase for $\\kappa > 2$, which vanishes in the thermodynamic limit. The\npersistence probability shows universal behaviour for $\\kappa>0$, however it is\nclearly different from the $\\kappa=0$ results when non-homogeneous initial\ncondition is considered. Exit probability shows universal behaviour for all\n$\\kappa \\geq 0$. The results are compared with other models in two dimensions\nhaving interactions beyond the first neighbour.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlation Matrix Spectra: A Tool for Detecting Non-apparent\n  Correlations?: It has been shown that, if a model displays long-range (power-law) spatial\ncorrelations, its equal-time correlation matrix of this model will also have a\npower law tail in the distribution of its high-lying eigenvalues. The purpose\nof this letter is to show that the converse is generally incorrect: a power-law\ntail in the high-lying eigenvalues of the correlation matrix may exist even in\nthe absence of equal-time power law correlations in the original model. We may\ntherefore view the study of the eigenvalue distribution of the correlation\nmatrix as a more powerful tool than the study of correlations, one which may in\nfact uncover structure, that would otherwise not be apparent. Specifically, we\nshow that in the Totally Asymmetric Simple Exclusion Process, whereas there are\nno clearly visible correlations in the steady state, the eigenvalues of its\ncorrelation matrix exhibit a rich structure which we describe in detail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Resetting with stochastic return through linear confining potential: We consider motion of an overdamped Brownian particle subject to stochastic\nresetting in one dimension. In contrast to the usual setting where the particle\nis instantaneously reset to a preferred location (say, the origin), here we\nconsider a finite time resetting process facilitated by an external linear\npotential $V(x)=\\lambda|x|~ (\\lambda>0)$. When resetting occurs, the trap is\nswitched on and the particle experiences a force $-\\partial_x V(x)$ which helps\nthe particle to return to the resetting location. The trap is switched off as\nsoon as the particle makes a first passage to the origin. Subsequently, the\nparticle resumes its free diffusion motion and the process keeps repeating. In\nthis set-up, the system attains a non-equilibrium steady state. We study the\nrelaxation to this steady state by analytically computing the position\ndistribution of the particle at all time and then analysing this distribution\nusing the spectral properties of the corresponding Fokker-Planck operator. As\nseen for the instantaneous resetting problem, we observe a `cone spreading'\nrelaxation with travelling fronts such that there is an inner core region\naround the resetting point that reaches the steady state, while the region\noutside the core still grows ballistically with time. In addition to the\nunusual relaxation phenomena, we compute the large deviation functions\nassociated to the corresponding probability density and find that the large\ndeviation functions describe a dynamical transition similar to what is seen\npreviously in case of instantaneous resetting. Notably, our method, based on\nspectral properties, complements the existing renewal formalism and reveals the\nintricate mathematical structure responsible for such relaxation phenomena. We\nverify our analytical results against extensive numerical simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Criterion for phase separation in one-dimensional driven systems: A general criterion for the existence of phase separation in driven\none-dimensional systems is proposed. It is suggested that phase separation is\nrelated to the size dependence of the steady-state currents of domains in the\nsystem. A quantitative criterion for the existence of phase separation is\nconjectured using a correspondence made between driven diffusive models and\nzero-range processes. Several driven diffusive models are discussed in light of\nthe conjecture.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-equilibrium steady state and induced currents of a\n  mesoscopically-glassy system: interplay of resistor-network theory and Sinai\n  physics: We introduce an explicit solution for the non-equilibrium steady state (NESS)\nof a ring that is coupled to a thermal bath, and is driven by an external hot\nsource with log-wide distribution of couplings. Having time scales that stretch\nover several decades is similar to glassy systems. Consequently there is a wide\nrange of driving intensities where the NESS is like that of a random walker in\na biased Brownian landscape. We investigate the resulting statistics of the\ninduced current $I$. For a single ring we discuss how $sign(I)$ fluctuates as\nthe intensity of the driving is increased, while for an ensemble of rings we\nhighlight the fingerprints of Sinai physics on the $abs(I)$ distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interplay between writhe and knotting for swollen and compact polymers: The role of the topology and its relation with the geometry of biopolymers\nunder different physical conditions is a nontrivial and interesting problem.\nAiming at understanding this issue for a related simpler system, we use Monte\nCarlo methods to investigate the interplay between writhe and knotting of ring\npolymers in good and poor solvents. The model that we consider is interacting\nself-avoiding polygons on the simple cubic lattice. For polygons with fixed\nknot type we find a writhe distribution whose average depends on the knot type\nbut is insensitive to the length $N$ of the polygon and to solvent conditions.\nThis \"topological contribution\" to the writhe distribution has a value that is\nconsistent with that of ideal knots. The standard deviation of the writhe\nincreases approximately as $\\sqrt{N}$ in both regimes and this constitutes a\ngeometrical contribution to the writhe. If the sum over all knot types is\nconsidered, the scaling of the standard deviation changes, for compact\npolygons, to $\\sim N^{0.6}$. We argue that this difference between the two\nregimes can be ascribed to the topological contribution to the writhe that, for\ncompact chains, overwhelms the geometrical one thanks to the presence of a\nlarge population of complex knots at relatively small values of $N$. For\npolygons with fixed writhe we find that the knot distribution depends on the\nchosen writhe, with the occurrence of achiral knots being considerably\nsuppressed for large writhe. In general, the occurrence of a given knot thus\ndepends on a nontrivial interplay between writhe, chain length, and solvent\nconditions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Enskog equation for confined elastic hard spheres: A kinetic equation for a system of elastic hard spheres or disks confined by\na hard wall of arbitrary shape is derived. It is a generalization of the\nmodified Enskog equation in which the effects of the confinement are taken into\naccount and it is supposed to be valid up to moderate densities. From the\nequation, balance equations for the hydrodynamic fields are derived,\nidentifying the collisional transfer contributions to the pressure tensor and\nheat flux. A Lyapunov functional, $\\mathcal{H}[f]$, is identified. For any\nsolution of the kinetic equation, $\\mathcal{H}$ decays monotonically in time\nuntil the system reaches the inhomogeneous equilibrium distribution, that is a\nMaxwellian distribution with a the density field consistent with equilibrium\nstatistical mechanics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Socioeconomic agents as active matter in nonequilibrium Sakoda-Schelling\n  models: How robust are socioeconomic agent-based models with respect to the details\nof the agents' decision rule? We tackle this question by considering an\noccupation model in the spirit of the Sakoda-Schelling model, historically\nintroduced to shed light on segregation dynamics among human groups. For a\nlarge class of utility functions and decision rules, we pinpoint the\nnonequilibrium nature of the agent dynamics, while recovering the\nequilibrium-like phase separation phenomenology. Within the mean field\napproximation we show how the model can be mapped, to some extent, onto an\nactive matter field description (Active Model B). Finally, we consider\nnon-reciprocal interactions between two populations, and show how they can lead\nto non-steady macroscopic behavior. We believe our approach provides a unifying\nframework to further study geography-dependent agent-based models, notably\npaving the way for joint consideration of population and price dynamics within\na field theoretic approach.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical, crossover, and correction-to-scaling exponents for isotropic\n  Lifshitz points to order $\\boldsymbol{(8-d)^2}$: A two-loop renormalization group analysis of the critical behaviour at an\nisotropic Lifshitz point is presented. Using dimensional regularization and\nminimal subtraction of poles, we obtain the expansions of the critical\nexponents $\\nu$ and $\\eta$, the crossover exponent $\\phi$, as well as the\n(related) wave-vector exponent $\\beta_q$, and the correction-to-scaling\nexponent $\\omega$ to second order in $\\epsilon_8=8-d$. These are compared with\nthe authors' recent $\\epsilon$-expansion results [{\\it Phys. Rev. B} {\\bf 62}\n(2000) 12338; {\\it Nucl. Phys. B} {\\bf 612} (2001) 340] for the general case of\nan $m$-axial Lifshitz point. It is shown that the expansions obtained here by a\ndirect calculation for the isotropic ($m=d$) Lifshitz point all follow from the\nlatter upon setting $m=8-\\epsilon_8$. This is so despite recent claims to the\ncontrary by de Albuquerque and Leite [{\\it J. Phys. A} {\\bf 35} (2002) 1807].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Investigating Extreme Dependences: Concepts and Tools: We investigate the relative information content of six measures of dependence\nbetween two random variables $X$ and $Y$ for large or extreme events for\nseveral models of interest for financial time series. The six measures of\ndependence are respectively the linear correlation $\\rho^+_v$ and Spearman's\nrho $\\rho_s(v)$ conditioned on signed exceedance of one variable above the\nthreshold $v$, or on both variables ($\\rho_u$), the linear correlation\n$\\rho^s_v$ conditioned on absolute value exceedance (or large volatility) of\none variable, the so-called asymptotic tail-dependence $\\lambda$ and a\nprobability-weighted tail dependence coefficient ${\\bar \\lambda}$. The models\nare the bivariate Gaussian distribution, the bivariate Student's distribution,\nand the factor model for various distributions of the factor. We offer explicit\nanalytical formulas as well as numerical estimations for these six measures of\ndependence in the limit where $v$ and $u$ go to infinity. This provides a\nquantitative proof that conditioning on exceedance leads to conditional\ncorrelation coefficients that may be very different from the unconditional\ncorrelation and gives a straightforward mechanism for fluctuations or changes\nof correlations, based on fluctuations of volatility or changes of trends.\nMoreover, these various measures of dependence exhibit different and sometimes\nopposite behaviors, suggesting that, somewhat similarly to risks whose adequate\ncharacterization requires an extension beyond the restricted one-dimensional\nmeasure in terms of the variance (volatility) to include all higher order\ncumulants or more generally the knowledge of the full distribution,\ntail-dependence has also a multidimensional character.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Tensor Networks: Phase transition phenomena on hyperbolic and fractal\n  geometries: One of the challenging problems in the condensed matter physics is to\nunderstand the quantum many-body systems, especially, their physical mechanisms\nbehind. Since there are only a few complete analytical solutions of these\nsystems, several numerical simulation methods have been proposed in recent\nyears. Amongst all of them, the Tensor Network algorithms have become\nincreasingly popular in recent years, especially for their adaptability to\nsimulate strongly correlated systems. The current work focuses on the\ngeneralization of such Tensor-Network-based algorithms, which are sufficiently\nrobust to describe critical phenomena and phase transitions of multistate spin\nHamiltonians in the thermodynamic limit. We have chosen two algorithms: the\nCorner Transfer Matrix Renormalization Group and the Higher-Order Tensor\nRenormalization Group. This work, based on tensor-network analysis, opens doors\nfor the understanding of phase transition and entanglement of the interacting\nsystems on the non-Euclidean geometries. We focus on three main topics: A new\nthermodynamic model of social influence, free energy is analyzed to classify\nthe phase transitions on an infinite set of the negatively curved geometries\nwhere a relation between the free energy and the Gaussian radius of the\ncurvature is conjectured, a unique tensor-based algorithm is proposed to study\nthe phase transition on fractal structures.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Competition Between Exchange and Anisotropy in a Pyrochlore Ferromagnet: The Ising-like spin ice model, with a macroscopically degenerate ground\nstate, has been shown to be approximated by several real materials. Here we\ninvestigate a model related to spin ice, in which the Ising spins are replaced\nby classical Heisenberg spins. These populate a cubic pyrochlore lattice and\nare coupled to nearest neighbours by a ferromagnetic exchange term J and to the\nlocal <1,1,1> axes by a single-ion anisotropy term D. The near neighbour spin\nice model corresponds to the case D/J infinite. For finite D/J we find that the\nmacroscopic degeneracy of spin ice is broken and the ground state is\nmagnetically ordered into a four-sublattice structure. The transition to this\nstate is first-order for D/J > 5 and second-order for D/J < 5 with the two\nregions separated by a tricritical point. We investigate the magnetic phase\ndiagram with an applied field along [1,0,0] and show that it can be considered\nanalogous to that of a ferroelectric.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Accessing power-law statistics under experimental constraints: Over the last decades, impressive progresses have been made in many\nexperimental domains, e.g. microscopic techniques such as single-particle\ntracking, leading to plethoric amounts of data. In a large variety of systems,\nfrom natural to socio-economic, the analysis of these experimental data\nconducted us to conclude about the omnipresence of power-laws. For example, in\nliving systems, we are used to observing anomalous diffusion, e.g. in the\nmotion of proteins within the cell. However, estimating the power-law exponents\nis challenging. Both technical constraints and experimental limitations affect\nthe statistics of observed data. Here, we investigate in detail the influence\nof two essential constraints in the experiment, namely, the temporal-spatial\nresolution and the time-window of the experiment. We study how the observed\ndistribution of an observable is modified by them and analytically derive the\nexpression of the power-law distribution for the observed distribution through\nthe scope of the experiment. We also apply our results on data from an\nexperimental study of the transport of mRNA-protein complexes along dendrites.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Modelling High-frequency Economic Time Series: The minute-by-minute move of the Hang Seng Index (HSI) data over a four-year\nperiod is analysed and shown to possess similar statistical features as those\nof other markets. Based on a mathematical theorem [S. B. Pope and E. S. C.\nChing, Phys. Fluids A {\\bf 5}, 1529 (1993)], we derive an analytic form for the\nprobability distribution function (PDF) of index moves from fitted functional\nforms of certain conditional averages of the time series. Furthermore,\nfollowing a recent work by Stolovitzky and Ching, we show that the observed PDF\ncan be reproduced by a Langevin process with a move-dependent noise amplitude.\nThe form of the Langevin equation can be determined directly from the market\ndata.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The three-state Potts antiferromagnet on plane quadrangulations: We study the antiferromagnetic 3-state Potts model on general (periodic)\nplane quadrangulations $\\Gamma$. Any quadrangulation can be built from a dual\npair $(G,G^*)$. Based on the duality properties of $G$, we propose a new\ncriterion to predict the phase diagram of this model. If $\\Gamma$ is of\nself-dual type (i.e., if $G$ is isomorphic to its dual $G^*$), the model has a\nzero-temperature critical point with central charge $c=1$, and it is disordered\nat all positive temperatures. If $\\Gamma$ is of non-self-dual type (i.e., if\n$G$ is not isomorphic to $G^*$), three ordered phases coexist at low\ntemperature, and the model is disordered at high temperature. In addition,\nthere is a finite-temperature critical point (separating these two phases)\nwhich belongs to the universality class of the ferromagnetic 3-state Potts\nmodel with central charge $c=4/5$. We have checked these conjectures by\nstudying four (resp. seven) quadrangulations of self-dual (resp. non-self-dual)\ntype, and using three complementary high-precision techniques: Monte-Carlo\nsimulations, transfer matrices, and critical polynomials. In all cases, we find\nagreement with the conjecture. We have also found that the\nWang-Swendsen-Kotecky Monte Carlo algorithm does not have (resp. does have)\ncritical slowing down at the corresponding critical point on quadrangulations\nof self-dual (resp. non-self-dual) type.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metropolis Monte Carlo algorithm based on the reparametrization\n  invariance: We introduce a modification of the well-known Metropolis importance sampling\nalgorithm by using a methodology inspired on the consideration of the\nreparametrization invariance of the microcanonical ensemble. The most important\nfeature of the present proposal is the possibility of performing a suitable\ndescription of microcanonical thermodynamic states during the first-order phase\ntransitions by using this local Monte Carlo algorithm.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Putative Liquid-Liquid Transition is a Liquid-Solid Transition in\n  Atomistic Models of Water, Part II: This paper extends our earlier studies of free energy functions of density\nand crystalline order parameters for models of supercooled water, which allows\nus to examine the possibility of two distinct metastable liquid phases [J.\nChem. Phys. 135, 134503 (2011) and arXiv:1107.0337v2]. Low-temperature\nreversible free energy surfaces of several different atomistic models are\ncomputed: mW water, TIP4P/2005 water, SW silicon and ST2 water, the last of\nthese comparing three different treatments of long-ranged forces. In each case,\nwe show that there is one stable or metastable liquid phase, and there is an\nice-like crystal phase. The time scales for crystallization in these systems\nfar exceed those of structural relaxation in the supercooled metastable liquid.\nWe show how this wide separation in time scales produces an illusion of a\nlow-temperature liquid-liquid transition. The phenomenon suggesting\nmetastability of two distinct liquid phases is actually coarsening of the\nordered ice-like phase, which we elucidate using both analytical theory and\ncomputer simulation. For the latter, we describe robust methods for computing\nreversible free energy surfaces, and we consider effects of electrostatic\nboundary conditions. We show that sensible alterations of models and boundary\nconditions produce no qualitative changes in low-temperature phase behaviors of\nthese systems, only marginal changes in equations of state. On the other hand,\nwe show that altering sampling time scales can produce large and qualitative\nnonequilibrium effects. Recent reports of evidence of a liquid-liquid critical\npoint in computer simulations of supercooled water are considered in this\nlight.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding probability and irreversibility in the Mori-Zwanzig\n  projection operator formalism: Explaining the emergence of stochastic irreversible macroscopic dynamics from\ntime-reversible deterministic microscopic dynamics is one of the key problems\nin philosophy of physics. The Mori-Zwanzig projection operator formalism, which\nis one of the most important methods of modern nonequilibrium statistical\nmechanics, allows for a systematic derivation of irreversible transport\nequations from reversible microdynamics and thus provides a useful framework\nfor understanding this issue. However, discussions of the Mori-Zwanzig\nformalism in philosophy of physics tend to focus on simple variants rather than\non the more sophisticated ones used in modern physical research. In this work,\nI will close this gap by studying the problems of probability and\nirreversibility using the example of Grabert's time-dependent projection\noperator formalism. This allows to give a more solid mathematical foundation to\nvarious concepts from the philosophical literature, in particular Wallace's\nsimple dynamical conjecture and Robertson's theory of autonomous macrodynamics.\nMoreover, I will explain how the Mori-Zwanzig formalism allows to resolve the\ntension between epistemic and ontic approaches to probability in statistical\nmechanics. Finally, I argue that the debate which interventionists and\ncoarse-grainers should really be having is related not to the question why\nthere is equilibration at all, but why it has the quantitative form it is found\nto have in experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Competition between Short-Ranged Attraction and Short-Ranged Repulsion\n  in Crowded Configurational Space; A Lattice Model Description: We describe a simple nearest-neighbor Ising model that is capable of\nsupporting a gas, liquid, crystal, in characteristic relationship to each\nother. As the parameters of the model are varied one obtains characteristic\npatterns of phase behavior reminiscent of continuum systems where the range of\nthe interaction is varied. The model also possesses dynamical arrest, and\nalthough we have not studied it in detail, these 'transitions' appear to have a\nreasonable relationship to the phases and their transitions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical Properties of the Final State in One-dimensional Ballistic\n  Aggregation: We investigate the long time behaviour of the one-dimensional ballistic\naggregation model that represents a sticky gas of N particles with random\ninitial positions and velocities, moving deterministically, and forming\naggregates when they collide. We obtain a closed formula for the stationary\nmeasure of the system which allows us to analyze some remarkable features of\nthe final `fan' state. In particular, we identify universal properties which\nare independent of the initial position and velocity distributions of the\nparticles. We study cluster distributions and derive exact results for extreme\nvalue statistics (because of correlations these distributions do not belong to\nthe Gumbel-Frechet-Weibull universality classes). We also derive the energy\ndistribution in the final state. This model generates dynamically many\ndifferent scales and can be viewed as one of the simplest exactly solvable\nmodel of N-body dissipative dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Network Mutual Information and Synchronization under Time\n  Transformations: We investigate the effect of general time transformations on the phase\nsynchronization (PS) phenomenon and the mutual information rate (MIR) between\npairs of nodes in dynamical networks. We demonstrate two important results\nconcerning the invariance of both PS and the MIR. Under time transformations PS\ncan neither be introduced nor destroyed and the MIR cannot be raised from zero.\nOn the other hand, for proper time transformations the timing between the\ncycles of the coupled oscillators can be largely improved. Finally, we discuss\nthe relevance of our findings for communication in dynamical networks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Random Force is a Force, of Course, of Coarse: Decomposing Complex\n  Enzyme Kinetics with Surrogate Models: The temporal autocorrelation (AC) function associated with monitoring order\nparameters characterizing conformational fluctuations of an enzyme is analyzed\nusing a collection of surrogate models. The surrogates considered are\nphenomenological stochastic differential equation (SDE) models. It is\ndemonstrated how an ensemble of such surrogate models, each surrogate being\ncalibrated from a single trajectory, indirectly contains information about\nunresolved conformational degrees of freedom. This ensemble can be used to\nconstruct complex temporal ACs associated with a \"non-Markovian\" process. The\nensemble of surrogates approach allows researchers to consider models more\nflexible than a mixture of exponentials to describe relaxation times and at the\nsame time gain physical information about the system. The relevance of this\ntype of analysis to matching single-molecule experiments to computer\nsimulations and how more complex stochastic processes can emerge from a mixture\nof simpler processes is also discussed. The ideas are illustrated on a toy SDE\nmodel and on molecular dynamics simulations of the enzyme dihydrofolate\nreductase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of the Noninteracting Bose Gas in a Two-Dimensional Box: Bose-Einstein condensation (BEC) of a noninteracting Bose gas of N particles\nin a two-dimensional box with Dirichlet boundary conditions is studied.\nConfirming previous work, we find that BEC occurs at finite N at low\ntemperatures T without the occurrence of a phase transition. The\nconventionally-defined transition temperature TE for an infinite 3D system is\nshown to correspond in a 2D system with finite N to a crossover temperature\nbetween a slow and rapid increase in the fractional boson occupation N0/N of\nthe ground state with decreasing T. We further show that TE ~ 1/log(N) at fixed\narea per boson, so in the thermodynamic limit there is no significant BEC in 2D\nat finite T. Thus, paradoxically, BEC only occurs in 2D at finite N with no\nphase transition associated with it. Calculations of thermodynamic properties\nversus T and area A are presented, including Helmholtz free energy, entropy S ,\npressure p, ratio of p to the energy density U/A, heat capacity at constant\nvolume (area) CV and at constant pressure Cp, isothermal compressibility\nkappa_T and thermal expansion coefficient alpha_p, obtained using both the\ngrand canonical ensemble (GCE) and canonical ensemble (CE) formalisms. The GCE\nformalism gives acceptable predictions for S, p, p/(U/A), kappa_T and alpha_p\nat large N, T and A, but fails for smaller values of these three parameters for\nwhich BEC becomes significant, whereas the CE formalism gives accurate results\nfor all thermodynamic properties of finite systems even at low T and/or A where\nBEC occurs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite size spectrum of the staggered six-vertex model with\n  $U_q(\\mathfrak{sl}(2))$-invariant boundary conditions: The finite size spectrum of the critical $\\mathbb{Z}_2$-staggered spin-$1/2$\nXXZ model with quantum group invariant boundary conditions is studied. For a\nparticular (self-dual) choice of the staggering the spectrum of conformal\nweights of this model has been recently been shown to have a continuous\ncomponent, similar as in the model with periodic boundary conditions whose\ncontinuum limit has been found to be described in terms of the non-compact\n$SU(2,\\mathbb{R})/U(1)$ Euclidean black hole conformal field theory (CFT). Here\nwe show that the same is true for a range of the staggering parameter. In\naddition we find that levels from the discrete part of the spectrum of this CFT\nemerge as the anisotropy is varied. The finite size amplitudes of both the\ncontinuous and the discrete levels are related to the corresponding eigenvalues\nof a quasi-momentum operator which commutes with the Hamiltonian and the\ntransfer matrix of the model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Manifestation of Random First Order Transition theory in Wigner glasses: We use Brownian dynamics simulations of a binary mixture of highly charged\nspherical colloidal particles to illustrate many of the implications of the\nRandom First Order Transition (RFOT) theory (PRA 40 1045 (1989)), which is the\nonly theory that provides a unified description of both the statics and\ndynamics of the liquid to glass transition. In accord with the RFOT, we find\nthat as the volume fraction of the colloidal particles \\f, the natural variable\nthat controls glass formation in colloidal systems, approaches \\f_A there is an\neffective ergodic to non-ergodic dynamical transition, which is signalled by a\ndramatic slowing down of diffusion. In addition, using the energy metric we\nshow that the system becomes non-ergodic as \\f_A is approached. The time t^*,\nat which the four-point dynamical susceptibility achieves a maximum, also\ndiverges near \\f_A. Remarkably, three independent measures(translational\ndiffusion coefficients, ergodic diffusion coefficients,as well t^*) all signal\nthat at \\f_A=0.1 ergodicity is effectively broken. The translation diffusion\nconstant, the ergodic diffusion constant, and (t^*)^-1 all vanish as\n(\\f_A-\\f)^g with both \\f_A and g being the roughly the same for all three\nquantities. Below \\f_A transport involves crossing suitable free energy\nbarriers. In this regime, the density-density correlation function decays as a\nstretched exponential exp(-t/tau_a)^b with b=0.45. The \\f-dependence of the\nrelaxation time \\tau_a is well fit using the VFT law with the ideal glass\ntransition occurring at \\f_K=0.47. By using an approximate measure of the local\nentropy (s_3) we show that below \\f_A the law of large numbers, which states\nthat the distribution of s_3 for a large subsample should be identical to the\nwhole sample, is not obeyed. The comprehensive analyses provided here for\nWigner glass forming charged colloidal suspensions fully validate the concepts\nof the RFOT.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "How a local active force modifies the structural properties of polymers: We study the dynamics of a polymer, described as a variant of a Rouse chain,\ndriven by an active terminal monomer (head). The local active force induces a\ntransition from a globule-like to an elongated state, as revealed by the study\nof the end-to-end distance, whose variance is analytically predicted under\nsuitable approximations. The change in the relaxation times of the Rouse-modes\nproduced by the local self-propulsion is consistent with the transition from\nglobule to elongated conformations. Moreover also the bond-bond spatial\ncorrelation for the chain head results to be affected and a gradient of\nover-stretched bonds along the chain is observed. We compare our numerical\nresults both with the phenomenological stiff-polymer theory and several\nanalytical predictions in the Rouse-chain approximation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the Surface Tensions of Binary Mixtures: For binary mixtures with fixed concentrations of the species, various\nrelationships between the surface tensions and the concentrations are briefly\nreviewed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase transition in a one-dimensional Ising ferromagnet at\n  zero-temperature under Glauber dynamics with a synchronous updating mode: In the past decade low-temperature Glauber dynamics for the one-dimensional\nIsing system has been several times observed experimentally and occurred to be\none of the most important theoretical approaches in a field of molecular\nnanomagnets. On the other hand, it has been shown recently that Glauber\ndynamics with the Metropolis flipping probability for the zero-temperature\nIsing ferromagnet under synchronous updating can lead surprisingly to the\nantiferromagnetic steady state. In this paper the generalized class of Glauber\ndynamics at zero-temperature will be considered and the relaxation into the\nground state, after a quench from high temperature, will be investigated. Using\nMonte Carlo simulations and a mean field approach, discontinuous phase\ntransition between ferromagnetic and antiferromagnetic phases for a\none-dimensional ferromagnet will be shown.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The non-equilibrium phase transition of the pair-contact process with\n  diffusion: The pair-contact process 2A->3A, 2A->0 with diffusion of individual particles\nis a simple branching-annihilation processes which exhibits a phase transition\nfrom an active into an absorbing phase with an unusual type of critical\nbehaviour which had not been seen before. Although the model has attracted\nconsiderable interest during the past few years it is not yet clear how its\ncritical behaviour can be characterized and to what extent the diffusive\npair-contact process represents an independent universality class. Recent\nresearch is reviewed and some standing open questions are outlined.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal microstructure and mechanical stability of jammed packings: Jammed packings' mechanical properties depend sensitively on their detailed\nlocal structure. Here we provide a complete characterization of the pair\ncorrelation close to contact and of the force distribution of jammed\nfrictionless spheres. In particular we discover a set of new scaling relations\nthat connect the behavior of particles bearing small forces and those bearing\nno force but that are almost in contact. By performing systematic\ninvestigations for spatial dimensions d=3-10, in a wide density range and using\ndifferent preparation protocols, we show that these scalings are indeed\nuniversal. We therefore establish clear milestones for the emergence of a\ncomplete microscopic theory of jamming. This description is also crucial for\nhigh-precision force experiments in granular systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Response to a small external force and fluctuations of a passive\n  particle in a one-dimensional diffusive environment: We investigate the long time behavior of a passive particle evolving in a\none-dimensional diffusive random environment, with diffusion constant $D$. We\nconsider two cases: (a) The particle is pulled forward by a small external\nconstant force, and (b) there is no systematic bias. Theoretical arguments and\nnumerical simulations provide evidence that the particle is eventually trapped\nby the environment. This is diagnosed in two ways: The asymptotic speed of the\nparticle scales quadratically with the external force as it goes to zero, and\nthe fluctuations scale diffusively in the unbiased environment, up to possible\nlogarithmic corrections in both cases. Moreover, in the large $D$ limit\n(homogenized regime), we find an important transient region giving rise to\nother, finite-size scalings, and we describe the cross-over to the true\nasymptotic behavior.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Topological footprints of the 1D Kitaev chain with long range\n  superconducting pairings at a finite temperature: We study the 1D Kitaev chain with long range superconductive pairing terms at\na finite temperature where the system is prepared in a mixed state in\nequilibrium with a heat reservoir maintained at a constant temperature $T$. In\norder to probe the footprint of the ground state topological behavior of the\nmodel at finite temperature, we look at two global quantities extracted out of\ntwo geometrical constructions: the Uhlmann and the interferometric phase.\nInterestingly, when the long-range effect dominates, the Uhlmann phase approach\nfails to reproduce the topological aspects of the model in the pure state\nlimit; on the other hand, the interferometric phase, though has a proper pure\nstate reduction, shows a behaviour independent of the ambient temperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Field-induced dynamics in the quantum Brownian oscillator: An exact\n  treatment: We consider a quantum linear oscillator coupled to a bath in equilibrium at\nan arbitrary temperature and then exposed to an external field arbitrary in\nform and strength. We then derive the reduced density operator in closed form\nof the coupled oscillator in a non-equilibrium state at an arbitrary time.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Localization threshold of Instantaneous Normal Modes from level-spacing\n  statistics: We study the statistics of level-spacing of Instantaneous Normal Modes in a\nsupercooled liquid. A detailed analysis allows to determine the mobility edge\nseparating extended and localized modes in the negative tail of the density of\nstates. We find that at temperature below the mode coupling temperature only a\nvery small fraction of negative eigenmodes are localized.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The influence of statistical properties of Fourier coefficients on\n  random surfaces: Many examples of natural systems can be described by random Gaussian\nsurfaces. Much can be learned by analyzing the Fourier expansion of the\nsurfaces, from which it is possible to determine the corresponding Hurst\nexponent and consequently establish the presence of scale invariance. We show\nthat this symmetry is not affected by the distribution of the modulus of the\nFourier coefficients. Furthermore, we investigate the role of the Fourier\nphases of random surfaces. In particular, we show how the surface is affected\nby a non-uniform distribution of phases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Gaussian fluctuations in an ideal bose-gas -- a simple model: Based on the canonical ensemble, we suggested the simple scheme for taking\ninto account Gaussian fluctuations in a finite system of ideal boson gas.\nWithin framework of scheme we investigated the influence of fluctuations on the\nparticle distribution in Bose -gas for two cases - with taking into account the\nnumber of particles in the ground state and without this assumption. The\ntemperature and fluctuation parameter dependences of the modified Bose-\nEinstein distribution have been determined. Also the dependence of the\ncondensation temperature on the fluctuation distribution parameter has been\nobtained.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Pushing the limits of EPD zeros method: The use of partition function zeros in the study of phase transition is\ngrowing in the last decade mainly due to improved numerical methods as well as\nnovel formulations and analysis. In this paper the impact of different\nparameters choice for the energy probability distribution (EPD) zeros recently\nintroduced by Costa et al is explored in search for optimal values. Our results\nindicate that the EPD method is very robust against parameter variations and\nonly small deviations on estimated critical temperatures are found even for\nlarge variation of parameters, allowing to obtain accurate results with low\ncomputational cost. A proposal to circumvent potential convergence issues of\nthe original algorithm is presented and validated for the case where it occurs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Intermolecular effects in the center-of-mass dynamics of unentangled\n  polymer fluids: We investigate the anomalous dynamics of unentangled polymer melts. The\nproposed equation of motion formally relates the anomalous center-of-mass\ndiffusion, as observed in computer simulations and experiments, to the nature\nof the effective intermolecular mean-force potential. An analytical\nGaussian-core form of the potential between the centers of mass of two polymers\nis derived, which agrees with computer simulations and allows the analytical\nsolution of the equation of motion. The calculated center-of-mass dynamics is\ncharacterized by an initial subdiffusive regime that persists for the spatial\nrange of the intermolecular mean-force potential, and for time intervals\nshorter than the first intramolecular relaxation time, in agreement with\nexperiments and computer simulations of unentangled polymer melt dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Large deviations and conditioning for chaotic non-invertible\n  deterministic maps: analysis via the forward deterministic dynamics and the\n  backward stochastic dynamics: The large deviations properties of trajectory observables for chaotic\nnon-invertible deterministic maps as studied recently by N. R. Smith, Phys.\nRev. E 106, L042202 (2022) and by R. Gutierrez, A. Canella-Ortiz, C.\nPerez-Espigares, arXiv:2304.13754 are revisited in order to analyze in detail\nthe similarities and the differences with the case of stochastic Markov chains.\nTo be concrete, we focus on the simplest example displaying the two essential\nproperties of local-stretching and global-folding, namely the doubling map $\nx_{t+1} = 2 x_t [\\text{mod} 1] $ on the real-space interval $x \\in [0,1[$ that\ncan be also analyzed via the decomposition $x= \\sum_{l=1}^{+\\infty}\n\\frac{\\sigma_l}{2^l} $ into binary coefficients $\\sigma_l=0,1$. The large\ndeviations properties of trajectory observables can be studied either via\ndeformations of the forward deterministic dynamics or via deformations of the\nbackward stochastic dynamics. Our main conclusions concerning the construction\nof the corresponding Doob canonical conditioned processes are: (i) non-trivial\nconditioned dynamics can be constructed only in the backward stochastic\nperspective where the reweighting of existing transitions is possible, and not\nin the forward deterministic perspective ; (ii) the corresponding conditioned\nsteady state is not smooth on the real-space interval $x \\in [0,1[$ and can be\nbetter characterized in the binary space $\\sigma_{l=1,2,..,+\\infty}$. As a\nconsequence, the backward stochastic dynamics in the binary space is also the\nmost appropriate framework to write the explicit large deviations at level 2\nfor the probability of the empirical density of long backward trajectories.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Renormalization-group study of the many-body localization transition in\n  one dimension: Using a new approximate strong-randomness renormalization group (RG), we\nstudy the many-body localized (MBL) phase and phase transition in\none-dimensional quantum systems with short-range interactions and quenched\ndisorder. Our RG is built on those of Zhang $\\textit{et al.}$ [1] and\nGoremykina $\\textit{et al.}$ [2], which are based on thermal and insulating\nblocks. Our main addition is to characterize each insulating block with two\nlengths: a physical length, and an internal decay length $\\zeta$ for its\neffective interactions. In this approach, the MBL phase is governed by a RG\nfixed line that is parametrized by a global decay length $\\tilde{\\zeta}$, and\nthe rare large thermal inclusions within the MBL phase have a fractal geometry.\nAs the phase transition is approached from within the MBL phase,\n$\\tilde{\\zeta}$ approaches the finite critical value corresponding to the\navalanche instability, and the fractal dimension of large thermal inclusions\napproaches zero. Our analysis is consistent with a Kosterlitz-Thouless-like RG\nflow, with no intermediate critical MBL phase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statics and dynamics of the ten-state nearest-neighbor Potts glass on\n  the simple-cubic lattice: We present the results of Monte Carlo simulations of two different Potts\nglass models with short range random interactions. In the first model a \\pm\nJ-distribution of the bonds is chosen, in the second model a Gaussian\ndistribution. In both cases the first two moments of the distribution are\nchosen to be J_0=-1, Delta J=+1, so that no ferromagnetic ordering of the Potts\nspins can occur. We find that for all temperatures investigated the spin glass\nsusceptibility remains finite, the spin glass order parameter remains zero, and\nthat the specific heat has only a smooth Schottky-like peak. These results can\nbe understood quantitatively by considering small but independent clusters of\nspins. Hence we have evidence that there is no static phase transition at any\nnonzero temperature. Consistent with these findings, only very minor size\neffects are observed, which implies that all correlation lengths of the models\nremain very short. We also compute for both models the time auto-correlation\nfunction C(t) of the Potts spins. While in the Gaussian model C(t) shows a\nsmooth uniform decay, the correlator for the \\pm J model has several distinct\nsteps. These steps correspond to the breaking of bonds in small clusters of\nferromagnetically coupled spins (dimers, trimers, etc.). The relaxation times\nfollow simple Arrhenius laws, with activation energies that are readily\ninterpreted within the cluster picture, giving evidence that the system does\nnot have a dynamic transition at a finite temperature. Hence we find that for\nthe present models all the transitions known for the mean-field version of the\nmodel are completely wiped out. Finally we also determine the time\nauto-correlation functions of individual spins, and show that the system is\ndynamically very heterogeneous.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An Efficient Monte-Carlo Method for Calculating Free-Energy in\n  Long-Range Interacting Systems: We present an efficient Monte-Carlo method for long-range interacting systems\nto calculate free energy as a function of an order parameter. In this method, a\nvariant of the Wang-Landau method regarding the order parameter is combined\nwith the stochastic cutoff method, which has recently been developed for\nlong-range interacting systems. This method enables us to calculate free energy\nin long-range interacting systems with reasonable computational time despite\nthe fact that no approximation is involved. This method is applied to a\nthree-dimensional magnetic dipolar system to measure free energy as a function\nof magnetization. By using the present method, we can calculate free energy for\na large system size of $16^3$ spins despite the presence of long-range magnetic\ndipolar interactions. We also discuss the merits and demerits of the present\nmethod in comparison with the conventional Wang-Landau method in which free\nenergy is calculated from the joint density of states of energy and order\nparameter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical Rare event simulation techniques for equilibrium and\n  non-equilibrium systems: I give an overview of rare event simulation techniques to generate dynamical\npathways across high free energy barriers. The methods on which I will\nconcentrate are the reactive flux approach, transition path sampling,\n(replica-exchange) transition interface sampling, partial path\nsampling/milestoning, and forward flux sampling. These methods have in common\nthat they aim to simulate true molecular dynamics trajectories at a much faster\nrate than naive brute force molecular dynamics. The advantages and\ndisadvantages of these methods are discussed and compared for a simple\none-dimensional test system. These numerical results reveal some important\npitfalls of the present non-equilibrium methods that have no easy solution and\nshow that caution is necessary when interpreting their results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bose-Einstein condensation under external conditions: We discuss the phenomenon of Bose-Einstein condensation under general\nexternal conditions using connections between partition sums and the\nheat-equation. Thermodynamical quantities like the critical temperature are\ngiven in terms of the heat-kernel coefficients of the associated Schr\\\"odinger\nequation. The general approach is applied to situations where the gas is\nconfined by arbitrary potentials or by boxes of arbitrary shape.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact thermodynamics and phase diagram of integrable t-J model with\n  chiral interaction: We study the phase diagram and finite temperature properties of an integrable\ngeneralization of the one-dimensional super-symmetric t-J model containing\ninteractions explicitly breaking parity-time reversal (PT) symmetries. To this\npurpose, we apply the quantum transfer matrix method which results in a finite\nset of non-linear integral equations. We obtain numerical solutions to these\nequations leading to results for thermodynamic quantities as function of\ntemperature, magnetic field, particle density and staggering parameter.\nStudying the maxima lines of entropy at low but non zero temperature reveals\nthe phase diagram of the model. There are ten different phases which we may\nclassify in terms of the qualitative behaviour of auxiliary functions, closely\nrelated to the dressed energy functions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Three lectures on statistical mechanics: These lectures were prepared for the 2014 PCMI graduate summer school and\nwere designed to be a lightweight introduction to statistical mechanics for\nmathematicians. The applications feature some of the themes of the summer\nschool: sphere packings and tilings.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Application of a time-convolutionless stochastic Schr\u00f6dinger equation\n  to energy transport and thermal relaxation: Quantum stochastic methods based on effective wave functions form a framework\nfor investigating the generally non-Markovian dynamics of a quantum-mechanical\nsystem coupled to a bath. They promise to be computationally superior to the\nmaster-equation approach, which is numerically expensive for large dimensions\nof the Hilbert space. Here, we numerically investigate the suitability of a\nknown stochastic Schr\\\"odinger equation that is local in time to give a\ndescription of thermal relaxation and energy transport. This stochastic\nSchr\\\"odinger equation can be solved with a moderate numerical cost, indeed\ncomparable to that of a Markovian system, and reproduces the dynamics of a\nsystem evolving according to a general non-Markovian master equation. After\nverifying that it describes thermal relaxation correctly, we apply it for the\nfirst time to the energy transport in a spin chain. We also discuss a portable\nalgorithm for the generation of the coloured noise associated with the\nnumerical solution of the non-Markovian dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Behavior of pressure and viscosity at high densities for two-dimensional\n  hard and soft granular materials: The pressure and the viscosity in two-dimensional sheared granular assemblies\nare investigated numerically. The behavior of both pressure and viscosity is\nsmoothly changing qualitatively when starting from a mono-disperse hard-disk\nsystem without dissipation and moving towards a system of (i) poly-disperse,\n(ii) soft particles with (iii) considerable dissipation.\n  In the rigid, elastic limit of mono-disperse systems, the viscosity is\napproximately inverse proportional to the area fraction difference from\n$\\phi_{\\eta} \\simeq 0.7$, but the pressure is still finite at $\\phi_{\\eta}$. In\nmoderately soft, dissipative and poly-disperse systems, on the other hand, we\nconfirm the recent theoretical prediction that both scaled pressure (divided by\nthe kinetic temperature $T$) and scaled viscosity (divided by $\\sqrt{T}$)\ndiverge at the same density, i.e., the jamming transition point $\\phi_J >\n\\phi_\\eta$, with the exponents -2 and -3, respectively. Furthermore, we observe\nthat the critical region of the jamming transition becomes invisible as the\nrestitution coefficient approaches unity, i.e. for vanishing dissipation.\n  In order to understand the conflict between these two different predictions\non the divergence of the pressure and the viscosity, the transition from soft\nto hard particles is studied in detail and the dimensionless control parameters\nare defined as ratios of various time-scales. We introduce a dimensionless\nnumber, i.e. the ratio of dissipation rate and shear rate, that can identify\nthe crossover from the scaling of very hard, i.e. rigid disks to the scaling in\nthe soft, jamming regime.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic dynamics of N correlated binary variables and non-extensive\n  statistical mechanics: The non-extensive statistical mechanics has been applied to describe a\nvariety of complex systems with inherent correlations and feedback loops. Here\nwe present a dynamical model based on previously proposed static model\nexhibiting in the thermodynamic limit the extensivity of the Tsallis entropy\nwith q<1 as well as a q-Gaussian distribution. The dynamical model consists of\na one-dimensional ring of particles characterized by correlated binary random\nvariables, which are allowed to flip according to a simple random walk rule.\nThe proposed dynamical model provides an insight how a mesoscopic dynamics\ncharacterized by the non-extensive statistical mechanics could emerge from a\nmicroscopic description of the system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effective Temperature in an Interacting, Externally Driven, Vertex\n  System: Theory and Experiment on Artificial Spin Ice: Frustrated arrays of interacting single-domain nanomagnets provide important\nmodel systems for statistical mechanics, because they map closely onto\nwell-studied vertex models and are amenable to direct imaging and custom\nengineering. Although these systems are manifestly athermal, we demonstrate\nthat the statistical properties of both hexagonal and square lattices can be\ndescribed by an effective temperature based on the magnetostatic energy of the\narrays. This temperature has predictive power for the moment configurations and\nis intimately related to how the moments are driven by an oscillating external\nfield.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of the Coarse-Graining Master Equation: We study the coarse-graining approach to derive a generator for the evolution\nof an open quantum system over a finite time interval. The approach does not\nrequire a secular approximation but nevertheless generally leads to a\nLindblad-Gorini-Kossakowski-Sudarshan generator. By combining the formalism\nwith Full Counting Statistics, we can demonstrate a consistent thermodynamic\nframework, once the switching work required for the coupling and decoupling\nwith the reservoir is included. Particularly, we can write the second law in\nstandard form, with the only difference that heat currents must be defined with\nrespect to the reservoir. We exemplify our findings with simple but pedagogical\nexamples.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Monte Carlo study of an anisotropic Ising multilayer with\n  antiferromagnetic interlayer couplings: We present a Monte Carlo study of the magnetic properties of an Ising\nmultilayer ferrimagnet. The system consists of two kinds of non-equivalent\nplanes, one of which is site-diluted. All intralayer couplings are\nferromagnetic. The different kinds of planes are stacked alternately and the\ninterlayer couplings are antiferromagnetic. We perform the simulations using\nthe Wolff algorithm and employ multiple histogram reweighting and finite-size\nscaling methods to analyze the data with special emphasis on the study of\ncompensation phenomena. Compensation and critical temperatures of the system\nare obtained as functions of the Hamiltonian parameters and we present a\ndetailed discussion about the contribution of each parameter to the presence or\nabsence of the compensation effect. A comparison is presented between our\nresults and those reported in the literature for the same model using the pair\napproximation. We also compare our results with those obtained through both the\npair approximation and Monte Carlo simulations for the bilayer system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuations of isolated and confined surface steps of monoatomic height: The temporal evolution of equilibrium fluctuations for surface steps of\nmonoatomic height is analyzed studying one-dimensional solid-on-solid models.\nUsing Monte Carlo simulations, fluctuations due to periphery-diffusion (PD) as\nwell as due to evaporation-condensation (EC) are considered, both for isolated\nsteps and steps confined by the presence of straight steps. For isolated steps,\nthe dependence of the characteristic power-laws, their exponents and\nprefactors, on temperature, slope, and curvature is elucidated, with the main\nemphasis on PD, taking into account finite-size effects. The entropic repulsion\ndue to a second straight step may lead, among others, to an interesting\ntransient power-law like growth of the fluctuations, for PD. Findings are\ncompared to results of previous Monte Carlo simulations and predictions based,\nmostly, on scaling arguments and Langevin theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous behavior of ideal Fermi gas below two dimensions: Normal behavior of the thermodynamic properties of a Fermi gas in $d>2$\ndimensions, integer or not, means monotonically increasing or decreasing of its\nspecific heat, chemical potential or isothermal sound velocity, all as\nfunctions of temperature. However, for $0<d<2$ dimensions these properties\ndevelop a ``hump'' (or ``trough'') which increases (or deepens) as $d\\to 0$.\nThough not the phase transition signaled by the sharp features (``cusp'' or\n``jump'') in those properties for the ideal Bose gas in $d>2$ (known as the\nBose-Einstein condensation), it is nevertheless an intriguing structural\nanomaly which we exhibit in detail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Freezing and clustering transitions for penetrable spheres: We consider a system of spherical particles interacting by means of a pair\npotential equal to a finite constant for interparticle distances smaller than\nthe sphere diameter and zero outside. The model may be a prototype for the\ninteraction between micelles in a solvent [C. Marquest and T. A. Witten, J.\nPhys. France 50, 1267 (1989)]. The phase diagram of these penetrable spheres is\ninvestigated using a combination of cell- and density functional theory for the\nsolid phase together with simulations for the fluid phase. The system displays\nunusual phase behavior due to the fact that, in the solid, the optimal\nconfiguration is achieved when certain fractions of lattice sites are occupied\nby more than one particle, a property that we call `clustering'. We find that\nfreezing from the fluid is followed, by increasing density, by a cascade of\nsecond-order, clustering transitions in the crystal.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum critical behavior of itinerant ferromagnets: We investigate the quantum phase transition of itinerant ferromagnets. It is\nshown that correlation effects in the underlying itinerant electron system lead\nto singularities in the order parameter field theory that result in an\neffective long-range interaction between the spin fluctuations. This\ninteraction turns out to be generically {\\em antiferromagnetic} for clean\nsystems. In disordered systems analogous correlation effects lead to even\nstronger singularities. The resulting long-range interaction is, however,\ngenerically ferromagnetic.\n  We discuss two possibilities for the ferromagnetic quantum phase transition.\nIn clean systems, the transition is generically of first order, as is\nexperimentally observed in MnSi. However, under certain conditions the\ntransition may be continuous with non-mean field critical behavior. In\ndisordered systems, one finds a very rich phase diagram showing first order and\ncontinuous phase transitions and several multicritical points.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Information Geometry of q-Gaussian Densities and Behaviors of Solutions\n  to Related Diffusion Equations: This paper presents new geometric aspects of the behaviors of solutions to\nthe porous medium equation (PME) and its associated equation. First we discuss\nthe Legendre structure with information geometry on the manifold of generalized\nexponential densities. Next by considering such a structure in particular on\nthe q-Gaussian densities, we derive several physically and geometrically\ninteresting properties of the solutions. They include, for example,\ncharacterization of the moment-conserving projection of a solution, evaluation\nof evolutional velocities of the second moments and the convergence rate to the\nmanifold in terms of the geodesic curves, divergence and so on.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of Granular Stratification: Spontaneous stratification in granular mixtures has been recently reported by\nH. A. Makse et al. [Nature 386, 379 (1997)]. Here we study experimentally the\ndynamical processes leading to spontaneous stratification. Using a high-speed\nvideo camera, we study a rapid flow regime where the rolling grains size\nsegregate during the avalanche. We characterize the dynamical process of\nstratification by measuring all relevant quantities: the velocity of the\nrolling grains, the velocity of the kink, the wavelength of the layers, the\nrate of collision between rolling and static grains, and all the angles of\nrepose characterizing the mixture. The wavelength of the layers behaves\nlinearly with the thickness of the layer of rolling grains (i.e., with the flow\nrate), in agreement with theoretical predictions. The velocity profile of the\ngrains in the rolling phase is a linear function of the position of the grains\nalong the moving layer. We also find that the speed of the upward-moving kink\nhas the same value as the mean speed of the downward-moving grains. We measure\nthe shape and size of the kink, as well as the profiles of the rolling and\nstatic phases of grains, and find agreement with recent theoretical\npredictions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mapping of the unoccupied states and relevant bosonic modes via the time\n  dependent momentum distribution: The unoccupied states of complex materials are difficult to measure, yet play\na key role in determining their properties. We propose a technique that can\nmeasure the unoccupied states, called time-resolved Compton scattering, which\nmeasures the time-dependent momentum distribution (TDMD). Using a\nnon-equilibrium Keldysh formalism, we study the TDMD for electrons coupled to a\nlattice in a pump-probe setup. We find a direct relation between temporal\noscillations in the TDMD and the dispersion of the underlying unoccupied\nstates, suggesting that both can be measured by time-resolved Compton\nscattering. We demonstrate the experimental feasibility by applying the method\nto a model of MgB$_2$ with realistic material parameters.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Preparation and relaxation of very stable glassy states of a simulated\n  liquid: We prepare metastable glassy states in a model glass-former made of\nLennard-Jones particles by sampling biased ensembles of trajectories with low\ndynamical activity. These trajectories form an inactive dynamical phase whose\n`fast' vibrational degrees of freedom are maintained at thermal equilibrium by\ncontact with a heat bath, while the `slow' structural degrees of freedom are\nlocated in deep valleys of the energy landscape. We examine the relaxation to\nequilibrium and the vibrational properties of these metastable states. The\nglassy states we prepare by our trajectory sampling method are very stable to\nthermal fluctuations and also more mechanically rigid than low-temperature\nequilibrated configurations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Third-harmonic exponent in three-dimensional N-vector models: We compute the crossover exponent associated with the spin-3 operator in\nthree-dimensional O(N) models. A six-loop field-theoretical calculation in the\nfixed-dimension approach gives $\\phi_3 = 0.601(10)$ for the experimentally\nrelevant case N=2 (XY model). The corresponding exponent $\\beta_3 = 1.413(10)$\nis compared with the experimental estimates obtained in materials undergoing a\nnormal-incommensurate structural transition and in liquid crystals at the\nsmectic-A--hexatic-B phase transition, finding good agreement.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Milestoning estimators of dissipation in systems observed at a coarse\n  resolution: When ignorance is truly bliss: Many non-equilibrium, active processes are observed at a coarse-grained\nlevel, where different microscopic configurations are projected onto the same\nobservable state. Such \"lumped\" observables display memory, and in many cases\nthe irreversible character of the underlying microscopic dynamics becomes\nblurred, e.g., when the projection hides dissipative cycles. As a result, the\nobservations appear less irreversible, and it is very challenging to infer the\ndegree of broken time-reversal symmetry. Here we show, contrary to intuition,\nthat by ignoring parts of the already coarse-grained state space we may -- via\na process called milestoning -- improve entropy-production estimates.\nMilestoning systematically renders observations \"closer to underlying\nmicroscopic dynamics\" and thereby improves thermodynamic inference from lumped\ndata assuming a given range of memory. Moreover, whereas the correct general\nphysical definition of time-reversal in the presence of memory remains unknown,\nwe here show by means of systematic, physically relevant examples that at least\nfor semi-Markov processes of first and second order, waiting-time contributions\narising from adopting a naive Markovian definition of time-reversal generally\nmust be discarded.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal threshold for the dynamical behavior of lattice systems with\n  long-range interactions: Dynamical properties of lattice systems with long-range pair interactions,\ndecaying like 1/r^{\\alpha} with the distance r, are investigated, in particular\nthe time scales governing the relaxation to equilibrium. Upon varying the\ninteraction range \\alpha, we find evidence for the existence of a threshold at\n\\alpha=d/2, dependent on the spatial dimension d, at which the relaxation\nbehavior changes qualitatively and the corresponding scaling exponents switch\nto a different regime. Based on analytical as well as numerical observations in\nsystems of vastly differing nature, ranging from quantum to classical, from\nferromagnetic to antiferromagnetic, and including a variety of lattice\nstructures, we conjecture this threshold and some of its characteristic\nproperties to be universal.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spontaneous symmetry breaking and Nambu-Goldstone modes in dissipative\n  systems: We discuss spontaneous breaking of internal symmetry and its Nambu-Goldstone\n(NG) modes in dissipative systems. We find that there exist two types of NG\nmodes in dissipative systems corresponding to type-A and type-B NG modes in\nHamiltonian systems. To demonstrate the symmetry breaking, we consider a $O(N)$\nscalar model obeying a Fokker-Planck equation. We show that the type-A NG modes\nin the dissipative system are diffusive modes, while they are propagating modes\nin Hamiltonian systems. We point out that this difference is caused by the\nexistence of two types of Noether charges, $Q_R^\\alpha$ and $Q_A^\\alpha$:\n$Q_R^\\alpha$ are symmetry generators of Hamiltonian systems, which are not\nconserved in dissipative systems. $Q_A^\\alpha$ are symmetry generators of\ndissipative systems described by the Fokker-Planck equation, which are\nconserved. We find that the NG modes are propagating modes if $Q_R^\\alpha$ are\nconserved, while those are diffusive modes if they are not conserved. We also\nconsider a $SU(2)\\times U(1)$ scalar model with a chemical potential to discuss\nthe type-B NG modes. We show that the type-B NG modes have a different\ndispersion relation from those in the Hamiltonian systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on ``Solution of Classical Stochastic One-Dimensional Many-Body\n  Systems'': In a recent Letter, Bares and Mobilia proposed the method to find solutions\nof the stochastic evolution operator $H=H_0 + {\\gamma\\over L} H_1$ with a\nnon-trivial quartic term $H_1$. They claim, ``Because of the conservation of\nprobability, an analog of the Wick theorem applies and all multipoint\ncorrelation functions can be computed.'' Using the Wick theorem, they expressed\nthe density correlation functions as solutions of a closed set of\nintegro-differential equations.\n  In this Comment, however, we show that applicability of Wick theorem is\nrestricted to the case $\\gamma = 0$ only.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random Walk over Basins of Attraction to Construct Ising Energy\n  Landscapes: An efficient algorithm is developed to construct disconnectivity graphs by a\nrandom walk over basins of attraction. This algorithm can detect a large number\nof local minima, find energy barriers between them, and estimate local thermal\naverages over each basin of attraction. It is applied to the SK spin glass\nHamiltonian where existing methods have difficulties even for a moderate number\nof spins. Finite-size results are used to make predictions in the thermodynamic\nlimit that match theoretical approximations and recent findings on the free\nenergy landscapes of SK spin glasses.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Einstein relation and hydrodynamics of nonequilibrium mass transport\n  processes: We obtain hydrodynamic descriptions of a broad class of conserved-mass\ntransport processes on a ring. These processes are governed by chipping,\ndiffusion and coalescence of masses, where microscopic probability weights in\ntheir nonequilibrium steady states, having nontrivial correlations, are not\nknown. In these processes, we analytically calculate two transport\ncoefficients, the bulk-diffusion coefficient and the conductivity. We,\nremarkably, find that the two transport coefficients obey an equilibriumlike\nEinstein relation, although the microscopic dynamics does not satisfy detailed\nbalance condition. Using macroscopic fluctuation theory, we also show that\nprobability of density fluctuations obtained from the hydrodynamic description\nis in complete agreement with the same derived earlier in [Phys. Rev. E 93,\n062135 (2016)] using an additivity property.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Modelling quasicrystals at positive temperature: We consider a two-dimensional lattice model of equilibrium statistical\nmechanics, using nearest neighbor interactions based on the matching conditions\nfor an aperiodic set of 16 Wang tiles. This model has uncountably many ground\nstate configurations, all of which are nonperiodic. The question addressed in\nthis paper is whether nonperiodicity persists at low but positive temperature.\nWe present arguments, mostly numerical, that this is indeed the case. In\nparticular, we define an appropriate order parameter, prove that it is\nidentically zero at high temperatures, and show by Monte Carlo simulation that\nit is nonzero at low temperatures.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlation Effects in Ultracold Two-Dimensional Bose Gases: We study various properties of an ultracold two-dimensional (2D) Bose gas\nthat are beyond a mean-field description. We first derive the effective\ninteraction for such a system as realized in current experiments, which\nrequires the use of an energy dependent $T$-matrix. Using this result, we then\nsolve the mean-field equation of state of the modified Popov theory, and\ncompare it with the usual Hartree-Fock theory. We show that even though the\nformer theory does not suffer from infrared divergences in both the normal and\nsuperfluid phases, there is an unphysical density discontinuity close to the\nBerezinskii-Kosterlitz-Thouless transition. We then improve upon the mean-field\ndescription by using a renormalization group approach and show how the density\ndiscontinuity is resolved. The flow equations in two dimensions, in particular,\nof the symmetry-broken phase, already contain some unique features pertinent to\nthe 2D XY model, even though vortices have not been included explicitly. We\nalso compute various many-body correlators, and show that correlation effects\nbeyond the Hartree-Fock theory are important already in the normal phase as\ncriticality is approached. We finally extend our results to the inhomogeneous\ncase of a trapped Bose gas using the local-density approximation and show that\nclose to criticality, the renormalization group approach is required for the\naccurate determination of the density profile.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nanowire reconstruction under external magnetic fields: We consider the different structures that a magnetic nanowire adsorbed on a\nsurface may adopt under the influence of external magnetic or electric fields.\nFirst, we propose a theoretical framework based on an Ising-like extension of\nthe 1D Frenkel-Kontorova model, which is analysed in detail using the transfer\nmatrix formalism, determining a rich phase diagram displaying structural\nreconstructions at finite fields and an antiferromagnetic-paramagnetic phase\ntransition of second order. Our conclusions are validated using ab initio\ncalculations with density functional theory, paving the way for the search of\nactual materials where this complex phenomenon can be observed in the\nlaboratory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum critical behaviors and decoherence of weakly coupled quantum\n  Ising models within an isolated global system: We discuss the quantum dynamics of an isolated composite system consisting of\nweakly interacting many-body subsystems. We focus on one of the subsystems, S,\nand study the dependence of its quantum correlations and decoherence rate on\nthe state of the weakly-coupled complementary part E, which represents the\nenvironment. As a theoretical laboratory, we consider a composite system made\nof two stacked quantum Ising chains, locally and homogeneously weakly coupled.\nOne of the chains is identified with the subsystem S under scrutiny, and the\nother one with the environment E. We investigate the behavior of S at\nequilibrium, when the global system is in its ground state, and under\nout-of-equilibrium conditions, when the global system evolves unitarily after a\nsoft quench of the coupling between S and E. When S develops quantum critical\ncorrelations in the weak-coupling regime, the associated scaling behavior\ncrucially depends on the quantum state of E whether it is characterized by\nshort-range correlations (analogous to those characterizing disordered phases\nin closed systems), algebraically decaying correlations (typical of critical\nsystems), or long-range correlations (typical of magnetized ordered phases). In\nparticular, different scaling behaviors, depending on the state of E, are\nobserved for the decoherence of the subsystem S, as demonstrated by the\ndifferent power-law divergences of the decoherence susceptibility that\nquantifies the sensitivity of the coherence to the interaction with E.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuations and correlations in hexagonal optical patterns: We analyze the influence of noise in transverse hexagonal patterns in\nnonlinear Kerr cavities. The near field fluctuations are determined by the\nneutrally stable Goldstone modes associated to translational invariance and by\nthe weakly damped soft modes. However these modes do not contribute to the far\nfield intensity fluctuations which are dominated by damped perturbations with\nthe same wave vectors than the pattern. We find strong correlations between the\nintensity fluctuations of any arbitrary pair of wave vectors of the pattern.\nCorrelation between pairs forming 120 degrees is larger than between pairs\nforming 180 degrees, contrary to what a naive interpretation of emission in\nterms of twin photons would suggest.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Knot probabilities in equilateral random polygons: We consider the probability of knotting in equilateral random polygons in\nEuclidean 3-dimensional space, which model, for instance, random polymers.\nResults from an extensive Monte Carlo dataset of random polygons indicate a\nuniversal scaling formula for the knotting probability with the number of\nedges. This scaling formula involves an exponential function, independent of\nknot type, with a power law factor that depends on the number of prime\ncomponents of the knot. The unknot, appearing as a composite knot with zero\ncomponents, scales with a small negative power law, contrasting with previous\nstudies that indicated a purely exponential scaling. The methodology\nincorporates several improvements over previous investigations: our random\npolygon data set is generated using a fast, unbiased algorithm, and knotting is\ndetected using an optimised set of knot invariants based on the Alexander\npolynomial.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The effect of disorder on the hierarchical modularity in complex systems: We consider a system hierarchically modular, if besides its hierarchical\nstructure it shows a sequence of scale separations from the point of view of\nsome functionality or property. Starting from regular, deterministic objects\nlike the Vicsek snowflake or the deterministic scale free network by Ravasz et\nal. we first characterize the hierarchical modularity by the periodicity of\nsome properties on a logarithmic scale indicating separation of scales. Then we\nintroduce randomness by keeping the scale freeness and other important\ncharacteristics of the objects and monitor the changes in the modularity. In\nthe presented examples sufficient amount of randomness destroys hierarchical\nmodularity. Our findings suggest that the experimentally observed hierarchical\nmodularity in systems with algebraically decaying clustering coefficients\nindicates a limited level of randomness.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Generalized Entropies and Statistical Mechanics: We consider the problem of defining free energy and other thermodynamic\nfunctions when the entropy is given as a general function of the probablity\ndistribution, including that for non extensive forms. We find that the free\nenergy, which is central to the determination of all other quantities, can be\nobtained uniquely numerically ebven when it is the root of a transcendental\nequation. In particular we study the cases for Tsallis form and a new form\nproposed by us recently. We compare the free energy, the internal energy and\nthe specific heat of a simple system two energy states for each of these forms.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Minimal entropy production in the presence of anisotropic fluctuations: Anisotropy in temperature, chemical potential, or ion concentration, provides\nthe fuel that feeds dynamical processes that sustain life. At the same time,\nanisotropy is a root cause of incurred losses manifested as entropy production.\nIn this work we consider a rudimentary model of an overdamped stochastic\nthermodynamic system in an anisotropic temperature heat bath, and study minimum\nentropy production when driving the system between thermodynamic states in\nfinite time. While entropy production in isotropic temperature environments can\nbe expressed in terms of the length (in the Wasserstein-2 metric) traversed by\nthe thermodynamic state of the system, anisotropy complicates substantially the\nmechanism of entropy production since, besides dissipation, seepage of energy\nbetween ambient anisotropic heat sources by way of the system dynamics is often\na major contributing factor. A key result of the paper is to show that in the\npresence of anisotropy, minimization of entropy production can once again be\nexpressed via a modified Optimal Mass Transport (OMT) problem. However, in\ncontrast to the isotropic situation that leads to a classical OMT problem and a\nWasserstein length, entropy production may not be identically zero when the\nthermodynamic state remains unchanged (unless one has control over\nnon-conservative forces); this is due to the fact that maintaining a\nNon-Equilibrium Steady-State (NESS) incurs an intrinsic entropic cost that can\nbe traced back to a seepage of heat between heat baths. As alluded to, NESSs\nrepresent hallmarks of life, since living matter by necessity operates far from\nequilibrium. Therefore, the question studied herein, to characterize minimal\nentropy production in anisotropic environments, appears of central importance\nin biological processes and on how such processes may have evolved to optimize\nfor available usage of resources.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metastability for a stochastic dynamics with a parallel heat bath\n  updating rule: We consider the problem of metastability for a stochastic dynamics with a\nparallel updating rule with single spin rates equal to those of the heat bath\nfor the Ising nearest neighbors interaction. We study the exit from the\nmetastable phase, we describe the typical exit path and evaluate the exit time.\nWe prove that the phenomenology of metastability is different from the one\nobserved in the case of the serial implementation of the heat bath dynamics. In\nparticular we prove that an intermediate chessboard phase appears during the\nexcursion from the minus metastable phase toward the plus stable phase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exploring Conformational Landscapes Along Anharmonic Low-Frequency\n  Vibrations: We aim to automatize the identification of collective variables to simplify\nand speed up enhanced sampling simulations of conformational dynamics in\nbiomolecules. We focus on anharmonic low-frequency vibrations that exhibit\nfluctuations on timescales faster than conformational transitions but describe\na path of least resistance towards structural change. A key challenge is that\nharmonic approximations are ill-suited to characterize these vibrations, which\nare observed at far-infrared frequencies and are easily excited by thermal\ncollisions at room temperature.\n  Here, we approached this problem with a frequency-selective anharmonic\n(FRESEAN) mode analysis that does not rely on harmonic approximations and\nsuccessfully isolates anharmonic low-frequency vibrations from short molecular\ndynamics simulation trajectories. We applied FRESEAN mode analysis to\nsimulations of alanine dipeptide, a common test system for enhanced sampling\nsimulation protocols, and compare the performance of isolated low-frequency\nvibrations to conventional user-defined collective variables (here backbone\ndihedral angles) in enhanced sampling simulations.\n  The comparison shows that enhanced sampling along anharmonic low-frequency\nvibrations not only reproduces known conformational dynamics but can even\nfurther improve sampling of slow transitions compared to user-defined\ncollective variables. Notably, free energy surfaces spanned by low-frequency\nanharmonic vibrational modes exhibit lower barriers associated with\nconformational transitions relative to representations in backbone dihedral\nspace. We thus conclude that anharmonic low-frequency vibrations provide a\npromising path for highly effective and fully automated enhanced sampling\nsimulations of conformational dynamics in biomolecules.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Forward-Flux Sampling with Jumpy Order Parameters: Forward-flux sampling (FFS) is a path sampling technique that has gained\nincreased popularity in recent years, and has been used to compute rates of\nrare event phenomena such as crystallization, condensation, hydrophobic\nevaporation, DNA hybridization and protein folding. The popularity of FFS is\nnot only due to its ease of implementation, but also because it is not very\nsensitive to the particular choice of an order parameter. The order parameter\nutilized in conventional FFS, however, still needs to satisfy a stringent\nsmoothness criterion in order to assure sequential crossing of FFS milestones.\nThis condition is usually violated for order parameters utilized for describing\naggregation phenomena such as crystallization. Here, we present a generalized\nFFS algorithm for which this smoothness criterion is no longer necessary, and\napply it to compute homogeneous crystal nucleation rates in several systems.\nOur numerical tests reveal that conventional FFS can sometimes underestimate\nthe nucleation rate by several orders of magnitude.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extreme event statistics of daily rainfall: Dynamical systems approach: We analyse the probability densities of daily rainfall amounts at a variety\nof locations on the Earth. The observed distributions of the amount of rainfall\nfit well to a q-exponential distribution with exponent q close to q=1.3. We\ndiscuss possible reasons for the emergence of this power law. On the contrary,\nthe waiting time distribution between rainy days is observed to follow a\nnear-exponential distribution. A careful investigation shows that a\nq-exponential with q=1.05 yields actually the best fit of the data. A Poisson\nprocess where the rate fluctuates slightly in a superstatistical way is\ndiscussed as a possible model for this. We discuss the extreme value statistics\nfor extreme daily rainfall, which can potentially lead to flooding. This is\ndescribed by Frechet distributions as the corresponding distributions of the\namount of daily rainfall decay with a power law. On the other hand, looking at\nextreme event statistics of waiting times between rainy days (leading to\ndroughts for very long dry periods) we obtain from the observed\nnear-exponential decay of waiting times an extreme event statistics close to\nGumbel distributions. We discuss superstatistical dynamical systems as simple\nmodels in this context.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the typical properties of inverse problems in statistical mechanics: In this work we consider the problem of extracting a set of interaction\nparameters from an high-dimensional dataset describing T independent\nconfigurations of a complex system composed of N binary units. This problem is\nformulated in the language of statistical mechanics as the problem of finding a\nfamily of couplings compatible with a corresponding set of empirical\nobservables in the limit of large N. We focus on the typical properties of its\nsolutions and highlight the possible spurious features which are associated\nwith this regime (model condensation, degenerate representations of data,\ncriticality of the inferred model). We present a class of models (complete\nmodels) for which the analytical solution of this inverse problem can be\nobtained, allowing us to characterize in this context the notion of stability\nand locality. We clarify the geometric interpretation of some of those aspects\nby using results of differential geometry, which provides means to quantify\nconsistency, stability and criticality in the inverse problem. In order to\nprovide simple illustrative examples of these concepts we finally apply these\nideas to datasets describing two stochastic processes (simulated realizations\nof a Hawkes point-process and a set of time-series describing financial\ntransactions in a real market).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Counter-ion density profile around charged cylinders: the\n  strong-coupling needle limit: Charged rod-like polymers are not able to bind all their neutralizing\ncounter-ions: a fraction of them evaporates while the others are said to be\ncondensed. We study here counter-ion condensation and its ramifications, both\nnumerically by means of Monte Carlo simulations employing a previously\nintroduced powerful logarithmic sampling of radial coordinates, and\nanalytically, with special emphasis on the strong-coupling regime. We focus on\nthe thin rod, or needle limit, that is naturally reached under strong coulombic\ncouplings, where the typical inter-particle spacing $a'$ along the rod is much\nlarger than its radius R. This regime is complementary and opposite to the\nsimpler thick rod case where $a'\\ll R$. We show that due account of counter-ion\nevaporation, a universal phenomenon in the sense that it occurs in the same\nclothing for both weakly and strongly coupled systems, allows to obtain\nexcellent agreement between the numerical simulations and the strong-coupling\ncalculations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Monte Carlo Results for Projected Self-Avoiding Polygons: A\n  Two-dimensional Model for Knotted Polymers: We introduce a two-dimensional lattice model for the description of knotted\npolymer rings. A polymer configuration is modeled by a closed polygon drawn on\nthe square diagonal lattice, with possible crossings describing pairs of\nstrands of polymer passing on top of each other. Each polygon configuration can\nbe viewed as the two- dimensional projection of a particular knot. We study\nnumerically the statistics of large polygons with a fixed knot type, using a\ngeneralization of the BFACF algorithm for self-avoiding walks. This new\nalgorithm incorporates both the displacement of crossings and the three types\nof Reidemeister transformations preserving the knot topology. Its ergodicity\nwithin a fixed knot type is not proven here rigorously but strong arguments in\nfavor of this ergodicity are given together with a tentative sketch of proof.\nAssuming this ergodicity, we obtain numerically the following results for the\nstatistics of knotted polygons: In the limit of a low crossing fugacity, we\nfind a localization along the polygon of all the primary factors forming the\nknot. Increasing the crossing fugacity gives rise to a transition from a\nself-avoiding walk to a branched polymer behavior.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Construction of the factorized steady state distribution in models of\n  mass transport: For a class of one-dimensional mass transport models we present a simple and\ndirect test on the chipping functions, which define the probabilities for mass\nto be transferred to neighbouring sites, to determine whether the stationary\ndistribution is factorized. In cases where the answer is affirmative, we\nprovide an explicit method for constructing the single-site weight function. As\nan illustration of the power of this approach, previously known results on the\nZero-range process and Asymmetric random average process are recovered in a few\nlines. We also construct new models, namely a generalized Zero-range process\nand a binomial chipping model, which have factorized steady states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Large Deviations of Convex Hulls of the \"True\" Self-Avoiding Random Walk: We study the distribution of the area and perimeter of the convex hull of the\n\"true\" self-avoiding random walk in a plane. Using a Markov chain Monte Carlo\nsampling method, we obtain the distributions also in their far tails, down to\nprobabilities like $10^{-800}$. This enables us to test previous conjectures\nregarding the scaling of the distribution and the large-deviation rate function\n$\\Phi$. In previous studies, e.g., for standard random walks, the whole\ndistribution was governed by the Flory exponent $\\nu$. We confirm this in the\npresent study by considering expected logarithmic corrections. On the other\nhand, the behavior of the rate function deviates from the expected form. For\nthis exception we give a qualitative reasoning.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Boltzmann's entropy during free expansion of an interacting ideal gas: In this work we study the evolution of Boltzmann's entropy in the context of\nfree expansion of a one dimensional interacting gas inside a box. Boltzmann's\nentropy is defined for single microstates and is given by the phase-space\nvolume occupied by microstates with the same value of macrovariables which are\ncoarse-grained physical observables. We demonstrate the idea of typicality in\nthe growth of the Boltzmann's entropy for two choices of macro-variables -- the\nsingle particle phase space distribution and the hydrodynamic fields. Due to\nthe presence of interaction, the growth curves for both these entropies are\nobserved to converge to a monotonically increasing limiting curve, on taking\nthe appropriate order of limits, of large system size and small coarse graining\nscale. Moreover, we observe that the limiting growth curves for the two choices\nof entropies are identical as implied by local thermal equilibrium. We also\ndiscuss issues related to finite size and finite coarse gaining scale which\nlead interesting features such as oscillations in the entropy growth curve. We\nalso discuss shocks observed in the hydrodynamic fields.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Levy Flights in Inhomogeneous Media: We investigate the impact of external periodic potentials on superdiffusive\nrandom walks known as Levy flights and show that even strongly superdiffusive\ntransport is substantially affected by the external field. Unlike ordinary\nrandom walks, Levy flights are surprisingly sensitive to the shape of the\npotential while their asymptotic behavior ceases to depend on the Levy index\n$\\mu $. Our analysis is based on a novel generalization of the Fokker-Planck\nequation suitable for systems in thermal equilibrium. Thus, the results\npresented are applicable to the large class of situations in which\nsuperdiffusion is caused by topological complexity, such as diffusion on folded\npolymers and scale-free networks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Generalized Theory of Landau Damping: Collisionless damping of electrical waves in plasma is investigated in the\nframe of the classical formulation of the problem. The new principle of\nregularization of the singular integral is used. The exact solution of the\ncorresponding dispersion equation is obtained. The results of calculations lead\nto existence of discrete spectrum of frequencies and discrete spectrum of\ndispersion curves. Analytical results are in good coincidence with results of\ndirect mathematical experiments. Key words: Foundations of the theory of\ntransport processes and statistical physics; Boltzmann physical kinetics;\ndamping of plasma waves, linear theory of wave`s propagation PACS: 67.55.Fa,\n67.55.Hc",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An axiomatic characterization of a two-parameter extended relative\n  entropy: The uniqueness theorem for a two-parameter extended relative entropy is\nproven. This result extends our previous one, the uniqueness theorem for a\none-parameter extended relative entropy, to a two-parameter case. In addition,\nthe properties of a two-parameter extended relative entropy are studied.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dominance of extreme statistics in a prototype many-body Brownian\n  ratchet: Many forms of cell motility rely on Brownian ratchet mechanisms that involve\nmultiple stochastic processes. We present a computational and theoretical study\nof the nonequilibrium statistical dynamics of such a many-body ratchet, in the\nspecific form of a growing polymer gel that pushes a diffusing obstacle. We\nfind that oft-neglected correlations among constituent filaments impact\nsteady-state kinetics and significantly deplete the gel's density within\nmolecular distances of its leading edge. These behaviors are captured\nquantitatively by a self-consistent theory for extreme fluctuations in\nfilaments' spatial distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nematic - Isotropic Transition in Porous Media - a Monte Carlo Study: We propose a lattice model to simulate the influence of porous medium on the\nNematic - Isotropic transition of liquid crystal confined to the pores. The\neffects of pore size and pore connectivity are modelled through a disorder\nparameter. Monte Carlo calculations based on the model leads to results that\ncompare well with experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Worm Algorithm for Two-Dimensional Spin Glasses: A worm algorithm is proposed for the two-dimensional spin glasses. The method\nis based on a low-temperature expansion of the partition function. The\nlow-temperature configurations of the spin glass on square lattice can be\nviewed as strings connecting pairs of frustrated plaquettes. The worm algorithm\ndirectly manipulates these strings. It is shown that the worm algorithm is as\nefficient as any other types of cluster or replica-exchange algorithms. The\nworm algorithm is even more efficient if free boundary conditions are used. We\nobtain accurate low-temperature specific heat data consistent with a form c =\nT^{-2} exp(-2J/(k_BT)), where T is temperature and J is coupling constant, for\nthe +/-J two-dimensional spin glass.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Variation along liquid isomorphs of the driving force for\n  crystallization: We investigate the variation of the driving force for crystallization of a\nsupercooled liquid along isomorphs, curves along which structure and dynamics\nare invariant. The variation is weak, and can be predicted accurately for the\nLennard-Jones fluid using a recently developed formalism and data at a\nreference temperature. More general analysis allows interpretation of\nexperimental data for molecular liquids such as dimethyl phthalate and\nindomethacin, and suggests that the isomorph scaling exponent $\\gamma$ in these\ncases is an increasing function of density, although this cannot be seen in\nmeasurements of viscosity or relaxation time.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on ``Deterministic equations of motion and phase ordering\n  dynamics'': Zheng [Phys. Rev. E {\\bf 61}, 153 (2000), cond-mat/9909324] claims that phase\nordering dynamics in the microcanonical $\\phi^4$ model displays unusual scaling\nlaws. We show here, performing more careful numerical investigations, that\nZheng only observed transient dynamics mostly due to the corrections to scaling\nintroduced by lattice effects, and that Ising-like (model A) phase ordering\nactually takes place at late times. Moreover, we argue that energy conservation\nmanifests itself in different corrections to scaling.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anisotropies of the Hamiltonian and the Wave Function: Inversion\n  Phenomena in Quantum Spin Chains: We investigate the inversion phenomenon between the XXZ anisotropies of the\nHamiltonian and the wave function in quantum spin chains, mainly focusing on\nthe S=1/2 trimerized XXZ model with the next-nearest-neighbor interactions. We\nhave obtained the ground-state phase diagram by use of the degenerate\nperturbation theory and the level spectroscopy analysis of the numerical data\ncalculated by the Lanczos method. In some parameter regions, the spin-fluid is\nrealized for the Ising-like anisotropy, and the Neel state for the XY-like\nanisotropy, against the ordinary situation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Instanton Approach to Large $N$ Harish-Chandra-Itzykson-Zuber Integrals: We reconsider the large $N$ asymptotics of Harish-Chandra-Itzykson-Zuber\nintegrals. We provide, using Dyson's Brownian motion and the method of\ninstantons, an alternative, transparent derivation of the Matytsin formalism\nfor the unitary case. Our method is easily generalized to the orthogonal and\nsymplectic ensembles. We obtain an explicit solution of Matytsin's equations in\nthe case of Wigner matrices, as well as a general expansion method in the\ndilute limit, when the spectrum of eigenvalues spreads over very wide regions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Resonant diffusion on solid surfaces: A new approach to Brownian motion of atomic clusters on solid surfaces is\ndeveloped. The main topic discussed is the dependence of the diffusion\ncoefficient on the fit between the surface static potential and the internal\ncluster configuration. It is shown this dependence is non-monotonous, which is\nthe essence of the so-called resonant diffusion. Assuming quicker inner motion\nof the cluster than its translation, adiabatic separation of these variables is\npossible and a relatively simple expression for the diffusion coefficient is\nobtained. In this way, the role of cluster vibrations is accounted for, thus\nleading to a more complex resonance in the cluster surface mobility.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous spin frustration enforced by a magnetoelastic coupling in the\n  mixed-spin Ising model on decorated planar lattices: The mixed spin-1/2 and spin-S Ising model on a decorated planar lattice\naccounting for lattice vibrations of decorating atoms is treated by making use\nof the canonical coordinate transformation, the decoration-iteration\ntransformation, and the harmonic approximation. It is shown that the\nmagnetoelastic coupling gives rise to an effective single-ion anisotropy and\nthree-site four-spin interaction, which are responsible for the anomalous spin\nfrustration of the decorating spins in virtue of a competition with the\nequilibrium nearest-neighbor exchange interaction between the nodal and\ndecorating spins. The ground-state and finite-temperature phase diagrams are\nconstructed for the particular case of the mixed spin-1/2 and spin-1 Ising\nmodel on a decorated square lattice for which thermal dependencies of the\nspontaneous magnetization and specific heat are also examined in detail. It is\nevidenced that a sufficiently strong magnetoelastic coupling leads to a\npeculiar coexistence of the antiferromagnetic long-range order of the nodal\nspins with the disorder of the decorating spins within the frustrated\nantiferromagnetic phase, which may also exhibit double reentrant phase\ntransitions. The investigated model displays a variety of temperature\ndependencies of the total specific heat, which may involve in its magnetic part\none or two logarithmic divergences apart from one or two additional round\nmaxima superimposed on a standard thermal dependence of the lattice part of the\nspecific heat.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dissolution in a field: We study the dissolution of a solid by continuous injection of reactive\n``acid'' particles at a single point, with the reactive particles undergoing\nbiased diffusion in the dissolved region. When acid encounters the substrate\nmaterial, both an acid particle and a unit of the material disappear. We find\nthat the lengths of the dissolved cavity parallel and perpendicular to the bias\ngrow as t^{2/(d+1)} and t^{1/(d+1)}, respectively, in d-dimensions, while the\nnumber of reactive particles within the cavity grows as t^{2/(d+1)}. We also\nobtain the exact density profile of the reactive particles and the relation\nbetween this profile and the motion of the dissolution boundary. The extension\nto variable acid strength is also discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Fractional entropy in Fractal phase space: properties and\n  characterization: A two parameter generalization of Boltzmann-Gibbs-Shannon entropy based on\nnatural logarithm is introduced. The generalization of the Shannon-Kinchinn\naxioms corresponding to the two parameter entropy is proposed and verified. We\npresent the relative entropy, Jensen-Shannon divergence measure and check their\nproperties. The Fisher information measure, relative Fisher information and the\nJensen-Fisher information corresponding to this entropy are also derived. The\ncanonical distribution maximizing this entropy is derived and is found to be in\nterms of the Lambert's W function. Also the Lesche stability and the\nthermodynamic stability conditions are verified. Finally we propose a\ngeneralization of a complexity measure and apply it to a two level system and a\nsystem obeying exponential distribution. The results are compared with the\ncorresponding ones obtained using a similar measure based on the Shannon\nentropy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dissipative Quantum Systems and the Heat Capacity Enigma: We present a detailed study of the quantum dissipative dynamics of a charged\nparticle in a magnetic field. Our focus of attention is the effect of\ndissipation on the low- and high-temperature behavior of the specific heat at\nconstant volume. After providing a brief overview of two distinct approaches to\nthe statistical mechanics of dissipative quantum systems, viz., the ensemble\napproach of Gibbs and the quantum Brownian motion approach due to Einstein, we\npresent exact analyses of the specific heat. While the low-temperature\nexpressions for the specific heat, based on the two approaches, are in\nconformity with power-law temperature-dependence, predicted by the third law of\nthermodynamics, and the high-temperature expressions are in agreement with the\nclassical equipartition theorem, there are surprising differences between the\ndependencies of the specific heat on different parameters in the theory, when\ncalculations are done from these two distinct methods. In particular, we find\npuzzling influences of boundary-confinement and the bath-induced spectral\ncutoff frequency. Further, when it comes to the issue of approach to\nequilibrium, based on the Einstein method, the way the asymptotic limit (time\ngoing to infinity) is taken, seems to assume significance.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A constrained stochastic state selection method applied to quantum spin\n  systems: We describe a further development of the stochastic state selection method,\nwhich is a kind of Monte Carlo method we have proposed in order to numerically\nstudy large quantum spin systems. In the stochastic state selection method we\nmake a sampling which is simultaneous for many states. This feature enables us\nto modify the method so that a number of given constraints are satisfied in\neach sampling. In this paper we discuss this modified stochastic state\nselection method that will be called the constrained stochastic state selection\nmethod in distinction from the previously proposed one (the conventional\nstochastic state selection method) in this paper. We argue that in virtue of\nthe constrained sampling some quantities obtained in each sampling become more\nreliable, i.e. their statistical fluctuations are less than those from the\nconventional stochastic state selection method. In numerical calculations of\nthe spin-1/2 quantum Heisenberg antiferromagnet on a 36-site triangular lattice\nwe explicitly show that data errors in our estimation of the ground state\nenergy are reduced. Then we successfully evaluate several low-lying energy\neigenvalues of the model on a 48-site lattice. Our results support that this\nsystem can be described by the theory based on the spontaneous symmetry\nbreaking in the semiclassical Neel ordered antiferromagnet.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dissipative Effects in Nonlinear Klein-Gordon Dynamics: We consider dissipation in a recently proposed nonlinear Klein-Gordon\ndynamics that admits soliton-like solutions of the power-law form\n$e_q^{i(kx-wt)}$, involving the $q$-exponential function naturally arising\nwithin the nonextensive thermostatistics [$e_q^z \\equiv [1+(1-q)z]^{1/(1-q)}$,\nwith $e_1^z=e^z$]. These basic solutions behave like free particles, complying,\nfor all values of $q$, with the de Broglie-Einstein relations $p=\\hbar k$,\n$E=\\hbar \\omega$ and satisfying a dispersion law corresponding to the\nrelativistic energy-momentum relation $E^2 = c^2p^2 + m^2c^4 $. The dissipative\neffects explored here are described by an evolution equation that can be\nregarded as a nonlinear version of the celebrated telegraphists equation,\nunifying within one single theoretical framework the nonlinear Klein-Gordon\nequation, a nonlinear Schroedinger equation, and the power-law diffusion\n(porous media) equation. The associated dynamics exhibits physically appealing\nsoliton-like traveling solutions of the $q$-plane wave form with a complex\nfrequency $\\omega$ and a $q$-Gaussian square modulus profile.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Collective excitations of a periodic Bose condensate in the Wannier\n  representation: We study the dispersion relation of the excitations of a dilute Bose-Einstein\ncondensate confined in a periodic optical potential and its Bloch oscillations\nin an accelerated frame. The problem is reduced to one-dimensionality through a\nrenormalization of the s-wave scattering length and the solution of the\nBogolubov - de Gennes equations is formulated in terms of the appropriate\nWannier functions. Some exact properties of a periodic one-dimensional\ncondensate are easily demonstrated: (i) the lowest band at positive energy\nrefers to phase modulations of the condensate and has a linear dispersion\nrelation near the Brillouin zone centre; (ii) the higher bands arise from the\nsuperposition of localized excitations with definite phase relationships; and\n(iii) the wavenumber-dependent current under a constant force in the\nsemiclassical transport regime vanishes at the zone boundaries. Early results\nby J. C. Slater [Phys. Rev. 87, 807 (1952)] on a soluble problem in electron\nenergy bands are used to specify the conditions under which the Wannier\nfunctions may be approximated by on-site tight-binding orbitals of harmonic-\noscillator form. In this approximation the connections between the low-lying\nexcitations in a lattice and those in a harmonic well are easily visualized.\nAnalytic results are obtained in the tight-binding scheme and are illustrated\nwith simple numerical calculations for the dispersion relation and\nsemiclassical transport in the lowest energy band, at values of the system\nparameters which are relevant to experiment.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram of asymmetric Fermi gas across Feshbach resonance: We study the phase diagram of the dilute two-component Fermi gas at zero\ntemperature as a function of the polarization and coupling strength. We map out\nthe detailed phase separations between superfluid and normal states near the\nFeshbach resonance. We show that there are three different coexistence of\nsuperfluid and normal phases corresponding to phase separated states between:\n(I) the partially polarized superfluid and the fully polarized normal phases,\n(II) the unpolarized superfluid and the fully polarized normal phases and (III)\nthe unpolarized superfluid and the partially polarized normal phases from\nstrong-coupling BEC side to weak-coupling BCS side. For pairing between two\nspecies, we found this phase separation regime gets wider and moves toward the\nBEC side for the majority species are heavier but shifts to BCS side and\nbecomes narrow if they are lighter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A complete theory of low-energy phase diagrams for two-dimensional\n  turbulence steady states and equilibria: For the 2D Euler equations and related models of geophysical flows, minima of\nenergy--Casimir variational problems are stable steady states of the equations\n(Arnol'd theorems). The same variational problems also describe sets of\nstatistical equilibria of the equations. In this paper, we make use of\nLyapunov--Schmidt reduction in order to study the bifurcation diagrams for\nthese variational problems, in the limit of small energy or, equivalently, of\nsmall departure from quadratic Casimir functionals. We show a generic\noccurrence of phase transitions, either continuous or discontinuous. We derive\nthe type of phase transitions for any domain geometry and any model analogous\nto the 2D Euler equations. The bifurcations depend crucially on a_4, the\nquartic coefficient in the Taylor expansion of the Casimir functional around\nits minima. Note that a_4 can be related to the fourth moment of the vorticity\nin the statistical mechanics framework. A tricritical point (bifurcation from a\ncontinuous to a discontinuous phase transition) often occurs when a_4 changes\nsign. The bifurcations depend also on possible constraints on the variational\nproblems (circulation, energy). These results show that the analytical results\nobtained with quadratic Casimir functionals by several authors are non-generic\n(not robust to a small change in the parameters).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Energy fluctuations of a Brownian particle freely moving in a liquid: We study the statistical properties of the variation of the kinetic energy of\na spherical Brownian particle that freely moves in an incompressible fluid at\nconstant temperature. Based on the underdamped version of the generalized\nLangevin equation that includes the inertia of both the particle and the\ndisplaced fluid, we derive an analytical expression for the probability density\nfunction of such a kinetic energy variation during an arbitrary time interval,\nwhich exactly amounts to the energy exchanged with the fluid in absence of\nexternal forces. We also determine all the moments of this probability\ndistribution, which can be fully expressed in terms of a function that is\nproportional to the velocity autocorrelation function of the particle. The\nderived expressions are verified by means of numerical simulations of the\nstochastic motion of a particle in a viscous liquid with hydrodynamic backflow\nfor representative values of the time-scales of the system. Furthermore, we\nalso investigate the effect of viscoelasticity on the statistics of the kinetic\nenergy variation of the particle, which reveals the existence of three distinct\nregimes of the energy exchange process depending on the values of the\nviscoelastic parameters of the fluid.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Resonant Activation Phenomenon for Non-Markovian Potential-Fluctuation\n  Processes: We consider a generalization of the model by Doering and Gadoua to\nnon-Markovian potential-switching generated by arbitrary renewal processes. For\nthe Markovian switching process, we extend the original results by Doering and\nGadoua by giving a complete description of the absorption process. For all\nnon-Markovian processes having the first moment of the waiting time\ndistributions, we get qualitatively the same results as in the Markovian case.\nHowever, for distributions without the first moment, the mean first passage\ntime curves do not exhibit the resonant activation minimum. We thus come to the\nconjecture that the generic mechanism of the resonant activation fails for\nfluctuating processes widely deviating from Markovian.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Broken Ergodicity in classically chaotic spin systems: A one dimensional classically chaotic spin chain with asymmetric coupling and\ntwo different inter-spin interactions, nearest neighbors and all-to-all, has\nbeen considered. Depending on the interaction range, dynamical properties, as\nergodicity and chaoticity are strongly different. Indeed, even in presence of\nchaoticity, the model displays a lack of ergodicity only in presence of all to\nall interaction and below an energy threshold, that persists in the\nthermodynamical limit. Energy threshold can be found analytically and results\ncan be generalized for a generic XY model with asymmetric coupling.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Computer simulation of fluid phase transitions: The task of accurately locating fluid phase boundaries by means of computer\nsimulation is hampered by problems associated with sampling both coexisting\nphases in a single simulation run. We explain the physical background to these\nproblems and describe how they can be tackled using a synthesis of biased Monte\nCarlo sampling and histogram extrapolation methods, married to a standard fluid\nsimulation algorithm. It is demonstrated that the combined approach provides a\npowerful method for tracing fluid phase boundaries.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Efficiency fluctuations of small machines with unknown losses: The efficiency statistics of a small thermodynamic machine has been recently\ninvestigated assuming that the total dissipation was a linear combination of\ntwo currents: the input and output currents. Here, we relax this standard\nassumption and reconsider the question of the efficiency fluctuations for a\nmachine involving three different processes, first in full generality and\nsecond for two different examples. Since the third process may not be\nmeasurable and/or may decrease the machine efficiency, our motivation is to\nstudy the effect of unknown losses in small machines.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonequilibrium work statistics of an Aharonov-Bohm flux: We investigate the statistics of work performed on a noninteracting electron\ngas confined into a ring as a threaded magnetic field is turned on. For an\nelectron gas initially prepared in a grand canonical state it is demonstrated\nthat the Jarzynski equality continues to hold in this case, with the free\nenergy replaced by the grand potential. The work distribution displays a marked\ndependence on the temperature. While in the classical (high temperature)\nregime, the work probability density function follows a Gaussian distribution\nand the free energy difference entering the Jarzynski equality is null, the\nfree energy difference is finite in the quantum regime, and the work\nprobability distribution function becomes multimodal. We point out the\ndependence of the work statistics on the number of electrons composing the\nsystem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Preroughening transitions in a model for Si and Ge (001) type crystal\n  surfaces: The uniaxial structure of Si and Ge (001) facets leads to nontrivial\ntopological properties of steps and hence to interesting equilibrium phase\ntransitions. The disordered flat phase and the preroughening transition can be\nstabilized without the need for step-step interactions. A model describing this\nis studied numerically by transfer matrix type finite-size-scaling of interface\nfree energies. Its phase diagram contains a flat, rough, and disordered flat\nphase, separated by roughening and preroughening transition lines. Our estimate\nfor the location of the multicritical point where the preroughening line merges\nwith the roughening line, predicts that Si and Ge (001) undergo preroughening\ninduced simultaneous deconstruction transitions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "First-order phase transition in $1d$ Potts model with long-range\n  interactions: The first-order phase transition in the one-dimensional $q$-state Potts model\nwith long-range interactions decaying with distance as $1/r^{1+\\sigma}$ has\nbeen studied by Monte Carlo numerical simulations for $0 < \\sigma \\le 1$ and\ninteger values of $q > 2$. On the basis of finite-size scaling analysis of\ninterface free energy $\\Delta F_L$, specific heat and Binder's fourth order\ncumulant, we obtain the first-order transition which occurs for $\\sigma$ below\na threshold value $\\sigma_c(q)$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reply to the comment on \"Avalanches and Non-Gaussian Fluctuations of the\n  Global Velocity of Imbibition Fronts\": In [R. Planet, S. Santucci and J. Ortin, Phys. Rev. Lett. 102, 094502\n(2009)], we reported that both the size and duration of the global avalanches\nobserved during a forced imbibition process follow power law distributions with\ncut-offs. Following a comment by G. Pruessner, we discuss here the right\nprocedure to perfom, in order to extract reliable exponents characterising\nthose pdf's.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An exact solution of the inelastic Boltzmann equation for the Couette\n  flow with uniform heat flux: In the steady Couette flow of a granular gas the sign of the heat flux\ngradient is governed by the competition between viscous heating and inelastic\ncooling. We show from the Boltzmann equation for inelastic Maxwell particles\nthat a special class of states exists where the viscous heating and the\ninelastic cooling exactly compensate each other at every point, resulting in a\nuniform heat flux. In this state the (reduced) shear rate is enslaved to the\ncoefficient of restitution $\\alpha$, so that the only free parameter is the\n(reduced) thermal gradient $\\epsilon$. It turns out that the reduced moments of\norder $k$ are polynomials of degree $k-2$ in $\\epsilon$, with coefficients that\nare nonlinear functions of $\\alpha$. In particular, the rheological properties\n($k=2$) are independent of $\\epsilon$ and coincide exactly with those of the\nsimple shear flow. The heat flux ($k=3$) is linear in the thermal gradient\n(generalized Fourier's law), but with an effective thermal conductivity\ndiffering from the Navier--Stokes one. In addition, a heat flux component\nparallel to the flow velocity and normal to the thermal gradient exists. The\ntheoretical predictions are validated by comparison with direct Monte Carlo\nsimulations for the same model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Escape from bounded domains driven by multi-variate $\u03b1$-stable\n  noises: In this paper we provide an analysis of a mean first passage time problem of\na random walker subject to a bi-variate $\\alpha$-stable L\\'evy type noise from\na 2-dimensional disk. For an appropriate choice of parameters the mean first\npassage time reveals non-trivial, non-monotonous dependence on the stability\nindex $\\alpha$ describing jumps' length asymptotics both for spherical and\nCartesian L\\'evy flights. Finally, we study escape from $d$-dimensional\nhyper-sphere showing that $d$-dimensional escape process can be used to\ndiscriminate between various types of multi-variate $\\alpha$-stable noises,\nespecially spherical and Cartesian L\\'evy flights.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Cellular Automaton Model for the Traffic Flow in Bogota: In this work we propose a car cellular automaton model that reproduces the\nexperimental behavior of traffic flows in Bogot\\'a. Our model includes three\nelements: hysteresis between the acceleration and brake gaps, a delay time in\nthe acceleration, and an instantaneous brake. The parameters of our model were\nobtained from direct measurements inside a car on motorways in Bogot\\'a. Next,\nwe simulated with this model the flux-density fundamental diagram for a\nsingle-lane traffic road and compared it with experimental data. Our\nsimulations are in very good agreement with the experimental measurements, not\njust in the shape of the fundamental diagram, but also in the numerical values\nfor both the road capacity and the density of maximal flux. Our model\nreproduces, too, the qualitative behavior of shock waves. In addition, our work\nidentifies the periodic boundary conditions as the source of false peaks in the\nfundamental diagram, when short roads are simulated, that have been also found\nin previous works. The phase transition between free and congested traffic is\nalso investigated by computing both the relaxation time and the order\nparameter. Our work shows how different the traffic behavior from one city to\nanother can be, and how important is to determine the model parameters for each\ncity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universality in volume law entanglement of pure quantum states: A pure quantum state can fully describe thermal equilibrium as long as one\nfocuses on local observables. Thermodynamic entropy can also be recovered as\nthe entanglement entropy of small subsystems. When the size of the subsystem\nincreases, however, quantum correlations break the correspondence and cause a\ncorrection to this simple volume-law. To elucidate the size dependence of the\nentanglement entropy is of essential importance in linking quantum physics with\nthermodynamics, and in addressing recent experiments in ultra-cold atoms. Here\nwe derive an analytic formula of the entanglement entropy for a class of pure\nstates called cTPQ states representing thermal equilibrium. We further find\nthat our formula applies universally to any sufficiently scrambled pure states\nrepresenting thermal equilibrium, i.e., general energy eigenstates of\nnon-integrable models and states after quantum quenches. Our universal formula\ncan be exploited as a diagnostic of chaotic systems; we can distinguish\nintegrable models from chaotic ones and detect many-body localization with high\naccuracy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonequilibrium Dynamic Phase transitions in ferromagnetic systems: Some\n  new phenomena: The nonequilibrium dynamic phase transition in ferromagnetic systems is\nreviewed. Very recent results of dynamic transition in kinetic Ising model and\nthat in Heisenberg ferromagnet is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Levy flights and Levy -Schroedinger semigroups: We analyze two different confining mechanisms for L\\'{e}vy flights in the\npresence of external potentials. One of them is due to a conservative force in\nthe corresponding Langevin equation. Another is implemented by\nLevy-Schroedinger semigroups which induce so-called topological Levy processes\n(Levy flights with locally modified jump rates in the master equation). Given a\nstationary probability function (pdf) associated with the Langevin-based\nfractional Fokker-Planck equation, we demonstrate that generically there exists\na topological L\\'{e}vy process with the very same invariant pdf and in the\nreverse.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact Analysis of ESR Shift in the Spin-1/2 Heisenberg Antiferromagnetic\n  Chain: A systematic perturbation theory is developed for the ESR shift and is\napplied to the spin-1/2 Heisenberg chain. Using the Bethe ansatz technique, we\nexactly analyze the resonance shift in the first order of perturbative\nexpansion with respect to an anisotropic exchange interaction. Exact result for\nthe whole range of temperature and magnetic field, as well as asymptotic\nbehavior in the low-temperature limit are presented. The obtained g-shift\nstrongly depends on magnetic fields at low temperature, showing a significant\ndeviation from the previous classical result.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical phase diagram of the dc-driven underdamped Frenkel-Kontorova\n  chain: Multistep dynamical phase transition from the locked to the running state of\natoms in response to a dc external force is studied by MD simulations of the\ngeneralized Frenkel-Kontorova model in the underdamped limit. We show that the\nhierarchy of transition recently reported [Braun et al, Phys. Rev. Lett. 78,\n1295 (1997)] strongly depends on the value of the friction constant. A simple\nphenomenological explanation for the friction dependence of the various\ncritical forces separating intermediate regimes is given.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic and magnetic properties of the Ising model with\n  nonmagnetic impurities: We consider a system of Ising spins s=1/2 with nonmagnetic impurities with\ncharge associated with pseudospin S=1. The charge density is fixed pursuant to\nthe concentration n. Analysis of the thermodynamic properties in the\none-dimensional case showed the presence of so-called pseudotransitions at the\nboundaries between the staggered charge ordering and (anti)ferromagnetic\nordering. In the case of n=0, a \"1st order\" pseudotransition was discovered.\nThis type of pseudotransition is inherent for a series of other one-dimensional\nfrustrated models. However, for n != 0 we discovered a new type of \"2nd order\"\npseudotransition, which had not previously been observed in other systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Description of the dynamics of a random chain with rigid constraints in\n  the path integral framework: In this work we discuss the dynamics of a three dimensional chain which is\ndescribed by generalized nonlinear sigma model The formula of the probability\ndistribution of two topologically entangled chain is provided. The interesting\ncase of a chain which can form only discrete angles with respect to the\n$z-$axis is also presented.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Chiral exponents in frustrated spin models with noncollinear ordering: We compute the chiral critical exponents for the chiral transition in\nfrustrated two- and three-component spin systems with noncollinear order, such\nas stacked triangular antiferromagnets (STA). For this purpose, we calculate\nand analyze the six-loop field-theoretical expansion of the\nrenormalization-group function associated with the chiral operator. The results\nare in satisfactory agreement with those obtained in the recent experiment on\nthe XY STA CsMnBr_3 reported by V. P. Plakhty et al., Phys. Rev. Lett. 85, 3942\n(2000), providing further support for the continuous nature of the chiral\ntransition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of interacting hard rods on a lattice: We present an exact derivation of the isobaric partition function of lattice\nhard rods with arbitrary nearest neighbor interactions. Free energy and all\nthermodynamics functions are derived accordingly and they written in a form\nthat is a suitable for numerical implementation. As an application, we have\nconsidered lattice rods with pure hard core interactions, rods with long range\ngravitational attraction and finally a charged hard rods with charged\nboundaries (Bose gas), a model that is relevant for studying several phenomena\nsuch as charge regulation, ionic liquids near charged interfaces, and an array\nof charged smectic layers or lipid multilayers. In all cases, thermodynamic\nanalysis have been done numerically using the Broyden algorithm.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Rare events in stochastic processes with sub-exponential distributions\n  and the Big Jump principle: Rare events in stochastic processes with heavy-tailed distributions are\ncontrolled by the big jump principle, which states that a rare large\nfluctuation is produced by a single event and not by an accumulation of\ncoherent small deviations. The principle has been rigorously proved for sums of\nindependent and identically distributed random variables and it has recently\nbeen extended to more complex stochastic processes involving L\\'evy\ndistributions, such as L\\'evy walks and the L\\'evy-Lorentz gas, using an\neffective rate approach. We review the general rate formalism and we extend its\napplicability to continuous time random walks and to the Lorentz gas, both with\nstretched exponential distributions, further enlarging its applicability. We\nderive an analytic form for the probability density functions for rare events\nin the two models, which clarify specific properties of stretched exponentials.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Energy Landscape and Isotropic Tensile Strength of n-Alkane Glasses: Submission has been withdrawn due to copyright issues.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling of wetting and pre-wetting transitions on nano-patterned walls: We consider a nano-patterned planar wall consisting of a periodic array of\nstripes of width $L$, which are completely wet by liquid (contact angle\n$\\theta=0$), separated by regions of width $D$ which are completely dry\n(contact angle $\\theta=\\pi)$. Using microscopic Density Functional Theory we\nshow that in the presence of long-ranged dispersion forces, the wall-gas\ninterface undergoes a first-order wetting transition, at bulk coexistence, as\nthe separation $D$ is reduced to a value $D_w\\propto\\ln L$, induced by the\nbridging between neighboring liquid droplets. Associated with this is a line of\npre-wetting transitions occurring off coexistence. By varying the stripe width\n$L$ we show that the pre-wetting line shows universal scaling behaviour and\ndata collapse. This verifies predictions based on mesoscopic models for the\nscaling properties associated with finite-size effects at complete wetting\nincluding the logarithmic singular contribution to the surface free-energy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Capturing exponential variance using polynomial resources: applying\n  tensor networks to non-equilibrium stochastic processes: Estimating the expected value of an observable appearing in a non-equilibrium\nstochastic process usually involves sampling. If the observable's variance is\nhigh, many samples are required. In contrast, we show that performing the same\ntask without sampling, using tensor network compression, efficiently captures\nhigh variances in systems of various geometries and dimensions. We provide\nexamples for which matching the accuracy of our efficient method would require\na sample size scaling exponentially with system size. In particular, the high\nvariance observable $\\mathrm{e}^{-\\beta W}$, motivated by Jarzynski's equality,\nwith $W$ the work done quenching from equilibrium at inverse temperature\n$\\beta$, is exactly and efficiently captured by tensor networks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Swarming in disordered environments: The emergence of collective motion, also known as flocking or swarming, in\ngroups of moving individuals who orient themselves using only information from\ntheir neighbors is a very general phenomenon that is manifested at multiple\nspatial and temporal scales. Swarms that occur in natural environments\ntypically have to contend with spatial disorder such as obstacles that hinder\nan individual's motion or communication with neighbors. We study swarming\nparticles, with both aligning and repulsive interactions, on percolated\nnetworks where topological disorder is modeled by the random removal of lattice\nbonds. We find that an infinitesimal amount of disorder can completely suppress\nswarming for particles that utilize only alignment interactions suggesting that\nalignment alone is insufficient. The addition of repulsive forces between\nparticles produces a critical phase transition from a collectively moving swarm\nto a disordered gas-like state. This novel phase transition is entirely driven\nby the amount of topological disorder in the particles environment and displays\ncritical features that are similar to those of 2D percolation, while occurring\nat a value of disorder that is far from the percolation critical point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistics of interfacial fluctuations of radially growing clusters: The dynamics of fluctuating radially growing interfaces is approached using\nthe formalism of stochastic growth equations on growing domains. This framework\nreveals a number of dynamic features arising during surface growth. For fast\ngrowth, dilution, which spatially reorders the incoming matter, is responsible\nfor the transmission of correlations. Its effects include the erasing of memory\nwith respect to the initial condition, a partial attenuation of geometrically\noriginated instabilities, and the restoring of universality in some special\ncases in which the critical exponents depend on the parameters of the equation\nof motion. In this sense, dilution rends the dynamics more similar to the usual\none of planar systems. This fast growth regime is also characterized by the\nspatial decorrelation of the interface, which in the case of radially growing\ninterfaces naturally originates rapid roughening and scale dependent\nfractality, and suggests the advent of a self-similar fractal dimension. The\ncenter of mass fluctuations of growing clusters are also studied, and our\nanalysis suggests the possible non-applicability of usual scalings to the long\nrange surface fluctuations of the radial Eden model. In fact, our study points\nto the fact that this model belongs to a dilution-free universality class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Edwards-like statistical mechanical description of the parking lot model\n  for vibrated granular materials: We apply the statistical mechanical approach based on the ``flat'' measure\nproposed by Edwards and coworkers to the parking lot model, a model that\nreproduces the main features of the phenomenology of vibrated granular\nmaterials. We first build the flat measure for the case of vanishingly small\ntapping strength and then generalize the approach to finite tapping strengths\nby introducing a new ``thermodynamic'' parameter, the available volume for\nparticle insertion, in addition to the particle density. This description is\nable to take into account the various memory effects observed in vibrated\ngranular media. Although not exact, the approach gives a good description of\nthe behavior of the parking-lot model in the regime of slow compaction.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Aspects of Nos\u00e9 and Nos\u00e9-Hoover Dynamics Elucidated: Some paradoxical aspects of the Nos\\'e and Nos\\'e-Hoover dynamics of 1984 and\nDettmann's dynamics of 1996 are elucidated. Phase-space descriptions of\nthermostated harmonic oscillator dynamics can be simultaneously expanding,\nincompressible, or contracting, as is described here by a variety of three- and\nfour-dimensional phase-space models. These findings illustrate some surprising\nconsequences when Liouville's continuity equation is applied to Hamiltonian\nflows.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimized effective potential method with exact exchange and static RPA\n  correlation: We present a new density-functional method of the self-consistent\nelectronic-structure calculation which does not exploit any local density\napproximations (LDA). We use the exchange-correlation energy which consists of\nthe exact exchange and the correlation energies in the random-phase\napproximation. The functional derivative of the correlation energy with respect\nto the density is obtained within a static approximation. For transition\nmetals, it is shown that the correlation potential gives rise to a large\ncontribution which has the opposite sign to the exchange potential. Resulting\neigenvalue dispersions and the magnetic moments are very close to those of\nLDA's and the experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the phase transition in the sublattice TASEP with stochastic blockage: We revisit the defect-induced nonequilibrium phase transition from a largely\nhomogeneous free-flow phase to a phase-separated congested phase in the\nsublattice totally asymmetric simple exclusion process (TASEP) with local\ndeterministic bulk dynamics and a stochastic defect that mimicks a random\nblockage. Exact results are obtained for the compressibility and density\ncorrelations for a stationary grandcanonical ensemble given by the matrix\nproduct ansatz. At the critical density the static compressibility diverges\nwhile in the phase separated state above the critical point the compressibility\nvanishes due to strong non-local correlations. These correlations arise from a\nlong range effective interaction between particles that appears in the\nstationary state despite the locality of the microscopic dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Coevolution of agents and networks: Opinion spreading and community\n  disconnection: We study a stochastic model for the coevolution of a process of opinion\nformation in a population of agents and the network which underlies their\ninteraction. Interaction links can break when agents fail to reach an opinion\nagreement. The structure of the network and the distribution of opinions over\nthe population evolve towards a state where the population is divided into\ndisconnected communities whose agents share the same opinion. The statistical\nproperties of this final state vary considerably as the model parameters are\nchanged. Community sizes and their internal connectivity are the quantities\nused to characterize such variations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact stochastic Liouville and Schr\u00f6dinger equations for open\n  systems: An universal form of kinetic equation for open systems is considered which\nnaturally unifies classical and quantum cases and allows to extend concept of\nwave function to open quantum systems. Corresponding stochastic Schr\\\"{o}dinger\nequation is derived and illustrated by the example of inelastic scattering in\nquantum conduction channel.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical Heterogeneities Below the Glass Transition: We present molecular dynamics simulations of a binary Lennard-Jones mixture\nat temperatures below the kinetic glass transition. The ``mobility'' of a\nparticle is characterized by the amplitude of its fluctuation around its\naverage position. The 5% particles with the largest/smallest mean amplitude are\nthus defined as the relatively most mobile/immobile particles. We investigate\nfor these 5% particles their spatial distribution and find them to be\ndistributed very heterogeneously in that mobile as well as immobile particles\nform clusters. The reason for this dynamic heterogeneity is traced back to the\nfact that mobile/immobile particles are surrounded by fewer/more neighbors\nwhich form an effectively wider/narrower cage. The dependence of our results on\nthe length of the simulation run indicates that individual particles have a\ncharacteristic mobility time scale, which can be approximated via the\nnon-Gaussian parameter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Direct evaluation of large-deviation functions: We introduce a numerical procedure to evaluate directly the probabilities of\nlarge deviations of physical quantities, such as current or density, that are\nlocal in time. The large-deviation functions are given in terms of the typical\nproperties of a modified dynamics, and since they no longer involve rare\nevents, can be evaluated efficiently and over a wider ranges of values. We\nillustrate the method with the current fluctuations of the Totally Asymmetric\nExclusion Process and with the work distribution of a driven Lorentz gas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quasi-phases and pseudo-transitions in one-dimensional models with\n  nearest neighbor interactions: There are some particular one-dimensional models, such as the\nIsing-Heisenberg spin models with a variety of chain structures, which exhibit\nunexpected behaviors quite similar to the first and second order phase\ntransition, which could be confused naively with an authentic phase transition.\nThrough the analysis of the first derivative of free energy, such as entropy,\nmagnetization, and internal energy, a \"sudden\" jump that closely resembles a\nfirst-order phase transition at finite temperature occurs. However, by\nanalyzing the second derivative of free energy, such as specific heat and\nmagnetic susceptibility at finite temperature, it behaves quite similarly to a\nsecond-order phase transition exhibiting an astonishingly sharp and fine peak.\nThe correlation length also confirms the evidence of this pseudo-transition\ntemperature, where a sharp peak occurs at the pseudo-critical temperature. We\nalso present the necessary conditions for the emergence of these quasi-phases\nand pseudo-transitions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random Networks Growing Under a Diameter Constraint: We study the growth of random networks under a constraint that the diameter,\ndefined as the average shortest path length between all nodes, remains\napproximately constant. We show that if the graph maintains the form of its\ndegree distribution then that distribution must be approximately scale-free\nwith an exponent between 2 and 3. The diameter constraint can be interpreted as\nan environmental selection pressure that may help explain the scale-free nature\nof graphs for which data is available at different times in their growth. Two\nexamples include graphs representing evolved biological pathways in cells and\nthe topology of the Internet backbone. Our assumptions and explanation are\nfound to be consistent with these data.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ising and anisotropic Heisenberg magnets with mobile defects: Motivated by experiments on (Sr,Ca,La)_14 Cu_24 O_41, a two-dimensional Ising\nmodel with mobile defects and a two-dimensional anisotropic Heisenberg\nantiferromagnet have been proposed and studied recently. We extend previous\ninvestigations by analysing phase diagrams of both models in external fields\nusing mainly Monte Carlo techniques. In the Ising case, the phase transition is\ndue to the thermal instability of defect stripes, in the Heisenberg case\nadditional spin-flop structures play an essential role.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mapping out of equilibrium into equilibrium in one-dimensional transport\n  models: Systems with conserved currents driven by reservoirs at the boundaries offer\nan opportunity for a general analytic study that is unparalleled in more\ngeneral out of equilibrium systems. The evolution of coarse-grained variables\nis governed by stochastic {\\em hydrodynamic} equations in the limit of small\nnoise.} As such it is amenable to a treatment formally equal to the\nsemiclassical limit of quantum mechanics, which reduces the problem of finding\nthe full distribution functions to the solution of a set of Hamiltonian\nequations. It is in general not possible to solve such equations explicitly,\nbut for an interesting set of problems (driven Symmetric Exclusion Process and\nKipnis-Marchioro-Presutti model) it can be done by a sequence of remarkable\nchanges of variables. We show that at the bottom of this `miracle' is the\nsurprising fact that these models can be taken through a non-local\ntransformation into isolated systems satisfying detailed balance, with\nprobability distribution given by the Gibbs-Boltzmann measure. This procedure\ncan in fact also be used to obtain an elegant solution of the much simpler\nproblem of non-interacting particles diffusing in a one-dimensional potential,\nagain using a transformation that maps the driven problem into an undriven one.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An Entropic Approach To Classical Density Functional Theory: The classical Density Functional Theory (DFT) is introduced as an application\nof entropic inference for inhomogeneous fluids at thermal equilibrium. It is\nshown that entropic inference reproduces the variational principle of DFT when\ninformation about expected density of particles is imposed. This process\nintroduces an intermediate family of trial density-parametrized probability\ndistributions, and consequently an intermediate entropy, from which the\npreferred one is found using the method of Maximum Entropy (MaxEnt). As an\napplication, the DFT model for slowly varying density is provided, and its\napproximation scheme is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Model study on steady heat capacity in driven stochastic systems: We explore two- and three-state Markov models driven out of thermal\nequilibrium by non-potential forces to demonstrate basic properties of the\nsteady heat capacity based on the concept of quasistatic excess heat. It is\nshown that large enough driving forces can make the steady heat capacity\nnegative. For both the low- and high-temperature regimes we propose an\napproximative thermodynamic scheme in terms of \"dynamically renormalized\"\neffective energy levels.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dispersive diffusion controlled distance dependent recombination in\n  amorphous semiconductors: The photoluminescence in amorphous semiconductors decays according to power\nlaw $t^{-delta}$ at long times. The photoluminescence is controlled by\ndispersive transport of electrons. The latter is usually characterized by the\npower $alpha$ of the transient current observed in the time-of-flight\nexperiments. Geminate recombination occurs by radiative tunneling which has a\ndistance dependence. In this paper, we formulate ways to calculate reaction\nrates and survival probabilities in the case carriers execute dispersive\ndiffusion with long-range reactivity. The method is applied to obtain tunneling\nrecombination rates under dispersive diffusion. The theoretical condition of\nobserving the relation $delta = alpha/2 + 1$ is obtained and theoretical\nrecombination rates are compared to the kinetics of observed photoluminescence\ndecay in the whole time range measured.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Advantages and challenges in coupling an ideal gas to atomistic models\n  in adaptive resolution simulations: In adaptive resolution simulations, molecular fluids are modeled employing\ndifferent levels of resolution in different subregions of the system. When\ntraveling from one region to the other, particles change their resolution on\nthe fly. One of the main advantages of such approaches is the computational\nefficiency gained in the coarse-grained region. In this respect the best\ncoarse-grained system to employ in the low resolution region would be the ideal\ngas, making intermolecular force calculations in the coarse-grained subdomain\nredundant. In this case, however, a smooth coupling is challenging due to the\nhigh energetic imbalance between typical liquids and a system of\nnon-interacting particles. In the present work, we investigate this approach,\nusing as a test case the most biologically relevant fluid, water. We\ndemonstrate that a successful coupling of water to the ideal gas can be\nachieved with current adaptive resolution methods, and discuss the issues that\nremain to be addressed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fractional Path Integral Monte Carlo: Fractional derivatives are nonlocal differential operators of real order that\noften appear in models of anomalous diffusion and a variety of nonlocal\nphenomena. Recently, a version of the Schr\\\"odinger Equation containing a\nfractional Laplacian has been proposed. In this work, we develop a Fractional\nPath Integral Monte Carlo algorithm that can be used to study the finite\ntemperature behavior of the time-independent Fractional Schr\\\"odinger Equation\nfor a variety of potentials. In so doing, we derive an analytic form for the\nfinite temperature fractional free particle density matrix and demonstrate how\nit can be sampled to acquire new sets of particle positions. We employ this\nalgorithm to simulate both the free particle and $^{4}$He (Aziz) Hamiltonians.\nWe find that the fractional Laplacian strongly encourages particle\ndelocalization, even in the presence of interactions, suggesting that\nfractional Hamiltonians may manifest atypical forms of condensation. Our work\nopens the door to studying fractional Hamiltonians with arbitrarily complex\npotentials that escape analytical solutions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Active Brownian Particles Escaping a Channel in Single File: Active particles may happen to be confined in channels so narrow that they\ncannot overtake each other (Single File conditions). This interesting situation\nreveals nontrivial physical features as a consequence of the strong\ninter-particle correlations developed in collective rearrangements. We consider\na minimal model for active Brownian particles with the aim of studying the\nmodifications introduced by activity with respect to the classical (passive)\nSingle File picture. Depending on whether their motion is dominated by\ntranslational or rotational diffusion, we find that active Brownian particles\nin Single File may arrange into clusters which are continuously merging and\nsplitting ({\\it active clusters}) or merely reproduce passive-motion paradigms,\nrespectively. We show that activity convey to self-propelled particles a\nstrategic advantage for trespassing narrow channels against external biases\n(e.g., the gravitational field).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spontaneous symmetry breaking in the finite, lattice quantum sine-Gordon\n  model: The spontaneous breaking of a global discrete translational symmetry in the\nfinite, lattice quantum sine-Gordon model is demonstrated by a density matrix\nrenormalization group. A phase diagram in the coupling constant - inverse\nsystem size plane is obtained. Comparison of the phase diagram with a\nWoomany-Wyld finite-size scaling leads to an identification of the\nBerezinskii-Kosterlitz-Thouless transition in the quantum sine-Gordon model as\nthe spontaneous symmetry breaking.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Heat Conduction, and the Lack Thereof, in Time-Reversible Dynamical\n  Systems: Generalized Nos\u00e9-Hoover Oscillators with a Temperature Gradient: We use nonequilibrium molecular dynamics to analyze and illustrate the\nqualitative differences between the one-thermostat and two-thermostat versions\nof equilibrium and nonequilibrium (heat-conducting) harmonic oscillators.\nConservative nonconducting regions can coexist with dissipative heat conducting\nregions in phase space with exactly the same imposed temperature field.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bose-Einstein Condensation in Classical Systems: It is shown, that Bose-Einstein statistical distributions can occur not only\nin quantum system, but in classical systems as well. The coherent dynamics of\nthe system, or equivalently autocatalytic dynamics in momentum space of the\nsystem is the main reason for the Bose-Einstein condensation. A coherence is\npossible in both quantum and classical systems, and in both cases can lead to\nBose-Einstein statistical distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Master Equation for Power Laws: We propose a new mechanism for generating power laws. Starting from a random\nwalk, we first outline a simple derivation of the Fokker-Planck equation. By\nanalogy, starting from a certain Markov chain, we derive a master equation for\npower laws that describes how the number of cascades changes over time\n(cascades are consecutive transitions that end when the initial state is\nreached). The partial differential equation has a closed form solution which\ngives an explicit dependence of the number of cascades on their size and on\ntime. Furthermore, the power law solution has a natural cut-off, a feature\noften seen in empirical data. This is due to the finite size a cascade can have\nin a finite time horizon. The derivation of the equation provides a\njustification for an exponent equal to 2, which agrees well with several\nempirical distributions, including Richardson's law on the size and frequency\nof deadly conflicts. Nevertheless, the equation can be solved for any exponent\nvalue. In addition, we propose an urn model where the number of consecutive\nball extractions follows a power law. In all cases, the power law is manifest\nover the entire range of cascade sizes, as shown through log-log plots in the\nfrequency and rank distributions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extended hydrodynamics from Enskog's equation: The bidimensional case: A heat conduction problem is studied using extended hydrodynamic equations\nobtained from Enskog's equation for a simple case of two planar systems in\ncontact through a porous wall. One of the systems is in equilibrium and the\nother one in a steady conductive state. The example is used to put to test the\npredictions which has been made with a new thermodynamic formalism.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous diffusion of scaled Brownian tracers: A model for anomalous transport of tracer particles diffusing in complex\nmedia in two dimensions is proposed. The model takes into account the\ncharacteristics of persistent motion that active bath transfer to the tracer,\nthus the model proposed in here extends active Brownian motion, for which the\nstochastic dynamics of the orientation of the propelling force is described by\nscale Brownian motion (sBm), identified by a the time dependent diffusivity of\nthe form $D_\\beta\\propto t^{\\beta-1}$, $\\beta>0$. If $\\beta\\neq1$, sBm is\nhighly non-stationary and suitable to describe such a non-equilibrium dynamics\ninduced by complex media. In this paper we provide analytical calculations and\ncomputer simulations to show that genuine anomalous diffusion emerge in the\nlong-time regime, with a time scaling of the mean square displacement\n$t^{2-\\beta}$, while ballistic transport $t^2$, characteristic of persistent\nmotion, is found in the short-time one. An analysis of the time dependence of\nthe kurtosis, and intermediate scattering function of the positions\ndistribution, as well as the propulsion auto-correlation function, which\ndefines the effective persistence time, are provided.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of two qubits in a spin-bath of Quantum anisotropic Heisenberg\n  XY coupling type: The dynamics of two 1/2-spin qubits under the influence of a quantum\nHeisenberg XY type spin-bath is studied. After the Holstein-Primakoff\ntransformation, a novel numerical polynomial scheme is used to give the\ntime-evolution calculation of the center qubits initially prepared in a product\nstate or a Bell state. Then the concurrence of the two qubits, the\n$z$-component moment of either of the subsystem spins and the fidelity of the\nsubsystem are shown, which exhibit sensitive dependence on the anisotropic\nparameter, the temperature, the coupling strength and the initial state. It is\nfound that (i) the larger the anisotropic parameter $\\gamma$, the bigger the\nprobability of maintaining the initial state of the two qubits; (ii) with\nincreasing temperature $T$, the bath plays a more strong destroy effect on the\ndynamics of the subsystem, so does the interaction $g_0$ between the subsystem\nand the bath; (iii) the time evolution of the subsystem is dependent on the\ninitial state. The revival of the concurrence does not always means the restore\nof the state. Further, the dynamical properties of the subsystem should be\njudged by the combination of concurrence and fidelity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamic critical properties of a one-dimensional probabilistic cellular\n  automaton: Dynamic properties of a one-dimensional probabilistic cellular automaton are\nstudied by monte-carlo simulation near a critical point which marks a\nsecond-order phase transition from a active state to a effectively unique\nabsorbing state. Values obtained for the dynamic critical exponents indicate\nthat the transition belongs to the universality class of directed percolation.\nFinally the model is compared with a previously studied one to show that a\ndifference in the nature of the absorbing states places them in different\nuniversality classes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-monotonic dependence on disorder in biased diffusion on small-world\n  networks: We report numerical simulations of a strongly biased diffusion process on a\none-dimensional substrate with directed shortcuts between randomly chosen\nsites, i.e. with a small-world-like structure. We find that, unlike many other\ndynamical phenomena on small-world networks, this process exhibits\nnon-monotonic dependence on the density of shortcuts. Specifically, the\ndiffusion time over a finite length is maximal at an intermediate density. This\ndensity scales with the length in a nontrivial manner, approaching zero as the\nlength grows. Longer diffusion times for intermediate shortcut densities can be\nascribed to the formation of cyclic paths where the diffusion process becomes\noccasionally trapped.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermal Transport in a Noncommutative Hydrodynamics: We find the hydrodynamic equations of a system of particles constrained to be\nin the lowest Landau level. We interpret the hydrodynamic theory as a\nHamiltonian system with the Poisson brackets between the hydrodynamic variables\ndetermined from the noncommutativity of space. We argue that the most general\nhydrodynamic theory can be obtained from this Hamiltonian system by allowing\nthe Righi-Leduc coefficient to be an arbitrary function of thermodynamic\nvariables. We compute the Righi-Leduc coefficients at high temperatures and\nshow that it satisfies the requirements of particle-hole symmetry, which we\noutline.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Sojourn probabilities in tubes and pathwise irreversibility for It\u00f4\n  processes: The sojourn probability of an It\\^o diffusion process, i.e. its probability\nto remain in the tubular neighborhood of a smooth path, is a central quantity\nin the study of path probabilities. For $N$-dimensional It\\^o processes with\nstate-dependent full-rank diffusion tensor, we derive a general expression for\nthe sojourn probability in tubes whose radii are small but finite, and fixed by\nthe metric of the ambient Euclidean space. The central quantity in our study is\nthe exit rate at which trajectories leave the tube for the first time. This has\nan interpretation as a Lagrangian and can be measured directly in experiment,\nunlike previously defined sojourn probabilities which depend on prior knowledge\nof the state-dependent diffusivity. We find that while in the limit of\nvanishing tube radius the ratio of sojourn probabilities for a pair of distinct\npaths is in general divergent, the same for a path and its time-reversal is\nalways convergent and finite. This provides a pathwise definition of\nirreversibility for It\\^o processes that is agnostic to the state-dependence of\nthe diffusivity. For one-dimensional systems we derive an explicit expression\nfor our Lagrangian in terms of the drift and diffusivity, and find that our\nresult differs from previously reported multiplicative-noise Lagrangians. We\nconfirm our result by comparing to numerical simulations, and relate our theory\nto the Stratonovich Lagrangian for multiplicative noise. For one-dimensional\nsystems, we discuss under which conditions the vanishing-radius limiting ratio\nof sojourn probabilities for a pair of forward and backward paths recovers the\nestablished pathwise entropy production. Finally, we demonstrate for our\none-dimensional example system that the most probable tube for a barrier\ncrossing depends sensitively on the tube radius, and hence on the tolerated\namount of fluctuations around the smooth reference path.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical aging of a ferromagnetic system from a completely ordered state: We adapt the non-linear $\\sigma$ model to study the nonequilibrium critical\ndynamics of O(n) symmetric ferromagnetic system. Using the renormalization\ngroup analysis in $d=2+\\epsilon$ dimensions we investigate the pure relaxation\nof the system starting from a completely ordered state. We find that the\naverage magnetization obeys the long-time scaling behavior almost immediately\nafter the system starts to evolve while the correlation and response functions\ndemonstrate scaling behavior which is typical for aging phenomena. The\ncorresponding fluctuation-dissipation ratio is computed to first order in\n$\\epsilon$ and the relation between transverse and longitudinal fluctuations is\ndiscussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Collective effects in spin-crossover chains with exchange interaction: The collective properties of spin-crossover chains are studied.\nSpin-crossover compounds contain ions with a low-spin ground state and low\nlying high-spin excited states and are of interest for molecular memory\napplications. Some of them naturally form one-dimensional chains. Elastic\ninteraction and Ising exchange interaction are taken into account. The\ntransfer-matrix approach is used to calculate the partition function, the\nfraction of ions in the high-spin state, the magnetization, susceptibility,\netc., exactly. The high-spin-low-spin degree of freedom leads to collective\neffects not present in simple spin chains. The ground-state phase diagram is\nmapped out and compared to the case with Heisenberg exchange interaction. The\nvarious phases give rise to characteristic behavior at nonzero temperatures,\nincluding sharp crossovers between low- and high-temperature regimes. A\nCurie-Weiss law for the susceptibility is derived and the paramagnetic Curie\ntemperature is calculated. Possible experiments to determine the exchange\ncoupling are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Pattern description of the ground state properties of the\n  one-dimensional axial next-nearest-neighbor Ising model in a transverse field: The description and understanding of the consequences of competing\ninteractions in various systems, both classical and quantum, are notoriously\ndifficult due to insufficient information involved in conventional concepts,\nfor example, order parameters and/or correlation functions. Here we go beyond\nthese conventional language and present a pattern picture to describe and\nunderstand the frustration physics by taking the one-dimensional (1D) axial\nnext-nearest-neighbor Ising (ANNNI) model in a transverse field as an example.\nThe system is dissected by the patterns, obtained by diagnonalizing the model\nHamiltonian in an operator space with a finite lattice size $4n$ ($n$: natural\nnumber) and periodic boundary condition. With increasing the frustration\nparameter, the system experiences successively various phases/metastates,\nidentified respectively as those with zero, two, four, $\\cdots$, $2n$\ndomains/kinks, where the first is the ferromagnetic phase and the last the\nantiphase. Except for the ferromagnetic phase and antiphase, the others should\nbe metastates, whose transitions are crossing over in nature. The results\nclarify the controversial issues about the phases in the 1D ANNNI model and\nprovide a starting point to study more complicated situations, for example, the\nfrustration systems in high dimensions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Large deviations for a stochastic model of heat flow: We investigate a one dimensional chain of $2N$ harmonic oscillators in which\nneighboring sites have their energies redistributed randomly. The sites $-N$\nand $N$ are in contact with thermal reservoirs at different temperature\n$\\tau_-$ and $\\tau_+$. Kipnis, Marchioro, and Presutti \\cite{KMP} proved that\nthis model satisfies {}Fourier's law and that in the hydrodynamical scaling\nlimit, when $N \\to \\infty$, the stationary state has a linear energy density\nprofile $\\bar \\theta(u)$, $u \\in [-1,1]$. We derive the large deviation\nfunction $S(\\theta(u))$ for the probability of finding, in the stationary\nstate, a profile $\\theta(u)$ different from $\\bar \\theta(u)$. The function\n$S(\\theta)$ has striking similarities to, but also large differences from, the\ncorresponding one of the symmetric exclusion process. Like the latter it is\nnonlocal and satisfies a variational equation. Unlike the latter it is not\nconvex and the Gaussian normal fluctuations are enhanced rather than suppressed\ncompared to the local equilibrium state. We also briefly discuss more general\nmodel and find the features common in these two and other models whose\n$S(\\theta)$ is known.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Density relaxation in conserved Manna sandpiles: We study relaxation of long-wavelength density perturbations in one\ndimensional conserved Manna sandpile. Far from criticality where correlation\nlength $\\xi$ is finite, relaxation of density profiles having wave numbers $k\n\\rightarrow 0$ is diffusive, with relaxation time $\\tau_R \\sim k^{-2}/D$ with\n$D$ being the density-dependent bulk-diffusion coefficient. Near criticality\nwith $k \\xi \\gsim 1$, the bulk diffusivity diverges and the transport becomes\nanomalous; accordingly, the relaxation time varies as $\\tau_R \\sim k^{-z}$,\nwith the dynamical exponent $z=2-(1-\\beta)/\\nu_{\\perp} < 2$, where $\\beta$ is\nthe critical order-parameter exponent and and $\\nu_{\\perp}$ is the critical\ncorrelation-length exponent. Relaxation of initially localized density profiles\non infinite critical background exhibits a self-similar structure. In this\ncase, the asymptotic scaling form of the time-dependent density profile is\nanalytically calculated: we find that, at long times $t$, the width $\\sigma$ of\nthe density perturbation grows anomalously, i.e., $\\sigma \\sim t^{w}$, with the\ngrowth exponent $\\omega=1/(1+\\beta) > 1/2$. In all cases, theoretical\npredictions are in reasonably good agreement with simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of the non-Markovianity and non-Gaussianity of active\n  environmental noises on engine performance: An active environment is a reservoir containing \\emph{active} materials, such\nas bacteria and Janus particles. Given the self-propelled motion of these\nmaterials, powered by chemical energy, an active environment has unique,\nnonequilibrium environmental noise. Recently, studies on engines that harvest\nenergy from active environments have attracted a great deal of attention\nbecause the theoretical and experimental findings indicate that these engines\noutperform conventional ones. Studies have explored the features of active\nenvironments essential for outperformance, such as the non-Gaussian or\nnon-Markovian nature of the active noise. However, these features have not yet\nbeen systematically investigated in a general setting. Therefore, we\nsystematically study the effects of the non-Gaussianity and non-Markovianity of\nactive noise on engine performance. We show that non-Gaussianity is irrelevant\nto the performance of an engine driven by {any linear force (including a\nharmonic trap) regardless of time dependency}, whereas non-Markovianity is\nrelevant. However, for a system driven by a general nonlinear force, both\nnon-Gaussianity and non-Markovianity enhance engine performance. Also, the\nmemory effect of an active reservoir should be considered when fabricating a\ncyclic engine.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Global topological control for synchronized dynamics on networks: A general scheme is proposed and tested to control the symmetry breaking\ninstability of a homogeneous solution of a spatially extended multispecies\nmodel, defined on a network. The inherent discreteness of the space makes it\npossible to act on the topology of the inter-nodes contacts to achieve the\ndesired degree of stabilization, without altering the dynamical parameters of\nthe model. Both symmetric and asymmetric couplings are considered. In this\nlatter setting the web of contacts is assumed to be balanced, for the\nhomogeneous equilibrium to exist. The performance of the proposed method are\nassessed, assuming the Complex Ginzburg-Landau equation as a reference model.\nIn this case, the implemented control allows one to stabilize the synchronous\nlimit cycle, hence time-dependent, uniform solution. A system of coupled real\nGinzburg-Landau equations is also investigated to obtain the topological\nstabilization of a homogeneous and constant fixed point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The noise intensity of a Markov chain: Stochastic transitions between discrete microscopic states play an important\nrole in many physical and biological systems. Often, these transitions lead to\nfluctuations on a macroscopic scale. A classic example from neuroscience is the\nstochastic opening and closing of ion channels and the resulting fluctuations\nin membrane current. When the microscopic transitions are fast, the macroscopic\nfluctuations are nearly uncorrelated and can be fully characterized by their\nmean and noise intensity. We show how, for an arbitrary Markov chain, the noise\nintensity can be determined from an algebraic equation, based on the transition\nrate matrix. We demonstrate the validity of the theory using an analytically\ntractable two-state Markovian dichotomous noise, an eight-state model for a\nCalcium channel subunit (De Young-Keizer model), and Markov models of the\nvoltage-gated Sodium and Potassium channels as they appear in a stochastic\nversion of the Hodgkin-Huxley model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram and critical exponents of a dissipative Ising spin chain\n  in a transverse magnetic field: We consider a one-dimensional Ising model in a transverse magnetic field\ncoupled to a dissipative heat bath. The phase diagram and the critical\nexponents are determined from extensive Monte Carlo simulations. It is shown\nthat the character of the quantum phase transition is radically altered from\nthe corresponding non-dissipative model and the double-well coupled to a\ndissipative heat bath with linear friction. Spatial couplings and the\ndissipative dynamics combine to form a new quantum criticality.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Palette-colouring: a belief-propagation approach: We consider a variation of the prototype combinatorial-optimisation problem\nknown as graph-colouring. Our optimisation goal is to colour the vertices of a\ngraph with a fixed number of colours, in a way to maximise the number of\ndifferent colours present in the set of nearest neighbours of each given\nvertex. This problem, which we pictorially call \"palette-colouring\", has been\nrecently addressed as a basic example of problem arising in the context of\ndistributed data storage. Even though it has not been proved to be NP complete,\nrandom search algorithms find the problem hard to solve. Heuristics based on a\nnaive belief propagation algorithm are observed to work quite well in certain\nconditions. In this paper, we build upon the mentioned result, working out the\ncorrect belief propagation algorithm, which needs to take into account the\nmany-body nature of the constraints present in this problem. This method\nimproves the naive belief propagation approach, at the cost of increased\ncomputational effort. We also investigate the emergence of a satisfiable to\nunsatisfiable \"phase transition\" as a function of the vertex mean degree, for\ndifferent ensembles of sparse random graphs in the large size (\"thermodynamic\")\nlimit.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Giant spin current rectification due to the interplay of negative\n  differential conductance and a non-uniform magnetic field: In XXZ chains, spin transport can be significantly suppressed when the\ninteractions in the chain and the bias of the dissipative driving are large\nenough. This phenomenon of negative differential conductance is caused by the\nformation of two oppositely polarized ferromagnetic domains at the edges of the\nchain. Here we show that this many-body effect, combined with a non-uniform\nmagnetic field, can allow a high degree of control of the spin current. In\nparticular, by studying all the possible combinations of a dichotomous local\nmagnetic field, we found that a configuration in which the magnetic field\npoints up for half of the chain and down for the other half, can result in\ngiant spin-current rectification, for example up to $10^8$ for a system with\n$8$ spins. Our results show clear indications that the rectification can\nincrease with the system size.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kramers-Wannier Duality of Statistical Mechanics Applied to the Boolean\n  Satisfiability Problem of Computer Science: We present a novel application of the Kramers-Wannier duality on one of the\nmost important problems of computer science, the Boolean satisfiability problem\n(SAT). More specifically, we focus on sharp-SAT or equivalently #SAT - the\nproblem of counting the number of solutions to a Boolean satisfaction formula.\n#SAT can be cast into a statistical-mechanical language, where it reduces to\ncalculating the partition function of an Ising spin Hamiltonian with multi-spin\ninteractions. We show that Kramers-Wannier duality can be generalized to apply\nto such multi-connected spin networks. We present an exact dual partner to #SAT\nand explicitly verify their equivalence with a few simple examples. It is shown\nthat the NP-completeness of the original problem maps on the complexity of the\ndual problem of enumerating the number of non-negative solutions to a\nDiophantine system of equations. We discuss the implications of this duality\nand the prospects of similar dualities applied to computer science problems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Virial statistical description of non-extensive hierarchical systems: In a first part the scope of classical thermodynamics and statistical\nmechanics is discussed in the broader context of formal dynamical systems,\nincluding computer programmes. In this context classical thermodynamics appears\nas a particular theory suited to a subset of all dynamical systems. A\nstatistical mechanics similar to the one derived with the microcanonical\nensemble emerges from dynamical systems provided it contains, 1) a finite\nnon-integrable part of its phase space which is, 2) ergodic at a satisfactory\ndegree after a finite time. The integrable part of phase space provides the\nconstraints that shape the particular system macroscopical properties, and the\nchaotic part provides well behaved statistical properties over a relevant\nfinite time. More generic semi-ergodic systems lead to intermittent behaviour,\nthus may be unsuited for a statistical description of steady states. Following\nthese lines of thought, in a second part non-extensive hierarchical systems\nwith statistical scale-invariance and power law interactions are explored. Only\nthe virial constraint, consistent with their microdynamics, is included. No\nassumptions of classical thermodynamics are used, in particular extensivity and\nlocal homogeneity. In the limit of a large hierarchical range new constraints\nemerge in some conditions that depend on the interaction law range. In\nparticular for the gravitational case, a velocity-site scaling relation is\nderived which is consistant with the ones empirically observed in the fractal\ninterstellar medium.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of structural models with a long-range interaction: glassy\n  versus non-glassy behavior: By making use of the Langevin dynamics and its generating functional (GF)\nformulation the influence of the long-range nature of the interaction on the\ntendency of the glass formation is systematically investigated. In doing so two\ntypes of models is considered: (i) the non-disordered model with a pure\nrepulsive type of interaction and (ii) the model with a randomly distributed\nstrength of interaction (a quenched disordered model). The long-ranged\npotential of interaction is scaled with a number of particles $N$ in such a way\nas to enable for GF the saddle-point treatment as well as the systematic 1/N -\nexpansion around it. We show that the non-disordered model has no glass\ntransition which is in line with the mean-field limit of the mode - coupling\ntheory (MCT) predictions. On the other hand the model with a long-range\ninteraction which above that has a quenched disorder leads to MC - equations\nwhich are generic for the $p$ - spin glass model and polymeric manifold in a\nrandom media.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The influence of measurement error on Maxwell's demon: In any general cycle of measurement, feedback and erasure, the measurement\nwill reduce the entropy of the system when information about the state is\nobtained, while erasure, according to Landauer's principle, is accompanied by a\ncorresponding increase in entropy due to the compression of logical and\nphysical phase space. The total process can in principle be fully reversible. A\nmeasurement error reduces the information obtained and the entropy decrease in\nthe system. The erasure still gives the same increase in entropy and the total\nprocess is irreversible. Another consequence of measurement error is that a bad\nfeedback is applied, which further increases the entropy production if the\nproper protocol adapted to the expected error rate is not applied. We consider\nthe effect of measurement error on a realistic single-electron box Szilard\nengine. We find the optimal protocol for the cycle as a function of the desired\npower $P$ and error $\\epsilon$, as well as the existence of a maximal power\n$P^{\\max}$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A large deviation perspective on ratio observables in reset processes:\n  robustness of rate functions: We study large deviations of a ratio observable in discrete-time reset\nprocesses. The ratio takes the form of a current divided by the number of reset\nsteps and as such it is not extensive in time. A large deviation rate function\ncan be derived for this observable via contraction from the joint probability\ndensity function of current and number of reset steps. The ratio rate function\nis differentiable and we argue that its qualitative shape is 'robust', i.e. it\nis generic for reset processes regardless of whether they have short- or\nlong-range correlations. We discuss similarities and differences with the rate\nfunction of the efficiency in stochastic thermodynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical branching processes in digital memcomputing machines: Memcomputing is a novel computing paradigm that employs time non-locality\n(memory) to solve combinatorial optimization problems. It can be realized in\npractice by means of non-linear dynamical systems whose point attractors\nrepresent the solutions of the original problem. It has been previously shown\nthat during the solution search digital memcomputing machines go through a\ntransient phase of avalanches (instantons) that promote dynamical long-range\norder. By employing mean-field arguments we predict that the distribution of\nthe avalanche sizes follows a Borel distribution typical of critical branching\nprocesses with exponent $\\tau= 3/2$. We corroborate this analysis by solving\nvarious random 3-SAT instances of the Boolean satisfiability problem. The\nnumerical results indicate a power-law distribution with exponent $\\tau = 1.51\n\\pm 0.02$, in very good agreement with the mean-field analysis. This indicates\nthat memcomputing machines self-tune to a critical state in which avalanches\nare characterized by a branching process, and that this state persists across\nthe majority of their evolution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlation function structure in square-gradient models of the\n  liquid-gas interface: Exact results and reliable approximations: In a recent article, we described how the microscopic structure of\ndensity-density correlations in the fluid interfacial region, for systems with\nshort-ranged forces, can be understood by considering the resonances of the\nlocal structure factor occurring at specific parallel wave-vectors $q$. Here,\nwe investigate this further by comparing approximations for the local structure\nfactor and correlation function against three new examples of analytically\nsolvable models within square-gradient theory. Our analysis further\ndemonstrates that these approximations describe the correlation function and\nstructure factor across the whole spectrum of wave-vectors, encapsulating the\ncross-over from the Goldstone mode divergence (at small $q$) to bulk-like\nbehaviour (at larger $q$). As shown, these approximations are exact for some\nsquare-gradient model potentials, and never more than a few percent inaccurate\nfor the others. Additionally, we show that they very accurately describe the\ncorrelation function structure for a model describing an interface near a\ntricritical point. In this case, there are no analytical solutions for the\ncorrelation functions, but the approximations are near indistinguishable from\nthe numerical solutions of the Ornstein-Zernike equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Euclidean operator growth and quantum chaos: We consider growth of local operators under Euclidean time evolution in\nlattice systems with local interactions. We derive rigorous bounds on the\noperator norm growth and then proceed to establish an analog of the\nLieb-Robinson bound for the spatial growth. In contrast to the Minkowski case\nwhen ballistic spreading of operators is universal, in the Euclidean case\nspatial growth is system-dependent and indicates if the system is integrable or\nchaotic. In the integrable case, the Euclidean spatial growth is at most\npolynomial. In the chaotic case, it is the fastest possible: exponential in 1D,\nwhile in higher dimensions and on Bethe lattices local operators can reach\nspatial infinity in finite Euclidean time. We use bounds on the Euclidean\ngrowth to establish constraints on individual matrix elements and operator\npower spectrum. We show that one-dimensional systems are special with the power\nspectrum always being superexponentially suppressed at large frequencies.\nFinally, we relate the bound on the Euclidean growth to the bound on the growth\nof Lanczos coefficients. To that end, we develop a path integral formalism for\nthe weighted Dyck paths and evaluate it using saddle point approximation. Using\na conjectural connection between the growth of the Lanczos coefficients and the\nLyapunov exponent controlling the growth of OTOCs, we propose an improved bound\non chaos valid at all temperatures.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exit versus escape in a stochastic dynamical system of neuronal networks\n  explains heterogenous bursting intervals: Neuronal networks can generate burst events. It remains unclear how to\nanalyse interburst periods and their statistics. We study here the phase-space\nof a mean-field model, based on synaptic short-term changes, that exhibit burst\nand interburst dynamics and we identify that interburst corresponds to the\nescape from a basin of attraction. Using stochastic simulations, we report here\nthat the distribution of the these durations do not match with the time to\nreach the boundary. We further analyse this phenomenon by studying a generic\nclass of two-dimensional dynamical systems perturbed by small noise that\nexhibits two peculiar behaviors: 1- the maximum associated to the probability\ndensity function is not located at the point attractor, which came as a\nsurprise. The distance between the maximum and the attractor increases with the\nnoise amplitude $\\sigma$, as we show using WKB approximation and numerical\nsimulations. 2- For such systems, exiting from the basin of attraction is not\nsufficient to characterize the entire escape time, due to trajectories that can\nreturn several times inside the basin of attraction after crossing the\nboundary, before eventually escaping far away. To conclude, long-interburst\ndurations are inherent properties of the dynamics and sould be expected in\nempirical time series.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Charged complexes at the surface of liquid helium: Charged clusters in liquid helium in an external electric field form a\ntwo-dimensional system below the helium surface. This 2D system undergoes a\nphase transition from a liquid to a Wigner crystal at rather high temperatures.\nContrary to the electron Wigner crystal, the Wigner lattice of charged clusters\ncan be detected directly.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Does a Single Eigenstate of a Hamiltonian Encode the Critical Behaviour\n  of its Finite-Temperature Phase Transition?: Recent work on the subject of isolated quantum thermalization has suggested\nthat an individual energy eigenstate of a non-integrable quantum system may\nencode a significant amount of information about that system's Hamiltonian. We\nprovide a theoretical argument, along with supporting numerics, that this\ninformation includes the critical behaviour of a system with a second-order,\nfinite-temperature phase transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Conditional maximum-entropy method for selecting prior distributions in\n  Bayesian statistics: The conditional maximum-entropy method (abbreviated here as C-MaxEnt) is\nformulated for selecting prior probability distributions in Bayesian statistics\nfor parameter estimation. This method is inspired by a statistical-mechanical\napproach to systems governed by dynamics with largely-separated time scales and\nis based on three key concepts: conjugate pairs of variables, dimensionless\nintegration measures with coarse-graining factors and partial maximization of\nthe joint entropy. The method enables one to calculate a prior purely from a\nlikelihood in a simple way. It is shown in particular how it not only yields\nJeffreys's rules but also reveals new structures hidden behind them.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Energy partition for anharmonic, undamped, classical oscillators: Using stochastic methods, general formulas for average kinetic and potential\nenergies for anharmonic, undamped (frictionless), classical oscillators are\nderived. It is demonstrated that for potentials of $|x|^\\nu$ ($\\nu>0$) type\nenergies are equipartitioned for the harmonic potential only. For potential\nwells weaker than parabolic potential energy dominates, while for potentials\nstronger than parabolic kinetic energy prevails. Due to energy conservation,\nthe variances of kinetic and potential energies are equal. In the limiting case\nof the infinite rectangular potential well ($\\nu\\to\\infty$) the whole energy is\nstored in the form of the kinetic energy and variances of energy distributions\nvanish.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the coexistence of dipolar frustration and criticality in\n  ferromagnets: In real magnets the tendency towards ferromagnetism, promoted by exchange\ncoupling, is usually frustrated by dipolar interaction. As a result, the\nuniformly ordered phase is replaced by modulated (multi-domain) phases,\ncharacterized by different order parameters rather than the global\nmagnetization. The transitions occurring within those modulated phases and\ntowards the disordered phase are generally not of second-order type.\nNevertheless, strong experimental evidence indicates that a standard critical\nbehavior is recovered when comparatively small fields are applied that\nstabilize the uniform phase. The resulting power laws are observed with respect\nto a putative critical point that falls in the portion of the phase diagram\noccupied by modulated phases, in line with an avoided-criticality scenario.\nHere we propose a generalization of the scaling hypothesis for ferromagnets,\nwhich explains this observation assuming that the dipolar interaction acts as a\nrelevant field, in the sense of renormalization group.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Particle escapes in an open quantum network via multiple leads: Quantum escapes of a particle from an end of a one-dimensional finite region\nto $N$ number of semi-infinite leads are discussed by a scattering theoretical\napproach. Depending on a potential barrier amplitude at the junction, the\nprobability $P(t)$ for a particle to remain in the finite region at time $t$\nshows two different decay behaviors after a long time; one is proportional to\n$N^{2}/t^{3}$ and another is proportional to $1/(N^{2}t)$. In addition, the\nvelocity $V(t)$ for a particle to leave from the finite region, defined from a\nprobability current of the particle position, decays in power $\\sim 1/t$\nasymptotically in time, independently of the number $N$ of leads and the\ninitial wave function, etc. For a finite time, the probability $P(t)$ decays\nexponentially in time with a smaller decay rate for more number $N$ of leads,\nand the velocity $V(t)$ shows a time-oscillation whose amplitude is larger for\nmore number $N$ of leads. Particle escapes from the both ends of a finite\nregion to multiple leads are also discussed by using a different boundary\ncondition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal entanglement signatures of interface conformal field theories: An interface connecting two distinct conformal field theories hosts rich\ncritical behaviors. In this work, we investigate the entanglement properties of\nsuch critical interface theories for probing the underlying universality. As\ninspired by holographic perspectives, we demonstrate vital features of various\nentanglement measures regarding such interfaces based on several paradigmatic\nlattice models. Crucially, for two subsystems adjacent at the interface, the\nmutual information and the reflected entropy exhibit identical leading\nlogarithmic scaling, giving an effective interface central charge that takes\nthe same value as the smaller central charge of the two conformal field\ntheories. Our work demonstrates that the entanglement measure offers a powerful\ntool to explore the rich physics in critical interface theories.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exit versus escape in a stochastic dynamical system of neuronal networks\n  explains heterogenous bursting intervals: Neuronal networks can generate burst events. It remains unclear how to\nanalyse interburst periods and their statistics. We study here the phase-space\nof a mean-field model, based on synaptic short-term changes, that exhibit burst\nand interburst dynamics and we identify that interburst corresponds to the\nescape from a basin of attraction. Using stochastic simulations, we report here\nthat the distribution of the these durations do not match with the time to\nreach the boundary. We further analyse this phenomenon by studying a generic\nclass of two-dimensional dynamical systems perturbed by small noise that\nexhibits two peculiar behaviors: 1- the maximum associated to the probability\ndensity function is not located at the point attractor, which came as a\nsurprise. The distance between the maximum and the attractor increases with the\nnoise amplitude $\\sigma$, as we show using WKB approximation and numerical\nsimulations. 2- For such systems, exiting from the basin of attraction is not\nsufficient to characterize the entire escape time, due to trajectories that can\nreturn several times inside the basin of attraction after crossing the\nboundary, before eventually escaping far away. To conclude, long-interburst\ndurations are inherent properties of the dynamics and sould be expected in\nempirical time series.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Weighted-ensemble Brownian dynamics simulation: Sampling of rare events\n  in non-equilibrium systems: We provide an algorithm based on weighted-ensemble (WE) methods, to\naccurately sample systems at steady state. Applying our method to different\none- and two-dimensional models, we succeed to calculate steady state\nprobabilities of order $10^{-300}$ and reproduce Arrhenius law for rates of\norder $10^{-280}$. Special attention is payed to the simulation of\nnon-potential systems where no detailed balance assumption exists. For this\nlarge class of stochastic systems, the stationary probability distribution\ndensity is often unknown and cannot be used as preknowledge during the\nsimulation. We compare the algorithms efficiency with standard Brownian\ndynamics simulations and other WE methods.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Boundary polarization in the six-vertex model: Vertical-arrow fluctuations near the boundaries in the six-vertex model on\nthe two-dimensional $N \\times N$ square lattice with the domain wall boundary\nconditions are considered. The one-point correlation function (`boundary\npolarization') is expressed via the partition function of the model on a\nsublattice. The partition function is represented in terms of standard objects\nin the theory of orthogonal polynomials. This representation is used to study\nthe large N limit: the presence of the boundary affects the macroscopic\nquantities of the model even in this limit. The logarithmic terms obtained are\ncompared with predictions from conformal field theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random sequential adsorption of straight rigid rods on a simple cubic\n  lattice: Random sequential adsorption of straight rigid rods of length $k$ ($k$-mers)\non a simple cubic lattice has been studied by numerical simulations and\nfinite-size scaling analysis. The calculations were performed by using a new\ntheoretical scheme, whose accuracy was verified by comparison with rigorous\nanalytical data. The results, obtained for \\textit{k} ranging from 2 to 64,\nrevealed that (i) in the case of dimers ($k=2$), the jamming coverage is\n$\\theta_j=0.918388(16)$. Our estimate of $\\theta_j$ differs significantly from\nthe previously reported value of $\\theta_j=0.799(2)$ [Y. Y. Tarasevich and V.\nA. Cherkasova, Eur. Phys. J. B \\textbf{60}, 97 (2007)]; (ii) $\\theta_j$\nexhibits a decreasing function when it is plotted in terms of the $k$-mer size,\nbeing $\\theta_j (\\infty)= 0.4045(19)$ the value of the limit coverage for large\n$k$'s; and (iii) the ratio between percolation threshold and jamming coverage\nshows a non-universal behavior, monotonically decreasing with increasing $k$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermal Casimir interactions for higher derivative field Lagrangians:\n  generalized Brazovskii models: We examine the Casimir effect for free statistical field theories which have\nHamiltonians with second order derivative terms. Examples of such Hamiltonians\narise from models of non-local electrostatics, membranes with non-zero bending\nrigidities and field theories of the Brazovskii type that arise for polymer\nsystems. The presence of a second derivative term means that new types of\nboundary conditions can be imposed, leading to a richer phenomenology of\ninteraction phenomena. In addition zero modes can be generated that are not\npresent in standard first derivative models, and it is these zero modes which\ngive rise to long range Casimir forces. Two physically distinct cases are\nconsidered: (i) unconfined fields, usually considered for finite size embedded\ninclusions in an infinite fluctuating medium, here in a two plate geometry the\nfluctuating field exists both inside and outside the plates, (ii) confined\nfields, where the field is absent outside the slab confined between the two\nplates. We show how these two physically distinct cases are mathematically\nrelated and discuss a wide range of commonly applied boundary conditions. We\nconcentrate our analysis to the critical region where the underlying bulk\nHamiltonian has zero modes and show that very exotic Casimir forces can arise,\ncharacterised by very long range effects and oscillatory behavior that can lead\nto strong metastability in the system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Contact process on generalized Fibonacci chains: infinite-modulation\n  criticality and double-log periodic oscillations: We study the nonequilibrium phase transition of the contact process with\naperiodic transition rates using a real-space renormalization group as well as\nMonte-Carlo simulations. The transition rates are modulated according to the\ngeneralized Fibonacci sequences defined by the inflation rules A $\\to$ AB$^k$\nand B $\\to$ A. For $k=1$ and 2, the aperiodic fluctuations are irrelevant, and\nthe nonequilibrium transition is in the clean directed percolation universality\nclass. For $k\\ge 3$, the aperiodic fluctuations are relevant. We develop a\ncomplete theory of the resulting unconventional \"infinite-modulation\" critical\npoint which is characterized by activated dynamical scaling. Moreover,\nobservables such as the survival probability and the size of the active cloud\ndisplay pronounced double-log periodic oscillations in time which reflect the\ndiscrete scale invariance of the aperiodic chains. We illustrate our theory by\nextensive numerical results, and we discuss relations to phase transitions in\nother quasiperiodic systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal scaling in active single-file dynamics: We study the single-file dynamics of three classes of active particles:\nrun-and-tumble particles, active Brownian particles and active\nOrnstein-Uhlenbeck particles. At high activity values, the particles,\ninteracting via purely repulsive and short-ranged forces, aggregate into\nseveral motile and dynamical clusters of comparable size, and do not display\nbulk phase-segregation. In this dynamical steady-state, we find that the\ncluster size distribution of these aggregates is a scaled function of the\ndensity and activity parameters across the three models of active particles\nwith the same scaling function. The velocity distribution of these motile\nclusters is non-Gaussian. We show that the effective dynamics of these clusters\ncan explain the observed emergent scaling of the mean-squared displacement of\ntagged particles for all the three models with identical scaling exponents and\nfunctions. Concomitant with the clustering seen at high activities, we observe\nthat the static density correlation function displays rich structures,\nincluding multiple peaks that are reminiscent of particle clustering induced by\neffective attractive interactions, while the dynamical variant shows\nnon-diffusive scaling. Our study reveals a universal scaling behavior in the\nsingle-file dynamics of interacting active particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Full decoherence induced by local fields in open spin chains with strong\n  boundary couplings: We investigate an open $XYZ$ spin $1/2$ chain driven out of equilibrium by\nboundary reservoirs targeting different spin orientations, aligned along the\nprincipal axes of anisotropy. We show that by tuning local magnetic fields,\napplied to spins at sites near the boundaries, one can change any\nnonequilibrium steady state to a fully uncorrelated Gibbsian state at infinite\ntemperature. This phenomenon occurs for strong boundary coupling and on a\ncritical manifold in the space of the fields amplitudes. The structure of this\nmanifold depends on the anisotropy degree of the model and on the parity of the\nchain size.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extension of the Lieb-Schultz-Mattis theorem: Lieb, Schultz and Mattis (LSM) studied the S=1/2 XXZ spin chain. Theorems of\nLSM's paper can be applied to broader models. In the original LSM theorem it\nwas assumed the nonfrustrating system. However, reconsidering the LSM theorem,\nwe can extend the LSM theorem for frustrating systems.\n  Next, several researchers have tried to extend the LSM theorem for excited\nstates. In the cases $S^{z}_{T} = \\pm 1,\\pm 2 \\cdots$, the lowest energy\neigenvalues are continuous for wave number $q$. But we find that their proofs\nare insufficient, and we improve them.\n  In addition, we can prove the LSM theory without the assumption of the\ndiscrete symmetry, which means that the LSM type theorems are applicable for\nDzyaloshinskii-Moriya type interactions or other nonsymmetric models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Staggered long-range order for diluted quantum spin models: We study an annealed site diluted quantum XY model with spin $S\\in\n\\frac{1}{2}\\mathbb{N}$. We find regions of the parameter space where, in spite\nof being a priori favourable for a densely occupied state, phases with\nstaggered occupancy occur at low temperatures.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diffusion of two molecular species in a crowded environment: theory and\n  experiments: Diffusion of a two component fluid is studied in the framework of\ndifferential equations, but where these equations are systematically derived\nfrom a well-defined microscopic model. The model has a finite carrying capacity\nimposed upon it at the mesoscopic level and this is shown to lead to non-linear\ncross diffusion terms that modify the conventional Fickean picture. After\nreviewing the derivation of the model, the experiments carried out to test the\nmodel are described. It is found that it can adequately explain the dynamics of\ntwo dense ink drops simultaneously evolving in a container filled with water.\nThe experiment shows that molecular crowding results in the formation of a\ndynamical barrier that prevents the mixing of the drops. This phenomenon is\nsuccessfully captured by the model. This suggests that the proposed model can\nbe justifiably viewed as a generalization of standard diffusion to a\nmultispecies setting, where crowding and steric interferences are taken into\naccount.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Drag forces in classical fields: Inclusions, or defects, moving at constant velocity through free classical\nfields are shown to be subject to a drag force which depends on the field\ndynamics and the coupling of the inclusion to the field. The results are used\nto predict the drag exerted on inclusions, such as proteins, in lipid membranes\ndue to their interaction with height and composition fluctuations. The force,\nmeasured in Monte Carlo simulations, on a point like magnetic field moving\nthrough an Ising ferromagnet is also well explained by these results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonexistence of the non-Gaussian fixed point predicted by the RG field\n  theory in 4-epsilon dimensions: The Ginzburg-Landau phase transition model is considered in d=4-epsilon\ndimensions within the renormalization group (RG) approach. The problem of\nexistence of the non-Gaussian fixed point is discussed. An equation is derived\nfrom the first principles of the RG theory (under the assumption that the fixed\npoint exists) for calculation of the correction-to-scaling term in the\nasymptotic expansion of the two-point correlation (Green's) function. It is\ndemonstrated clearly that, within the framework of the standard methods (well\njustified in the vicinity of the fixed point) used in the perturbative RG\ntheory, this equation leads to an unremovable contradiction with the known RG\nresults. Thus, in its very basics, the RG field theory in 4-epsilon dimensions\nis contradictory. To avoid the contradiction, we conclude that such a\nnon-Gaussian fixed point, as predicted by the RG field theory, does not exist.\nOur consideration does not exclude existence of a different fixed point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interface growth in two dimensions: A Loewner-equation approach: The problem of Laplacian growth in two dimensions is considered within the\nLoewner-equation framework. Initially the problem of fingered growth recently\ndiscussed by Gubiec and Szymczak [T. Gubiec and P. Szymczak, Phys. Rev. E 77,\n041602 (2008)] is revisited and a new exact solution for a three-finger\nconfiguration is reported. Then a general class of growth models for an\ninterface growing in the upper-half plane is introduced and the corresponding\nLoewner equation for the problem is derived. Several examples are given\nincluding interfaces with one or more tips as well as multiple growing\ninterfaces. A generalization of our interface growth model in terms of\n``Loewner domains,'' where the growth rule is specified by a time evolving\nmeasure, is briefly discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bogolyubov approximation for diagonal model of an interacting Bose gas: We study, using the Bogolyubov approximation, the thermodynamic behaviour of\na superstable Bose system whose energy operator in the second-quantized form\ncontains a nonlinear expression in the occupation numbers operators. We prove\nthat for all values of the chemical potential satisfying $\\mu > \\lambda(0)$,\nwhere $\\lambda (0)\\leq 0$ is the lowest energy value, the system undergoes\nBose--Einstein condensation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase Transitions in the Multicomponent Widom-Rowlinson Model and in\n  Hard Cubes on the BCC--Lattice: We use Monte Carlo techniques and analytical methods to study the phase\ndiagram of the M--component Widom-Rowlinson model on the bcc-lattice: there are\nM species all with the same fugacity z and a nearest neighbor hard core\nexclusion between unlike particles. Simulations show that for M greater or\nequal 3 there is a ``crystal phase'' for z lying between z_c(M) and z_d(M)\nwhile for z > z_d(M) there are M demixed phases each consisting mostly of one\nspecies. For M=2 there is a direct second order transition from the gas phase\nto the demixed phase while for M greater or equal 3 the transition at z_d(M)\nappears to be first order putting it in the Potts model universality class. For\nM large, Pirogov-Sinai theory gives z_d(M) ~ M-2+2/(3M^2) + ... . In the\ncrystal phase the particles preferentially occupy one of the sublattices,\nindependent of species, i.e. spatial symmetry but not particle symmetry is\nbroken. For M to infinity this transition approaches that of the one component\nhard cube gas with fugacity y = zM. We find by direct simulations of such a\nsystem a transition at y_c ~ 0.71 which is consistent with the simulation\nz_c(M) for large M. This transition appears to be always of the Ising type.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mass distribution exponents for growing trees: We investigate the statistics of trees grown from some initial tree by\nattaching links to preexisting vertices, with attachment probabilities\ndepending only on the valence of these vertices. We consider the asymptotic\nmass distribution that measures the repartition of the mass of large trees\nbetween their different subtrees. This distribution is shown to be a broad\ndistribution and we derive explicit expressions for scaling exponents that\ncharacterize its behavior when one subtree is much smaller than the others. We\nshow in particular the existence of various regimes with different values of\nthese mass distribution exponents. Our results are corroborated by a number of\nexact solutions for particular solvable cases, as well as by numerical\nsimulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Monte Carlo Chord Length Sampling for $d$-dimensional Markov binary\n  mixtures: The Chord Length Sampling (CLS) algorithm is a powerful Monte Carlo method\nthat models the effects of stochastic media on particle transport by generating\non-the-fly the material interfaces seen by the random walkers during their\ntrajectories. This annealed disorder approach, which formally consists of\nsolving the approximate Levermore-Pomraning equations for linear particle\ntransport, enables a considerable speed-up with respect to transport in\nquenched disorder, where ensemble-averaging of the Boltzmann equation with\nrespect to all possible realizations is needed. However, CLS intrinsically\nneglects the correlations induced by the spatial disorder, so that the accuracy\nof the solutions obtained by using this algorithm must be carefully verified\nwith respect to reference solutions based on quenched disorder realizations.\nWhen the disorder is described by Markov mixing statistics, such comparisons\nhave been attempted so far only for one-dimensional geometries, of the rod or\nslab type. In this work we extend these results to Markov media in\ntwo-dimensional (extruded) and three-dimensional geometries, by revisiting the\nclassical set of benchmark configurations originally proposed by Adams, Larsen\nand Pomraning, and extended by Brantley. In particular, we examine the\ndiscrepancies between CLS and reference solutions for scalar particle flux and\ntransmission/reflection coefficients as a function of the material properties\nof the benchmark specifications and of the system dimensionality.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Single-ion anisotropy in Haldane chains and form factor of the O(3)\n  nonlinear sigma model: We consider spin-1 Haldane chains with single-ion anisotropy, which exists in\nknown Haldane chain materials. We develop a perturbation theory in terms of\nanisotropy, where magnon-magnon interaction is important even in the low\ntemperature limit. The exact two-particle form factor in the O(3) nonlinear\nsigma model leads to quantitative predictions on several dynamical properties\nincluding dynamical structure factor and electron spin resonance frequency\nshift. These agree very well with numerical results, and with experimental data\non the Haldane chain material Ni(C$_5$H$_{14}$N$_2$)$_2$N$_3$(PF$_6$).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Singularities of the renormalization group flow for random elastic\n  manifolds: We consider the singularities of the zero temperature renormalization group\nflow for random elastic manifolds. When starting from small scales, this flow\ngoes through two particular points $l^{*}$ and $l_{c}$, where the average value\nof the random squared potential $<U^{2}>$ turnes negative ($l^{*}$) and where\nthe fourth derivative of the potential correlator becomes infinite at the\norigin ($l_{c}$). The latter point sets the scale where simple perturbation\ntheory breaks down as a consequence of the competition between many metastable\nstates. We show that under physically well defined circumstances $l_{c}<l^{*}$\nand thus the apparent renormalization of $<U^{2}>$ to negative values does not\ntake place.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Deterministic particle flows for constraining stochastic nonlinear\n  systems: Devising optimal interventions for constraining stochastic systems is a\nchallenging endeavour that has to confront the interplay between randomness and\nnonlinearity. Existing methods for identifying the necessary dynamical\nadjustments resort either to space discretising solutions of ensuing partial\ndifferential equations, or to iterative stochastic path sampling schemes. Yet,\nboth approaches become computationally demanding for increasing system\ndimension. Here, we propose a generally applicable and practically feasible\nnon-iterative methodology for obtaining optimal dynamical interventions for\ndiffusive nonlinear systems. We estimate the necessary controls from an\ninteracting particle approximation to the logarithmic gradient of two forward\nprobability flows evolved following deterministic particle dynamics. Applied to\nseveral biologically inspired models, we show that our method provides the\nnecessary optimal controls in settings with terminal-, transient-, or\ngeneralised collective-state constraints and arbitrary system dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dimensional crossover in dipolar magnetic layers: We investigate the static critical behaviour of a uniaxial magnetic layer,\nwith finite thickness L in one direction, yet infinitely extended in the\nremaining d dimensions. The magnetic dipole-dipole interaction is taken into\naccount. We apply a variant of Wilson's momentum shell renormalisation group\napproach to describe the crossover between the critical behaviour of the 3-D\nIsing, 2-d Ising, 3-D uniaxial dipolar, and the 2-d uniaxial dipolar\nuniversality classes. The corresponding renormalisation group fixed points are\nin addition to different effective dimensionalities characterised by distinct\nanalytic structures of the propagator, and are consequently associated with\nvarying upper critical dimensions. While the limiting cases can be discussed by\nmeans of dimensional epsilon expansions with respect to the appropriate upper\ncritical dimensions, respectively, the crossover features must be addressed in\nterms of the renormalisation group flow trajectories at fixed dimensionality d.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the apparent failure of the topological theory of phase transitions: The topological theory of phase transitions has its strong point in two\ntheorems proving that, for a wide class of physical systems, phase transitions\nnecessarily stem from topological changes of some submanifolds of configuration\nspace. It has been recently argued that the $2D$ lattice $\\phi^4$-model\nprovides a counterexample that falsifies this theory. It is here shown that\nthis is not the case: the phase transition of this model stems from an\nasymptotic ($N\\to\\infty$) change of topology of the energy level sets, in spite\nof the absence of critical points of the potential in correspondence of the\ntransition energy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Tracer dispersion in two-dimensional rough fractures: Tracer diffusion and hydrodynamic dispersion in two-dimensional fractures\nwith self-affine roughness is studied by analytic and numerical methods.\nNumerical simulations were performed via the lattice-Boltzmann approach, using\na new boundary condition for tracer particles that improves the accuracy of the\nmethod. The reduction in the diffusive transport, due to the fractal geometry\nof the fracture surfaces, is analyzed for different fracture apertures. In the\nlimit of small aperture fluctuations we derive the correction to the diffusive\ncoefficient in terms of the tortuosity, which accounts for the irregular\ngeometry of the fractures. Dispersion is studied when the two fracture surfaces\nare simple displaced normally to the mean fracture plane, and when there is a\nlateral shift as well. Numerical results are analyzed using the\n$\\Lambda$-parameter, related to convective transport within the fracture, and\nsimple arguments based on lubrication approximation. At very low P\\'eclet\nnumber, in the case where fracture surfaces are laterally shifted, we show\nusing several different methods that convective transport reduces dispersion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On Conservation Laws, Relaxation and Pre-relaxation after a Quantum\n  Quench: We consider the time evolution following a quantum quench in spin-1/2 chains.\nIt is well known that local conservation laws constrain the dynamics and,\neventually, the stationary behavior of local observables. We show that some\nwidely studied models, like the quantum XY model, possess extra families of\nlocal conservation laws in addition to the translation invariant ones. As a\nconsequence, the additional charges must be included in the generalized Gibbs\nensemble that describes the stationary properties. The effects go well beyond a\nsimple redefinition of the stationary state. The time evolution of a\nnon-translation invariant state under a (translation invariant) Hamiltonian\nwith a perturbation that weakly breaks the hidden symmetries underlying the\nextra conservation laws exhibits pre-relaxation. In addition, in the limit of\nsmall perturbation, the time evolution following pre-relaxation can be\ndescribed by means of a time-dependent generalized Gibbs ensemble.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metastable and Unstable Dynamics in multi-phase lattice Boltzmann: We quantitatively characterize the metastability in a multi-phase lattice\nBoltzmann model. The structure factor of density fluctuations is theoretically\nobtained and numerically verified to a high precision, for all simulated\nwave-vectors and reduced temperatures. The static structure factor is found to\nconsistently diverge as the temperature approaches the critical-point or the\ndensity approaches the spinodal line at a sub-critical temperature.\nTheoretically predicted critical exponents are observed in both cases. Finally,\nthe phase separation in the unstable branch follows the same pattern, i.e. the\ngeneration of interfaces with different topology, as observed in molecular\ndynamics simulations. All results can be independently reproduced through the\n``idea.deploy\" framework https://github.com/lullimat/idea.deploy",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Counting edge modes via dynamics of boundary spin impurities: We study dynamics of the one-dimensional Ising model in the presence of\nstatic symmetry-breaking boundary field via the two-time autocorrelation\nfunction of the boundary spin. We find that the correlations decay as a power\nlaw. We uncover a dynamical phase diagram where, upon tuning the strength of\nthe boundary field, we observe distinct power laws that directly correspond to\nchanges in the number of edge modes as the boundary and bulk magnetic field are\nvaried. We suggest how the universal physics can be demonstrated in current\nexperimental setups, such as Rydberg chains.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-sinusoidal current and current reversals in a gating ratchet: In this work, the ratchet dynamics of Brownian particles driven by an\nexternal sinusoidal (harmonic) force is investigated. The gating ratchet effect\nis observed when another harmonic is used to modulate the spatially symmetric\npotential in which the particles move. For small amplitudes of the harmonics,\nit is shown that the current (average velocity) of particles exhibits a\nsinusoidal shape as a function of a precise combination of the phases of both\nharmonics. By increasing the amplitudes of the harmonics beyond the small-limit\nregime, departures from the sinusoidal behavior are observed and current\nreversals can also be induced. These current reversals persist even for the\noverdamped dynamics of the particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Avalanche dynamics in hierarchical fiber bundles: Heterogeneous materials are often organized in a hierarchical manner, where a\nbasic unit is repeated over multiple scales.The structure then acquires a\nself-similar pattern. Examples of such structure are found in various\nbiological and synthetic materials. The hierarchical structure can have\nsignificant consequences for the failure strength and the mechanical response\nof such systems. Here we consider a fiber bundle model with hierarchical\nstructure and study the effect of the self-similar arrangement on the avalanche\ndynamics exhibited by the model during the approach to failure. We show that\nthe failure strength of the model generally decreases in a hierarchical\nstructure, as opposed to the situation where no such hierarchy exists. However,\nwe also report a special arrangement of the hierarchy for which the failure\nthreshold could be substantially above that of a non hierarchical reference\nstructure.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diffusion in Curved Spacetimes: Using simple kinematical arguments, we derive the Fokker-Planck equation for\ndiffusion processes in curved spacetimes. In the case of Brownian motion, it\ncoincides with Eckart's relativistic heat equation (albeit in a simpler form),\nand therefore provides a microscopic justification for his phenomenological\nheat-flux ansatz. Furthermore, we obtain the small-time asymptotic expansion of\nthe mean square displacement of Brownian motion in static spacetimes. Beyond\ngeneral relativity itself, this result has potential applications in analogue\ngravitational systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuation Relations For Adiabatic Pumping: We derive an extended fluctuation relation for an open system coupled with\ntwo reservoirs under adiabatic one-cycle modulation. We confirm that the\ngeometric phase caused by the Berry-Sintisyn-Nemenman curvature in the\nparameter space generates non-Gaussian fluctuations. This non-Gaussianity is\nenhanced for the instantaneous fluctuation relation when the bias between the\ntwo reservoirs disappears.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extracting Work from a single heat bath using velocity dependent\n  feedback: Thermodynamics of nanoscale devices is an active area of research. Despite\ntheir noisy surround- ing they often produce mechanical work (e.g. micro-heat\nengines) or display rectified Brownian motion (e.g. molecular motors). This\ninvokes the research in terms of experimentally quantifiable thermodynamic\nefficiencies. To enhance the efficiency of such devices, close-loop control is\nan useful technique. Here a single Brownian particle is driven by a harmonic\nconfinement with time-periodic contraction and expansion, together with a\nvelocity feedback that acts on the particle only when the trap contracts. Due\nto this feedback we are able to extract thermodynamic work out of the system\nhaving single heat bath without violating the Second Law of Thermodynamics. We\nanalyse the system using stochastic thermodynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Sensitivity to the initial conditions of the Time-Dependent Density\n  Functional Theory: Time-Dependent Density Functional Theory is mathematically formulated through\nnon-linear coupled time-dependent 3-dimensional partial differential equations\nand it is natural to expect a strong sensitivity of its solutions to variations\nof the initial conditions, akin to the butterfly effect ubiquitous in classical\ndynamics. Since the Schr\\\"odinger equation for an interacting many-body system\nis however linear and mathematically the exact equations of the Density\nFunctional Theory reproduce the corresponding one-body properties, it would\nfollow that the Lyapunov exponents are also vanishing within a Density\nFunctional Theory framework. Whether for realistic implementations of the\nTime-Dependent Density Functional Theory the question of absence of the\nbutterfly effect and whether the dynamics provided is indeed a predictable\ntheory was never discussed. At the same time, since the time-dependent density\nfunctional theory is a unique tool allowing us the study of non-equilibrium\ndynamics of strongly interacting many-fermion systems, the question of\npredictability of this theoretical framework is of paramount importance. Our\nanalysis, for a number of quantum superfluid many-body systems (unitary Fermi\ngas, nuclear fission, and heavy-ion collisions) with a classical equivalent\nnumber of degrees of freedom ${\\cal O}(10^{10})$ and larger, suggests that its\nmaximum Lyapunov exponents are negligible for all practical purposes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the entanglement entropy for a XY spin chain: The entanglement entropy for the ground state of a XY spin chain is related\nto the corner transfer matrices of the triangular Ising model and expressed in\nclosed form.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Connection Between Minimum of Solubility and Temperature of Maximum\n  Density in an Associating Lattice Gas Model: In this paper we investigate the solubility of a hard - sphere gas in a\nsolvent modeled as an associating lattice gas (ALG). The solution phase diagram\nfor solute at 5% is compared with the phase diagram of the original solute free\nmodel. Model properties are investigated thr ough Monte Carlo simulations and a\ncluster approximation. The model solubility is computed via simulations and\nshown to exhibit a minimum as a function of temperature. The line of minimum\nsolubility (TmS) coincides with the line of maximum density (TMD) for different\nsolvent chemical potentials.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics and thermodynamics of a topological transition in spin ice\n  materials under strain: We study single crystals of Dy$_2$Ti$_2$O$_7$ and Ho$_2$Ti$_2$O$_7$ under\nmagnetic field and stress applied along their [001] direction. We find that\nmany of the features that the emergent gauge field of spin ice confers to the\nmacroscopic magnetic properties are preserved in spite of the finite\ntemperature. The magnetisation vs. field shows an upward convexity within a\nbroad range of fields, while the static and dynamic susceptibilities present a\npeculiar peak. Following this feature for both compounds, we determine a single\nexperimental transition curve: that for the Kasteleyn transition in three\ndimensions, proposed more than a decade ago. Additionally, we observe that\ncompression up to $-0.8\\%$ along [001] does not significantly change the\nthermodynamics. However, the dynamical response of Ho$_2$Ti$_2$O$_7$ is quite\nsensitive to changes introduced in the ${\\rm Ho}^{3+}$ environment. Uniaxial\ncompression can thus open up experimental access to equilibrium properties of\nspin ice at low temperatures.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Realization of Levy flights as continuous processes: On the basis of multivariate Langevin processes we present a realization of\nLevy flights as a continuous process. For the simple case of a particle moving\nunder the influence of friction and a velocity dependent stochastic force we\nexplicitly derive the generalized Langevin equation and the corresponding\ngeneralized Fokker-Planck equation describing Levy flights. Our procedure is\nsimilar to the treatment of the Kramers-Fokker Planck equation in the\nSmoluchowski limit. The proposed approach forms a feasible way of tackling Levy\nflights in inhomogeneous media or systems with boundaries what is up to now a\nchallenging problem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Some Finite Size Effects in Simulations of Glass Dynamics: We present the results of a molecular dynamics computer simulation in which\nwe investigate the dynamics of silica. By considering different system sizes,\nwe show that in simulations of the dynamics of this strong glass former\nsurprisingly large finite size effects are present. In particular we\ndemonstrate that the relaxation times of the incoherent intermediate scattering\nfunction and the time dependence of the mean squared displacement are affected\nby such finite size effects. By compressing the system to high densities, we\ntransform it to a fragile glass former and find that for that system these\ntypes of finite size effects are much weaker.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the Conversion of Work into Heat: Microscopic Models and Macroscopic\n  Equations: We summarize and extend some of the results obtained recently for the\nmicroscopic and macroscopic behavior of a pinned harmonic chain, with random\nvelocity flips at Poissonian times, acted on by a periodic force {at one end}\nand in contact with a heat bath at the other end. Here we consider the case\nwhere the system is in contact with two heat baths at different temperatures\nand a periodic force is applied at any position. This leads in the hydrodynamic\nlimit to a heat equation for the temperature profile with a discontinuous slope\nat the position where the force acts. Higher dimensional systems, unpinned\ncases and anharmonic interactions are also considered.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phonon Thermodynamics versus Electron-Phonon Models: Applying the path integral formalism we study the equilibrium thermodynamics\nof the phonon field both in the Holstein and in the Su-Schrieffer-Heeger\nmodels. The anharmonic cumulant series, dependent on the peculiar source\ncurrents of the {\\it e-ph} models, have been computed versus temperature in the\ncase of a low energy oscillator. The cutoff in the series expansion has been\ndetermined, in the low $T$ limit, using the constraint of the third law of\nthermodynamics. In the Holstein model, the free energy derivatives do not show\nany contribution ascribable to {\\it e-ph} anharmonic effect. We find signatures\nof large {\\it e-ph} anharmonicities in the Su-Schrieffer-Heeger model mainly\nvisible in the temperature dependent peak displayed by the phonon heat\ncapacity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Counting metastable states in a kinetically constrained model using a\n  patch repetition analysis: We analyse metastable states in the East model, using a recently-proposed\npatch-repetition analysis based on time-averaged density profiles. The results\nreveal a hierarchy of states of varying lifetimes, consistent with previous\nstudies in which the metastable states were identified and used to explain the\nglassy dynamics of the model. We establish a mapping between these states and\nconfigurations of systems of hard rods, which allows us to analyse both typical\nand atypical metastable states. We discuss connections between the complexity\nof metastable states and large-deviation functions of dynamical quantities,\nboth in the context of the East model and more generally in glassy systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Conservation-laws-preserving algorithms for spin dynamics simulations: We propose new algorithms for numerical integration of the equations of\nmotion for classical spin systems with fixed spatial site positions. The\nalgorithms are derived on the basis of a mid-point scheme in conjunction with\nthe multiple time staging propagation. Contrary to existing predictor-corrector\nand decomposition approaches, the algorithms introduced preserve all the\nintegrals of motion inherent in the basic equations. As is demonstrated for a\nlattice ferromagnet model, the present approach appears to be more efficient\neven over the recently developed decomposition method.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Criticality and self-organization in branching processes: application to\n  natural hazards: The statistics of natural catastrophes contains very counter-intuitive\nresults. Using earthquakes as a working example, we show that the energy\nradiated by such events follows a power-law or Pareto distribution. This means,\nin theory, that the expected value of the energy does not exist (is infinite),\nand in practice, that the mean of a finite set of data in not representative of\nthe full population. Also, the distribution presents scale invariance, which\nimplies that it is not possible to define a characteristic scale for the\nenergy. A simple model to account for this peculiar statistics is a branching\nprocess: the activation or slip of a fault segment can trigger other segments\nto slip, with a certain probability, and so on. Although not recognized\ninitially by seismologists, this is a particular case of the stochastic process\nstudied by Galton and Watson one hundred years in advance, in order to model\nthe extinction of (prominent) families. Using the formalism of probability\ngenerating functions we will be able to derive, in an accessible way, the main\nproperties of these models. Remarkably, a power-law distribution of energies is\nonly recovered in a very special case, when the branching process is at the\nonset of attenuation and intensification, i.e., at criticality. In order to\naccount for this fact, we introduce the self-organized critical models, in\nwhich, by means of some feedback mechanism, the critical state becomes an\nattractor in the evolution of such systems. Analogies with statistical physics\nare drawn. The bulk of the material presented here is self-contained, as only\nelementary probability and mathematics are needed to start to read.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mechanisms of Granular Spontaneous Stratification and Segregation in\n  Two-Dimensional Silos: Spontaneous stratification of granular mixtures has been reported by Makse et\nal. [Nature 386, 379 (1997)] when a mixture of grains differing in size and\nshape is poured in a quasi-two-dimensional heap. We study this phenomenon using\ntwo different approaches. First, we introduce a cellular automaton model that\nillustrates clearly the physical mechanism; the model displays stratification\nwhenever the large grains are rougher than the small grains, in agreement with\nthe experiments. Moreover, the dynamics are close to those of the experiments,\nwhere the layers are built through a ``kink'' at which the rolling grains are\nstopped. Second, we develop a continuum approach, based on a recently\nintroduced set of coupled equations for surface flows of granular mixtures that\nallows us to make quantitative predictions for relevant quantities. We study\nthe continuum model in two limit regimes: the large flux or thick flow regime,\nwhere the percolation effect (i.e., segregation of the rolling grains in the\nflow) is important, and the small flux or thin flow regime, where all the\nrolling grains are in contact with the surface of the sandpile. We find that\nthe wavelength of the layers behaves linearly with the flux of grains. We\nobtain analytical predictions for the shape of the kink giving rise to\nstratification as well as the profile of the rolling and static species when\nsegregation of the species is observed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Classical no-cloning theorem under Liouville dynamics by non-Csisz\u00e1r\n  f-divergence: The Csisz\\'ar f-divergence, which is a class of information distances, is\nknown to offer a useful tool for analysing the classical counterpart of the\ncloning operations that are quantum mechanically impossible for the factorized\nand marginality classical probability distributions under Liouville dynamics.\nWe show that a class of information distances that does not belong to this\ndivergence class also allows for the formulation of a classical analogue of the\nquantum no-cloning theorem. We address a family of nonlinear Liouville-like\nequations, and generic distances, to obtain constraints on the corresponding\nfunctional forms, associated with the formulation of classical analogue of the\nno-cloning principle.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic model of self-driven two-species objects in the context of\n  the pedestrian dynamics: In this work we propose a model to describe the statistical fluctuations of\nthe self-driven objects (species A) walking against an opposite crowd (species\nB) in order to simulate the regime characterized by stop-and-go waves in the\ncontext of pedestrian dynamics. By using the concept of single-biased random\nwalks (SBRW), this setup is modeled both via partial differential equations and\nby Monte-Carlo simulations. The problem is non-interacting until the opposite\nparticles visit the same cell of the considered particle. In this situation,\ndelays on the residence time of the particles per cell depends on the\nconcentration of particles of opposite species. We analyzed the fluctuations on\nthe position of particles and our results show a non-regular diffusion\ncharacterized by long-tailed and asymmetric distributions which is better\nfitted by some chromatograph distributions found in the literature. We also\nshow that effects of the reverse crowd particles is able to enlarge the\ndispersion of target particles in relation to the non-biased case ($\\alpha =0$)\nafter observing a small decrease of this dispersion",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hidden slow degrees of freedom and fluctuation theorems: an analytically\n  solvable model: In some situations in stochastic thermodynamics not all relevant slow degrees\nof freedom are accessible. Consequently, one adopts an effective description\ninvolving only the visible degrees of freedom. This gives rise to an apparent\nentropy production that violates standard fluctuation theorems. We present an\nanalytically solvable model illustrating how the fluctuation theorems are\nmodified. Furthermore, we define an alternative to the apparent entropy\nproduction: the marginal entropy production which fulfills the fluctuation\ntheorems in the usual form. We show that the non-Markovianity of the visible\nprocess is responsible for the deviations in the fluctuation theorems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mapping a Homopolymer onto a Model Fluid: We describe a linear homopolymer using a Grand Canonical ensemble formalism,\na statistical representation that is very convenient for formal manipulations.\nWe investigate the properties of a system where only next neighbor interactions\nand an external, confining, field are present, and then show how a general pair\ninteraction can be introduced perturbatively, making use of a Mayer expansion.\nThrough a diagrammatic analysis, we shall show how constitutive equations\nderived for the polymeric system are equivalent to the Ornstein-Zernike and\nP.Y. equations for a simple fluid, and find the implications of such a mapping\nfor the simple situation of Van der Waals mean field model for the fluid.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "From crystal to amorphopus: a novel route towards unjamming in soft disk\n  packings: It is presented a numerical study on the unjamming packing fraction of bi-\nand polydisperse disk packings, which are generated through compression of a\nmonodisperse crystal. In bidisperse systems, a fraction f_+ = 40% up to 80% of\nthe total number of particles have their radii increased by \\Delta R, while the\nrest has their radii decreased by the same amount. Polydisperse packings are\nprepared by changing all particle radii according to a uniform distribution in\nthe range [-\\Delta R,\\Delta R]. The results indicate that the critical packing\nfraction is never larger than the value for the initial monodisperse crystal,\n\\phi = \\pi/12, and that the lowest value achieved is approximately the one for\nrandom close packing. These results are seen as a consequence of the interplay\nbetween the increase in small-small particle contacts and the local crystalline\norder provided by the large-large particle contacts.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the universal Gaussian behavior of Driven Lattice Gases at\n  short-times: The dynamic and static critical behaviors of driven and equilibrium lattice\ngas models are studied in two spatial dimensions. We show that in the\nshort-time regime immediately following a critical quench, the dynamics of the\ntransverse order parameters, auto-correlations, and Binder cumulant are\nconsistent with the prediction of a Gaussian, $i.e.,$ non-interacting,\neffective theory, both for the equilibrium lattice gas and its nonequilibrium\ncounterparts. Such a \"super-universal\" behavior is observed only at short times\nafter a critical quench, while the various models display their distinct\nbehaviors in the stationary states, described by the corresponding, known\nuniversality classes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quasiperiodicity in the $\u03b1-$Fermi-Pasta-Ulam-Tsingou problem\n  revisited: an approach using ideas from wave turbulence: The Fermi-Pasta-Ulam-Tsingou (FPUT) problem addresses fundamental questions\nin statistical physics, and attempts to understand the origin of recurrences in\nthe system have led to many great advances in nonlinear dynamics and\nmathematical physics. In this work we revisit the problem and study\nquasiperiodic recurrences in the weakly nonlinear $\\alpha-$FPUT system in more\ndetail. We aim to reconstruct the quasiperiodic behaviour observed in the\noriginal paper from the canonical transformation used to remove the three wave\ninteractions, which is necessary before applying the wave turbulence formalism.\nWe expect the construction to match the observed quasiperiodicity if we are in\nthe weakly nonlinear regime. Surprisingly, in our work we show that this is not\nalways the case and in particular, the recurrences observed in the original\npaper cannot be constructed by our method. We attribute this disagreement to\nthe presence of small denominators in the canonical transformation used to\nremove the three wave interactions before arriving at the starting point of\nwave turbulence. We also show that these small denominators are present even in\nthe weakly nonlinear regime, and they become more significant as the system\nsize is increased. We also discuss our results in the context of the problem of\nequilibration in the $\\alpha-$FPUT system, and point out some mathematical\nchallenges when the wave turbulence formalism is applied to explain\nthermalization in the $\\alpha-$FPUT problem. We argue that certain aspects of\nthe $\\alpha-$FPUT system such as presence of the stochasticity threshold,\nthermalization in the thermodynamic limit and the cause of quasiperiodicity are\nnot clear, and that they require further mathematical and numerical studies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Peierls instability for the Holstein model: We consider the static Holstein model, describing a chain of Fermions\ninteracting with a classical phonon field, when the interaction is weak and the\ndensity is a rational number. We show that the energy of the system, as a\nfunction of the phonon field, has two stationary points, defined up to a\nlattice translation, which are local minima in the space of fields periodic\nwith period equal to the inverse of the density.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Power-Law Time Distribution of Large Earthquakes: We study the statistical properties of time distribution of seimicity in\nCalifornia by means of a new method of analysis, the Diffusion Entropy. We find\nthat the distribution of time intervals between a large earthquake (the main\nshock of a given seismic sequence) and the next one does not obey Poisson\nstatistics, as assumed by the current models. We prove that this distribution\nis an inverse power law with an exponent $\\mu=2.06 \\pm 0.01$. We propose the\nLong-Range model, reproducing the main properties of the diffusion entropy and\ndescribing the seismic triggering mechanisms induced by large earthquakes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding how both the partitions of a bipartite network affect its\n  one-mode projection: It is a well-known fact that the degree distribution (DD) of the nodes in a\npartition of a bipartite network influences the DD of its one-mode projection\non that partition. However, there are no studies exploring the effect of the DD\nof the other partition on the one-mode projection. In this article, we show\nthat the DD of the other partition, in fact, has a very strong influence on the\nDD of the one-mode projection. We establish this fact by deriving the exact or\napproximate closed-forms of the DD of the one-mode projection through the\napplication of generating function formalism followed by the method of\niterative convolution. The results are cross-validated through appropriate\nsimulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding the Frequency Distribution of Mechanically Stable Disk\n  Packings: Relative frequencies of mechanically stable (MS) packings of frictionless\nbidisperse disks are studied numerically in small systems. The packings are\ncreated by successively compressing or decompressing a system of soft purely\nrepulsive disks, followed by energy minimization, until only infinitesimal\nparticle overlaps remain. For systems of up to 14 particles most of the MS\npackings were generated. We find that the packings are not equally probable as\nhas been assumed in recent thermodynamic descriptions of granular systems.\nInstead, the frequency distribution, averaged over each packing-fraction\ninterval $\\Delta \\phi$, grows exponentially with increasing $\\phi$. Moreover,\nwithin each packing-fraction interval MS packings occur with frequencies $f_k$\nthat differ by many orders of magnitude. Also, key features of the frequency\ndistribution do not change when we significantly alter the packing-generation\nalgorithm--for example frequent packings remain frequent and rare ones remain\nrare. These results indicate that the frequency distribution of MS packings is\nstrongly influenced by geometrical properties of the multidimensional\nconfiguration space. By adding thermal fluctuations to a set of the MS\npackings, we were able to examine a number of local features of configuration\nspace near each packing including the time required for a given packing to\nbreak to a distinct one, which enabled us to estimate the energy barriers that\nseparate one packing from another. We found a positive correlation between the\npacking frequencies and the heights of the lowest energy barriers $\\epsilon_0$.\nWe also examined displacement fluctuations away from the MS packings to\ncorrelate the size and shape of the local basins near each packing to the\npacking frequencies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relaxation of nonequilibrium populations after a pump: the breaking of\n  Mathiessen$'$s rule: From the early days of many-body physics, it was realized that the\nself-energy governs the relaxation or lifetime of the retarded Green$'$s\nfunction. So it seems reasonable to directly extend those results into the\nnonequilibrium domain. But experiments and calculations of the response of\nquantum materials to a pump show that the relationship between the relaxation\nand the self-energy only holds in special cases. Experimentally, the decay time\nfor a population to relax back to equilibrium and the linewidth measured in a\nlinear-response angle-resolved photoemission spectroscopy differ by large\namounts. Theoretically, aside from the weak-coupling regime where the\nrelationship holds, one also finds deviations and additionally one sees\nviolations of Mathiessen$'$s rule. In this work, we examine whether looking at\nan effective transport relaxation time helps to analyze the decay times of\nexcited populations as they relax back to equilibrium. We conclude that it may\ndo a little better, but it has a fitting parameter for the overall scale which\nmust be determined.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "First-passage and extreme-value statistics of a particle subject to a\n  constant force plus a random force: We consider a particle which moves on the x axis and is subject to a constant\nforce, such as gravity, plus a random force in the form of Gaussian white\nnoise. We analyze the statistics of first arrival at point $x_1$ of a particle\nwhich starts at $x_0$ with velocity $v_0$. The probability that the particle\nhas not yet arrived at $x_1$ after a time $t$, the mean time of first arrival,\nand the velocity distribution at first arrival are all considered. We also\nstudy the statistics of the first return of the particle to its starting point.\nFinally, we point out that the extreme-value statistics of the particle and the\nfirst-passage statistics are closely related, and we derive the distribution of\nthe maximum displacement $m={\\rm max}_t[x(t)]$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Persistence discontinuity in disordered contact processes with\n  long-range interactions: We study the local persistence probability during non-stationary time\nevolutions in disordered contact processes with long-range interactions by a\ncombination of the strong-disorder renormalization group (SDRG) method, a\nphenomenological theory of rare regions, and numerical simulations. We find\nthat, for interactions decaying as an inverse power of the distance, the\npersistence probability tends to a non-zero limit not only in the inactive\nphase but also in the critical point. Thus, unlike in the contact process with\nshort-range interactions, the persistence in the limit $t\\to\\infty$ is a\ndiscontinuous function of the control parameter. For stretched exponentially\ndecaying interactions, the limiting value of the persistence is found to remain\ncontinuous, similar to the model with short-range interactions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Theoretical construction of 1D anyon models: One-dimensional anyon models are renewedly constructed by using path integral\nformalism. A statistical interaction term is introduced to realize the anyonic\nexchange statistics. The quantum mechanics formulation of statistical\ntransmutation is presented.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Transient anomalous diffusion in heterogeneous media with stochastic\n  resetting: We investigate a diffusion process in heterogeneous media where particles\nstochastically reset to their initial positions at a constant rate. The\nheterogeneous media is modeled using a spatial-dependent diffusion coefficient\nwith a power-law dependence on particles' positions. We use the Green function\napproach to obtain exact solutions for the probability distribution of\nparticles' positions and the mean square displacement. These results are\nfurther compared and agree with numerical simulations of a Langevin equation.\nWe also study the first-passage time problem associated with this diffusion\nprocess and obtain an exact expression for the mean first-passage time. Our\nfindings show that this system exhibits non-Gaussian distributions, transient\nanomalous diffusion (sub- or superdiffusion) and stationary states that\nsimultaneously depend on the media heterogeneity and the resetting rate. We\nfurther demonstrate that the media heterogeneity non-trivially affect the mean\nfirst-passage time, yielding an optimal resetting rate for which this quantity\ndisplays a minimum.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Analytic model of thermalization: Quantum emulation of classical\n  cellular automata: We introduce a novel method of quantum emulation of a classical reversible\ncellular automaton. By applying this method to a chaotic cellular automaton,\nthe obtained quantum many-body system thermalizes while all the energy\neigenstates and eigenvalues are solvable. These explicit solutions allow us to\nverify the validity of some scenarios of thermalization to this system. We find\nthat two leading scenarios, the eigenstate thermalization hypothesis scenario\nand the large effective dimension scenario, do not explain thermalization in\nthis model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hidden Criticality of Counterion Condensation Near a Charged Cylinder: We study the condensation transition of counterions on a charged cylinder via\nMonte Carlo simulations. Varying the cylinder radius systematically in relation\nto the system size, we find that all counterions are bound to the cylinder and\nthe heat capacity shows a drop at a finite Manning parameter. A finite-size\nscaling analysis is carried out to confirm the criticality of the complete\ncondensation transition, yielding the same critical exponents with the Manning\ntransition. We show that the existence of the complete condensation is\nessential to explain how the condensation nature alters from continuous to\ndiscontinuous transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Microscopic theory of the glassy dynamics of passive and active network\n  materials: Signatures of glassy dynamics have been identified experimentally for a rich\nvariety of materials in which molecular networks provide rigidity. Here we\npresent a theoretical framework to study the glassy behavior of both passive\nand active network materials. We construct a general microscopic network model\nthat incorporates nonlinear elasticity of individual filaments and steric\nconstraints due to crowding. Based on constructive analogies between structural\nglass forming liquids and random field Ising magnets implemented using a\nheterogeneous self-consistent phonon method, our scheme provides a microscopic\napproach to determine the mismatch surface tension and the configurational\nentropy, which compete in determining the barrier for structural rearrangements\nwithin the random first order transition theory of escape from a local energy\nminimum. The influence of crosslinking on the fragility of inorganic network\nglass formers is recapitulated by the model. For active network materials, the\nmapping, which correlates the glassy characteristics to the network\narchitecture and properties of nonequilibrium motor processes, is shown to\ncapture several key experimental observations on the cytoskeleton of living\ncells: Highly connected tense networks behave as strong glass formers; intense\nmotor action promotes reconfiguration. The fact that our model assuming a\nnegative motor susceptibility predicts the latter suggests that on average the\nmotorized processes in living cells do resist the imposed mechanical load. Our\ncalculations also identify a spinodal point where simultaneously the mismatch\npenalty vanishes and the mechanical stability of amorphous packing disappears.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hidden slow degrees of freedom and fluctuation theorems: an analytically\n  solvable model: In some situations in stochastic thermodynamics not all relevant slow degrees\nof freedom are accessible. Consequently, one adopts an effective description\ninvolving only the visible degrees of freedom. This gives rise to an apparent\nentropy production that violates standard fluctuation theorems. We present an\nanalytically solvable model illustrating how the fluctuation theorems are\nmodified. Furthermore, we define an alternative to the apparent entropy\nproduction: the marginal entropy production which fulfills the fluctuation\ntheorems in the usual form. We show that the non-Markovianity of the visible\nprocess is responsible for the deviations in the fluctuation theorems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The second law and fluctuations of work: The case against quantum\n  fluctuation theorems: We study how Thomson's formulation of the second law: no work is extracted\nfrom an equilibrium ensemble by a cyclic process, emerges in the quantum\nsituation through the averaging over fluctuations of work. The latter concept\nis carefully defined for an ensemble of quantum systems interacting with\nmacroscopic sources of work. The approach is based on first splitting a mixed\nquantum ensemble into pure subensembles, which according to quantum mechanics\nare maximally complete and irreducible. The splitting is done by filtering the\noutcomes of a measurement process. A critical review is given of two other\napproaches to fluctuations of work proposed in the literature. It is shown that\nin contrast to those ones, the present definition {\\it i)} is consistent with\nthe physical meaning of the concept of work as mechanical energy lost by the\nmacroscopic sources, or, equivalently, as the average energy acquired by the\nensemble; {\\it ii)} applies to an arbitrary non-equilibrium state. There is no\ndirect generalization of the classical work-fluctuation theorem to the proper\nquantum domain. This implies some non-classical scenarios for the emergence of\nthe second law.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nucleation of Market Shocks in Sornette-Ide model: The Sornette-Ide differential equation of herding and rational trader\nbehaviour together with very small random noise is shown to lead to crashes or\nbubbles where the price change goes to infinity after an unpredictable time.\nAbout 100 time steps before this singularity, a few predictable roughly\nlog-periodic oscillations are seen.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Efficient stochastic thermostatting of path integral molecular dynamics: The path integral molecular dynamics (PIMD) method provides a convenient way\nto compute the quantum mechanical structural and thermodynamic properties of\ncondensed phase systems at the expense of introducing an additional set of\nhigh-frequency normal modes on top of the physical vibrations of the system.\nEfficiently sampling such a wide range of frequencies provides a considerable\nthermostatting challenge. Here we introduce a simple stochastic path integral\nLangevin equation (PILE) thermostat which exploits an analytic knowledge of the\nfree path integral normal mode frequencies. We also apply a recently-developed\ncolored-noise thermostat based on a generalized Langevin equation (GLE), which\nautomatically achieves a similar, frequency-optimized sampling. The sampling\nefficiencies of these thermostats are compared with that of the more\nconventional Nos\\'e-Hoover chain (NHC) thermostat for a number of physically\nrelevant properties of the liquid water and hydrogen-in-palladium systems. In\nnearly every case, the new PILE thermostat is found to perform just as well as\nthe NHC thermostat while allowing for a computationally more efficient\nimplementation. The GLE thermostat also proves to be very robust delivering a\nnear-optimum sampling efficiency in all of the cases considered. We suspect\nthat these simple stochastic thermostats will therefore find useful application\nin many future PIMD simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "3-Dimensional Multilayered 6-vertex Statistical Model: Exact Solution: Solvable via Bethe Ansatz (BA) anisotropic statistical model on cubic lattice\nconsisting of locally interacting 6-vertex planes, is studied. Symmetries of BA\nlead to infinite hierarchy of possible phases, which is further restricted by\nnumerical simulations. The model is solved for arbitrary value of the\ninterlayer coupling constant. Resulting is the phase diagram in general\n3-parameter space. Exact mapping onto the models with some inhomogenious sets\nof interlayer coupling constants is established.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Equivalent-neighbor Potts models in two dimensions: We investigate the two-dimensional $q=3$ and 4 Potts models with a variable\ninteraction range by means of Monte Carlo simulations. We locate the phase\ntransitions for several interaction ranges as expressed by the number $z$ of\nequivalent neighbors. For not too large $z$, the transitions fit well in the\nuniversality classes of the short-range Potts models. However, at longer ranges\nthe transitions become discontinuous. For $q=3$ we locate a tricritical point\nseparating the continuous and discontinuous transitions near $z=80$, and a\ncritical fixed point between $z=8$ and 12. For $q=4$ the transition becomes\ndiscontinuous for $z > 16$. The scaling behavior of the $q=4$ model with $z=16$\napproximates that of the $q=4$ merged critical-tricritical fixed point\npredicted by the renormalization scenario.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Efficient Simulation of Low Temperature Physics in One-Dimensional\n  Gapless Systems: We discuss the computational efficiency of the finite temperature simulation\nwith the minimally entangled typical thermal states (METTS). To argue that\nMETTS can be efficiently represented as matrix product states, we present an\nanalytic upper bound for the average entanglement Renyi entropy of METTS for\nRenyi index $0<q\\leq 1$. In particular, for 1D gapless systems described by\nCFTs, the upper bound scales as $\\mathcal{O}(c N^0 \\log \\beta)$ where $c$ is\nthe central charge and $N$ is the system size. Furthermore, we numerically find\nthat the average Renyi entropy exhibits a universal behavior characterized by\nthe central charge and is roughly given by half of the analytic upper bound.\nBased on these results, we show that METTS provide a significant speedup\ncompared to employing the purification method to analyze thermal equilibrium\nstates at low temperatures in 1D gapless systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cutting-Plane Algorithms and Solution Whitening for the Vertex-Cover\n  Problem: The phase-transition behavior of the NP-hard vertex-cover (VC) combinatorial\noptimization problem is studied numerically by linear programming (LP) on\nensembles of random graphs. As the basic Simplex (SX) algorithm suitable for\nsuch LPs may produce incomplete solutions for sufficiently complex graphs, the\napplication of cutting-plane (CP) methods is sought. We consider Gomory and\n{0,1/2} cuts. We measure the probability of obtaining complete solutions with\nthese approaches as a function of the average node degree c and observe\ntransition between typically complete and incomplete phase regions. While not\ngenerally complete solutions are obtained for graphs of arbitrarily high\ncomplexity, the CP approaches still advance the boundary in comparison to the\npure SX algorithm, beyond the known replica-symmetry breaking (RSB) transition\nat c=e=2.718... . In fact, our results provide evidence for another algorithmic\ntransition at c=2.90(2).\n  Besides this, we quantify the transition between easy and hard solvability of\nthe VC problem also in terms of numerical effort. Further we study the\nso-called whitening of the solution, which is a measure for the degree of\nfreedom that single vertices experience with respect to degenerate solutions.\nInspection of the quantities related to clusters of white vertices reveals that\nwhitening is affected, only slightly but measurably, by the RSB transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random walks in unweighted and weighted modular scale-free networks with\n  a perfect trap: Designing optimal structure favorable to diffusion and effectively\ncontrolling the trapping process are crucial in the study of trapping\nproblem---random walks with a single trap. In this paper, we study the trapping\nproblem occurring on unweighted and weighted networks, respectively. The\nnetworks under consideration display the striking scale-free, small-world, and\nmodular properties, as observed in diverse real-world systems. For binary\nnetworks, we concentrate on three cases of trapping problems with the trap\nlocated at a peripheral node, a neighbor of the root with the least\nconnectivity, and a farthest node, respectively. For weighted networks with\nedge weights controlled by a parameter, we also study three trapping problems,\nin which the trap is placed separately at the root, a neighbor of the root with\nthe least degree, and a farthest node. For all the trapping problems, we obtain\nthe analytical formulas for the average trapping time (ATT) measuring the\nefficiency of the trapping process, as well as the leading scaling of ATT. We\nshow that for all the trapping problems in the binary networks with a trap\nlocated at different nodes, the dominating scalings of ATT reach the possible\nminimum scalings, implying that the networks have optimal structure that is\nadvantageous to efficient trapping. Furthermore, we show that for trapping in\nthe weighted networks, the ATT is controlled by the weight parameter, through\nmodifying which, the ATT can behave superlinealy, linearly, sublinearly, or\nlogarithmically with the system size. This work could help improving the design\nof systems with efficient trapping process and offers new insight into control\nof trapping in complex systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact results for a generalized spin-1/2 Ising-Heisenberg diamond chain\n  with the second-neighbor interaction between nodal spins: The ground state and thermodynamics of a generalized spin-1/2\nIsing-Heisenberg diamond chain with the second-neighbor interaction between\nnodal spins are calculated exactly using the mapping method based on the\ndecoration-iteration transformation. Rigorous results for the magnetization,\nsusceptibility, and heat capacity are investigated in dependence on temperature\nand magnetic field for the frustrated diamond spin chain with the\nantiferromagnetic Ising and Heisenberg interactions. It is demonstrated that\nthe second-neighbor interaction between nodal spins gives rise to a greater\ndiversity of low-temperature magnetization curves, which may include an\nintermediate plateau at two-third of the saturation magnetization related to\nthe classical ferrimagnetic (up-up-up-down-up-up-...) ground state with\ntranslationally broken symmetry besides an intermediate one-third magnetization\nplateau reflecting the translationally invariant quantum ferrimagnetic\n(monomer-dimer) spin arrangement.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Enhancement of stability of metastable states in the presence of\n  L\u00e9vy noise: The barrier crossing event for superdiffusion in the form of symmetric\nL\\'{e}vy flights is investigated. We derive from the fractional Fokker-Planck\nequation a general differential equation with the corresponding conditions\nuseful to calculate the mean residence time of a particle in a fixed interval\nfor an arbitrary smooth potential profile, in particular metastable, with a\nsink and a L\\'{e}vy noise with an arbitrary index $\\alpha$. A closed expression\nin quadrature of the nonlinear relaxation time for L\\'{e}vy flights with the\nindex $\\alpha =1$ in cubic metastable potential is obtained. Enhancement of the\nmean residence time in the metastable state, analytically derived, due to\nL\\'{e}vy noise is found.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Resonant suppression of thermal stability of the nanoparticle\n  magnetization by a rotating magnetic field: We study the thermal stability of the periodic (P) and quasi-periodic (Q)\nprecessional modes of the nanoparticle magnetic moment induced by a rotating\nmagnetic field. An analytical method for determining the lifetime of the P mode\nin the case of high anisotropy barrier and small amplitudes of the rotating\nfield is developed within the Fokker-Planck formalism. In general case, the\nthermal stability of both P and Q modes is investigated by numerical simulation\nof the stochastic Landau-Lifshitz equation. We show analytically and\nnumerically that the lifetime is a nonmonotonic function of the rotating field\nfrequency which, depending on the direction of field rotation, has either a\npronounced maximum or a deep minimum near the Larmor frequency.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous Behavior of the Zero Field Susceptibility of the Ising Model\n  on the Cayley Tree: It is found that the zero field susceptibility chi of the Ising model on the\nCayley tree exhibits unusually weak divergence at the critical point Tc. The\nsusceptibility amplitude is found to diverge at Tc proportionally to the tree\ngeneration level n, while the behavior of chi is otherwise analytic in the\nvicinity of Tc, with the critical exponent gamma=0.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Thermodynamic Casimir Effect in $^4$He Films near $T_\u03bb$: Monte\n  Carlo Results: The universal finite-size scaling function of the critical Casimir force for\nthe three dimensional XY universality class with Dirichlet boundary conditions\nis determined using Monte Carlo simulations. The results are in excellent\nagreement with recent experiments on $^4$He Films at the superfluid transition\nand with available theoretical predictions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Driving, conservation and absorbing states in sandpiles: We use a phenomenological field theory, reflecting the symmetries and\nconservation laws of sandpiles, to compare the driven dissipative sandpile,\nwidely studied in the context of self-organized criticality, with the\ncorresponding fixed-energy model. The latter displays an absorbing-state phase\ntransition with upper critical dimension $d_c=4$. We show that the driven model\nexhibits a fundamentally different approach to the critical point, and compute\na subset of critical exponents. We present numerical simulations in support of\nour theoretical predictions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stable quasicrystalline ground states: We give a strong evidence that noncrystalline materials such as quasicrystals\nor incommensurate solids are not exceptions but rather are generic in some\nregions of a phase space. We show this by constructing classical lattice-gas\nmodels with translation-invariant, finite-range interactions and with a unique\nquasiperiodic ground state which is stable against small perturbations of\ntwo-body potentials. More generally, we provide a criterion for stability of\nnonperiodic ground states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fixation in cyclically competing species on a directed graph with\n  quenched disorder: A simple model of cyclically competing species on a directed graph with\nquenched disorder is proposed as an extension of the rock-paper-scissors model.\nBy assuming that the effects of loops in a directed random graph can be ignored\nin the thermodynamic limit, it is proved for any finite disorder that the\nsystem fixates to a frozen configuration when the species number $s$ is larger\nthan the spatial connectivity $c$, and otherwise stays active. Nontrivial lower\nand upper bounds for the persistence probability of a site never changing its\nstate are also analytically computed. The obtained bounds and numerical\nsimulations support the existence of a phase transition as a function of\ndisorder for $1<c_l(s)\\le c <s$, with a $s$-dependent threshold of the\nconnectivity $c_l(s)$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of the mesoscopic thermoelectric heat engine beyond the\n  linear-response regime: Mesoscopic thermoelectric heat engine is much anticipated as a device that\nallows us to utilize with high efficiency wasted heat inaccessible by\nconventional heat engines. However, the derivation of the heat current in this\nengine seems to be either not general or described too briefly, even\ninappropriate in some cases. In this paper, we give a clear-cut derivation of\nthe heat current of the engine with suitable assumptions beyond the\nlinear-response regime. It resolves the confusion in the definition of the heat\ncurrent in the linear-response regime. After verifying that we can construct\nthe same formalism as that of the cyclic engine, we find the following two\ninteresting results within the Landauer-B\\\"uttiker formalism: the efficiency of\nthe mesoscopic thermoelectric engine reaches the Carnot efficiency if and only\nif the transmission probability is finite at a specific energy and zero\notherwise; the unitarity of the transmission probability guarantees the second\nlaw of thermodynamics, invalidating Benenti et al.'s argument in the\nlinear-response regime that one could obtain a finite power with the Carnot\nefficiency under a broken time-reversal symmetry. These results demonstrate how\nquantum mechanics constraints thermodynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diffusion-limited reactions in dynamic heterogeneous media: Most biochemical reactions in living cells rely on diffusive search for\ntarget molecules or regions in a heterogeneous overcrowded cytoplasmic medium.\nRapid re-arrangements of the medium constantly change the effective diffusivity\nfelt locally by a diffusing particle and thus impact the distribution of the\nfirst-passage time to a reaction event. Here, we investigate the effect of\nthese dynamic spatio-temporal heterogeneities onto diffusion-limited reactions.\nWe describe a general mathematical framework to translate many results for\nordinary homogeneous Brownian motion to heterogeneous diffusion. In particular,\nwe derive the probability density of the first-passage time to a reaction event\nand show how the dynamic disorder broadens the distribution and increases the\nlikelihood of both short and long trajectories to reactive targets. While the\ndisorder slows down reaction kinetics on average, its dynamic character is\nbeneficial for a faster search and realization of an individual reaction event\ntriggered by a single molecule.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ferromagnetic ordering in graphs with arbitrary degree distribution: We present a detailed study of the phase diagram of the Ising model in random\ngraphs with arbitrary degree distribution. By using the replica method we\ncompute exactly the value of the critical temperature and the associated\ncritical exponents as a function of the minimum and maximum degree, and the\ndegree distribution characterizing the graph. As expected, there is a\nferromagnetic transition provided <k> <= <k^2> < \\infty. However, if the fourth\nmoment of the degree distribution is not finite then non-trivial scaling\nexponents are obtained. These results are analyzed for the particular case of\npower-law distributed random graphs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Derivation and Improvements of the Quantum Canonical Ensemble from a\n  Regularized Microcanonical Ensemble: We develop a regularization of the quantum microcanonical ensemble, called a\nGaussian ensemble, which can be used for derivation of the canonical ensemble\nfrom microcanonical principles. The derivation differs from the usual methods\nby giving an explanation for the, at the first sight unreasonable,\neffectiveness of the canonical ensemble when applied to certain small,\nisolated, systems. This method also allows a direct identification between the\nparameters of the microcanonical and the canonical ensemble and it yields\nsimple indicators and rigorous bounds for the effectiveness of the\napproximation. Finally, we derive an asymptotic expansion of the microcanonical\ncorrections to the canonical ensemble for those systems, which are near, but\nnot quite, at the thermodynamical limit and show how and why the canonical\nensemble can be applied also for systems with exponentially increasing density\nof states. The aim throughout the paper is to keep mathematical rigour intact\nwhile attempting to produce results both physically and practically\ninteresting.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Size effects on generation recombination noise: We carry out an analytical theory of generation-recombination noise for a two\nlevel resistor model which goes beyond those presently available by including\nthe effects of both space charge fluctuations and diffusion current. Finite\nsize effects are found responsible for the saturation of the low frequency\ncurrent spectral density at high enough applied voltages. The saturation\nbehaviour is controlled essentially by the correlations coming from the long\nrange Coulomb interaction. It is suggested that the saturation of the current\nfluctuations for high voltage bias constitutes a general feature of\ngeneration-recombination noise.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Canonical thermalization: For quantum systems that are weakly coupled to a much 'bigger' environment,\nthermalization of possibly far from equilibrium initial ensembles is\ndemonstrated: for sufficiently large times, the ensemble is for all practical\npurposes indistinguishable from a canonical density operator under conditions\nthat are satisfied under many, if not all, experimentally realistic conditions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuation-dissipation relations far from equilibrium: The fluctuation-dissipation (F-D) theorem is a fundamental result for systems\nnear thermodynamic equilibrium, and justifies studies between microscopic and\nmacroscopic properties. It states that the nonequilibrium relaxation dynamics\nis related to the spontaneous fluctuation at equilibrium. Most processes in\nNature are out of equilibrium, for which we have limited theory. Common wisdom\nbelieves the F-D theorem is violated in general for systems far from\nequilibrium. Recently we show that dynamics of a dissipative system described\nby stochastic differential equations can be mapped to that of a thermostated\nHamiltonian system, with a nonequilibrium steady state of the former\ncorresponding to the equilibrium state of the latter. Her we derived the\ncorresponding F-D theorem, and tested with several examples. We suggest further\nstudies exploiting the analogy between a general dissipative system appearing\nin various science branches and a Hamiltonian system. Especially we discussed\nthe implications of this work on biological network studies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fractional calculus and continuous-time finance II: the waiting-time\n  distribution: We complement the theory of tick-by-tick dynamics of financial markets based\non a Continuous-Time Random Walk (CTRW) model recently proposed by Scalas et\nal., and we point out its consistency with the behaviour observed in the\nwaiting-time distribution for BUND future prices traded at LIFFE, London.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hybrid quantum-classical method for simulating high-temperature dynamics\n  of nuclear spins in solids: First-principles calculations of high-temperature spin dynamics in solids in\nthe context of nuclear magnetic resonance (NMR) is a long-standing problem,\nwhose conclusive solution can significantly advance the applications of NMR as\na diagnostic tool for material properties. In this work, we propose a new\nhybrid quantum-classical method for computing NMR free induction decay(FID) for\nspin $1/2$ lattices. The method is based on the simulations of a finite cluster\nof spins $1/2$ coupled to an environment of interacting classical spins via a\ncorrelation-preserving scheme. Such simulations are shown to lead to accurate\nFID predictions for one-, two- and three-dimensional lattices with a broad\nvariety of interactions. The accuracy of these predictions can be efficiently\nestimated by varying the size of quantum clusters used in the simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An information theory-based approach for optimal model reduction of\n  biomolecules: In the theoretical modelling of a physical system a crucial step consists in\nthe identification of those degrees of freedom that enable a synthetic, yet\ninformative representation of it. While in some cases this selection can be\ncarried out on the basis of intuition and experience, a straightforward\ndiscrimination of the important features from the negligible ones is difficult\nfor many complex systems, most notably heteropolymers and large biomolecules.\nWe here present a thermodynamics-based theoretical framework to gauge the\neffectiveness of a given simplified representation by measuring its information\ncontent. We employ this method to identify those reduced descriptions of\nproteins, in terms of a subset of their atoms, that retain the largest amount\nof information from the original model; we show that these highly informative\nrepresentations share common features that are intrinsically related to the\nbiological properties of the proteins under examination, thereby establishing a\nbridge between protein structure, energetics, and function.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Level Set Percolation in Two-Dimensional Gaussian Free Field: The nature of level set percolation in the two-dimension Gaussian Free Field\nhas been an elusive question. Using a loop-model mapping, we show that there is\na nontrivial percolation transition, and characterize the critical point. In\nparticular, the correlation length diverges exponentially, and the critical\nclusters are \"logarithmic fractals\", whose area scales with the linear size as\n$A \\sim L^2 / \\sqrt{\\ln L}$. The two-point connectivity also decays as the log\nof the distance. We corroborate our theory by numerical simulations. Possible\nCFT interpretations are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kardar-Parisi-Zhang universality in two-component driven diffusive\n  models: Symmetry and renormalization group perspectives: We elucidate the universal spatio-temporal scaling properties of the\ntime-dependent correlation functions in a class of two-component\none-dimensional (1D) driven diffusive system that consists of two coupled\nasymmetric exclusion process. By using a perturbative renormalization group\nframework, we show that the relevant scaling exponents have values same as\nthose for the 1D Kardar-Parisi-Zhang (KPZ) equation. We connect these universal\nscaling exponents with the symmetries of the model equations. We thus establish\nthat these models belong to the 1D KPZ universality class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical thermodynamics of a two dimensional relativistic gas: In this article we study a fully relativistic model of a two dimensional\nhard-disk gas. This model avoids the general problems associated with\nrelativistic particle collisions and is therefore an ideal system to study\nrelativistic effects in statistical thermodynamics. We study this model using\nmolecular-dynamics simulation, concentrating on the velocity distribution\nfunctions. We obtain results for $x$ and $y$ components of velocity in the rest\nframe ($\\Gamma$) as well as the moving frame ($\\Gamma'$). Our results confirm\nthat J\\\"{u}ttner distribution is the correct generalization of\nMaxwell-Boltzmann distribution. We obtain the same \"temperature\" parameter\n$\\beta$ for both frames consistent with a recent study of a limited\none-dimensional model. We also address the controversial topic of temperature\ntransformation. We show that while local thermal equilibrium holds in the\nmoving frame, relying on statistical methods such as distribution functions or\nequipartition theorem are ultimately inconclusive in deciding on a correct\ntemperature transformation law (if any).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Condensate density and superfluid mass density of a dilute Bose gas near\n  the condensation transition: We derive, through analysis of the structure of diagrammatic perturbation\ntheory, the scaling behavior of the condensate and superfluid mass density of a\ndilute Bose gas just below the condensation transition. Sufficiently below the\ncritical temperature, $T_c$, the system is governed by the mean field\n(Bogoliubov) description of the particle excitations. Close to $T_c$, however,\nmean field breaks down and the system undergoes a second order phase\ntransition, rather than the first order transition predicted in Bogoliubov\ntheory. Both condensation and superfluidity occur at the same critical\ntemperature, $T_c$ and have similar scaling functions below $T_c$, but\ndifferent finite size scaling at $T_c$ to leading order in the system size.\nThrough a simple self-consistent two loop calculation we derive the critical\nexponent for the condensate fraction, $2\\beta\\simeq 0.66$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Work distribution in thermal processes: We find the moment generating function (mgf) of the nonequilibrium work for\nopen systems undergoing a thermal process, ie, when the stochastic dynamics\nmaps thermal states into time dependent thermal states. The mgf is given in\nterms of a temperature-like scalar satisfying a first order ODE. We apply the\nresult to some paradigmatic situations: a levitated nanoparticle in a breathing\noptical trap, a brownian particle in a box with a moving piston and a two state\nsystem driven by an external field, where the work mgfs are obtained for\ndifferent timescales and compared with Monte Carlo simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Machine-learning detection of the Berezinskii-Kosterlitz-Thouless\n  transition and the second-order phase transition in the XXZ models: We propose two machine-learning methods based on neural networks, which we\nrespectively call the phase-classification method and the\ntemperature-identification method, for detecting different types of phase\ntransitions in the XXZ models without prior knowledge of their critical\ntemperatures. The XXZ models have exchange couplings which are anisotropic in\nthe spin space where the strength is represented by a parameter $\\Delta(>0)$.\nThe models exhibit the second-order phase transition when $\\Delta>1$, whereas\nthe Berezinskii-Kosterlitz-Thouless (BKT) phase transition when $\\Delta<1$. In\nthe phase-classification method, the neural network is trained using spin or\nvortex configurations of well-known classical spin models other than the XXZ\nmodels, e.g., the Ising models and the XY models, to classify those of the XXZ\nmodels to corresponding phases. We demonstrate that the trained neural network\nsuccessfully detects the phase transitions for both $\\Delta>1$ and $\\Delta<1$,\nand the evaluated critical temperatures coincide well with those evaluated by\nconventional numerical calculations. In the temperature-identification method,\non the other hand, the neural network is trained so as to identify temperatures\nat which the input spin or vortex configurations are generated by the Monte\nCarlo thermalization. The critical temperatures are evaluated by analyzing the\noptimized weight matrix, which coincide with the result of numerical\ncalculation for the second-order phase transition in the Ising-like XXZ model\nwith $\\Delta=1.05$ but cannot be determined uniquely for the BKT transition in\nthe XY-like XXZ model with $\\Delta=0.95$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling behavior of a square-lattice Ising model with competing\n  interactions in a uniform field: Transfer-matrix methods, with the help of finite-size scaling and conformal\ninvariance concepts, are used to investigate the critical behavior of\ntwo-dimensional square-lattice Ising spin-1/2 systems with first- and\nsecond-neighbor interactions, both antiferromagnetic, in a uniform external\nfield. On the critical curve separating collinearly-ordered and paramagnetic\nphases, our estimates of the conformal anomaly $c$ are very close to unity,\nindicating the presence of continuously-varying exponents. This is confirmed by\ndirect calculations, which also lend support to a weak-universality picture;\nhowever, small but consistent deviations from the Ising-like values $\\eta=1/4$,\n$\\gamma/\\nu=7/4$, $\\beta/\\nu=1/8$ are found. For higher fields, on the line\nseparating row-shifted $(2 \\times 2)$ and disordered phases, we find values of\nthe exponent $\\eta$ very close to zero.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "General Relation between Entanglement and Fluctuations in One Dimension: In one dimension very general results from conformal field theory and exact\ncalculations for certain quantum spin systems have established universal\nscaling properties of the entanglement entropy between two parts of a critical\nsystem. Using both analytical and numerical methods, we show that if particle\nnumber or spin is conserved, fluctuations in a subsystem obey identical scaling\nas a function of subsystem size, suggesting that fluctuations are a useful\nquantity for determining the scaling of entanglement, especially in higher\ndimensions. We investigate the effects of boundaries and subleading corrections\nfor critical spin and bosonic chains.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Transition probabilities and dynamic structure factor in the ASEP\n  conditioned on strong flux: We consider the asymmetric simple exclusion processes (ASEP) on a ring\nconstrained to produce an atypically large flux, or an extreme activity. Using\nquantum free fermion techniques we find the time-dependent conditional\ntransition probabilities and the exact dynamical structure factor under such\nconditioned dynamics. In the thermodynamic limit we obtain the explicit scaling\nform. This gives a direct proof that the dynamical exponent in the extreme\ncurrent regime is $z=1$ rather than the KPZ exponent $z=3/2$ which\ncharacterizes the ASEP in the regime of typical currents. Some of our results\nextend to the activity in the partially asymmetric simple exclusion process,\nincluding the symmetric case.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Number Fluctuation and the Fundamental Theorem of Arithmetic: We consider N bosons occupying a discrete set of single-particle quantum\nstates in an isolated trap. Usually, for a given excitation energy, there are\nmany combinations of exciting different number of particles from the ground\nstate, resulting in a fluctuation of the ground state population. As a counter\nexample, we take the quantum spectrum to be logarithms of the prime number\nsequence, and using the fundamental theorem of arithmetic, find that the ground\nstate fluctuation vanishes exactly for all excitations. The use of the standard\ncanonical or grand canonical ensembles, on the other hand, gives substantial\nnumber fluctuation for the ground state. This difference between the\nmicrocanonical and canonical results cannot be accounted for within the\nframework of equilibrium statistical mechanics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On dissipation in crackling noise systems: We consider the amount of energy dissipated during individual avalanches at\nthe depinning transition of disordered and athermal elastic systems. Analytical\nprogress is possible in the case of the Alessandro-Beatrice-Bertotti-Montorsi\n(ABBM) model for Barkhausen noise, due to an exact mapping between the energy\nreleased in an avalanche and the area below a Brownian path until its first\nzero-crossing. Scaling arguments and examination of an extended mean-field\nmodel with internal structure show that dissipation relates to a critical\nexponent recently found in a study of the rounding of the depinning transition\nin presence of activated dynamics. A new numerical method to compute the\ndynamic exponent at depinning in terms of blocked and marginally stable\nconfigurations is proposed, and a kind of `dissipative anomaly'- with\npotentially important consequences for nonequilibrium statistical mechanics- is\ndiscussed. We conclude that for depinning systems the size of an avalanche does\nnot constitute by itself a univocal measure of the energy dissipated.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ergodicity breaking in one-dimensional reaction-diffusion systems: We investigate one-dimensional driven diffusive systems where particles may\nalso be created and annihilated in the bulk with sufficiently small rate. In an\nopen geometry, i.e., coupled to particle reservoirs at the two ends, these\nsystems can exhibit ergodicity breaking in the thermodynamic limit. The\ntriggering mechanism is the random motion of a shock in an effective potential.\nBased on this physical picture we provide a simple condition for the existence\nof a non-ergodic phase in the phase diagram of such systems. In the\nthermodynamic limit this phase exhibits two or more stationary states. However,\nfor finite systems transitions between these states are possible. It is shown\nthat the mean lifetime of such a metastable state is exponentially large in\nsystem-size. As an example the ASEP with the A0A--AAA reaction kinetics is\nanalyzed in detail. We present a detailed discussion of the phase diagram of\nthis particular model which indeed exhibits a phase with broken ergodicity. We\nmeasure the lifetime of the metastable states with a Monte Carlo simulation in\norder to confirm our analytical findings.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Model simplification and loss of irreversibility: In this paper, we reveal a general relationship between model simplification\nand irreversibility based on the model of continuous-time Markov chains with\ntime-scale separation. According to the topological structure of the fast\nprocess, we divide the states of the chain into the transient states and the\nrecurrent states. We show that a two-time-scale chain can be simplified to a\nreduced chain in two different ways: removal of the transient states and\naggregation of the recurrent states. Both the two operations will lead to a\ndecrease in the entropy production rate and its adiabatic part and will keep\nits non-adiabatic part the same. This suggests that although model\nsimplification can retain almost all the dynamic information of the chain, it\nwill lose some thermodynamic information as a trade-off.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Fluctuation-Response Relation as a Probe of Long-Range Correlations in\n  Non-Equilibrium Quantum and Classical Fluids: The absence of a simple fluctuation-dissipation theorem is a major obstacle\nfor studying systems that are not in thermodynamic equilibrium. We show that\nfor a fluid in a non-equilibrium steady state characterized by a constant\ntemperature gradient the commutator correlation functions are still related to\nresponse functions; however, the relation is to the bilinear response of\nproducts of two observables, rather than to a single linear response function\nas is the case in equilibrium. This modified fluctuation-response relation\nholds for both quantum and classical systems. It is both motivated and informed\nby the long-range correlations that exist in such a steady state and allows for\nprobing them via response experiments. This is of particular interest in\nquantum fluids, where the direct observation of fluctuations by light\nscattering would be difficult. In classical fluids it is known that the\ncoupling of the temperature gradient to the diffusive shear velocity leads to\ncorrelations of various observables, in particular temperature fluctuations,\nthat do not decay as a function of distance, but rather extend over the entire\nsystem. We investigate the nature of these correlations in a fermionic quantum\nfluid and show that the crucial coupling between the temperature gradient and\nvelocity fluctuations is the same as in the classical case. Accordingly, the\nnature of the long-ranged correlations in the hydrodynamic regime also is the\nsame. However, as one enters the collisionless regime in the low-temperature\nlimit the nature of the velocity fluctuations changes: they become ballistic\nrather than diffusive. As a result, correlations of the temperature and other\nobservables are still singular in the long-wavelength limit, but the\nsingularity is weaker than in the hydrodynamic regime.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Physical realization and possible identification of topological\n  excitations in quantum Heisenberg ferromagnet on lattice: Physical configurations corresponding to topological excitations present in\nthe XY limit of a quantum spin 1/2 Heisenberg ferromagnet, are investigated on\na two dimensional square lattice. Quantum vortices(anti-vortices) are\nconstructed in terms of terms of coherent spin field components and the crucial\nrole of the associated Wess-Zumino term is highlighted. It is shown that this\nterm can identify a large class of vortices(anti-vortices). In particular the\nexcitations with odd topological charge belonging to this class, are found to\nexhibit a self-similar pattern regarding the internal charge distribution. Our\nformalism is distinctly different from the coventional approach for the\nconstruction of quantum vortices(anti-vortices).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Emergence of extended Newtonian gravity from thermodynamics: Discovery of a novel thermodynamic aspect of nonrelativistic gravity is\nreported. Here, initially, an unspecified scalar field potential is considered\nand treated not as an externally applied field but as a thermodynamic variable\non an equal footing with the fluid variables. It is shown that the second law\nof thermodynamics imposes a stringent constraint on the field, and, quite\nremarkably, the allowable field turns out to be only of gravity. The resulting\nfield equation for the gravitational potential derived from the analysis of the\nentropy production rate contains a dissipative term due to irreversibility. It\nis found that the system relaxes to the conventional theory of Newtonian\ngravity up to a certain spatial scale, whereas on the larger scale there\nemerges non-Newtonian gravity described by a nonlinear field equation\ncontaining a single coefficient. A comment is made on an estimation of the\ncoefficient that has its origin in the thermodynamic property of the system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Melting of Rare-Gas Crystals: Monte Carlo Simulation versus Experiments: We study the melting transition in crystals of rare gas Ar, Xe, and Kr by the\nuse of extensive Monte Carlo simulations with the Lennard-Jones potential. The\nparameters of this potential have been deduced by Bernardes in 1958 from\nexperiments of rare gas in the gaseous phase. It is amazing that the parameters\nof such a popular potential were not fully tested so far. In order to carry out\nprecise tests, we have written a high-performance Monte Carlo program which\nallows in particular to take into account correctly the periodic boundary\nconditions to reduce surface effects and to reduce CPU time. Using the\nBernardes parameters, we find that the melting temperature of several rare gas\nis from 13 to 20% higher than that obtained from experiments. We have\nthroughout studied the case of Ar by examining both finite-size and\ncutoff-distance effects. In order to get a good agreement with the experimental\nmelting temperature, we propose a modification of these parameters to describe\nbetter the melting of rare-gas crystals.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic Framework for Compact q-Gaussian Distributions: Recent works have associated systems of particles, characterized by\nshort-range repulsive interactions and evolving under overdamped motion, to a\nnonlinear Fokker-Planck equation within the class of nonextensive statistical\nmechanics, with a nonlinear diffusion contribution whose exponent is given by\n$\\nu=2-q$. The particular case $\\nu=2$ applies to interacting vortices in\ntype-II superconductors, whereas $\\nu>2$ covers systems of particles\ncharacterized by short-range power-law interactions, where correlations among\nparticles are taken into account. In the former case, several studies presented\na consistent thermodynamic framework based on the definition of an effective\ntemperature $\\theta$ (presenting experimental values much higher than typical\nroom temperatures $T$, so that thermal noise could be neglected), conjugated to\na generalized entropy $s_{\\nu}$ (with $\\nu=2$). Herein, the whole thermodynamic\nscheme is revisited and extended to systems of particles interacting\nrepulsively, through short-ranged potentials, described by an entropy\n$s_{\\nu}$, with $\\nu>1$, covering the $\\nu=2$ (vortices in type-II\nsuperconductors) and $\\nu>2$ (short-range power-law interactions) physical\nexamples. The main results achieved are: (a) The definition of an effective\ntemperature $\\theta$ conjugated to the entropy $s_{\\nu}$; (b) The construction\nof a Carnot cycle, whose efficiency is shown to be\n$\\eta=1-(\\theta_2/\\theta_1)$, where $\\theta_1$ and $\\theta_2$ are the effective\ntemperatures associated with two isothermal transformations, with\n$\\theta_1>\\theta_2$; (c) Thermodynamic potentials, Maxwell relations, and\nresponse functions. The present thermodynamic framework, for a system of\ninteracting particles under the above-mentioned conditions, and associated to\nan entropy $s_{\\nu}$, with $\\nu>1$, certainly enlarges the possibility of\nexperimental verifications.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Free energy calculations of a proton transfer reaction by simulated\n  tempering umbrella sampling first principles molecular dynamics simulations: A new simulated tempering method, which is referred to as simulated tempering\numbrella sampling, for calculating the free energy of chemical reactions is\nproposed. First principles molecular dynamics simulations with this simulated\ntempering were performed in order to study the intramolecular proton transfer\nreaction of malonaldehyde in aqueous solution. Conformational sampling in\nreaction coordinate space can be easily enhanced with this method, and the free\nenergy along a reaction coordinate can be calculated accurately. Moreover, the\nsimulated tempering umbrella sampling provides trajectory data more efficiently\nthan the conventional umbrella sampling method.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Solution of the 2-star model of a network: The p-star model or exponential random graph is among the oldest and\nbest-known of network models. Here we give an analytic solution for the\nparticular case of the 2-star model, which is one of the most fundamental of\nexponential random graphs. We derive expressions for a number of quantities of\ninterest in the model and show that the degenerate region of the parameter\nspace observed in computer simulations is a spontaneously symmetry broken phase\nseparated from the normal phase of the model by a conventional continuous phase\ntransition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Line Shape Broadening in Surface Diffusion of Interacting Adsorbates\n  with Quasielastic He Atom Scattering: The experimental line shape broadening observed in adsorbate diffusion on\nmetal surfaces with increasing coverage is usually related to the nature of the\nadsorbate-adsorbate interaction. Here we show that this broadening can also be\nunderstood in terms of a fully stochastic model just considering two noise\nsources: (i) a Gaussian white noise accounting for the surface friction, and\n(ii) a shot noise replacing the physical adsorbate-adsorbate interaction\npotential. Furthermore, contrary to what could be expected, for relatively weak\nadsorbate-substrate interactions the opposite effect is predicted: line shapes\nget narrower with increasing coverage.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "What do generalized entropies look like? An axiomatic approach for\n  complex, non-ergodic systems: Shannon and Khinchin showed that assuming four information theoretic axioms\nthe entropy must be of Boltzmann-Gibbs type, $S=-\\sum_i p_i \\log p_i$. Here we\nnote that in physical systems one of these axioms may be violated. For\nnon-ergodic systems the so called separation axiom (Shannon-Khinchin axiom 4)\nwill in general not be valid. We show that when this axiom is violated the\nentropy takes a more general form, $S_{c,d}\\propto \\sum_i ^W \\Gamma(d+1, 1- c\n\\log p_i)$, where $c$ and $d$ are scaling exponents and $\\Gamma(a,b)$ is the\nincomplete gamma function. The exponents $(c,d)$ define equivalence classes for\nall interacting and non interacting systems and unambiguously characterize any\nstatistical system in its thermodynamic limit. The proof is possible because of\ntwo newly discovered scaling laws which any entropic form has to fulfill, if\nthe first three Shannon-Khinchin axioms hold. $(c,d)$ can be used to define\nequivalence classes of statistical systems. A series of known entropies can be\nclassified in terms of these equivalence classes. We show that the\ncorresponding distribution functions are special forms of Lambert-${\\cal W}$\nexponentials containing -- as special cases -- Boltzmann, stretched exponential\nand Tsallis distributions (power-laws). In the derivation we assume trace form\nentropies, $S=\\sum_i g(p_i)$, with $g$ some function, however more general\nentropic forms can be classified along the same scaling analysis.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ground-state fidelity and tensor network states for quantum spin tubes: An efficient algorithm is developed for quantum spin tubes in the context of\nthe tensor network representations. It allows to efficiently compute the\nground-state fidelity per lattice site, which in turn enables us to identify\nquantum critical points, at which quantum spin tubes undergo quantum phase\ntransitions. As an illustration, we investigate the isosceles spin 1/2\nantiferromagnetic three-leg Heisenberg tube. Our simulation results suggest\nthat two Kosterlitz-Thouless transitions occur as the degree of asymmetry of\nthe rung interaction is tuned, thus offering an alternative route towards a\nresolution to the conflicting results on this issue arising from the density\nmatrix renormalization group.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Derivation of a statistical model for classical systems obeying\n  fractional exclusion principle: The violation of the Pauli principle has been surmised in several models of\nthe Fractional Exclusion Statistics and successfully applied to several quantum\nsystems. In this paper, a classical alternative of the exclusion statistics is\nstudied using the maximum entropy methods. The difference between the\nBose-Einstein statistics and the Maxwell-Boltzmann statistics is understood in\nterms of a separable quantity, namely the degree of indistinguishability.\nStarting from the usual Maxwell-Boltzmann microstate counting formula, a\nspecial restriction related to the degree of indistinguishability is\nincorporated using Lagrange multipliers to derive the probability distribution\nfunction at equilibrium under NVE conditions. It is found that the resulting\nprobability distribution function generates real positive values within the\npermissible range of parameters. For a dilute system, the probability\ndistribution function is intermediate between the Fermi-Dirac and Bose-Einstein\nstatistics and follows the exclusion principle. Properties of various variables\nof this novel statistical model are studied and possible application to\nclassical thermodynamics is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Long-term Relaxation of a Composite System in Partial Contact with a\n  Heat Bath: We study relaxational behavior from a highly excited state for a composite\nsystem in partial contact with a heat bath, motivated by an experimental report\nof long-term energy storage in protein molecules. The system consists of two\ncoupled elements: The first element is in direct contact with a heat bath,\nwhile the second element interacts only with the first element. Due to this\nindirect contact with the heat bath, energy injected into the second element\ndissipates very slowly, according to a power law, whereas that injected into\nthe first one exhibits exponential dissipation. The relaxation equation\ndescribing this dissipation is obtained analytically for both the underdamped\nand overdamped limits. Numerical confirmation is given for both cases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stretched-Gaussian asymptotics of the truncated L\u00e9vy flights for the\n  diffusion in nonhomogeneous media: The L\\'evy, jumping process, defined in terms of the jumping size\ndistribution and the waiting time distribution, is considered. The jumping rate\ndepends on the process value. The fractional diffusion equation, which contains\nthe variable diffusion coefficient, is solved in the diffusion limit. That\nsolution resolves itself to the stretched Gaussian when the order parameter\n$\\mu\\to2$. The truncation of the L\\'evy flights, in the exponential and\npower-law form, is introduced and the corresponding random walk process is\nsimulated by the Monte Carlo method. The stretched Gaussian tails are found in\nboth cases. The time which is needed to reach the limiting distribution\nstrongly depends on the jumping rate parameter. When the cutoff function falls\nslowly, the tail of the distribution appears to be algebraic.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Matrix Kesten Recursion, Inverse-Wishart Ensemble and Fermions in a\n  Morse Potential: The random variable $1+z_1+z_1z_2+\\dots$ appears in many contexts and was\nshown by Kesten to exhibit a heavy tail distribution. We consider natural\nextensions of this variable and its associated recursion to $N \\times N$\nmatrices either real symmetric $\\beta=1$ or complex Hermitian $\\beta=2$. In the\ncontinuum limit of this recursion, we show that the matrix distribution\nconverges to the inverse-Wishart ensemble of random matrices. The full dynamics\nis solved using a mapping to $N$ fermions in a Morse potential, which are\nnon-interacting for $\\beta=2$. At finite $N$ the distribution of eigenvalues\nexhibits heavy tails, generalizing Kesten's results in the scalar case. The\ndensity of fermions in this potential is studied for large $N$, and the\npower-law tail of the eigenvalue distribution is related to the properties of\nthe so-called determinantal Bessel process which describes the hard edge\nuniversality of random matrices. For the discrete matrix recursion, using free\nprobability in the large $N$ limit, we obtain a self-consistent equation for\nthe stationary distribution. The relation of our results to recent works of\nRider and Valk\\'o, Grabsch and Texier, as well as Ossipov, is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The three faces of entropy for complex systems -- information,\n  thermodynamics and the maxent principle: There are three ways to conceptualize entropy: entropy as an extensive\nthermodynamic quantity of physical systems (Clausius, Boltzmann, Gibbs),\nentropy as a measure for information production of ergodic sources (Shannon),\nand entropy as a means for statistical inference on multinomial Bernoulli\nprocesses (Jaynes maximum entropy principle). Even though these notions are\nfundamentally different concepts, the functional form of the entropy for\nthermodynamic systems in equilibrium, for ergodic sources in information\ntheory, and for independent sampling processes in statistical systems, is\ndegenerate, $H(p)=-\\sum_i p_i\\log p_i$. For many complex systems, which are\ntypically history-dependent, non-ergodic and non-multinomial, this is no longer\nthe case. Here we show that for such processes the three entropy concepts lead\nto different functional forms of entropy. We explicitly compute these entropy\nfunctionals for three concrete examples. For Polya urn processes, which are\nsimple self-reinforcing processes, the source information rate is $S_{\\rm\nIT}=\\frac{1}{1-c}\\frac1N \\log N$, the thermodynamical (extensive) entropy is\n$(c,d)$-entropy, $S_{\\rm EXT}=S_{(c,0)}$, and the entropy in the maxent\nprinciple (MEP) is $S_{\\rm MEP}(p)=-\\sum_i \\log p_i$. For sample space reducing\n(SSR) processes, which are simple path-dependent processes that are associated\nwith power law statistics, the information rate is $S_{\\rm IT}=1+ \\frac12 \\log\nW$, the extensive entropy is $S_{\\rm EXT}=H(p)$, and the maxent result is\n$S_{\\rm MEP}(p)=H(p/p_1)+H(1-p/p_1)$. Finally, for multinomial mixture\nprocesses, the information rate is given by the conditional entropy $\\langle\nH\\rangle_f$, with respect to the mixing kernel $f$, the extensive entropy is\ngiven by $H$, and the MEP functional corresponds one-to-one to the logarithm of\nthe mixing kernel.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Note on the Kaplan-Yorke dimension and linear transport coefficients: A number of relations between the Kaplan-Yorke dimension, phase space\ncontraction, transport coefficients and the maximal Lyapunov exponents are\ngiven for dissipative thermostatted systems, subject to a small external field\nin a nonequilibrium stationary state. A condition for the extensivity of phase\nspace dimension reduction is given. A new expression for the transport\ncoefficients in terms of the Kaplan-Yorke dimension is derived. Alternatively,\nthe Kaplan-Yorke dimension for a dissipative macroscopic system can be\nexpressed in terms of the transport coefficients of the system. The agreement\nwith computer simulations for an atomic fluid at small shear rates is very\ngood.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Defect Fluctuations and Lifetimes in Disordered Yukawa Systems: We examine the time dependent defect fluctuations and lifetimes for a\nbidisperse disordered assembly of Yukawa particles. At high temperatures, the\nnoise spectrum of fluctuations is white and the coordination number lifetimes\nhave a stretched exponential distribution. At lower temperatures, the system\ndynamically freezes, the defect fluctuations exhibit a 1/f spectrum, and there\nis a power law distribution of the coordination number lifetimes. Our results\nindicate that topological defect fluctuations may be a useful way to\ncharacterize systems exhibiting dynamical heterogeneities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Many-body Green's function theory of Heisenberg films: The treatment of Heisenberg films with many-body Green's function theory\n(GFT) is reviewed. The basic equations of GFT are derived in sufficient detail\nso that the rest of the paper can be understood without having to consult\nfurther literature. The main part of the paper is concerned with applications\nof the formalism to ferromagnetic, antiferromagnetic and coupled\nferromagnetic-antiferromagnetic Heisenberg films based on a generalized\nTyablikov (RPA) decoupling of the exchange interaction and exchange anisotropy\nterms and an Anderson-Callen decoupling for a weak single-ion anisotropy. We\nnot only give a consistent description of our own work but also refer\nextensively to related investigations. We discuss in particular the\nreorientation of the magnetization as a function of the temperature and film\nthickness. If the single-ion anisotropy is strong, it can be treated exactly by\ngoing to higher-order Green's functions. We also discuss the extension of the\ntheory beyond RPA. Finally the limitations of GFT is pointed out.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diatomic molecules in ultracold Fermi gases - Novel composite bosons: We give a brief overview of recent studies of weakly bound homonuclear\nmolecules in ultracold two-component Fermi gases. It is emphasized that they\nrepresent novel composite bosons, which exhibit features of Fermi statistics at\nshort intermolecular distances. In particular, Pauli exclusion principle for\nidentical fermionic atoms provides a strong suppression of collisional\nrelaxation of such molecules into deep bound states. We then analyze\nheteronuclear molecules which are expected to be formed in mixtures of\ndifferent fermionic atoms. It is found how an increase in the mass ratio for\nthe constituent atoms changes the physics of collisional stability of such\nmolecules compared to the case of homonuclear ones. We discuss Bose-Einstein\ncondensation of these composite bosons and draw prospects for future studies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical density-density correlations in the one-dimensional Bose gas: The zero-temperature dynamical structure factor of the one-dimensional Bose\ngas with delta-function interaction (Lieb-Liniger model) is computed using a\nhybrid theoretical/numerical method based on the exact Bethe Ansatz solution,\nwhich allows to interpolate continuously between the weakly-coupled\nThomas-Fermi and strongly-coupled Tonks-Girardeau regimes. The results should\nbe experimentally accessible with Bragg spectroscopy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scale Invariant Dynamics of Surface Growth: We describe in detail and extend a recently introduced nonperturbative\nrenormalization group (RG) method for surface growth. The scale invariant\ndynamics which is the key ingredient of the calculation is obtained as the\nfixed point of a RG transformation relating the representation of the\nmicroscopic process at two different coarse-grained scales. We review the RG\ncalculation for systems in the Kardar-Parisi-Zhang universality class and\ncompute the roughness exponent for the strong coupling phase in dimensions from\n1 to 9. Discussions of the approximations involved and possible improvements\nare also presented. Moreover, very strong evidence of the absence of a finite\nupper critical dimension for KPZ growth is presented. Finally, we apply the\nmethod to the linear Edwards-Wilkinson dynamics where we reproduce the known\nexact results, proving the ability of the method to capture qualitatively\ndifferent behaviors.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on \"Tsallis power laws and finite baths with negative heat\n  capacity\" [Phys. Rev. E 88, 042126 (2013)]: In [Phys. Rev. E 88, 042126 (2013)] it is stated that Tsallis distributions\ndo not emerge from thermalization with a \"bath\" of finite, energy-independent,\nheat capacity. We report evidence for the contrary.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "How many eigenvalues of a Gaussian random matrix are positive?: We study the probability distribution of the index ${\\mathcal N}_+$, i.e.,\nthe number of positive eigenvalues of an $N\\times N$ Gaussian random matrix. We\nshow analytically that, for large $N$ and large $\\mathcal{N}_+$ with the\nfraction $0\\le c=\\mathcal{N}_+/N\\le 1$ of positive eigenvalues fixed, the index\ndistribution $\\mathcal{P}({\\mathcal N}_+=cN,N)\\sim\\exp[-\\beta N^2 \\Phi(c)]$\nwhere $\\beta$ is the Dyson index characterizing the Gaussian ensemble. The\nassociated large deviation rate function $\\Phi(c)$ is computed explicitly for\nall $0\\leq c \\leq 1$. It is independent of $\\beta$ and displays a quadratic\nform modulated by a logarithmic singularity around $c=1/2$. As a consequence,\nthe distribution of the index has a Gaussian form near the peak, but with a\nvariance $\\Delta(N)$ of index fluctuations growing as $\\Delta(N)\\sim \\log\nN/\\beta\\pi^2$ for large $N$. For $\\beta=2$, this result is independently\nconfirmed against an exact finite $N$ formula, yielding $\\Delta(N)= \\log\nN/2\\pi^2 +C+\\mathcal{O}(N^{-1})$ for large $N$, where the constant $C$ has the\nnontrivial value $C=(\\gamma+1+3\\log 2)/2\\pi^2\\simeq 0.185248...$ and\n$\\gamma=0.5772...$ is the Euler constant. We also determine for large $N$ the\nprobability that the interval $[\\zeta_1,\\zeta_2]$ is free of eigenvalues. Part\nof these results have been announced in a recent letter [\\textit{Phys. Rev.\nLett.} {\\bf 103}, 220603 (2009)].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random walks and Brownian motion: A method of computation for\n  first-passage times and related quantities in confined geometries: In this paper we present a computation of the mean first-passage times both\nfor a random walk in a discrete bounded lattice, between a starting site and a\ntarget site, and for a Brownian motion in a bounded domain, where the target is\na sphere. In both cases, we also discuss the case of two targets, including\nsplitting probabilities, and conditional mean first-passage times. In addition,\nwe study the higher-order moments and the full distribution of the\nfirst-passage time. These results significantly extend our earlier contribution\n[Phys. Rev. Lett. 95, 260601].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The expression of ensemble average internal energy in long-range\n  interaction complex system and its statistical physical properties: In this paper, we attempt to derive the expression of ensemble average\ninternal energy in long-range interaction complex system. Further, the Shannon\nentropy hypothesis is used to derive the probability distribution function of\nenergy. It is worth mentioning that the probability distribution function of\nenergy can be equivalent to the q-Gaussian distribution given by Tsallis based\non nonextensive entropy. In order to verify the practical significance of this\nmodel, it is applied to the older subject of income system. The classic income\ndistribution is two-stage, the most recognized low-income distribution is the\nexponential form, and the high-income distribution is the recognized Pareto\npower law distribution. The probability distribution can explain the entire\ndistribution of United States income data. In addition, the internal energy,\nentropy and temperature of the United States income system can be calculated,\nand the economic crisis in the United States in recent years can be presented.\nIt is believed that the model will be further improved and extended to other\nareas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Assessment of kinetic theories for moderately dense granular binary\n  mixtures: Shear viscosity coefficient: Two different kinetic theories [J. Solsvik and E. Manger (SM-theory), Phys.\nFluids \\textbf{33}, 043321 (2021) and V. Garz\\'o, J. W. Dufty, and C. M. Hrenya\n(GDH-theory), Phys. Rev. E \\textbf{76}, 031303 (2007)] are considered to\ndetermine the shear viscosity $\\eta$ for a moderately dense granular binary\nmixture of smooth hard spheres. The mixture is subjected to a simple shear flow\nand heated by the action of an external driving force (Gaussian thermostat)\nthat exactly compensates the energy dissipated in collisions. The set of Enskog\nkinetic equations is the starting point to obtain the dependence of $\\eta$ on\nthe control parameters of the mixture: solid fraction, concentration, mass and\ndiameter ratios, and coefficients of normal restitution. While the expression\nof $\\eta$ found in the SM-theory is based on the assumption of Maxwellian\ndistributions for the velocity distribution functions of each species, the\nGDH-theory solves the Enskog equation by means of the Chapman--Enskog method to\nfirst order in the shear rate. To assess the accuracy of both kinetic theories,\nthe Enskog equation is numerically solved by means of the direct simulation\nMonte Carlo (DSMC) method. The simulation is carried out for a mixture under\nsimple shear flow, using the thermostat to control the cooling effects. Given\nthat the SM-theory predicts a vanishing kinetic contribution to the shear\nviscosity, the comparison between theory and simulations is essentially made at\nthe level of the collisional contribution $\\eta_c$ to the shear viscosity. The\nresults clearly show that the GDH-theory compares with simulations much better\nthan the SM-theory over a wide range of values of the coefficients of\nrestitution, the volume fraction, and the parameters of the mixture (masses,\ndiameters, and concentration).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hierarchical Organization in Complex Networks: Many real networks in nature and society share two generic properties: they\nare scale-free and they display a high degree of clustering. We show that these\ntwo features are the consequence of a hierarchical organization, implying that\nsmall groups of nodes organize in a hierarchical manner into increasingly large\ngroups, while maintaining a scale-free topology. In hierarchical networks the\ndegree of clustering characterizing the different groups follows a strict\nscaling law, which can be used to identify the presence of a hierarchical\norganization in real networks. We find that several real networks, such as the\nWorld Wide Web, actor network, the Internet at the domain level and the\nsemantic web obey this scaling law, indicating that hierarchy is a fundamental\ncharacteristic of many complex systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the maximum entropy principle and the minimization of the Fisher\n  information in Tsallis statistics: We give a new proof of the theorems on the maximum entropy principle in\nTsallis statistics. That is, we show that the $q$-canonical distribution\nattains the maximum value of the Tsallis entropy, subject to the constraint on\nthe $q$-expectation value and the $q$-Gaussian distribution attains the maximum\nvalue of the Tsallis entropy, subject to the constraint on the $q$-variance, as\napplications of the nonnegativity of the Tsallis relative entropy, without\nusing the Lagrange multipliers method. In addition, we define a $q$-Fisher\ninformation and then prove a $q$-Cram\\'er-Rao inequality that the $q$-Gaussian\ndistribution with special $q$-variances attains the minimum value of the\n$q$-Fisher information.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical Properties of the Slithering Snake Algorithm: A numerical test\n  of the activated reptation hypothesis: The correlations in the motion of reptating polymers in their melt are\ninvestigated by means of kinetic Monte Carlo simulations of the three\ndimensional slithering snake version of the bond-fluctuation model.\n  Surprisingly, the slithering snake dynamics becomes inconsistent with\nclassical reptation predictions at high chain overlap (either chain length $N$\nor volume fraction $\\phi$) where the relaxation times increase much faster than\nexpected.\n  This is due to the anomalous curvilinear diffusion in a finite time window\nwhose upper bound $\\tau_+$ is set by the chain end density $\\phi/N$. Density\nfluctuations created by passing chain ends allow a reference polymer to break\nout of the local cage of immobile obstacles created by neighboring chains.\n  The dynamics of dense solutions of snakes at $t \\ll \\tau_+$ is identical to\nthat of a benchmark system where all but one chain are frozen. We demonstrate\nthat it is the slow creeping of a chain out of its correlation hole which\ncauses the subdiffusive dynamical regime.\n  Our results are in good qualitative agreement with the activated reptation\nscheme proposed recently by Semenov and Rubinstein [Eur. Phys. J. B, {\\bf 1}\n(1998) 87].\n  Additionally, we briefly comment on the relevance of local relaxation\npathways within a slithering snake scheme. Our preliminary results suggest that\na judicious choice of the ratio of local to slithering snake moves is crucial\nto equilibrate a melt of long chains efficiently.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effect of Strong Magnetic Fields on the Equilibrium of a Degenerate Gas\n  of Nucleons and Electrons: We obtain the equations that define the equilibrium of a homogeneous\nrelativistic gas of neutrons, protons and electrons in a constant magnetic\nfield as applied to the conditions that probably occur near the center of\nneutron stars. We compute the relative densities of the particles at\nequilibrium and the Fermi momentum of electrons in the strong magnetic field as\nfunction of the density of neutrons and the magnetic field induction. Novel\nfeatures are revealed as to the ratio of the number of protons to the number of\nneutrons at equilibrium in the presence of large magnetic fields.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A recipe for an unpredictable random number generator: In this work we present a model for computation of random processes in\ndigital computers which solves the problem of periodic sequences and hidden\nerrors produced by correlations. We show that systems with non-invertible\nnon-linearities can produce unpredictable sequences of independent random\nnumbers. We illustrate our result with some numerical calculations related with\nrandom walks simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entanglement, combinatorics and finite-size effects in spin-chains: We carry out a systematic study of the exact block entanglement in XXZ\nspin-chain at Delta=-1/2. We present, the first analytic expressions for\nreduced density matrices of n spins in a chain of length L (for n<=6 and\narbitrary but odd L) of a truly interacting model. The entanglement entropy,\nthe moments of the reduced density matrix, and its spectrum are then easily\nderived. We explicitely construct the \"entanglement Hamiltonian\" as the\nlogarithm of this matrix. Exploiting the degeneracy of the ground-state, we\nfind the scaling behavior of entanglement of the zero-temperature mixed state.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Homogeneous bubble nucleation in water at negative pressure: A Voronoi\n  polyhedra analysis: We investigate vapor bubble nucleation in metastable TIP4P/2005 water at\nnegative pressure via the Mean First Passage Time (MFPT) method using the\nvolume of the largest bubble as a local order parameter. We identify the\nbubbles in the system by means of a Voronoi-based analysis of the Molecular\nDynamics trajectories. By comparing the features of the tessellation of liquid\nwater at ambient conditions to those of the same system with an empty cavity we\nare able to discriminate vapor (or interfacial) molecules from the bulk ones.\nThis information is used to follow the time evolution of the largest bubble\nuntil the system cavitates at 280 K above and below the spinodal line. At the\npressure above the spinodal line, the MFPT curve shows the expected shape for a\nmoderately metastable liquid from which we estimate the bubble nucleation rate\nand the size of the critical cluster. The nucleation rate estimated using\nClassical Nucleation Theory turns out to be about 8 order of magnitude lower\nthan the one we compute by means of MFPT. The behavior at the pressure below\nthe spinodal line, where the liquid is thermodynamically unstable, is\nremarkably different, the MFPT curve being a monotonous function without any\ninflection point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamic asset trees and Black Monday: The minimum spanning tree, based on the concept of ultrametricity, is\nconstructed from the correlation matrix of stock returns. The dynamics of this\nasset tree can be characterised by its normalised length and the mean\noccupation layer, as measured from an appropriately chosen centre called the\n`central node'. We show how the tree length shrinks during a stock market\ncrisis, Black Monday in this case, and how a strong reconfiguration takes\nplace, resulting in topological shrinking of the tree.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Disordered systems and Burgers' turbulence: Talk presented at the International Conference on Mathematical Physics\n(Brisbane 1997). This is an introduction to recent work on the scaling and\nintermittency in forced Burgers turbulence. The mapping between Burgers'\nequation and the problem of a directed polymer in a random medium is used in\norder to study the fully developped turbulence in the limit of large\ndimensions. The stirring force corresponds to a quenched (spatio temporal)\nrandom potential for the polymer, correlated on large distances. A replica\nsymmetry breaking solution of the polymer problem provides the full probability\ndistribution of the velocity difference $u(r)$ between points separated by a\ndistance $r$ much smaller than the correlation length of the forcing. This\nexhibits a very strong intermittency which is related to regions of shock\nwaves, in the fluid, and to the existence of metastable states in the directed\npolymer problem. We also mention some recent computations on the finite\ndimensional problem, based on various analytical approaches (instantons,\noperator product expansion, mapping to directed polymers), as well as a\nconjecture on the relevance of Burgers equation (with the length scale playing\nthe role of time) for the description of the functional renormalisation group\nflow for the effective pinning potential of a manifold pinned by impurities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical transition in the TASEP with Langmuir kinetics: mean-field\n  theory: We develop a mean-field theory for the totally asymmetric simple exclusion\nprocess (TASEP) with open boundaries, in order to investigate the so-called\ndynamical transition. The latter phenomenon appears as a singularity in the\nrelaxation rate of the system toward its non-equilibrium steady state. In the\nhigh-density (low-density) phase, the relaxation rate becomes independent of\nthe injection (extraction) rate, at a certain critical value of the parameter\nitself, and this transition is not accompanied by any qualitative change in the\nsteady-state behavior. We characterize the relaxation rate by providing\nrigorous bounds, which become tight in the thermodynamic limit. These results\nare generalized to the TASEP with Langmuir kinetics, where particles can also\nbind to empty sites or unbind from occupied ones, in the symmetric case of\nequal binding/unbinding rates. The theory predicts a dynamical transition to\noccur in this case as well.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Driven tracers in narrow channels: Steady state properties of a driven tracer moving in a narrow two dimensional\n(2D) channel of quiescent medium are studied. The tracer drives the system out\nof equilibrium, perturbs the density and pressure fields, and gives the bath\nparticles a nonzero average velocity, creating a current in the channel. Three\nmodels in which the confining effect of the channel is probed are analyzed and\ncompared in this study: the first is the simple symmetric exclusion process\n(SSEP), for which the stationary density profile and the pressure on the walls\nin the frame of the tracer are computed. We show that the tracer acts like a\ndipolar source in an average velocity field. The spatial structure of this 2D\nstrip is then simplified to a one dimensional SSEP, in which exchanges of\nposition between the tracer and the bath particles are allowed. Using a\ncombination of mean field theory and exact solution in the limit where no\nexchange is allowed, gives good predictions of the velocity of the tracer and\nthe density field. Finally, we show that results obtained for the 1D SSEP with\nexchanges also apply to a gas of overdamped hard disks in a narrow channel. The\ncorrespondence between the parameters of the SSEP and of the gas of hard disks\nis systematic and follows from simple intuitive arguments. Our analytical\nresults are checked numerically.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Predictive statistical mechanics and macroscopic time evolution. A model\n  for closed Hamiltonian systems: Predictive statistical mechanics is a form of inference from available data,\nwithout additional assumptions, for predicting reproducible phenomena. By\napplying it to systems with Hamiltonian dynamics, a problem of predicting the\nmacroscopic time evolution of the system in the case of incomplete information\nabout the microscopic dynamics was considered. In the model of a closed\nHamiltonian system (i.e. system that can exchange energy but not particles with\nthe environment) that with the Liouville equation uses the concepts of\ninformation theory, analysis was conducted of the loss of correlation between\nthe initial phase space paths and final microstates, and the related loss of\ninformation about the state of the system. It is demonstrated that applying the\nprinciple of maximum information entropy by maximizing the conditional\ninformation entropy, subject to the constraint given by the Liouville equation\naveraged over the phase space, leads to a definition of the rate of change of\nentropy without any additional assumptions. In the subsequent paper\n(http://arxiv.org/abs/1506.02625) this basic model is generalized further and\nbrought into direct connection with the results of nonequilibrium theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kibble-Zurek mechanism and infinitely slow annealing through critical\n  points: We revisit the Kibble-Zurek mechanism by analyzing the dynamics of phase\nordering systems during an infinitely slow annealing across a second order\nphase transition. We elucidate the time and cooling rate dependence of the\ntypical growing length and we use it to predict the number of topological\ndefects left over in the symmetry broken phase as a function of time, both\nclose and far from the critical region. Our results extend the Kibble-Zurek\nmechanism and reveal its limitations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Equilibrium Equality for Free Energy Difference: Jarzynski Equality (JE) and the thermodynamic integration method are\nconventional methods to calculate free energy difference (FED) between two\nequilibrium states with constant temperature of a system. However, a number of\nensemble samples should be generated to reach high accuracy for a system with\nlarge size, which consumes a lot computational resource. Previous work had\ntried to replace the non-equilibrium quantities with equilibrium quantities in\nJE by introducing a virtual integrable system and it had promoted the\nefficiency in calculating FED between different equilibrium states with\nconstant temperature. To overcome the downside that the FED for two equilibrium\nstates with different temperature can't be calculated efficiently in previous\nwork, this article derives out the Equilibrium Equality for FED between any two\ndifferent equilibrium states by deriving out the equality for FED between\nstates with different temperatures and then combining the equality for FED\nbetween states with different volumes. The equality presented in this article\nexpresses FED between any two equilibrium states as an ensemble average in one\nequilibrium state, which enable the FED between any two equilibrium states can\nbe determined by generating only one canonical ensemble and thus the samples\nneeded are dramatically less and the efficiency is promoted a lot. Plus, the\neffectiveness and efficiency of the equality are examined in Toda-Lattice model\nwith different dimensions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relaxation and coarsening of weakly-interacting breathers in a\n  simplified DNLS chain: The Discrete NonLinear Schr\\\"odinger (DNLS) equation displays a parameter\nregion characterized by the presence of localized excitations (breathers).\nWhile their formation is well understood and it is expected that the asymptotic\nconfiguration comprises a single breather on top of a background, it is not\nclear why the dynamics of a multi-breather configuration is essentially frozen.\nIn order to investigate this question, we introduce simple stochastic models,\ncharacterized by suitable conservation laws. We focus on the role of the\ncoupling strength between localized excitations and background. In the DNLS\nmodel, higher breathers interact more weakly, as a result of their faster\nrotation. In our stochastic models, the strength of the coupling is controlled\ndirectly by an amplitude-dependent parameter. In the case of a power-law\ndecrease, the associated coarsening process undergoes a slowing down if the\ndecay rate is larger than a critical value. In the case of an exponential\ndecrease, a freezing effect is observed that is reminiscent of the scenario\nobserved in the DNLS. This last regime arises spontaneously when direct energy\ndiffusion between breathers and background is blocked below a certain\nthreshold.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum Annealing - Foundations and Frontiers: We briefly review various computational methods for the solution of\noptimization problems. First, several classical methods such as Metropolis\nalgorithm and simulated annealing are discussed. We continue with a description\nof quantum methods, namely adiabatic quantum computation and quantum annealing.\nNext, the new D-Wave computer and the recent progress in the field claimed by\nthe D-Wave group are discussed. We present a set of criteria which could help\nin testing the quantum features of these computers. We conclude with a list of\nconsiderations with regard to future research.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A first--order irreversible thermodynamic approach to a simple energy\n  converter: Several authors have shown that dissipative thermal cycle models based on\nFinite-Time Thermodynamics exhibit loop-shaped curves of power output versus\nefficiency, such as it occurs with actual dissipative thermal engines. Within\nthe context of First-Order Irreversible Thermodynamics (FOIT), in this work we\nshow that for an energy converter consisting of two coupled fluxes it is also\npossible to find loop-shaped curves of both power output and the so-called\necological function against efficiency. In a previous work Stucki [J.W. Stucki,\nEur. J. Biochem. vol. 109, 269 (1980)] used a FOIT-approach to describe the\nmodes of thermodynamic performance of oxidative phosphorylation involved in\nATP-synthesis within mithochondrias. In that work the author did not use the\nmentioned loop-shaped curves and he proposed that oxidative phosphorylation\noperates in a steady state simultaneously at minimum entropy production and\nmaximum efficiency, by means of a conductance matching condition between\nextreme states of zero and infinite conductances respectively. In the present\nwork we show that all Stucki's results about the oxidative phosphorylation\nenergetics can be obtained without the so-called conductance matching\ncondition. On the other hand, we also show that the minimum entropy production\nstate implies both null power output and efficiency and therefore this state is\nnot fulfilled by the oxidative phosphorylation performance. Our results suggest\nthat actual efficiency values of oxidative phosphorylation performance are\nbetter described by a mode of operation consisting in the simultaneous\nmaximization of the so-called ecological function and the efficiency.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The N-steps Invasion Percolation Model: A new kind of invasion percolation is introduced in order to take into\naccount the inertia of the invader fluid. The inertia strength is controlled by\nthe number N of pores (or steps) invaded after the perimeter rupture. The new\nmodel belongs to a different class of universality with the fractal dimensions\nof the percolating clusters depending on N. A blocking phenomenon takes place\nin two dimensions. It imposes an upper bound value on N. For pore sizes larger\nthan the critical threshold, the acceptance profile exhibits a permanent tail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "ac-driven Brownian motors: a Fokker-Planck treatment: We consider a primary model of ac-driven Brownian motors, i.e., a classical\nparticle placed in a spatial-time periodic potential and coupled to a heat\nbath. The effects of fluctuations and dissipations are studied by a\ntime-dependent Fokker-Planck equation. The approach allows us to map the\noriginal stochastic problem onto a system of ordinary linear algebraic\nequations. The solution of the system provides complete information about\nratchet transport, avoiding such disadvantages of direct stochastic\ncalculations as long transients and large statistical fluctuations. The\nFokker-Planck approach to dynamical ratchets is instructive and opens the space\nfor further generalizations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A kinetic Ising model study of dynamical correlations in confined\n  fluids: Emergence of both fast and slow time scales: Experiments and computer simulation studies have revealed existence of rich\ndynamics in the orientational relaxation of molecules in confined systems such\nas water in reverse micelles, cyclodextrin cavities and nano-tubes. Here we\nintroduce a novel finite length one dimensional Ising model to investigate the\npropagation and the annihilation of dynamical correlations in finite systems\nand to understand the intriguing shortening of the orientational relaxation\ntime that has been reported for small sized reverse micelles. In our finite\nsized model, the two spins at the two end cells are oriented in the opposite\ndirections, to mimic the effects of surface that in real system fixes water\norientation in the opposite directions. This produces opposite polarizations to\npropagate inside from the surface and to produce bulk-like condition at the\ncentre. This model can be solved analytically for short chains. For long chains\nwe solve the model numerically with Glauber spin flip dynamics (and also with\nMetropolis single-spin flip Monte Carlo algorithm). We show that model nicely\nreproduces many of the features observed in experiments. Due to the destructive\ninterference among correlations that propagate from the surface to the core,\none of the rotational relaxation time components decays faster than the bulk.\nIn general, the relaxation of spins is non-exponential due to the interplay\nbetween various interactions. In the limit of strong coupling between the spins\nor in the limit of low temperature, the nature of relaxation of the spins\nundergoes a qualitative change with the emergence of a homogeneous dynamics\nwhere decay is predominantly exponential, again in agreement with experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Bottom-Up Model of Self-Organized Criticality on Networks: The Bak-Tang-Wiesenfeld (BTW) sandpile process is an archetypal, stylized\nmodel of complex systems with a critical point as an attractor of their\ndynamics. This phenomenon, called self-organized criticality (SOC), appears to\noccur ubiquitously in both nature and technology. Initially introduced on the\n2D lattice, the BTW process has been studied on network structures with great\nanalytical successes in the estimation of macroscopic quantities, such as the\nexponents of asymptotically power-law distributions. In this article, we take a\nmicroscopic perspective and study the inner workings of the process through\nboth numerical and rigorous analysis. Our simulations reveal fundamental flaws\nin the assumptions of past phenomenological models, the same models that\nallowed accurate macroscopic predictions; we mathematically justify why\nuniversality may explain these past successes. Next, starting from scratch, we\nobtain microscopic understanding that enables mechanistic models; such models\ncan, for example, distinguish a cascade's area from its size. In the special\ncase of a 3-regular network, we use self-consistency arguments to obtain a\nzero-parameters, mechanistic (bottom-up) approximation that reproduces\nnontrivial correlations observed in simulations and that allows the study of\nthe BTW process on networks in regimes otherwise prohibitively costly to\ninvestigate. We then generalize some of these results to configuration model\nnetworks and explain how one could continue the generalization. The numerous\ntools and methods presented herein are known to enable studying the effects of\ncontrolling the BTW process and other self-organizing systems. More broadly,\nour use of multitype branching processes to capture information bouncing\nback-and-forth in a network could inspire analogous models of systems in which\nconsequences spread in a bidirectional fashion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Specific heats of quantum double-well systems: Specific heats of quantum systems with symmetric and asymmetric double-well\npotentials have been calculated. In numerical calculations of their specific\nheats, we have adopted the combined method which takes into account not only\neigenvalues of $\\epsilon_n$ for $0 \\leq n \\leq N_m$ obtained by the\nenergy-matrix diagonalization but also their extrapolated ones for $N_m+1 \\leq\nn < \\infty$ ($N_m=20$ or 30). Calculated specific heats are shown to be rather\ndifferent from counterparts of a harmonic oscillator. In particular, specific\nheats of symmetric double-well systems at very low temperatures have the\nSchottky-type anomaly, which is rooted to a small energy gap in low-lying\ntwo-level eigenstates induced by a tunneling through the potential barrier. The\nSchottky-type anomaly is removed when an asymmetry is introduced into the\ndouble-well potential. It has been pointed out that the specific-heat\ncalculation of a double-well system reported by Feranchuk, Ulyanenkov and\nKuz'min [Chem. Phys. 157, 61 (1991)] is misleading because the zeroth-order\noperator method they adopted neglects crucially important off-diagonal\ncontributions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Roughening Transition of Interfaces in Disordered Systems: The behavior of interfaces in the presence of both lattice pinning and random\nfield (RF) or random bond (RB) disorder is studied using scaling arguments and\nfunctional renormalization techniques. For the first time we show that there is\na continuous disorder driven roughening transition from a flat to a rough state\nfor internal interface dimensions 2<D<4. The critical exponents are calculated\nin an \\epsilon-expansion. At the transition the interface shows a\nsuperuniversal logarithmic roughness for both RF and RB systems. A transition\ndoes not exist at the upper critical dimension D_c=4. The transition is\nexpected to be observable in systems with dipolar interactions by tuning the\ntemperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Landau thermodynamic potential for BaTiO_3: In the paper, the description of the dielectric and ferroelectric properties\nof BaTiO_3 single crystals using Landau thermodynamic potential is addressed.\nOur results suggest that when using the sixth-power free energy expansion of\nthe thermodynamic potential, remarkably different values of the fourth-power\ncoefficient, \\beta (the coefficient of P^4_i terms), are required to adequately\nreproduce the nonlinear dielectric behavior of the paraelectric phase and the\nelectric field induced ferroelectric phase, respectively. In contrast, the\neighth-power expansion with a common set of coefficients enables a good\ndescription for both phases at the same time. These features, together with the\ndata available in literature, strongly attest to the necessity of the\neighth-power terms in Landau thermodynamic potential of BaTiO_3. In addition,\nthe fourth-power coefficients, \\beta and \\xi (the coefficient of P^2_i P^2_j\nterms), were evaluated from the nonlinear dielectric responses along [001],\n[011], and [111] orientations in the paraelectric phase. Appreciable\ntemperature dependence was evidenced for both coefficients above T_C. Further\nanalysis on the linear dielectric response of the single domain crystal in the\ntetragonal phase demonstrated that temperature dependent anharmonic\ncoefficients are also necessary for an adequate description of the dielectric\nbehavior in the ferroelectric phase. As a consequence, an eighth-power\nthermodynamic potential, with some of the anharmonic coefficients being\ntemperature dependent, was proposed and compared with the existing potentials.\nIn general, the potential proposed in this work exhibits a higher quality in\nreproducing the dielectric and ferroelectric properties of this prototypic\nferroelectric substance.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact solution of the geometrically frustrated spin-1/2 Ising-Heisenberg\n  model on the triangulated Kagome (triangles-in-triangles) lattice: The geometric frustration of the spin-1/2 Ising-Heisenberg model on the\ntriangulated Kagome (triangles-in-triangles) lattice is investigated within the\nframework of an exact analytical method based on the generalized star-triangle\nmapping transformation. Ground-state and finite-temperature phase diagrams are\nobtained along with other exact results for the partition function, Helmholtz\nfree energy, internal energy, entropy, and specific heat, by establishing a\nprecise mapping relationship to the corresponding spin-1/2 Ising model on the\nKagome lattice. It is shown that the residual entropy of the disordered spin\nliquid phase is for the quantum Ising-Heisenberg model significantly lower than\nfor its semi-classical Ising limit (S_0/N_T k_B = 0.2806 and 0.4752,\nrespectively), which implies that quantum fluctuations partially lift a\nmacroscopic degeneracy of the ground-state manifold in the frustrated regime.\nThe investigated model system has an obvious relevance to a series of polymeric\ncoordination compounds Cu_9X_2(cpa)_6 (X=F, Cl, Br and cpa=carboxypentonic\nacid) for which we made a theoretical prediction about the temperature\ndependence of zero-field specific heat.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Building Entanglement Entropy out of Correlation Functions for\n  Interacting Fermions: We provide a prescription to construct R\\'{e}nyi and von Neumann entropy of a\nsystem of interacting fermions from a knowledge of its correlation functions.\nWe show that R\\'{e}nyi entanglement entropy of interacting fermions in\narbitrary dimensions can be represented by a Schwinger Keldysh free energy on\nreplicated manifolds with a current between the replicas. The current is local\nin real space and is present only in the subsystem which is not integrated out.\nThis allows us to construct a diagrammatic representation of entanglement\nentropy in terms of connected correlators in the standard field theory with no\nreplicas. This construction is agnostic to how the correlators are calculated,\nand one can use calculated, simulated or measured values of the correlators in\nthis formula. Using this diagrammatic representation, one can decompose\nentanglement into contributions which depend on the one-particle correlator,\ntwo particle correlator and so on. We provide analytic formula for the\none-particle contribution and a diagrammatic construction for higher order\ncontributions. We show how this construction can be extended for von-Neumann\nentropy through analytic continuation. For a practical implementation of a\nquantum state, where one usually has information only about few-particle\ncorrelators, this provides an approximate way of calculating entanglement\ncommensurate with the limited knowledge about the underlying quantum state.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Physical swap dynamics, shortcuts to relaxation and entropy production\n  in dissipative Rydberg gases: Dense Rydberg gases are out-of-equilibrium systems where strong\ndensity-density interactions give rise to effective kinetic constraints. They\ncause dynamic arrest associated with highly-constrained many-body\nconfigurations, leading to slow relaxation and glassy behavior. Multi-component\nRydberg gases feature additional long-range interactions such as\nexcitation-exchange. These are analogous to particle swaps used to artificially\naccelerate relaxation in simulations of atomistic models of classical glass\nformers. In Rydberg gases, however, swaps are real physical processes, which\nprovide dynamical shortcuts to relaxation. They permit the accelerated approach\nto stationarity in experiment and at the same time have an impact on the\nnon-equilibrium stationary state. In particular their interplay with radiative\ndecay processes amplifies irreversibility of the dynamics, an effect which we\nquantify via the entropy production at stationarity. Our work highlights an\nintriguing analogy between real dynamical processes in Rydberg gases and\nartificial dynamics underlying advanced Monte Carlo methods. Moreover, it\ndelivers a quantitative characterization of the dramatic effect swaps have on\nthe structure and dynamics of their stationary state.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Continuity Conditions for the Radial Distribution Function of\n  Square-Well Fluids: The continuity conditions of the radial distribution function g(r) and its\nclose relative the cavity function y(r) are studied in the context of the\nPercus-Yevick (PY) integral equation for 3D square-well fluids. The cases\ncorresponding to a well width, (w-1)*d, equal to a fraction of the diameter of\nthe hard core, d/m, with m=1,2,3 have been considered. In these cases, it is\nproved that the function y(r) and its first derivative are everywhere\ncontinuous but eventually the derivative of some order becomes discontinuous at\nthe points (n+1)d/m, n=0,1,... . The order of continuity (the highest order\nderivative of y(r) being continuous at a given point) is found to be\nproportional to n in the first case (m=1) and to 2*n in the other two cases\n(m=2,3), for large values of n. Moreover, derivatives of y(r) up to third order\nare continuous at r=d and r=w*d for w=3/2 and w=4/3 but only the first\nderivative is continuous for w=2. This can be understood as a non-linear\nresonance effect.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Route from discreteness to the continuum for the non-logarithmic\n  $q$-entropy: The existence and exact form of the continuum expression of the discrete\nnonlogarithmic $q$-entropy is an important open problem in generalized\nthermostatistics, since its possible lack implies that nonlogarithmic\n$q$-entropy is irrelevant for the continuous classical systems. In this work,\nwe show how the discrete nonlogarithmic $q$-entropy in fact converges in the\ncontinuous limit and the negative of the $q$-entropy with continuous variables\nis demonstrated to lead to the (Csisz{\\'a}r type) $q$-relative entropy just as\nthe relation between the continuous Boltzmann-Gibbs expression and the\nKullback-Leibler relative entropy. As a result, we conclude that there is no\nobstacle for the applicability of the $q$-entropy to the continuous classical\nphysical systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extinction rates of established spatial populations: This paper deals with extinction of an isolated population caused by\nintrinsic noise. We model the population dynamics in a \"refuge\" as a Markov\nprocess which involves births and deaths on discrete lattice sites and random\nmigrations between neighboring sites. In extinction scenario I the zero\npopulation size is a repelling fixed point of the on-site deterministic\ndynamics. In extinction scenario II the zero population size is an attracting\nfixed point, corresponding to what is known in ecology as Allee effect.\nAssuming a large population size, we develop WKB (Wentzel-Kramers-Brillouin)\napproximation to the master equation. The resulting Hamilton's equations encode\nthe most probable path of the population toward extinction and the mean time to\nextinction. In the fast-migration limit these equations coincide, up to a\ncanonical transformation, with those obtained, in a different way, by Elgart\nand Kamenev (2004). We classify possible regimes of population extinction with\nand without an Allee effect and for different types of refuge and solve several\nexamples analytically and numerically. For a very strong Allee effect the\nextinction problem can be mapped into the over-damped limit of theory of\nhomogeneous nucleation due to Langer (1969). In this regime, and for very long\nsystems, we predict an optimal refuge size that maximizes the mean time to\nextinction.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entropy and forecasting complexity of hidden Markov models, matrix\n  product states, and observable operator models: In a series of three papers, Jurgens and Crutchfield recently proposed a\nsupposedly novel method to compute entropies of hidden Markov models (HMMs),\ndiscussed in detail its relationship to iterated function systems, and applied\nit to compute their ``ambiguity rates\", a concept supposedly introduced by\nClaude Shannon. We point out that the basic formalism is not new (it is the\nwell known ``forward algorithm\" for HMMs), and that all three papers have also\nserious other faults.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Superoperator coupled cluster method for nonequilibrium density matrix: We develop a superoperator coupled cluster method for nonequilibrium open\nmany-body quantum systems described by the Lindblad master equation. The method\nis universal and applicable to systems of interacting fermions, bosons or their\nmixtures. We present a general theory and consider its application to the\nproblem of quantum transport through the system with electron-phonon\ncorrelations. The results are assessed against the perturbation theory and\nnonequilibrium configuration interaction theory calculations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Analysis of a generalised Boltzmann equation for anomalous diffusion\n  under time-dependent fields: The generalised Boltzmann equation which treats the combined localised and\ndelocalised nature of transport present in certain materials is extended to\naccommodate time-dependent fields. In particular, AC fields are shown to be a\nmeans to probe the trapping and detrapping rates of materials under certain\nconditions. Conditions leading to dispersive transport are considered, and the\nsignature of fractional/anomalous diffusion under AC electric fields is\npresented.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Slow Kinetics of Brownian Maxima: We study extreme-value statistics of Brownian trajectories in one dimension.\nWe define the maximum as the largest position to date and compare maxima of two\nparticles undergoing independent Brownian motion. We focus on the probability\nP(t) that the two maxima remain ordered up to time t, and find the algebraic\ndecay P ~ t^(-beta) with exponent beta=1/4. When the two particles have\ndiffusion constants D1 and D2, the exponent depends on the mobilities,\nbeta=(1/pi)arctan[sqrt(D2/D1)]. We also use numerical simulations to\ninvestigate maxima of multiple particles in one dimension and the largest\nextension of particles in higher dimensions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low self-affine exponents of fracture surfaces of glass ceramics: The geometry of post mortem rough fracture surfaces of porous glass ceramics\nmade of sintered glass beads is shown experimentally to be self-affine with an\nexponent zeta=0.40 (0.04) remarkably lower than the 'universal' value zeta=0.8\nfrequently measured for many materials. This low value of zeta is similar to\nthat found for sandstone samples of similar micro structure and is also\npractically independent on the porosity phi in the range investigated (3% < phi\n< 26%) as well as on the bead diameter d and of the crack growth velocity. In\ncontrast, the roughness amplitude normalized by d increases linearly with phi\nwhile it is still independent, within experimental error, of d and of the crack\npropagation velocity. An interpretation of this variation is suggested in terms\nof a transition from transgranular to intergranular fracture propagation with\nno influence, however, on the exponent zeta.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-equilibrium dynamics in the quantum Brownian oscillator and the\n  second law of thermodynamics: We initially prepare a quantum linear oscillator weakly coupled to a bath in\nequilibrium at an arbitrary temperature. We disturb this system by varying a\nHamiltonian parameter of the coupled oscillator, namely, either its spring\nconstant or mass according to an arbitrary but pre-determined protocol in order\nto perform external work on it. We then derive a closed expression for the\nreduced density operator of the coupled oscillator along this non-equilibrium\nprocess as well as the exact expression pertaining to the corresponding\nquasi-static process. This immediately allows us to analytically discuss the\nsecond law of thermodynamics for non-equilibrium processes. Then we derive a\nClausius inequality and obtain its validity supporting the second law, as a\nconsistent generalization of the Clausius equality valid for the quasi-static\ncounterpart, introduced in [1].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase transitions in Ising models on directed networks: We examine Ising models with heat-bath dynamics on directed networks. Our\nsimulations show that Ising models on directed triangular and simple cubic\nlattices undergo a phase transition that most likely belongs to the Ising\nuniversality class. On the directed square lattice the model remains\nparamagnetic at any positive temperature as already reported in some previous\nstudies. We also examine random directed graphs and show that contrary to\nundirected ones, percolation of directed bonds does not guarantee ferromagnetic\nordering. Only above a certain threshold a random directed graph can support\nfinite-temperature ferromagnetic ordering. Such behaviour is found also for\nout-homogeneous random graphs, but in this case the analysis of magnetic and\npercolative properties can be done exactly. Directed random graphs also differ\nfrom undirected ones with respect to zero-temperature freezing. Only at low\nconnectivity they remain trapped in a disordered configuration. Above a certain\nthreshold, however, the zero-temperature dynamics quickly drives the model\ntoward a broken symmetry (magnetized) state. Only above this threshold, which\nis almost twice as large as the percolation threshold, we expect the Ising\nmodel to have a positive critical temperature. With a very good accuracy, the\nbehaviour on directed random graphs is reproduced within a certain approximate\nscheme.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Classical stochastic approach to quantum mechanics and quantum\n  thermodynamics: We derive the equations of quantum mechanics and quantum thermodynamics from\nthe assumption that a quantum system can be described by an underlying\nclassical system of particles. Each component $\\phi_j$ of the wave vector is\nunderstood as a stochastic complex variable whose real and imaginary parts are\nproportional to the coordinate and momentum associated to a degree of freedom\nof the underlying classical system. From the classical stochastic equations of\nmotion, we derive a general equation for the covariance matrix of the wave\nvector which turns out to be of the Lindblad type. When the noise changes only\nthe phase of $\\phi_j$, the Schr\\\"odinger and the quantum Liouville equation are\nobtained. The component $\\psi_j$ of the wave vector obeying the Schr\\\"odinger\nequation is related to stochastic wave vector by\n$|\\psi_j|^2=\\langle|\\phi_j|^2\\rangle$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Pseudo-$\u03b5$ Expansion and Renormalized Coupling Constants at\n  Criticality: Universal values of dimensional effective coupling constants $g_{2k}$ that\ndetermine nonlinear susceptibilities $\\chi_{2k}$ and enter the scaling equation\nof state are calculated for $n$-vector field theory within the\npseudo-$\\epsilon$ expansion approach. Pseudo-$\\epsilon$ expansions for $g_6$\nand $g_8$ at criticality are derived for arbitrary $n$. Analogous series for\nratios $R_6 = g_6/g_4^2$ and $R_8 = g_8/g_4^3$ figuring in the equation of\nstate are also found and the pseudo-$\\epsilon$ expansion for Wilson fixed point\nlocation $g_{4}^*$ descending from the six-loop RG expansion for\n$\\beta$-function is reported. Numerical results are presented for $0 \\le n \\le\n64$ with main attention paid to physically important cases $n = 0, 1, 2, 3$.\nPseudo-$\\epsilon$ expansions for quartic and sextic couplings have rapidly\ndiminishing coefficients, so Pad\\'e resummation turns out to be sufficient to\nyield high-precision numerical estimates. Moreover, direct summation of these\nseries with optimal truncation gives the values of $g_4^*$ and $R_6^*$ almost\nas accurate as those provided by Pad\\'e technique. Pseudo-$\\epsilon$ expansion\nestimates for $g_8^*$ and $R_8^*$ are found to be much worse than that for the\nlower-order couplings independently on the resummation method employed.\nNumerical effectiveness of the pseudo-$\\epsilon$ expansion approach in two\ndimensions is also studied. Pseudo-$\\epsilon$ expansion for $g_4^*$ originating\nfrom the five-loop RG series for $\\beta$-function of 2D $\\lambda\\phi^4$ field\ntheory is used to get numerical estimates for $n$ ranging from 0 to 64. The\napproach discussed gives accurate enough values of $g_{4}^*$ down to $n = 2$\nand leads to fair estimates for Ising and polymer ($n = 0$) models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cluster formation and anomalous fundamental diagram in an ant trail\n  model: A recently proposed stochastic cellular automaton model ({\\it J. Phys. A 35,\nL573 (2002)}), motivated by the motions of ants in a trail, is investigated in\ndetail in this paper. The flux of ants in this model is sensitive to the\nprobability of evaporation of pheromone, and the average speed of the ants\nvaries non-monotonically with their density. This remarkable property is\nanalyzed here using phenomenological and microscopic approximations thereby\nelucidating the nature of the spatio-temporal organization of the ants. We find\nthat the observations can be understood by the formation of loose clusters,\ni.e. space regions of enhanced, but not maximal, density.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Circuits in random graphs: from local trees to global loops: We compute the number of circuits and of loops with multiple crossings in\nrandom regular graphs. We discuss the importance of this issue for the validity\nof the cavity approach. On the one side we obtain analytic results for the\ninfinite volume limit in agreement with existing exact results. On the other\nside we implement a counting algorithm, enumerate circuits at finite N and draw\nsome general conclusions about the finite N behavior of the circuits.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "First quantum corrections for a hydrodynamics of a nonideal Bose gas: In the paper we consider a hydrodynamical description of a nonideal Bose gas\nin one-loop approximation. We calculate an effective action which consists of\nmean field contributions and first quantum correction. This provides the\nequations of motion for the density and velocity of the gas where both mean\nfield contributions and fluctuations are presented. To fulfill the calculation\nwe make use of the formalism of functional integrals to map the problem to a\nproblem of quantum gravity to benefit from a well-developed technique in this\nfield. This effective action provides all correlation functions for the system\nand is a basis for a consideration of dynamics of the gas. Response functions\nare briefly discussed. Applications to the trapped bosons are reviewed.\nTogether with Ref.\\cite{IS} the paper provide complete description of the\ncondensate fraction and the deplition in the case of Bose condensed gases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An appetizer to modern developments on the Kardar-Parisi-Zhang\n  universality class: The Kardar-Parisi-Zhang (KPZ) universality class describes a broad range of\nnon-equilibrium fluctuations, including those of growing interfaces, directed\npolymers and particle transport, to name but a few. Since the year 2000, our\nunderstanding of the one-dimensional KPZ class has been completely renewed by\nmathematical physics approaches based on exact solutions. Mathematical physics\nhas played a central role since then, leading to a myriad of new developments,\nbut their implications are clearly not limited to mathematics -- as a matter of\nfact, it can also be studied experimentally. The aim of these lecture notes is\nto provide an introduction to the field that is accessible to non-specialists,\nreviewing basic properties of the KPZ class and highlighting main physical\noutcomes of mathematical developments since the year 2000. It is written in a\nbrief and self-contained manner, with emphasis put on physical intuitions and\nimplications, while only a small (and mostly not the latest) fraction of\nmathematical developments could be covered. Liquid-crystal experiments by the\nauthor and coworkers are also reviewed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Landau Theory for the Mpemba Effect Through Phase Transitions: The Mpemba effect describes the situation in which a hot system cools faster\nthan an identical copy that is initiated at a colder temperature. In many of\nthe experimental observations of the effect, e.g. in water and clathrate\nhydrates, it is defined by the phase transition timing. However, none of the\ntheoretical investigations so far considered the timing of the phase\ntransition, and most of the abstract models used to explore the Mpemba effect\ndo not have a phase transition. We use the phenomenological Landau theory for\nphase transitions to identify the second order phase transition time, and\ndemonstrate with a concrete example that a Mpemba effect can exist in such\nmodels.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Isomorphic classical molecular dynamics model for an excess electron in\n  a supercritical fluid: Ring polymer molecular dynamics (RPMD) is used to directly simulate the\ndynamics of an excess electron in a supercritical fluid over a broad range of\ndensities. The accuracy of the RPMD model is tested against numerically exact\npath integral statistics through the use of analytical continuation techniques.\nAt low fluid densities, the RPMD model substantially underestimates the\ncontribution of delocalized states to the dynamics of the excess electron.\nHowever, with increasing solvent density, the RPMD model improves, nearly\nsatisfying analytical continuation constraints at densities approaching those\nof typical liquids. In the high density regime, quantum dispersion\nsubstantially decreases the self-diffusion of the solvated electron.\n  In this regime where the dynamics of the electron is strongly coupled to the\ndynamics of the atoms in the fluid, trajectories that can reveal diffusive\nmotion of the electron are long in comparison to $\\beta\\hbar$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Arrested States formed on Quenching Spin Chains with Competing\n  Interactions and Conserved Dynamics: We study the effects of rapidly cooling to T = 0 a spin chain with conserved\ndynamics and competing interactions. Depending on the degree of competition,\nthe system is found to get arrested in different kinds of metastable states.\nThe most interesting of these has an inhomogeneous mixture of interspersed\nactive and quiescent regions. In this state, the steady-state autocorrelation\nfunction decays as a stretched exponential $\\sim\n\\exp(-{(t/\\tau_{o})}^{{1}\\over{3}})$, and there is a two-step relaxation to\nequilibrium when the temperature is raised slightly.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reply to the comment on: \"Thermostatistics of Overdamped Motion of\n  Interacting Particles\" [arXiv:1104.0697] by Y. Levin and R. Pakter: We show that the comment [arXiv:1104.0697] by Levin and Pakter on our work\n[arXiv:1008.1421] is conceptually unfounded, contains misleading\ninterpretations, and is based on results of questionable applicability. We\ninitially provide arguments to evince that, inexplicably, these authors simply\nchoose to categorically dismiss our elaborated and solid conceptual approach,\nresults and analysis, without employing any fundamental concepts or tools from\nStatistical Physics. We then demonstrate that the results of Levin and Pakter\ndo not present any evidence against, but rather corroborates, our conclusions.\nIn fact, the results shown in their comment correspond to a confining potential\nthat is 1000 times stronger than the typical valued utilized in our study,\ntherefore explaining the discrepancy between their results and ours.\nFurthermore, in this regime where higher vortex densities are involved, vortex\ncores might get so close to each other that can no longer be treated as\npoint-like defects. As a consequence, Ginzburg-Landau equations should be\nemployed instead, meaning that the physical conditions implied by the results\nof Levin and Pakter should be considered with caution in the context of the\nPhysics of interacting superconducting vortexes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Determination of Nonequilibrium Temperature and Pressure using Clausius\n  Equality in a State with Memory: A Simple Model Calculation: Use of the extended definition of heat dQ=deQ+diQ converts the Clausius\ninequality dS greater than or equal to deQ/T0 into an equality dS=dQ/T\ninvolving the nonequilibrium temperature T of the system having the\nconventional interpretation that heat flows from hot to cold. The equality is\napplied to the exact quantum evolution of a 1-dimensional ideal gas free\nexpansion. In a first ever calculation of its kind in an expansion which\nretains the memory of initial state, we determine the nonequilibrium\ntemperature T and pressure P, which are then compared with the ratio P/T\nobtained by an independent method to show the consistency of the nonequilibrium\nformulation. We find that the quantum evolution by itself cannot eliminate the\nmemory effect.cannot eliminate the memory effect; hence, it cannot thermalize\nthe system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Some measure theory on stacks of graphs: We apply a theorem of Wick to rewrite certain classes of exponential measures\non random graphs as integrals of Feynman-Gibbs type, on the real line. The\nanalytic properties of these measures can then be studied in terms of phase\ntransitions; spaces of scale-free trees are a particularly interesting example.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entanglement dynamics in critical random quantum Ising chain with\n  perturbations: We simulate the entanglement dynamics in a critical random quantum Ising\nchain with generic perturbations using the time-evolving block decimation\nalgorithm. Starting from a product state, we observe super-logarithmic growth\nof entanglement entropy with time. The numerical result is consistent with the\nanalytical prediction of Vosk and Altman using a real-space renormalization\ngroup technique.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Physical insights from imaginary-time density--density correlation\n  functions: The accurate theoretical description of the dynamic properties of correlated\nquantum many-body systems such as the dynamic structure factor\n$S(\\mathbf{q},\\omega)$ constitutes an important task in many fields.\nUnfortunately, highly accurate quantum Monte Carlo methods are usually\nrestricted to the imaginary time domain, and the analytic continuation of the\nimaginary time density--density correlation function $F(\\mathbf{q},\\tau)$ to\nreal frequencies is a notoriously hard problem. In this work, we argue that no\nsuch analytic continuation is required as $F(\\mathbf{q},\\tau)$ contains, by\ndefinition, the same physical information as $S(\\mathbf{q},\\omega)$, only in an\nunfamiliar representation. Specifically, we show how we can directly extract\nkey information such as the temperature or quasi-particle excitation energies\nfrom the $\\tau$-domain, which is highly relevant for equation-of-state\nmeasurements of matter under extreme conditions. As a practical example, we\nconsider \\emph{ab initio} path integral Monte Carlo results for the uniform\nelectron gas (UEG), and demonstrate that even nontrivial processes such as the\n\\emph{roton feature} of the UEG at low density straightforwardly manifest in\n$F(\\mathbf{q},\\tau)$. In fact, directly working in the $\\tau$-domain is\nadvantageous for many reasons and holds the enticing promise for unprecedented\nagreement between theory and experiment.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical Mechanics of Double sinh-Gordon Kinks: We study the classical thermodynamics of the double sinh-Gordon (DSHG) theory\nin 1+1 dimensions. This model theory has a double well potential, thus allowing\nfor the existence of kinks and antikinks. Though it is nonintegrable, the DSHG\nmodel is remarkably amenable to analysis. Below we obtain exact single kink and\nkink lattice solutions as well as the asymptotic kink-antikink interaction. In\nthe continuum limit, finding the classical partition function is equivalent to\nsolving for the ground state of a Schrodinger-like equation obtained via the\ntransfer integral method. For the DSHG model, this equation turns out to be\nquasi-exactly solvable. We exploit this property to obtain exact energy\neigenvalues and wavefunctions for several temperatures both above and below the\nsymmetry breaking transition temperature. The availability of exact results\nprovides an excellent testing ground for large scale Langevin simulations. The\nprobability distribution function (PDF) calculated from Langevin dynamics is\nfound to be in striking agreement with the exact PDF obtained from the ground\nstate wavefunction. This validation points to the utility of a PDF-based\ncomputation of thermodynamics utilizing Langevin methods. In addition to the\nPDF, field-field and field fluctuation correlation functions were computed and\nalso found to be in excellent agreement with the exact results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Friction effects and clogging in a cellular automaton model for\n  pedestrian dynamics: We investigate the role of conflicts in pedestrian traffic, i.e. situations\nwhere two or more people try to enter the same space. Therefore a recently\nintroduced cellular automaton model for pedestrian dynamics is extended by a\nfriction parameter $\\mu$. This parameter controls the probability that the\nmovement of all particles involved in a conflict is denied at one time step. It\nis shown that these conflicts are not an undesirable artefact of the parallel\nupdate scheme, but are important for a correct description of the dynamics. The\nfriction parameter $\\mu$ can be interpreted as a kind of internal local\npressure between the pedestrians which becomes important in regions of high\ndensity, ocurring e.g. in panic situations. We present simulations of the\nevacuation of a large room with one door. It is found that friction has not\nonly quantitative effects, but can also lead to qualitative changes, e.g. of\nthe dependence of the evacuation time on the system parameters. We also observe\nsimilarities to the flow of granular materials, e.g. arching effects.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Dilemma of Bose Solids: is He Supersolid?: Nearly a decade ago the old controversy about possible superfluid flow in the\nground state of solid He4 was revived by the apparent experimental observation\nof such superflow. Although the experimentalists have recently retracted, very\npublicly, some of the observations on which such a claim was based, other\nconfirming observations of which there is no reason for doubt remain on the\nrecord. Meanwhile theoretical arguments bolstered by some experimental evidence\nstrongly favor the existence of supersolidity in the Bose-Hubbard model, and\nthese arguments would seem to extend to solid He. The true situation thus is\napparently extraordinarily opaque. The situation is complicated by the fact\nthat all accurate simulation studies on Heuse the uniform sign hypothesis which\nconfines them to the phase-coherent state, which is, in principle, supersolid,\nso that no accurate simulations of the true, classical solid exist. There is\ngreat confusion as to the nature of the ground state wave-function for a bose\nquantum solid, and we suggest that until that question is cleared up none of\nthese dilemmas will be resolved.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Collective dynamics in systems of active Brownian particles with\n  dissipative interactions: We use computer simulations to study the onset of collective motion in\nsystems of interacting active particles. Our model is a swarm of active\nBrownian particles with internal energy depot and interactions inspired by the\ndissipative particle dynamics method, imposing pairwise friction force on the\nnearest neighbours. We study orientational ordering in a 2D system as a\nfunction of energy influx rate and particle density. The model demonstrates a\ntransition into the ordered state on increasing the particle density and\nincreasing the input power. Although both the alignment mechanism and the\ncharacter of individual motion in our model differ from those in the\nwell-studied Vicsek model, it demonstrates identical statistical properties and\nphase behaviour.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic Hard-Sphere Dynamics for Hydrodynamics of Non-Ideal Fluids: A novel stochastic fluid model is proposed with non-ideal structure factor\nconsistent with compressibility, and adjustable transport coefficients. This\nStochastic Hard Sphere Dynamics (SHSD) algorithm is a modification of the\nDirect Simulation Monte Carlo (DSMC) algorithm and has several computational\nadvantages over event-driven hard-sphere molecular dynamics. Surprisingly, SHSD\nresults in an equation of state and pair correlation function identical to that\nof a deterministic Hamiltonian system of penetrable spheres interacting with\nlinear core pair potentials. The fluctuating hydrodynamic behavior of the SHSD\nfluid is verified for the Brownian motion of a nano-particle suspended in a\ncompressible solvent.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Evolution of the System with Singular Multiplicative Noise: The governed equations for the order parameter, one-time and two-time\ncorrelators are obtained on the basis of the Langevin equation with the white\nmultiplicative noise which amplitude $x^{a}$ is determined by an exponent\n$0<a<1$ ($x$ being a stochastic variable). It turns out that equation for\nautocorrelator includes an anomalous average of the power-law function with the\nfractional exponent $2a$. Determination of this average for the stochastic\nsystem with a self-similar phase space is performed. It is shown that at\n$a>1/2$, when the system is disordered, the correlator behaves\nnon-monotonically in the course of time, whereas the autocorrelator is\nincreased monotonically. At $a<1/2$ the phase portrait of the system evolution\ndivides into two domains: at small initial values of the order parameter, the\nsystem evolves to a disordered state, as above; within the ordered domain it is\nattracted to the point having the finite values of the autocorrelator and order\nparameter. The long-time asymptotes are defined to show that, within the\ndisordered domain, the autocorrelator decays hyperbolically and the order\nparameter behaves as the power-law function with fractional exponent $-2(1-a)$.\nCorrespondingly, within the ordered domain, the behavior of both dependencies\nis exponential with an index proportional to $-t\\ln t$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Density-feedback control in traffic and transport far from equilibrium: A bottleneck situation in one-lane traffic-flow is typically modelled with a\nconstant demand of entering cars. However, in practice this demand may depend\non the density of cars in the bottleneck. The present paper studies a simple\nbimodal realization of this mechanism to which we refer to as density-feedback\ncontrol (DFC): If the actual density in the bottleneck is above a certain\nthreshold, the reservoir density of possibly entering cars is reduced to a\ndifferent constant value. By numerical solution of the discretized viscid\nBurgers equation a rich stationary phase diagram is found. In order to maximize\nthe flow, which is the goal of typical traffic-management strategies, we find\nthe optimal choice of the threshold. Analytical results are verified by\ncomputer simulations of the microscopic TASEP with DFC.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Langevin canonical approach to the dynamics of chiral two level\n  systems. Thermal averages and heat capacity: A Langevin canonical framework for a chiral two--level system coupled to a\nbath of harmonic oscillators is developed within a coupling scheme different to\nthe well known spin-boson model. Thermal equilibrium values are reached at\nasymptotic times by solving the corresponding set of non--linear coupled\nequations in a Markovian regime. In particular, phase difference thermal values\n(or, equivalently, the so--called coherence factor) and heat capacity through\nenergy fluctuations are obtained and discussed in terms of tunneling rates and\nasymmetries.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Generalized Tsallis Thermostatistics of Magnetic Systems: In this study, our effort is to introduce Tsallis thermostatistics in some\ndetails and to give a brief review of the magnetic systems which have been\nstudied in the frame of this formalism.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The ground state energy of the Edwards-Anderson spin glass model with a\n  parallel tempering Monte Carlo algorithm: We study the efficiency of parallel tempering Monte Carlo technique for\ncalculating true ground states of the Edwards-Anderson spin glass model.\nBimodal and Gaussian bond distributions were considered in two and\nthree-dimensional lattices. By a systematic analysis we find a simple formula\nto estimate the values of the parameters needed in the algorithm to find the GS\nwith a fixed average probability. We also study the performance of the\nalgorithm for single samples, quantifying the difference between samples where\nthe GS is hard, or easy, to find. The GS energies we obtain are in good\nagreement with the values found in the literature. Our results show that the\nperformance of the parallel tempering technique is comparable to more powerful\nheuristics developed to find the ground state of Ising spin glass systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random walks on uniform and non-uniform combs and brushes: We consider random walks on comb- and brush-like graphs consisting of a base\n(of fractal dimension $D$) decorated with attached side-groups. The graphs are\nalso characterized by the fractal dimension $D_a$ of a set of anchor points\nwhere side-groups are attached to the base. Two types of graphs are considered.\nGraphs of the first type are uniform in the sense that anchor points are\ndistributed periodically over the base, and thus form a subset of the base with\ndimension $D_a=D$. Graphs of the second type are decorated with side-groups in\na regular yet non-uniform way: the set of anchor points has fractal dimension\nsmaller than that of the base, $D_a<D$. For uniform graphs, a qualitative\nmethod for evaluating the sub-diffusion exponent suggested by Forte et al. for\ncombs ($D=1$) is extended for brushes ($D>1$) and numerically tested for the\nSierpinski brush (with the base and anchor set built on the same Sierpinski\ngasket). As an example of nonuniform graphs we consider the Cantor comb\ncomposed of a one-dimensional base and side-groups, the latter attached to the\nformer at anchor points forming the Cantor set. A peculiar feature of this and\nother nonuniform systems is a long-lived regime of super-diffusive transport\nwhen side-groups are of a finite size.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Decay of Metastable States: Sharp Transition from Quantum to Classical\n  Behavior: The decay rate of metastable states is determined at high temperatures by\nthermal activation, whereas at temperatures close to zero quantum tunneling is\nrelevant. At some temperature $T_{c}$ the transition from classical to\nquantum-dominated decay occurs. The transition can be first-order like, with a\ndiscontinuous first derivative of the Euclidean action, or smooth with only a\nsecond derivative developing a jump. In the former case the crossover\ntemperature $T_{c}$ cannot be calculated perturbatively and must be found as\nthe intersection point of the Euclidean actions calculated at low and high\ntemperatures. In this paper we present a sufficient criterion for a first-order\ntransition in tunneling problems and apply it to the problem of the tunneling\nof strings. It is shown that the problem of the depinning of a massive string\nfrom a linear defect in the presence of an arbitrarily strong dissipation\nexhibits a first-order transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonlinear response and emerging nonequilibrium micro-structures for\n  biased diffusion in confined crowding environments: We study analytically the dynamics and the micro-structural changes of a host\nmedium caused by a driven tracer particle moving in a confined, quiescent\nmolecular crowding environment. Imitating typical settings of active\nmicro-rheology experiments, we consider here a minimal model comprising a\ngeometrically confined lattice system -- a two-dimensional strip-like or a\nthree-dimensional capillary-like -- populated by two types of hard-core\nparticles with stochastic dynamics -- a tracer particle driven by a constant\nexternal force and bath particles moving completely at random. Resorting to a\ndecoupling scheme, which permits us to go beyond the linear-response\napproximation (Stokes regime) for arbitrary densities of the lattice gas\nparticles, we determine the force-velocity relation for the tracer particle and\nthe stationary density profiles of the host medium particles around it. These\nresults are validated a posteriori by extensive numerical simulations for a\nwide range of parameters. Our theoretical analysis reveals two striking\nfeatures: a) We show that, under certain conditions, the terminal velocity of\nthe driven tracer particle is a nonmonotonic function of the force, so that in\nsome parameter range the differential mobility becomes negative, and b) the\nbiased particle drives the whole system into a nonequilibrium steady-state with\na stationary particle density profile past the tracer, which decays\nexponentially, in sharp contrast with the behavior observed for unbounded\nlattices, where an algebraic decay is known to take place.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Describing the ground state of quantum systems through statistical\n  mechanics: We present a statistical mechanics description to study the ground state of\nquantum systems. In this approach, averages for the complete system are\ncalculated over the non-interacting energy levels. Taking different interaction\nparameter, the particles of the system fall into non-interacting microstates,\ncorresponding to different occupation probabilities for these energy levels.\nUsing this novel thermodynamic interpretation we study the Hubbard model for\nthe case of two electrons in two sites and for the half-filled band on a\none-dimensional lattice. We show that the form of the entropy depends on the\nspecific system considered.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Boltzmann temperature and Lagrange multiplier: We consider the relation between the Boltzmann temperature and the Lagrange\nmultipliers associated with energy average in the nonextensive\nthermostatistics. In Tsallis' canonical ensemble, the Boltzmann temperature\ndepends on energy through the probability distribution unless $q=1$. It is\nshown that the so-called 'physical temperature' introduced in [Phys. Lett. A\n\\textbf{281} (2001) 126] is nothing but the ensemble average of the Boltzmann\ntemperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Glassy behaviour in an exactly solved spin system with a ferromagnetic\n  transition: We show that applying simple dynamical rules to Baxter's eight-vertex model\nleads to a system which resembles a glass-forming liquid. There are analogies\nwith liquid, supercooled liquid, glassy and crystalline states. The disordered\nphases exhibit strong dynamical heterogeneity at low temperatures, which may be\ndescribed in terms of an emergent mobility field. Their dynamics are\nwell-described by a simple model with trivial thermodynamics, but an emergent\nkinetic constraint. We show that the (second order) thermodynamic transition to\nthe ordered phase may be interpreted in terms of confinement of the excitations\nin the mobility field. We also describe the aging of disordered states towards\nthe ordered phase, in terms of simple rate equations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Equilibrium Microcanonical Annealing for First-Order Phase Transitions: A framework is presented for carrying out simulations of equilibrium systems\nin the microcanonical ensemble using annealing in an energy ceiling. The\nframework encompasses an equilibrium version of simulated annealing, population\nannealing and hybrid algorithms that interpolate between these extremes. These\nequilibrium, microcanonical annealing algorithms are applied to the thermal\nfirst-order transition in the 20-state, two-dimensional Potts model. All of\nthese algorithms are observed to perform well at the first-order transition\nthough for the system sizes studied here, equilibrium simulated annealing is\nmost efficient.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "High Precision Fourier Monte Carlo Simulation of Crystalline Membranes: We report an essential improvement of the plain Fourier Monte Carlo algorithm\nthat promises to be a powerful tool for investigating critical behavior in a\nlarge class of lattice models, in particular those containing microscopic or\neffective long-ranged interactions. On tuning the Monte Carlo acceptance rates\nseparately for each wave vector, we are able to drastically reduce critical\nslowing down. We illustrate the resulting efficiency and unprecedented accuracy\nof our algorithm with a calculation of the universal elastic properties of\ncrystalline membranes in the flat phase and derive a numerical estimate eta =\n0.795(10) for the critical exponent eta that challenges those derived from\nother recent simulations. The large system sizes accessible to our present\nalgorithm also allow to demonstrate that insufficiently taking into account\ncorrections to scaling may severely hamper a finite size scaling analysis. This\nobservation may also help to clarify the apparent disagreement of published\nnumerical estimates of eta in the existing literature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Boundary drive induced formation of aggregate condensates in stochastic\n  transport with short-range interactions: We discuss the effects of particle exchange through open boundaries and the\ninduced drive on the phase structure and condensation phenomena of a stochastic\ntransport process with tunable short-range interactions featuring\npair-factorized steady states (PFSS) in the closed system. In this model, the\nsteady state of the particle hopping process can be tuned to yield properties\nfrom the zero-range process (ZRP) condensation model to those of models with\nspa- tially extended condensates. By varying the particle exchange rates as\nwell as the presence of a global drift, we observe a phase transition from a\nfree particle gas to a phase with condensates aggregated to the boundaries.\nWhile this transition is similar to previous results for the ZRP, we find that\nthe mechanism is different as the presence of the boundary actually influences\nthe interaction due to the non-zero interaction range.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Granular gas of viscoelastic particles in a homogeneous cooling state: Kinetic properties of a granular gas of viscoelastic particles in a\nhomogeneous cooling state are studied analytically and numerically. We employ\nthe most recent expression for the velocity-dependent restitution coefficient\nfor colliding viscoelastic particles, which allows to describe systems with\nlarge inelasticity. In contrast to previous studies, the third coefficient a3\nof the Sonine polynomials expansion of the velocity distribution function is\ntaken into account. We observe a complicated evolution of this coefficient.\nMoreover, we find that a3 is always of the same order of magnitude as the\nleading second Sonine coefficient a2; this contradicts the existing hypothesis\nthat the subsequent Sonine coefficients a2, a3 ..., are of an ascending order\nof a small parameter, characterizing particles inelasticity. We analyze\nevolution of the high-energy tail of the velocity distribution function. In\nparticular, we study the time dependence of the tail amplitude and of the\nthreshold velocity, which demarcates the main part of the velocity distribution\nand the high-energy part. We also study evolution of the self-diffusion\ncoefficient D and explore the impact of the third Sonine coefficient on the\nself-diffusion. Our analytical predictions for the third Sonine coefficient,\nthreshold velocity and the self-diffusion coefficient are in a good agreement\nwith the numerical finding.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Power-law distributions for the areas of the basins of attraction on a\n  potential energy landscape: Energy landscape approaches have become increasingly popular for analysing a\nwide variety of chemical physics phenomena. Basic to many of these applications\nhas been the inherent structure mapping, which divides up the potential energy\nlandscape into basins of attraction surrounding the minima. Here, we probe the\nnature of this division by introducing a method to compute the basin area\ndistribution and applying it to some archetypal supercooled liquids. We find\nthat this probability distribution is a power law over a large number of\ndecades with the lower-energy minima having larger basins of attraction.\nInterestingly, the exponent for this power law is approximately the same as\nthat for a high-dimensional Apollonian packing, providing further support for\nthe suggestion that there is a strong analogy between the way the energy\nlandscape is divided into basins, and the way that space is packed in\nself-similar, space-filling hypersphere packings, such as the Apollonian\npacking. These results suggest that the basins of attraction provide a\nfractal-like tiling of the energy landscape, and that a scale-free pattern of\nconnections between the minima is a general property of energy landscapes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Force fluctuation in a driven elastic chain: We study the dynamics of an elastic chain driven on a disordered substrate\nand analyze numerically the statistics of force fluctuations at the depinning\ntransition. The probability distribution function of the amplitude of the slip\nevents for small velocities is a power law with an exponent $+AFw-tau$\ndepending on the driving velocity. This result is in qualitative agreement with\nexperimental measurements performed on sliding elastic surfaces with\nmacroscopic asperities. We explore the properties of the depinning transition\nas a function of the driving mode (i.e. constant force or constant velocity)\nand compute the force-velocity diagram using finite size scaling methods. The\nscaling exponents are in excellent agreement with the values expected in\ninterface models and, contrary to previous studies, we found no difference in\nthe exponents for periodic and disordered chains.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Binary data corruption due to a Brownian agent II: two dimensions,\n  competing agents, and generalized couplings: This work is a continuation of our previous investigation of binary data\ncorruption due to a Brownian agent [T. J. Newman and W. Triampo, preprint\ncond-mat/9811237]. We extend our study in three main directions which allow us\nto make closer contact with real bistable systems. These are i) a detailed\nanalysis of two dimensions, ii) the case of competing agents, and iii) the\ncases of asymmetric and quenched random couplings. Most of our results are\nobtained by extending our original phenomenological model, and are supported by\nextensive numerical simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of collapsing and exploding Bose-Einstein condensates: We explored the dynamics of how a Bose-Einstein condensate collapses and\nsubsequently explodes when the balance of forces governing the size and shape\nof the condensate is suddenly altered. A condensate's equilibrium size and\nshape is strongly affected by the inter-atomic interactions. Our ability to\ninduce a collapse by switching the interactions from repulsive to attractive by\ntuning an externally-applied magnetic field yields a wealth of detailed\ninformation on the violent collapse process. We observe anisotropic atom bursts\nthat explode from the condensate, atoms leaving the condensate in undetected\nforms, spikes appearing in the condensate wave function, and oscillating\nremnant condensates that survive the collapse. These all have curious\ndependencies on time, the strength of the interaction, and the number of\ncondensate atoms. Although ours would seem to be a simple well-characterized\nsystem, our measurements reveal many interesting phenomena that challenge\ntheoretical models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Consistent description of kinetics and hydrodynamics of dusty plasma: A consistent statistical description of kinetics and hydrodynamics of dusty\nplasma is proposed based on the Zubarev nonequilibrium statistical operator\nmethod. For the case of partial dynamics the nonequilibrium statistical\noperator and the generalized transport equations for a consistent description\nof kinetics of dust particles and hydrodynamics of electrons, ions and neutral\natoms are obtained. In the approximation of weakly nonequilibrium process a\nspectrum of collective excitations of dusty plasma is investigated in the\nhydrodynamic limit.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metastability in the Hamiltonian Mean Field model and Kuramoto model: We briefly discuss the state of the art on the anomalous dynamics of the\nHamiltonian Mean Field model. We stress the important role of the initial\nconditions for understanding the microscopic nature of the intriguing\nmetastable quasi stationary states observed in the model and the connections to\nTsallis statistics and glassy dynamics. We also present new results on the\nexistence of metastable states in the Kuramoto model and discuss the\nsimilarities with those found in the HMF model. The existence of metastability\nseem to be quite a common phenomenon in fully coupled systems, whose origin\ncould be also interpreted as a dynamical mechanism preventing or hindering\nsinchronization.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effect of Constraint Relaxation on the Minimum Vertex Cover Problem in\n  Random Graphs: A statistical-mechanical study of the effect of constraint relaxation on the\nminimum vertex cover problem in Erd\\H{o}s-R\\'enyi random graphs is presented.\nUsing a penalty-method formulation for constraint relaxation, typical\nproperties of solutions, including infeasible solutions that violate the\nconstraints, are analyzed by means of the replica method and cavity method. The\nproblem involves a competition between reducing the number of vertices to be\ncovered and satisfying the edge constraints. The analysis under the\nreplica-symmetric (RS) ansatz clarifies that the competition leads to\ndegeneracies in the vertex and edge states, which determine the quantitative\nproperties of the system, such as the cover and penalty ratios. A precise\nanalysis of these effects improves the accuracy of RS approximation for the\nminimum cover ratio in the replica symmetry breaking (RSB) region. Furthermore,\nthe analysis based on the RS cavity method indicates that the RS/RSB boundary\nof the ground states with respect to the mean degree of the graphs is expanded,\nand the critical temperature is lowered by constraint relaxation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fermionic R-operator approach for the small-polaron model with open\n  boundary condition: Exact integrability and algebraic Bethe ansatz of the small-polaron model\nwith the open boundary condition are discussed in the framework of the quantum\ninverse scattering method (QISM). We employ a new approach where the fermionic\nR-operator which consists of fermion operators is a key object. It satisfies\nthe Yang-Baxter equation and the reflection equation with its corresponding\nK-operator. Two kinds of 'super-transposition' for the fermion operators are\ndefined and the dual reflection equation is obtained. These equations prove the\nintegrability and the Bethe ansatz equation which agrees with the one obtained\nfrom the graded Yang-Baxter equation and the graded reflection equations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact relaxation in a class of non-equilibrium quantum lattice systems: A reasonable physical intuition in the study of interacting quantum systems\nsays that, independent of the initial state, the system will tend to\nequilibrate. In this work we study a setting where relaxation to a steady state\nis exact, namely for the Bose-Hubbard model where the system is quenched from a\nMott quantum phase to the strong superfluid regime. We find that the evolving\nstate locally relaxes to a steady state with maximum entropy constrained by\nsecond moments, maximizing the entanglement, to a state which is different from\nthe thermal state of the new Hamiltonian. Remarkably, in the infinite system\nlimit this relaxation is true for all large times, and no time average is\nnecessary. For large but finite system size we give a time interval for which\nthe system locally \"looks relaxed\" up to a prescribed error. Our argument\nincludes a central limit theorem for harmonic systems and exploits the finite\nspeed of sound. Additionally, we show that for all periodic initial\nconfigurations, reminiscent of charge density waves, the system relaxes\nlocally. We sketch experimentally accessible signatures in optical lattices as\nwell as implications for the foundations of quantum statistical mechanics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Self-Consistent Theory of Rupture by Progressive Diffuse Damage: We analyze a self-consistent theory of crack growth controlled by a\ncumulative damage variable d(t) dependent on stress history. As a function of\nthe damage exponent $m$, which controls the rate of damage dd/dt \\propto\nsigma^m as a function of local stress $\\sigma$, we find two regimes. For 0 < m\n< 2, the model predicts a finite-time singularity. This retrieves previous\nresults by Zobnin for m=1 and by Bradley and Wu for 0 < m < 2. To improve on\nthis self-consistent theory which neglects the dependence of stress on damage,\nwe apply the functional renormalization method of Yukalov and Gluzman and find\nthat divergences are replaced by singularities with exponents in agreement with\nthose found in acoustic emission experiments. For m =2 and m > 2, the rupture\ndynamics is not defined without the introduction of a regularizing scheme. We\ninvestigate three regularization schemes involving respectively a saturation of\ndamage, a minimum distance of approach to the crack tip and a fixed stress\nmaximum. In the first and third schemes, the finite-time singularity is\nreplaced by a crack dynamics defined for all times but which is controlled by\neither the existence of a microscopic scale at which the stress is regularized\nor by the maximum sustainable stress. In the second scheme, a finite-time\nsingularity is again found. In the first two schemes within this regime m > 2,\nthe theory has no continuous limit.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Accurate Estimation of Diffusion Coefficients and their Uncertainties\n  from Computer Simulation: Self-diffusion coefficients, $D^*$, are routinely estimated from molecular\ndynamics simulations by fitting a linear model to the observed mean-squared\ndisplacements (MSDs) of mobile species. MSDs derived from simulation suffer\nfrom statistical noise, which introduces uncertainty in the resulting estimate\nof $D^*$. An optimal scheme for estimating $D^*$ will minimise this\nuncertainty, i.e., will have high statistical efficiency, and will give an\naccurate estimate of the uncertainty itself. We present a scheme for estimating\n$D^*$ from a single simulation trajectory with high statistical efficiency and\naccurately estimating the uncertainty in the predicted value. The statistical\ndistribution of MSDs observable from a given simulation is modelled as a\nmultivariate normal distribution using an analytical covariance matrix for an\nequivalent system of freely diffusing particles, which we parameterise from the\navailable simulation data. We then perform Bayesian regression to sample the\ndistribution of linear models that are compatible with this model multivariate\nnormal distribution, to obtain a statistically efficient estimate of $D^*$ and\nan accurate estimate of the associated statistical uncertainty.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Derivation of the percolation threshold for the network model of\n  Barabasi and Albert: The percolation threshold of the network model by Barabasi and Albert\n(BA-model) [Science 286, 509 (1999)] has thus far only been 'guessed' based on\nsimulations and comparison with other models. Due to the still uncertain\ninfluence of correlations, the reference to other models cannot be justified.\nIn this paper, we explicitly derive the well-known values for the BA-model. To\nunderline the importance of a null model like that of Barabasi and Albert, we\nclose with two basic remarks. First, we establish a connection between the\nabundance of scale-free networks in nature and the fact that power-law tails in\nthe degree distribution result only from (at least asymptotically) linear\npreferential attachment: Only in the case of linear preferential attachment\ndoes a minimum of topological knowledge about the network suffice for the\nattachment process. Second, we propose a very simple and realistic extension of\nthe BA-model that accounts for clustering. We discuss the influence of\nclustering on the percolation properties.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Towards entanglement negativity of two disjoint intervals for a one\n  dimensional free fermion: We study the moments of the partial transpose of the reduced density matrix\nof two intervals for the free massless Dirac fermion. By means of a direct\ncalculation based on coherent state path integral, we find an analytic form for\nthese moments in terms of the Riemann theta function. We show that the moments\nof arbitrary order are equal to the same quantities for the compactified boson\nat the self-dual point. These equalities imply the non trivial result that also\nthe negativity of the free fermion and the self-dual boson are equal.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Percolation approach to glassy dynamics with continuously broken\n  ergodicity: We show that the relaxation dynamics near a glass transition with continuous\nergodicity breaking can be endowed with a geometric interpretation based on\npercolation theory. At mean-field level this approach is consistent with the\nmode-coupling theory (MCT) of type-A liquid-glass transitions and allows to\ndisentangle the universal and nonuniversal contributions to MCT relaxation\nexponents. Scaling predictions for the time correlation function are\nsuccessfully tested in the F12 schematic model and facilitated spin systems on\na Bethe lattice. Our approach immediately suggests the extension of MCT scaling\nlaws to finite spatial dimensions and yields new predictions for dynamic\nrelaxation exponents below an upper critical dimension of 6.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Brownian motion under annihilation dynamics: The behavior of a heavy tagged intruder immersed in a bath of particles\nevolving under ballistic annihilation dynamics is investigated. The\nFokker-Planck equation for this system is derived and the peculiarities of the\ncorresponding diffusive behavior are worked out. In the long time limit, the\nintruder velocity distribution function approaches a Gaussian form, but with a\ndifferent temperature from its bath counterpart. As a consequence of the\ncontinuous decay of particles in the bath, the mean squared displacement\nincreases exponentially in the collision per particle time scale. Analytical\nresults are finally successfully tested against Monte Carlo numerical\nsimulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An exact solution to asymptotic Bethe equation: We present an exact solution to the asymptotic Bethe equation of weakly\nanisotropic Heisenberg spin chain, which is a set of non-linear algebraic\nequations. The solution describes the low-energy excitations above\nferromagnetic ground state with fixed magnetisation, and it has a close\nrelation to generalised Jacobi polynomial. It is equivalent to a generalised\nStieltjes problem and in the continuous limit, it becomes a Riemann-Hilbert\nproblem closely related to the finite-gap solutions of classical\nLandau-Lifshitz field theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlation function structure in square-gradient models of the\n  liquid-gas interface: Exact results and reliable approximations: In a recent article, we described how the microscopic structure of\ndensity-density correlations in the fluid interfacial region, for systems with\nshort-ranged forces, can be understood by considering the resonances of the\nlocal structure factor occurring at specific parallel wave-vectors $q$. Here,\nwe investigate this further by comparing approximations for the local structure\nfactor and correlation function against three new examples of analytically\nsolvable models within square-gradient theory. Our analysis further\ndemonstrates that these approximations describe the correlation function and\nstructure factor across the whole spectrum of wave-vectors, encapsulating the\ncross-over from the Goldstone mode divergence (at small $q$) to bulk-like\nbehaviour (at larger $q$). As shown, these approximations are exact for some\nsquare-gradient model potentials, and never more than a few percent inaccurate\nfor the others. Additionally, we show that they very accurately describe the\ncorrelation function structure for a model describing an interface near a\ntricritical point. In this case, there are no analytical solutions for the\ncorrelation functions, but the approximations are near indistinguishable from\nthe numerical solutions of the Ornstein-Zernike equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entanglement Spectra and Entanglement Thermodynamics of Hofstadter\n  Bilayers: We study Hofstadter bilayers, i.e. coupled hopping models on two-dimensional\nsquare lattices in a perpendicular magnetic field. Upon tracing out one of the\nlayers, we find an explicit expression for the resulting entanglement spectrum\nin terms of the energy eigenvalues of the underlying monolayer system. For\nstrongly coupled layers the entanglement Hamiltonian is proportional to the\nenergetic Hamiltonian of the monolayer system. The proportionality factor,\nhowever, cannot be interpreted as the inverse thermodynamic temperature, but\nrepresents a phenomenological temperature scale. We derive an explicit relation\nbetween both temperature scales which is in close analogy to a standard result\nof classic thermodynamics. In the limit of vanishing temperature, thermodynamic\nquantities such as entropy and inner energy approach their ground-state values,\nbut show a fractal structure as a function of magnetic flux.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Numerical exploration of the Aging effects in spin systems: An interesting concept that has been underexplored in the context of\ntime-dependent simulations is the correlation of total magnetization, $C(t)$%.\nOne of its main advantages over directly studying magnetization is that we do\nnot need to meticulously prepare initial magnetizations. This is because the\nevolutions are computed from initial states with spins that are independent and\ncompletely random. In this paper, we take an important step in demonstrating\nthat even for time evolutions from other initial conditions, $C(t_{0},t)$, a\nsuitable scaling can be performed to obtain universal power laws. We\nspecifically consider the significant role played by the second moment of\nmagnetization. Additionally, we complement the study by conducting a recent\ninvestigation of random matrices, which are applied to determine the critical\nproperties of the system. Our results show that the aging in the time series of\nmagnetization influences the spectral properties of matrices and their ability\nto determine the critical temperature of systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal Order and Gap Statistics of Critical Branching Brownian Motion: We study the order statistics of one dimensional branching Brownian motion in\nwhich particles either diffuse (with diffusion constant $D$), die (with rate\n$d$) or split into two particles (with rate $b$). At the critical point $b=d$\nwhich we focus on, we show that, at large time $t$, the particles are\ncollectively bunched together. We find indeed that there are two length scales\nin the system: (i) the diffusive length scale $\\sim \\sqrt{Dt}$ which controls\nthe collective fluctuations of the whole bunch and (ii) the length scale of the\ngap between the bunched particles $\\sim \\sqrt{D/b}$. We compute the probability\ndistribution function $P(g_k,t|n)$ of the $k$th gap $g_k = x_k - x_{k+1}$\nbetween the $k$th and $(k+1)$th particles given that the system contains\nexactly $n>k$ particles at time $t$. We show that at large $t$, it converges to\na stationary distribution $P(g_k,t\\to \\infty|n) = p(g_k|n)$ with an algebraic\ntail $p(g_k|n) \\sim 8(D/b) g_k^{-3}$, for $g_k \\gg 1$, independent of $k$ and\n$n$. We verify our predictions with Monte Carlo simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effective Floquet-Gibbs states for dissipative quantum systems: A periodically driven quantum system, when coupled to a heat bath, relaxes to\na non-equilibrium asymptotic state. In the general situation, the retrieval of\nthis asymptotic state presents a rather non-trivial task. It was recently shown\nthat in the limit of an infinitesimal coupling, using so-called rotating wave\napproximation (RWA), and under strict conditions imposed on the time-dependent\nsystem Hamiltonian, the asymptotic state can attain the Gibbs form. A\nFloquet-Gibbs state is characterized by a density matrix which is diagonal in\nthe Floquet basis of the system Hamiltonian with the diagonal elements obeying\na Gibbs distribution, being parametrized by the corresponding Floquet\nquasi-energies. Addressing the non-adiabatic driving regime, upon using the\nMagnus expansion, we employ the concept of a corresponding effective Floquet\nHamiltonian. In doing so we go beyond the conventionally used RWA and\ndemonstrate that the idea of Floquet-Gibbs states can be extended to the\nrealistic case of a weak, although finite system-bath coupling, herein termed\neffective Floquet-Gibbs states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Prediction, Retrodiction, and The Amount of Information Stored in the\n  Present: We introduce an ambidextrous view of stochastic dynamical systems, comparing\ntheir forward-time and reverse-time representations and then integrating them\ninto a single time-symmetric representation. The perspective is useful\ntheoretically, computationally, and conceptually. Mathematically, we prove that\nthe excess entropy--a familiar measure of organization in complex systems--is\nthe mutual information not only between the past and future, but also between\nthe predictive and retrodictive causal states. Practically, we exploit the\nconnection between prediction and retrodiction to directly calculate the excess\nentropy. Conceptually, these lead one to discover new system invariants for\nstochastic dynamical systems: crypticity (information accessibility) and causal\nirreversibility. Ultimately, we introduce a time-symmetric representation that\nunifies all these quantities, compressing the two directional representations\ninto one. The resulting compression offers a new conception of the amount of\ninformation stored in the present.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimal Work Extraction and the Minimum Description Length Principle: We discuss work extraction from classical information engines (e.g.,\nSzil\\'ard) with $N$-particles, $q$ partitions, and initial arbitrary\nnon-equilibrium states. In particular, we focus on their {\\em optimal}\nbehaviour, which includes the measurement of a set of quantities $\\Phi$ with a\nfeedback protocol that extracts the maximal average amount of work. We show\nthat the optimal non-equilibrium state to which the engine should be driven\nbefore the measurement is given by the normalised maximum-likelihood\nprobability distribution of a statistical model that admits $\\Phi$ as\nsufficient statistics. Furthermore, we show that the minimax universal code\nredundancy $\\mathcal{R}^*$ associated to this model, provides an upper bound to\nthe work that the demon can extract on average from the cycle, in units of\n$k_{\\rm B}T$. We also find that, in the limit of $N$ large, the maximum average\nextracted work cannot exceed $H[\\Phi]/2$, i.e. one half times the Shannon\nentropy of the measurement. Our results establish a connection between optimal\nwork extraction in stochastic thermodynamics and optimal universal data\ncompression, providing design principles for optimal information engines. In\nparticular, they suggest that: (i) optimal coding is thermodynamically\nefficient, and (ii) it is essential to drive the system into a critical state\nin order to achieve optimal performance.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-KPZ modes in two-species driven diffusive systems: Using mode coupling theory and dynamical Monte-Carlo simulations we\ninvestigate the scaling behaviour of the dynamical structure function of a\ntwo-species asymmetric simple exclusion process, consisting of two coupled\nsingle-lane asymmetric simple exclusion processes. We demonstrate the\nappearence of a superdiffusive mode with dynamical exponent $z=5/3$ in the\ndensity fluctuations, along with a KPZ mode with $z=3/2$ and argue that this\nphenomenon is generic for short-ranged driven diffusive systems with more than\none conserved density. When the dynamics is symmetric under the interchange of\nthe two lanes a diffusive mode with $z=2$ appears instead of the non-KPZ\nsuperdiffusive mode.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A fluctuation relation for weakly ergodic aging systems: A fluctuation relation for aging systems is introduced, and verified by\nextensive numerical simulations. It is based on the hypothesis of partial\nequilibration over phase space regions in a scenario of entropy-driven\nrelaxation. The relation provides a simple alternative method, amenable of\nexperimental implementation, to measure replica symmetry breaking parameters in\naging systems. The connection with the effective temperatures obtained from the\nfluctuation-dissipation theorem is discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stationary behaviour of observables after a quantum quench in the\n  spin-1/2 Heisenberg XXZ chain: We consider a quantum quench in the spin-1/2 Heisenberg XXZ chain. At late\ntimes after the quench it is believed that the expectation values of local\noperators approach time-independent values, that are described by a generalized\nGibbs ensemble. Employing a quantum transfer matrix approach we show how to\ndetermine short-range correlation functions in such generalized Gibbs ensembles\nfor a class of initial states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Magnetic Properties of the Metamagnet Ising Model in a three-dimensional\n  Lattice in a Random and Uniform Field: By employing the Monte Carlo technique we study the behavior of Metamagnet\nIsing Model in a random field. The phase diagram is obtained by using the\nalgorithm of Glaubr in a cubic lattice of linear size $L$ with values ranging\nfrom 16 to 42 and with periodic boundary conditions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Prethermalization in periodically-driven nonreciprocal many-body spin\n  systems: We analyze a new class of time-periodic nonreciprocal dynamics in interacting\nchaotic classical spin systems, whose equations of motion are conservative\n(phase-space-volume-preserving) yet possess no symplectic structure. As a\nresult, the dynamics of the system cannot be derived from any time-dependent\nHamiltonian. In the high-frequency limit, we find that the magnetization\ndynamics features a long-lived metastable plateau, whose duration is controlled\nby the fourth power of the drive frequency. However, due to the lack of an\neffective Hamiltonian, the prethermal state the system evolves into cannot be\nunderstood within the framework of the canonical ensemble. We propose a\nHamiltonian extension of the system using auxiliary degrees of freedom, in\nwhich the original spins constitute an open yet nondissipative subsystem. This\nallows us to perturbatively derive effective equations of motion that\nmanifestly display symplecticity breaking at leading order in the inverse\nfrequency. We thus extend the notion of prethermal dynamics, observed in the\nhigh-frequency limit of periodically-driven systems, to nonreciprocal systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Giant leaps and long excursions: fluctuation mechanisms in systems with\n  long-range memory: We analyse large deviations of time-averaged quantities in stochastic\nprocesses with long-range memory, where the dynamics at time t depends itself\non the value q_t of the time-averaged quantity. First we consider the elephant\nrandom walk and a Gaussian variant of this model, identifying two mechanisms\nfor unusual fluctuation behaviour, which differ from the Markovian case. In\nparticular, the memory can lead to large deviation principles with reduced\nspeeds, and to non-analytic rate functions. We then explain how the mechanisms\noperating in these two models are generic for memory-dependent dynamics and\nshow other examples including a non-Markovian symmetric exclusion process.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Minimal Model of Stochastic Athermal Systems: Origin of Non-Gaussian\n  Noise: For a wide class of stochastic athermal systems, we derive Langevin-like\nequations driven by non-Gaussian noise, starting from master equations and\ndeveloping a new asymptotic expansion. We found an explicit condition whereby\nthe non-Gaussian properties of the athermal noise become dominant for tracer\nparticles associated with both thermal and athermal environments. Furthermore,\nwe derive an inverse formula to infer microscopic properties of the athermal\nbath from the statistics of the tracer particle. We apply our formulation to a\ngranular motor under viscous friction, and analytically obtain the angular\nvelocity distribution function. Our theory demonstrates that the non-Gaussian\nLangevin equation is the minimal model of athermal systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Magnetization Transfer by a Quantum Ring Device: We show that a tight-binding model device consisting of a laterally connected\nring at half filling in a tangent time-dependent magnetic field can in\nprinciple be designed to pump a purely spin current. The process exploits the\nspin-orbit interaction in the ring. This behavior is understood analytically\nand found to be robust with respect to temperature and small deviations from\nhalf filling.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Noise influence on solid-liquid transition of ultrathin lubricant film: The melting of ultrathin lubricant film by friction between atomically flat\nsurfaces is studied. The additive noises of the elastic shear stress and\nstrain, and the temperature are introduced for building a phase diagram with\nthe domains of sliding, stick-slip, and dry friction. It is shown that increase\nof the strain noise intensity causes the lubricant film melting even at low\ntemperatures of the friction surfaces.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Strong-coupling critical behavior in three-dimensional lattice Abelian\n  gauge models with charged $N$-component scalar fields and $SO(N)$ symmetry: We consider a three-dimensional lattice Abelian Higgs gauge model for a\ncharged $N$-component scalar field ${\\phi}$, which is invariant under $SO(N)$\nglobal transformations for generic values of the parameters. We focus on the\nstrong-coupling regime, in which the kinetic Hamiltonian term for the gauge\nfield is a small perturbation, which is irrelevant for the critical behavior.\nThe Hamiltonian depends on a parameter $v$ which determines the global symmetry\nof the model and the symmetry of the low-temperature phases. We present\nrenormalization-group predictions, based on a Landau-Ginzburg-Wilson effective\ndescription that relies on the identification of the appropriate order\nparameter and on the symmetry-breaking patterns that occur at the\nstrong-coupling phase transitions. For $v=0$, the global symmetry group of the\nmodel is $SU(N)$; the corresponding model may undergo continuous transitions\nonly for $N=2$. For $v\\not=0$, i.e., in the $SO(N)$ symmetric case, continuous\ntransitions (in the Heisenberg universality class) are possible also for $N=3$\nand 4. We perform Monte Carlo simulations for $N=2,3,4,6$, to verify the\nrenormalization-group predictions. Finite-size scaling analyses of the\nnumerical data are in full agreement.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic Geometry, Phase Transitions, and the Widom Line: We construct a novel approach, based on thermodynamic geometry, to\ncharacterize first-order phase transitions from a microscopic perspective,\nthrough the scalar curvature in the equilibrium thermodynamic state space. Our\nmethod resolves key theoretical issues in macroscopic thermodynamic constructs,\nand furthermore characterizes the Widom line through the maxima of the\ncorrelation length, which is captured by the thermodynamic scalar curvature. As\nan illustration of our method, we use it in conjunction with the mean field Van\nder Waals equation of state to predict the coexistence curve and the Widom\nline. Where closely applicable, it provides excellent agreement with\nexperimental data. The universality of our method is indicated by direct\ncalculations from the NIST database.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Local pressure of confined fluids inside nanoslit pores -- A density\n  functional theory prediction: In this work, the local pressure of fluids confined inside nanoslit pores is\npredicted within the framework of the density functional theory. The\nEuler-Lagrange equation in the density functional theory of statistical\nmechanics is used to obtain the force balance equation which leads to a general\nequation to predict the local normal component of the pressure tensor. Our\napproach yields a general equation for predicting the normal pressure of\nconfined fluids and it satisfies the exact bulk thermodynamics equation when\nthe pore width approaches infinity. As two basic examples, we report the\nsolution of the general equation for hard-sphere (HS) and Lennard-Jones (LJ)\nfluids confined between two parallel-structureless hard walls. To do so, we use\nthe modified fundamental measure theory (mFMT) to obtain the normal pressure\nfor hard-sphere confined fluid and mFMT incorporated with the Rosenfeld\nperturbative DFT for the LJ fluid. Effects of different variables including\npore width, bulk density and temperature on the behavior of normal pressure are\nstudied and reported. Our predicted results show that in both HS and LJ cases\nthe confined fluids normal pressure has an oscillatory behavior and the number\nof oscillations increases with bulk density and temperature. The oscillations\nalso become broad and smooth with pore width at a constant temperature and bulk\ndensity. In comparison with the HS confined fluid, the values of normal\npressure for the LJ confined fluid as well as its oscillations at all distances\nfrom the walls are less profound.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonextensive Entropy, Prior PDFs and Spontaneous Symmetry Breaking: We show that using nonextensive entropy can lead to spontaneous symmetry\nbreaking when a parameter changes its value from that applicable for a\nsymmetric domain, as in field theory. We give the physical reasons and also\nshow that even for symmetric Dirichlet priors, such a defnition of the entropy\nand the parameter value can lead to asymmetry when entropy is maximized.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cardy's Formula for some Dependent Percolation Models: We prove Cardy's formula for rectangular crossing probabilities in dependent\nsite percolation models that arise from a deterministic cellular automaton with\na random initial state. The cellular automaton corresponds to the\nzero-temperature case of Domany's stochastic Ising ferromagnet on the hexagonal\nlattice H (with alternating updates of two sublattices); it may also be\nrealized on the triangular lattice T with flips when a site disagrees with six,\nfive and sometimes four of its six neighbors.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The delayed uncoupled continuous-time random walks do not provide a\n  model for the telegraph equation: It has been alleged in several papers that the so called delayed\ncontinuous-time random walks (DCTRWs) provide a model for the one-dimensional\ntelegraph equation at microscopic level. This conclusion, being widespread now,\nis strange, since the telegraph equation describes phenomena with finite\npropagation speed, while the velocity of the motion of particles in the DCTRWs\nis infinite. In this paper we investigate how accurate are the approximations\nto the DCTRWs provided by the telegraph equation. We show that the diffusion\nequation, being the correct limit of the DCTRWs, gives better approximations in\n$L_2$ norm to the DCTRWs than the telegraph equation. We conclude therefore\nthat, first, the DCTRWs do not provide any correct microscopic interpretation\nof the one-dimensional telegraph equation, and second, the kinetic (exact)\nmodel of the telegraph equation is different from the model based on the\nDCTRWs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding the phenomenon of viscous slowing down of glass-forming\n  liquids from the static pair correlation function: A theory which uses data of the static pair-correlation function is developed\nto calculate quantities associated with the viscous slowing down of supercooled\nliquids. We calculate value of the energy fluctuations that determine the\nnumber of stable bonds a particle forms with neighbors from data of the\nstructural relaxation time. The number of bonds and the activation energy for\nrelaxation are shown to increase sharply in a narrow temperature range close to\nthe glass temperature. The configurational entropy calculated from values of\nthe configurational fluctuations is found in good agreement with the value\ndetermined from simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite-temperature quantum discordant criticality: In quantum statistical mechanics, finite-temperature phase transitions are\ntypically governed by classical field theories. In this context, the role of\nquantum correlations is unclear: recent contributions have shown how\nentanglement is typically very short-ranged, and thus uninformative about\nlong-ranged critical correlations. In this work, we show the existence of\nfinite-temperature phase transitions where a broader form of quantum\ncorrelation than entanglement, the entropic quantum discord, can display\ngenuine signatures of critical behavior. We consider integrable bosonic field\ntheories in both two- and three-dimensional lattices, and show how the two-mode\nGaussian discord decays algebraically with the distance even in cases where the\nentanglement negativity vanishes beyond nearest-neighbor separations.\nSystematically approaching the zero-temperature limit allows us to connect\ndiscord to entanglement, drawing a generic picture of quantum correlations and\ncritical behavior that naturally describes the transition between entangled and\ndiscordant quantum matter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Computing phase diagrams for a quasicrystal-forming patchy-particle\n  system: We introduce an approach to computing the free energy of quasicrystals, which\nwe use to calculate phase diagrams for systems of two-dimensional patchy\nparticles with five regularly arranged patches that have previously been shown\nto form dodecagonal quasicrystals. We find that the quasicrystal is a\nthermodynamically stable phase for a wide range of conditions and remains a\nrobust feature of the system as the potential's parameters are varied. We also\ndemonstrate that the quasicrystal is entropically stabilised over its\ncrystalline approximants.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Heaps' law, statistics of shared components and temporal patterns from a\n  sample-space-reducing process: Zipf's law is a hallmark of several complex systems with a modular structure,\nsuch as books composed by words or genomes composed by genes. In these\ncomponent systems, Zipf's law describes the empirical power law distribution of\ncomponent frequencies. Stochastic processes based on a sample-space-reducing\n(SSR) mechanism, in which the number of accessible states reduces as the system\nevolves, have been recently proposed as a simple explanation for the ubiquitous\nemergence of this law. However, many complex component systems are\ncharacterized by other statistical patterns beyond Zipf's law, such as a\nsublinear growth of the component vocabulary with the system size, known as\nHeap's law, and a specific statistics of shared components. This work shows,\nwith analytical calculations and simulations, that these statistical properties\ncan emerge jointly from a SSR mechanism, thus making it an appropriate\nparameter-poor representation for component systems. Several alternative (and\nequally simple) models, for example based on the preferential attachment\nmechanism, can also reproduce Heaps' and Zipf's laws, suggesting that\nadditional statistical properties should be taken into account to select the\nmost-likely generative process for a specific system. Along this line, we will\nshow that the temporal component distribution predicted by the SSR model is\nmarkedly different from the one emerging from the popular rich-gets-richer\nmechanism. A comparison with empirical data from natural language indicates\nthat the SSR process can be chosen as a better candidate model for text\ngeneration based on this statistical property. Finally, a limitation of the SSR\nmodel in reproducing the empirical \"burstiness\" of word appearances in texts\nwill be pointed out, thus indicating a possible direction for extensions of the\nbasic SSR process.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Differences between regular and random order of updates in damage\n  spreading simulations: We investigate the spreading of damage in the three-dimensional Ising model\nby means of large-scale Monte-Carlo simulations. Within the Glauber dynamics we\nuse different rules for the order in which the sites are updated. We find that\nthe stationary damage values and the spreading temperature are different for\ndifferent update order. In particular, random update order leads to larger\ndamage and a lower spreading temperature than regular order. Consequently,\ndamage spreading in the Ising model is non-universal not only with respect to\ndifferent update algorithms (e.g. Glauber vs. heat-bath dynamics) as already\nknown, but even with respect to the order of sites.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Power-law behaviors from the two-variable Langevin equation: Ito's and\n  Stratonovich's Fokker-Planck equations: We study power-law behaviors produced from the stochastically dynamical\nsystem governed by the well-known two-variable Langevin equations. The\nstationary solutions of the corresponding Ito's, Stratonovich's and the\nZwanzig's (the backward Ito's) Fokker-Planck equations are solved under a new\nfluctuation-dissipation relation, which are presented in a unified form of the\npower-law distributions with a power index containing two parameter kappa and\nsigma, where kappa measures a distance away from the thermal equilibrium and\nsigma distinguishes the above three forms of the Fokker-Planck equations. The\nnumerical calculations show that the Ito's, the Stratonovich's and the\nZwanzig's form of the power-law distributions are all exactly the stationary\nsolutions based on the two-variable Langevin equations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical Properties of the Models of Small Magnetic Particles of the\n  Antiferromagnet MnF2: The static critical behavior of the models of small magnetic particles of the\nreal two sublattice antiferromagnet MnF2 is investigated by the Monte Carlo\nmethod taking into account the interaction of the second nearest neighbors.\nSystems with open boundaries are considered to estimate the influence of the\nsizes of particles on the pattern of their critical behavior. The behavior of\nthermodynamic functions in the phase transition region is investigated. The\ndata on the maxima of the temperature dependences of heat capacity and magnetic\nsusceptibility are shown to be insufficient to unambiguously determine the\neffective temperture of the phase transition in the models of small magnetic\nparticles. This requires an additional investigation of the spatial orientation\nof the sublattice (sublattices) magnetization vector for the models under\nstudy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reaction-diffusion processes and metapopulation models in heterogeneous\n  networks: Dynamical reaction-diffusion processes and meta-population models are\nstandard modeling approaches for a wide variety of phenomena in which local\nquantities - such as density, potential and particles - diffuse and interact\naccording to the physical laws. Here, we study the behavior of two basic\nreaction-diffusion processes ($B \\to A$ and $A+B \\to 2B$) defined on networks\nwith heterogeneous topology and no limit on the nodes' occupation number. We\ninvestigate the effect of network topology on the basic properties of the\nsystem's phase diagram and find that the network heterogeneity sustains the\nreaction activity even in the limit of a vanishing density of particles,\neventually suppressing the critical point in density driven phase transitions,\nwhereas phase transition and critical points, independent of the particle\ndensity, are not altered by topological fluctuations. This work lays out a\ntheoretical and computational microscopic framework for the study of a wide\nrange of realistic meta-populations models and agent-based models that include\nthe complex features of real world networks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Many-body Localization with Dipoles: Systems of strongly interacting dipoles offer an attractive platform to study\nmany-body localized phases, owing to their long coherence times and strong\ninteractions. We explore conditions under which such localized phases persist\nin the presence of power-law interactions and supplement our analytic treatment\nwith numerical evidence of localized states in one dimension. We propose and\nanalyze several experimental systems that can be used to observe and probe such\nstates, including ultracold polar molecules and solid-state magnetic spin\nimpurities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Financial Modeling and Option Theory with the Truncated Levy Process: In recent studies the truncated Levy process (TLP) has been shown to be very\npromising for the modeling of financial dynamics. In contrast to the Levy\nprocess, the TLP has finite moments and can account for both the previously\nobserved excess kurtosis at short timescales, along with the slow convergence\nto Gaussian at longer timescales. I further test the truncated Levy paradigm\nusing high frequency data from the Australian All Ordinaries share market\nindex. I then consider, for the early Levy dominated regime, the issue of\noption hedging for two different hedging strategies that are in some sense\noptimal. These are compared with the usual delta hedging approach and found to\ndiffer significantly. I also derive the natural generalization of the\nBlack-Scholes option pricing formula when the underlying security is modeled by\na geometric TLP. This generalization would not be possible without the\ntruncation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of feedback controlled systems: We compute the entropy reduction in feedback controlled systems due to the\nrepeated operation of the controller. This was the lacking ingredient to\nestablish the thermodynamics of these systems, and in particular of Maxwell's\ndemons. We illustrate some of the consequences of our general results by\nderiving the maximum work that can be extracted from isothermal feedback\ncontrolled systems. As a case example, we finally study a simple system that\nperforms an isothermal information-fueled particle pumping.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics and correlations in Motzkin and Fredkin spin chains: The Motzkin and Fredkin quantum spin chains are described by frustration-free\nHamiltonians recently introduced and studied because of their anomalous\nbehaviors in the correlation functions and in the entanglement properties. In\nthis paper we analyze their quantum dynamical properties, focusing in\nparticular on the time evolution of the excitations driven by a quantum quench,\nlooking at the correlations functions of spin operators defined along different\ndirections, and discussing the results in relation with the cluster\ndecomposition property.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interevent time distribution, burst, and hybrid percolation transition: Critical phenomena of a second-order percolation transition are known to be\nindependent of cluster merging or pruning process. However, those of a hybrid\npercolation transition (HPT), mixed properties of both first-order and\nsecond-order transitions, depend on the processes. The HPT induced by cluster\nmerging is more intrigue and little understood than the other. Here, we\nconstruct a theoretical framework using the so-called restricted percolation\nmodel. In this model, clusters are ranked by size and partitioned into small-\nand large-cluster sets. As the cluster rankings are updated by cluster\ncoalescence, clusters may move back and forth across the set boundary. The\ninter-event time (IET) between two consecutive crossing times have two\ndistributions with power-law decays, which in turn characterize the criticality\nof the HPT. A burst of such crossing events occurs and signals the upcoming\ntransition. We discuss a related phenomenon to this critical dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A new effective-field technique for the ferromagnetic spin-1 Blume-Capel\n  model in a transverse crystal field: A new approximating technique is developed so as to study the quantum\nferromagnetic spin-1 Blume-Capel model in the presence of a transverse crystal\nfield in the square lattice. Our proposal consists of approaching the spin\nsystem by considering islands of finite clusters whose frontiers are surrounded\nby non-interacting spins that are treated by the effective-field theory. The\nresulting phase diagram is qualitatively correct, in contrast to most\neffective-field treatments, in which the first-order line exhibits spurious\nbehavior by not being perpendicular to the anisotropy axis at low temperatures.\nThe effect of the transverse anisotropy is also verified by the presence of\nquantum phase transitions. The possibility of using larger sizes constitutes an\nadvantage to other approaches where the implementation of larger sizes is\ncostly computationally.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "From Linear to Nonlinear Responses of Thermal Pure Quantum States: We propose a self-validating scheme to calculate the unbiased responses of\nquantum many-body systems to external fields of arbibraty strength at any\ntemperature. By switching on a specified field to a thermal pure quantum state\nof an isolated system, and tracking its time evolution, one can observe an\nintrinsic thermalization process driven solely by many-body effects. The\ntransient behavior before thermalization contains rich information on excited\nstates, giving the linear and nonlinear response functions at all frequencies.\nWe uncover the necessary conditions to clarify the applicability of this\nformalism, supported by a proper definition of the nonlinear response function.\nThe accuracy of the protocol is guaranteed by a rigorous upper bound of error\nexponentially decreasing with system size, and is well implemented in the\nsimple ferromagnetic Heisenberg chain, whose response at high fields exhibits a\nnonlinear band deformation. We further extract the characteristic features of\nexcitation of the spin-1/2 kagome antiferromagnet; the wavenumber-insensitive\nlinear responses from the possible spin liquid ground state, and the\nsignificantly broad nonlinear peaks which should be generated from numerous\ncollisions of quasi-particles, that are beyond the perturbative description.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Evaluating the RiskMetrics Methodology in Measuring Volatility and\n  Value-at-Risk in Financial Markets: We analyze the performance of RiskMetrics, a widely used methodology for\nmeasuring market risk. Based on the assumption of normally distributed returns,\nthe RiskMetrics model completely ignores the presence of fat tails in the\ndistribution function, which is an important feature of financial data.\nNevertheless, it was commonly found that RiskMetrics performs satisfactorily\nwell, and therefore the technique has become widely used in the financial\nindustry. We find, however, that the success of RiskMetrics is the artifact of\nthe choice of the risk measure. First, the outstanding performance of\nvolatility estimates is basically due to the choice of a very short (one-period\nahead) forecasting horizon. Second, the satisfactory performance in obtaining\nValue-at-Risk by simply multiplying volatility with a constant factor is mainly\ndue to the choice of the particular significance level.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "q-Gaussians in the porous-medium equation: stability and time evolution: The stability of $q$-Gaussian distributions as particular solutions of the\nlinear diffusion equation and its generalized nonlinear form,\n$\\pderiv{P(x,t)}{t} = D \\pderiv{^2 [P(x,t)]^{2-q}}{x^2}$, the\n\\emph{porous-medium equation}, is investigated through both numerical and\nanalytical approaches. It is shown that an \\emph{initial} $q$-Gaussian,\ncharacterized by an index $q_i$, approaches the \\emph{final}, asymptotic\nsolution, characterized by an index $q$, in such a way that the relaxation rule\nfor the kurtosis evolves in time according to a $q$-exponential, with a\n\\emph{relaxation} index $q_{\\rm rel} \\equiv q_{\\rm rel}(q)$. In some cases,\nparticularly when one attempts to transform an infinite-variance distribution\n($q_i \\ge 5/3$) into a finite-variance one ($q<5/3$), the relaxation towards\nthe asymptotic solution may occur very slowly in time. This fact might shed\nsome light on the slow relaxation, for some long-range-interacting many-body\nHamiltonian systems, from long-standing quasi-stationary states to the ultimate\nthermal equilibrium state.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonlinear transport in inelastic Maxwell mixtures under simple shear\n  flow: The Boltzmann equation for inelastic Maxwell models is used to analyze\nnonlinear transport in a granular binary mixture in the steady simple shear\nflow. Two different transport processes are studied. First, the rheological\nproperties (shear and normal stresses) are obtained by solving exactly the\nvelocity moment equations. Second, the diffusion tensor of impurities immersed\nin a sheared inelastic Maxwell gas is explicitly determined from a perturbation\nsolution through first order in the concentration gradient. The corresponding\nreference state of this expansion corresponds to the solution derived in the\n(pure) shear flow problem. All these transport coefficients are given in terms\nof the restitution coefficients and the parameters of the mixture (ratios of\nmasses, concentration, and sizes). The results are compared with those obtained\nanalytically for inelastic hard spheres in the first Sonine approximation and\nby means of Monte Carlo simulations. The comparison between the results\nobtained for both interaction models shows a good agreement over a wide range\nvalues of the parameter space.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bose-Einstein Condensation, the Lambda Transition, and Superfluidity for\n  Interacting Bosons: Bose-Einstein condensation and the $\\lambda$-transition are described in\nmolecular detail for bosons interacting with a pair potential. New phenomena\nare identified that are absent in the usual ideal gas treatment. Monte Carlo\nsimulations of Lennard-Jones helium-4 neglecting ground momentum state bosons\ngive a diverging heat capacity approaching the transition. Pure permutation\nloops give continuous growth in the occupancy of the ground momentum state.\nMixed ground and excited momentum state permutation loops give a discontinuous\ntransition to the condensed phase. The consequent latent heat for the\n$\\lambda$-transition is 3\\% of the total energy. The predicted critical\nvelocity for superfluid flow is within a factor of three of the measured values\nover three orders of magnitude in pore diameter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Refrustration and competing orders in the prototypical Dy2Ti2O7 spin ice\n  material: Spin ices, frustrated magnetic materials analogous to common water ice, are\nexemplars of high frustration in three dimensions. Recent experimental studies\nof the low-temperature properties of the paradigmatic Dy$_2$Ti$_2$O$_7$ spin\nice material, in particular whether the predicted transition to long-range\norder occurs, raise questions as per the currently accepted microscopic model\nof this system. In this work, we combine Monte Carlo simulations and mean-field\ntheory calculations to analyze data from magnetization, elastic neutron\nscattering and specific heat measurements on Dy$_2$Ti$_2$O$_7$. We also\nreconsider the possible importance of the nuclear specific heat, $C_{\\rm nuc}$,\nin Dy$_2$Ti$_2$O$_7$. We find that $C_{\\rm nuc}$ is not entirely negligible\nbelow a temperature $\\sim 0.5$ K and must be taken into account in a\nquantitative analysis of the calorimetric data of this compound below that\ntemperature. We find that small effective exchange interactions compete with\nthe magnetostatic dipolar interaction responsible for the main spin ice\nphenomenology. This causes an unexpected \"refrustration\" of the long-range\norder that would be expected from the incompletely self-screened dipolar\ninteraction and which positions the material at the boundary between two\ncompeting classical long-range ordered ground states. This allows for the\nmanifestation of new physical low-temperature phenomena in Dy$_2$Ti$_2$O$_7$,\nas exposed by recent specific heat measurements. We show that among the four\nmost likely causes for the observed upturn of the specific heat at low\ntemperature -- an exchange-induced transition to long-range order, quantum\nnon-Ising (transverse) terms in the effective spin Hamiltonian, the nuclear\nhyperfine contribution and random disorder -- only the last appears to be\nreasonably able to explain the calorimetric data.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling functions and amplitude ratios for the Potts model on an\n  uncorrelated scale-free network: We study the critical behaviour of the $q$-state Potts model on an\nuncorrelated scale-free network having a power-law node degree distribution\nwith a decay exponent $\\lambda$. Previous data show that the phase diagram of\nthe model in the $q,\\lambda$ plane in the second order phase transition regime\ncontains three regions, each being characterized by a different set of critical\nexponents. In this paper we complete these results by finding analytic\nexpressions for the scaling functions and critical amplitude ratios in the\nabove mentioned regions. Similar to the previously found critical exponents,\nthe scaling functions and amplitude ratios appear to be $\\lambda$-dependent. In\nthis way, we give a comprehensive description of the critical behaviour in a\nnew universality class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Fluid Dynamic Model for the Movement of Pedestrians: A kind of fluid dynamic description for the collective movement of\npedestrians is developed on the basis of a Boltzmann-like gaskinetic model. The\ndifferences between these pedestrian specific equations and those for ordinary\nfluids are worked out, for example concerning the mechanism of relaxation to\nequilibrium, the role of ``pressure'', the special influence of internal\nfriction and the origin of ``temperature''. Some interesting results are\nderived that can be compared to real situations, for example the development of\nwalking lanes and of pedestrian jams, the propagation of waves, and the\nbehavior on a dance floor. Possible applications of the model to town- and\ntraffic-planning are outlined.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Synchronization and directed percolation in coupled map lattices: We study a synchronization mechanism, based on one-way coupling of\nall-or-nothing type, applied to coupled map lattices with several different\nlocal rules. By analyzing the metric and the topological distance between the\ntwo systems, we found two different regimes: a strong chaos phase in which the\ntransition has a directed percolation character and a weak chaos phase in which\nthe synchronization transition occurs abruptly. We are able to derive some\nanalytical approximations for the location of the transition point and the\ncritical properties of the system.\n  We propose to use the characteristics of this transition as indicators of the\nspatial propagation of chaoticity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of the randomly distributed magnetic field on the phase diagrams\n  of the transverse Ising thin film: The effect of the zero centered Gaussian random magnetic field distribution\non the phase diagrams and ground state magnetizations of the transverse Ising\nthin film has been investigated. As a formulation, the differential operator\ntechnique and decoupling approximation within the effective field theory has\nbeen used. The variation of the phase diagrams with the Gaussian distribution\nwidth (\\sigma) has been obtained and particular attention has been paid on the\nevolution of the special point coordinate with distribution parameter. In\naddition, the ground state longitudinal and transverse magnetization behaviors\nhave been investigated in detail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase separation in a wedge. Exact results: The exact theory of phase separation in a two-dimensional wedge is derived\nfrom the properties of the order parameter and boundary condition changing\noperators in field theory. For a shallow wedge we determine the passage\nprobability for an interface with endpoints on the boundary. For generic\nopening angles we exhibit the fundamental origin of the filling transition\ncondition and of the property known as wedge covariance.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase separation in fluids exposed to spatially periodic external fields: We consider the liquid-vapor type phase transition for fluids confined within\nspatially periodic external fields. For a fluid in d=3 dimensions, the periodic\nfield induces an additional phase, characterized by large density modulations\nalong the field direction. At the triple point, all three phases (modulated,\nvapor, and liquid) coexist. At temperatures slightly above the triple point and\nfor low (high) values of the chemical potential, two-phase coexistence between\nthe modulated phase and the vapor (liquid) is observed. We study this\nphenomenon using computer simulations and mean-field theory for the Ising\nmodel. The theory shows that, in order for the modulated phase to arise, the\nfield wavelength must exceed a threshold value. We also find an extremely low\ntension of the interface between the modulated phase and the vapor/liquid\nphases. The tension is of the order 10^{-4} kB T per squared lattice spacing,\nwhere kB is the Boltzmann constant, and T the temperature. In order to detect\nsuch low tensions, a new simulation method is proposed. We also consider the\ncase of d=2 dimensions. The modulated phase then does not survive, leading to a\nradically different phase diagram.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An extended scaling analysis of the S=1/2 Ising ferromagnet on the\n  simple cubic lattice: It is often assumed that for treating numerical (or experimental) data on\ncontinuous transitions the formal analysis derived from the Renormalization\nGroup Theory can only be applied over a narrow temperature range, the \"critical\nregion\"; outside this region correction terms proliferate rendering attempts to\napply the formalism hopeless. This pessimistic conclusion follows largely from\na choice of scaling variables and scaling expressions which is traditional but\nwhich is very inefficient for data covering wide temperature ranges. An\nalternative \"extended caling\" approach can be made where the choice of scaling\nvariables and scaling expressions is rationalized in the light of well\nestablished high temperature series expansion developments. We present the\nextended scaling approach in detail, and outline the numerical technique used\nto study the 3d Ising model. After a discussion of the exact expressions for\nthe historic 1d Ising spin chain model as an illustration, an exhaustive\nanalysis of high quality numerical data on the canonical simple cubic lattice\n3d Ising model is given. It is shown that in both models, with appropriate\nscaling variables and scaling expressions (in which leading correction terms\nare taken into account where necessary), critical behavior extends from Tc up\nto infinite temperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Jamming vs. Caging in Three Dimensional Jamming Percolation: We investigate a three-dimensional kinetically-constrained model that\nexhibits two types of phase transitions at different densities. At the jamming\ndensity $ \\rho_J $ there is a mixed-order phase transition in which a finite\nfraction of the particles become frozen, but the other particles may still\ndiffuse throughout the system. At the caging density $ \\rho_C > \\rho_J $, the\nmobile particles are trapped in finite cages and no longer diffuse. The caging\ntransition occurs due to a percolation transition of the unfrozen sites, and we\nnumerically find that it is a continuous transition with the same critical\nexponents as random percolation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Landauer's erasure principle in non-equilibrium systems: In two recent papers, Maroney and Turgut separately and independently show\ngeneralisations of Landauer's erasure principle to indeterministic logical\noperations, as well as to logical states with variable energies and entropies.\nHere we show that, although Turgut's generalisation seems more powerful, in\nthat it implies but is not implied by Maroney's and that it does not rely upon\ninitial probability distributions over logical states, it does not hold for\nnon-equilibrium states, while Maroney's generalisation holds even in\nnon-equilibrium. While a generalisation of Turgut's inequality to\nnon-equilibrium seems possible, it lacks the properties that makes the\nequilibrium inequality appealing. The non-equilibrium generalisation also no\nlonger implies Maroney's inequality, which may still be derived independently.\nFurthermore, we show that Turgut's inequality can only give a necessary, but\nnot sufficient, criteria for thermodynamic reversibility. Maroney's inequality\ngives the necessary and sufficient conditions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic PDEs: domain formation in dynamic transitions: Spatiotemporal evolution in the real Ginzburg-Landau equation is studied with\nspace-time noise and a slowly increasing critical parameter. Analytical\nestimates for the characteristic size of the domains formed in a slow sweep\nthrough the critical point agree with the results of finite difference solution\nof the stochastic PDEs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Three lemmas on the dynamic cavity method: We study the dynamic cavity method for dilute kinetic Ising models with\nsynchronous update rules. For the parallel update rule we find for fully\nasymmetric models that the dynamic cavity equations reduce to a Markovian\ndynamics of the (time-dependent) marginal probabilities. For the random\nsequential update rule, also an instantiation of a synchronous update rule, we\nfind on the other hand that the dynamic cavity equations do not reduce to a\nMarkovian dynamics, unless an additional assumption of time factorization is\nintroduced. For symmetric models we show that a fixed point of ordinary Belief\npropagation is also a fixed point of the dynamic cavity equations in the time\nfactorized approximation. For clarity, the conclusions of the paper are\nformulated as three lemmas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exactly solvable model of stochastic heat engine: Optimization of power,\n  its fluctuations and efficiency: We investigate a stochastic heat engine based on an over-damped particle\ndiffusing on the positive real axis in an externally driven time-periodic\nlog-harmonic potential. The periodic driving is composed of two isothermal and\ntwo adiabatic branches. Within our specific setting we verify the recent\nuniversal results regarding efficiency at maximum power and discuss properties\nof the optimal protocol. Namely, we show that for certain fixed parameters the\noptimal protocol maximizes not only the output power but also the efficiency.\nMoreover, we calculate the variance of the output work and discuss the\npossibility to minimize fluctuations of the output power.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Transport coefficients for hard-sphere relativistic gas: Transport coefficients are of crucial importance in theoretical as well as\nexperimental studies. Despite substantial research on classical hard\nsphere/disk gases in low and high density regimes, a thorough investigation of\ntransport coefficients for massive relativistic systems is missing in the\nliterature. In this work a fully relativistic molecular dynamics simulation is\nemployed to numerically obtain the transport coefficients of a hard sphere\nrelativistic gas based on Helfand-Einstein expressions. The numerical data are\nthen used to check the accuracy of Chapmann-Enskog (CE) predictions in a wide\nrange of temperature. The results indicate that while simulation data in low\ntemperature regime agrees very well with theoretical predictions, it begins to\nshow deviations as temperature rises, except for the thermal conductivity which\nfits very well to CE theory in the whole range of temperature. Since our\nsimulations are done in low density regimes, where CE approximation is expected\nto be valid, the observed deviations can be attributed to the inaccuracy of\nlinear CE theory in extremely relativistic cases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extended loop algorithm for pyrochlore Heisenberg spin models with\n  spin-ice type degeneracy: application to spin-glass transition in\n  antiferromagnets coupled to local lattice distortions: For Ising spin models which bear the spin-ice type macroscopic\n(quasi-)degeneracy, conventional classical Monte Carlo (MC) simulation using\nsingle spin flips suffers from dynamical freezing at low temperatures ($T$). A\nsimilar difficulty is seen also in a family of Heisenberg spin models with\neasy-axis anisotropy or biquadratic interactions. In the Ising case, the\ndifficulty is avoided by introducing a non-local update based on the loop\nalgorithm. We present an extension of the loop algorithm to the Heisenberg\ncase. As an example of its application, we review our recent study on\nspin-glass (SG) transition in a bond-disordered Heisenberg antiferromagnet\ncoupled to local lattice distortions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Towards lattice-gas description of low-temperature properties above the\n  Haldane and cluster-based Haldane ground states of a mixed spin-(1,1/2)\n  Heisenberg octahedral chain: The rich ground-state phase diagram of the mixed spin-(1,1/2) Heisenberg\noctahedral chain was previously elaborated from effective mixed-spin Heisenberg\nchains, which were derived by employing a local conservation of a total spin on\nsquare plaquettes of an octahedral chain. Here we present a comprehensive\nanalysis of the thermodynamic properties of this model. In the highly\nfrustrated parameter region the lowest-energy eigenstates of the mixed-spin\nHeisenberg octahedral chain belong to flat bands, which allow a precise\ndescription of low-temperature magnetic properties within the localized-magnon\napproach exploiting a classical lattice-gas model of hard-core monomers. The\npresent article provides a more comprehensive version of the localized-magnon\napproach, which extends the range of its validity down to a less frustrated\nparameter region involving the Haldane and cluster-based Haldane ground states.\nA comparison between results of the developed localized-magnon theory and\naccurate numerical methods such as full exact diagonalization and\nfinite-temperature Lanczos technique convincingly evidence that the\nlow-temperature magnetic properties above the Haldane and the cluster-based\nHaldane ground states can be extracted from a classical lattice-gas model of\nhard-core monomers and dimers, which is additionally supplemented by a\nhard-core particle spanned over the whole lattice representing the gapped\nHaldane phase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Precision-dissipation trade-off for driven stochastic systems: In this paper, I derive a closed expression for how precisely a small-scaled\nsystem can follow a pre-defined trajectory, while keeping its dissipation below\na fixed limit. The total amount of dissipation is approximately inversely\nproportional to the expected deviation from the pre-defined trajectory. The\noptimal driving protocol is derived and it is shown that associated\ntime-dependent probability distribution conserves its shape throughout the\nprotocol. Potential applications are discussed in the context of bit erasure\nand electronic circuits.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the CFT describing the spin clusters in 2d Potts model: We have considered clusters of like spin in the Q-Potts model, the spin Potts\nclusters. Using Monte Carlo simulations, we studied these clusters on a square\nlattice with periodic boundary conditions for values of Q in [1,4]. We continue\nthe work initiated with Delfino and Viti (2013) by measuring the universal\nfinite size corrections of the two-point connectivity. The numerical data are\nperfectly compatible with the CFT prediction, thus supporting the existence of\na consistent CFT, still unknown, describing the connectivity Potts spin\nclusters. We provided in particular new insights on the energy field of such\ntheory. For Q=2, we found a good agreement with the prediction that the Ising\nspin clusters behave as the Fortuin-Kasteleyn ones at the tri-critical point of\nthe dilute 1-Potts model. We show that the structure constants are likely to be\ngiven by the imaginary Liouville structure constants, consistently with the\nresults of Delfino et al. (2013) and of Ang and Sun (2021). For Q different\nfrom 2 instead, the structure constants we measure do not correspond to any\nknown bootstrap solutions. The validity of our analysis is backed up by the\nmeasures of the spin Potts clusters wrapping probability for Q=3. We evaluate\nthe main critical exponents and the correction to the scaling. A new exact and\ncompact expression for the torus one-point of the Q-Potts energy field is also\ngiven.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fidelity susceptibility of the quantum Ising model in the transverse\n  field: The exact solution: We derive an exact closed-form expression for fidelity susceptibility of the\nquantum Ising model in the transverse field. We also establish an exact\none-to-one correspondence between fidelity susceptibility in the ferromagnetic\nand paramagnetic phases of this model. Elegant summation formulas are obtained\nas a by-product of these studies.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Breaking of scale invariance in the time dependence of correlation\n  functions in isotropic and homogeneous turbulence: In this paper, we present theoretical results on the statistical properties\nof stationary, homogeneous and isotropic turbulence in incompressible flows in\nthree dimensions. Within the framework of the Non-Perturbative Renormalization\nGroup, we derive a closed renormalization flow equation for a generic $n$-point\ncorrelation (and response) function for large wave-numbers with respect to the\ninverse integral scale. The closure is obtained from a controlled expansion and\nrelies on extended symmetries of the Navier-Stokes field theory. It yields the\nexact leading behavior of the flow equation at large wave-numbers $|\\vec p_i|$,\nand for arbitrary time differences $t_i$ in the stationary state. Furthermore,\nwe obtain the form of the general solution of the corresponding fixed point\nequation, which yields the analytical form of the leading wave-number and time\ndependence of $n$-point correlation functions, for large wave-numbers and both\nfor small $t_i$ and in the limit $t_i\\to \\infty$. At small $t_i$, the leading\ncontribution at large wave-number is logarithmically equivalent to $-\\alpha\n(\\epsilon L)^{2/3}|\\sum t_i \\vec p_i|^2$, where $\\alpha$ is a nonuniversal\nconstant, $L$ the integral scale and $\\varepsilon$ the mean energy injection\nrate. For the 2-point function, the $(t p)^2$ dependence is known to originate\nfrom the sweeping effect. The derived formula embodies the generalization of\nthe effect of sweeping to $n-$point correlation functions. At large wave-number\nand large $t_i$, we show that the $t_i^2$ dependence in the leading order\ncontribution crosses over to a $|t_i|$ dependence. The expression of the\ncorrelation functions in this regime was not derived before, even for the\n2-point function. Both predictions can be tested in direct numerical\nsimulations and in experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metastable states in the FPU system: In this letter we report numerical results giving, as a function of time, the\nenergy fluctuation of a Fermi-Pasta-Ulam system in dynamical contact with a\nheat bath, the initial data of the FPU system being extracted from a Gibbs\ndistribution at the same temperature of the bath. The aim is to get information\non the specific heat of the FPU system in the spirit of the\nfluctuation--dissipation theorem. While the standard equilibrium result is\nrecovered at high temperatures, there exists a critical temperature below which\nthe energy fluctuation as a function of time tends to an asymptotic value\nsensibly lower than the one expected at equilibrium. This fact appears to\nexhibit the existence of a metastable state for generic initial conditions. An\nanalogous phenomenon of metastability was up to now observed in FPU systems\nonly for exceptional initial data having vanishing Gibbs measure, namely\nexcitations of a few low--frequency modes (as in the original FPU work).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "One-dimensional Superdiffusive Heat Propagation Induced by Optical\n  Phonon-Phonon Interactions: It is known that one-dimensional anomalous heat propagation is usually\ncharacterized by a L\\'{e}vy walk superdiffusive spreading function with two\nside peaks located on the fronts due to the finite velocity of acoustic\nphonons, and in the case when the acoustic phonons vanish, e.g., due to the\nphonon-lattice interactions such that the system's momentum is not conserved,\nthe side peaks will disappear and a normal Gaussian diffusive heat propagating\nbehavior will be observed. Here we show that there exists another type of\nsuperdiffusive, non-Gaussian heat propagation but without side peaks in a\ntypical nonacoustic, momentum-nonconserving system. It implies that thermal\ntransport in this system disobeys the Fourier law, in clear contrast with the\nexisting theoretical predictions. The underlying mechanism is related to a\nnovel effect of optical phonon-phonon interactions. These findings may open a\nnew avenue for further exploring thermal transport in low dimensions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Two-stage random sequential adsorption of discorectangles and disks on a\n  two-dimensional surface: The different variants of two-stage random sequential adsorption (RSA) models\nfor packing of disks and discorectangles on a two-dimensional (2D) surface were\ninvestigated. In the SD model, the discorectangles were first deposited and\nthen the disks were added. In the DS model, the disks were first deposited and\nthen discorectangles were added. At the first stage the particles were\ndeposited up to the selected concentration and at the final (second) stage the\nparticles were deposited up to the saturated (jamming) state. The main\nparameters of the models were the concentration of particles deposited at the\nfirst stage, aspect ratio of the discorectangles $\\varepsilon$ (length to\ndiameter of ratio $\\varepsilon=l/d$) and disk diameter $D$. All distances were\nmeasured using the value of $d$ as a unit of measurement of linear dimensions,\nthe disk diameter was varied in the interval $D \\in [1-10]$, and the aspect\nratio value was varied in the interval $\\varepsilon\\in [1-50]$. The\ndependencies of the jamming coverage of particles deposited at the second stage\nversus the parameters of the models were analyzed. The presence of first\ndeposited particles for both models regulated the maximum possible disk\ndiameter, $D_{max}$ (SD model) or the maximum aspect ratio, $\\varepsilon_{max}$\n(DS model). This behavior was explained by the deposition of particles in the\nsecond stage into triangular (SD model) or elongated (DS model) pores formed by\nparticles deposited at the first stage. The percolation connectivity of disks\n(SD model) and discorectangles (DS model) for the particles with a hard core\nand a soft shell structure was analyzed. The disconnectedness was ensured by\noverlapping of soft shells. The dependencies of connectivity versus the\nparameters of SD and DS models were also analyzed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ergodicity of non-Hamiltonian equilibrium systems: It is well known that ergodic theory can be used to formally prove a weak\nform of relaxation to equilibrium for finite, mixing, Hamiltonian systems. In\nthis Letter we extend this proof to any dynamics that preserves a mixing\nequilibrium distribution. The proof uses an approach similar to that used in\numbrella sampling, and demonstrates the need for a form of ergodic consistency\nof the initial and final distribution. This weak relaxation only applies to\naverages of physical properties. It says nothing about whether the distribution\nof states relaxes towards the equilibrium distribution or how long the\nrelaxation of physical averages takes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Self-tuning of threshold for a two-state system: A two-state system (TSS) under time-periodic perturbations (to be regarded as\ninput signals) is studied in connection with self-tuning (ST) of threshold and\nstochastic resonance (SR). By ST, we observe the improvement of signal-to-noise\nratio (SNR) in a weak noise region. Analytic approach to a tuning equation\nreveals that SNR improvement is possible also for a large noise region and this\nis demonstrated by Monte Carlo simulations of hopping processes in a TSS. ST\nand SR are discussed from a little more physical point of energy transfer\n(dissipation) rate, which behaves in a similar way as SNR. Finally ST is\nconsidered briefly for a double-well potential system (DWPS), which is closely\nrelated to the TSS.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Frustration of signed networks: How does it affect the thermodynamic\n  properties of a system?: Signed networks with positive and negative interaction are widely observed in\nthe real systems. The negative links would induce frustration, then affect\nglobal properties of the system. Based on previous studies, frustration of\nsigned networks is investigated and quantified. Frustrations of $\\pm J$\n(Edwards-Anderson) Ising model with a concentration $p$ of negative bonds,\nconstructed on different networks, such as triangular lattice, square lattice\nand random regular networks (RRN) with connectivity $k=6$ are estimated by\ntheoretical and numerical approaches. Based on the quantitative measurement of\nfrustration, its effects on phase transitions characterized by order parameter\n$q_{EA}$ are studied. The relationship of critical temperature $T_c$ with the\nquantified frustration $\\mu$ is given by mean-field theory. It shows that $T_c$\ndecreases linearly with frustration $\\mu$ . The theory is checked by numerical\nestimations, such as the Metropolis algorithm and Replica Symmetric Population\nDynamics Algorithm. The numerical estimates are consistent well with the\nmean-field prediction.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Symmetry Hierarchy and Thermalization Frustration in Graphene\n  Nanoresonators: As the essential cause of the intrinsic dissipation that limits the quality\nof graphene nanoresonators, intermodal energy transfer is also a key issue in\nthermalization dynamics. Typically systems with larger initial energy demand\nshorter time to be thermalized. However, we find quantitatively that instead of\nbecoming shorter, the equipartition time of the graphene nanoresonator can\nincrease abruptly by one order of magnitude. This thermalization frustration\nemerges due to the partition of the normal modes based on the hierarchical\nsymmetry, and a sensitive on-off switching of the energy flow channels between\nsymmetry classes controlled by Mathieu instabilities. The results uncover the\ndecisive roles of symmetry in the thermalization at the nanoscale, and may also\nlead to strategies for improving the performance of graphene nanoresonators.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dissipation, interaction and relative entropy: Many thermodynamic relations involve inequalities, with equality if a process\ndoes not involve dissipation. In this article we provide equalities in which\nthe dissipative contribution is shown to involve the relative entropy (a.k.a.\nKullback-Leibler divergence). The processes considered are general time\nevolutions both in classical and quantum mechanics, and the initial state is\nsometimes thermal, sometimes partially so. As an application, the relative\nentropy is related to transport coefficients.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Extended-range percolation in complex networks: Classical percolation theory underlies many processes of information transfer\nalong the links of a network. In these standard situations, the requirement for\ntwo nodes to be able to communicate is the presence of at least one\nuninterrupted path of nodes between them. In a variety of more recent data\ntransmission protocols, such as the communication of noisy data via\nerror-correcting repeaters, both in classical and quantum networks, the\nrequirement of an uninterrupted path is too strict: two nodes may be able to\ncommunicate even if all paths between them have interruptions/gaps consisting\nof nodes that may corrupt the message. In such a case a different approach is\nneeded. We develop the theoretical framework for extended-range percolation in\nnetworks, describing the fundamental connectivity properties relevant to such\nmodels of information transfer. We obtain exact results, for any range $R$, for\ninfinite random uncorrelated networks and we provide a message-passing\nformulation that works well in sparse real-world networks. The interplay of the\nextended range and heterogeneity leads to novel critical behavior in scale-free\nnetworks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Counterintuitive effect of gravity on the heat capacity of a metal\n  sphere: re-examination of a well-known problem: A well-known high-school problem asking the final temperature of two spheres\nthat are given the same amount of heat, one lying on a table and the other\nhanging from a thread, is re-examined. The conventional solution states that\nthe sphere on the table ends up colder, since thermal expansion raises its\ncenter of mass. It is found that this solution violates the second law of\nthermodynamics and is therefore incorrect. Two different new solutions are\nproposed. The first uses statistical mechanics, while the second is based on\npurely classical thermodynamical arguments. It is found that gravity produces a\ncounterintuitive effect on the heat capacity, and the new answer to the problem\ngoes in the opposite direction of what traditionally thought.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimal traffic organisation in ants under crowded conditions: Efficient transportation, a hot topic in nonlinear science, is essential for\nmodern societies and the survival of biological species. Biological evolution\nhas generated a rich variety of successful solutions, which have inspired\nengineers to design optimized artificial systems. Foraging ants, for example,\nform attractive trails that support the exploitation of initially unknown food\nsources in almost the minimum possible time. However, can this strategy cope\nwith bottleneck situations, when interactions cause delays that reduce the\noverall flow? Here, we present an experimental study of ants confronted with\ntwo alternative routes. We find that pheromone-based attraction generates one\ntrail at low densities, whereas at a high level of crowding, another trail is\nestablished before traffic volume is affected, which guarantees that an optimal\nrate of food return is maintained. This bifurcation phenomenon is explained by\na nonlinear modelling approach. Surprisingly, the underlying mechanism is based\non inhibitory interactions. It implies capacity reserves, a limitation of the\ndensity-induced speed reduction, and a sufficient pheromone concentration for\nreliable trail perception. The balancing mechanism between cohesive and\ndispersive forces appears to be generic in natural, urban and transportation\nsystems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Evidence of Unconventional Universality Class in a Two-Dimensional\n  Dimerized Quantum Heisenberg Model: The two-dimensional $J$-$J^\\prime$ dimerized quantum Heisenberg model is\nstudied on the square lattice by means of (stochastic series expansion) quantum\nMonte Carlo simulations as a function of the coupling ratio\n\\hbox{$\\alpha=J^\\prime/J$}. The critical point of the order-disorder quantum\nphase transition in the $J$-$J^\\prime$ model is determined as\n\\hbox{$\\alpha_\\mathrm{c}=2.5196(2)$} by finite-size scaling for up to\napproximately $10 000$ quantum spins. By comparing six dimerized models we\nshow, contrary to the current belief, that the critical exponents of the\n$J$-$J^\\prime$ model are not in agreement with the three-dimensional classical\nHeisenberg universality class. This lends support to the notion of nontrivial\ncritical excitations at the quantum critical point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum quench dynamics in the transverse-field Ising model: A numerical\n  expansion in linked rectangular clusters: We study quantum quenches in the transverse-field Ising model defined on\ndifferent lattice geometries such as chains, two- and three-leg ladders, and\ntwo-dimensional square lattices. Starting from fully polarized initial states,\nwe consider the dynamics of the transverse and the longitudinal magnetization\nfor quenches to weak, strong, and critical values of the transverse field. To\nthis end, we rely on an efficient combination of numerical linked cluster\nexpansions (NLCEs) and a forward propagation of pure states in real time. As a\nmain result, we demonstrate that NLCEs comprising solely rectangular clusters\nprovide a promising approach to study the real-time dynamics of two-dimensional\nquantum many-body systems directly in the thermodynamic limit. By comparing to\nexisting data from the literature, we unveil that NLCEs yield converged results\non time scales which are competitive to other state-of-the-art numerical\nmethods.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Velocity Distribution for Strings in Phase Ordering Kinetics: The continuity equations expressing conservation of string defect charge can\nbe used to find an explicit expression for the string velocity field in terms\nof the order parameter in the case of an O(n) symmetric time-dependent\nGinzburg-Landau model. This expression for the velocity is used to find the\nstring velocity probability distribution in the case of phase-ordering kinetics\nfor a nonconserved order parameter. For long times $t$ after the quench,\nvelocities scale as $t^{-1/2}$. There is a large velocity tail in the\ndistribution corresponding to annihilation of defects which goes as\n$V^{-(2d+2-n)}$ for both point and string defects in $d$ spatial dimensions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Preparation of a quantum state with one molecule at each site of an\n  optical lattice: Ultracold gases in optical lattices are of great interest, because these\nsystems bear a great potential for applications in quantum simulations and\nquantum information processing, in particular when using particles with a\nlong-range dipole-dipole interaction, such as polar molecules. Here we show the\npreparation of a quantum state with exactly one molecule at each site of an\noptical lattice. The molecules are produced from an atomic Mott insulator with\na density profile chosen such that the central region of the gas contains two\natoms per lattice site. A Feshbach resonance is used to associate the atom\npairs to molecules. Remaining atoms can be removed with blast light. The\ntechnique does not rely on the molecule-molecule interaction properties and is\ntherefore applicable to many systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Probabilistic Breakdown Phenomenon at On-Ramp Bottlenecks in Three-Phase\n  Traffic Theory: A nucleation model for the breakdown phenomenon in freeway free traffic flow\nat an on-ramp bottleneck is presented. This model, which can explain empirical\nresults on the breakdown phenomenon, is based on assumptions of three-phase\ntraffic theory in which the breakdown phenomenon is related to a first-order\nphase transition from the \"free flow\" phase to the \"synchronized flow\" phase.\nThe main idea of this nucleation model is that random synchronized flow\nnucleation occurs within a metastable inhomogeneous steady state associated\nwith a deterministic local perturbation in free flow, which can be considered\n\"deterministic vehicle cluster\" in free flow at the bottleneck. This\ndeterministic vehicle cluster in free flow is motionless and exists permanent\nat the bottleneck due to the on-ramp inflow. In the nucleation model, traffic\nbreakdown nucleation occurs through a random increase in vehicle number within\nthis deterministic vehicle cluster, if the amplitude of the resulting random\nvehicle cluster exceeds some critical amplitude. The mean time delay and the\nassociated nucleation rate of speed breakdown at the bottleneck are found and\ninvestigated. The nucleation rate of traffic breakdown as a function of the\nflow rates to the on-ramp and upstream of the bottleneck is studied. The\nnucleation model and the associated results exhibit qualitative different\ncharacteristics than those found earlier in other traffic flow nucleation\nmodels. Boundaries for speed breakdown in the diagram of congested patterns at\nthe bottleneck are found. These boundaries are qualitatively correlated with\nnumerical results of simulation of microscopic traffic flow models in the\ncontext of three-phase traffic theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bound states of the $\u03c6^4$ model via the nonperturbative\n  renormalization group: Using the nonperturbative renormalization group, we study the existence of\nbound states in the symmetry-broken phase of the scalar $\\phi^4$ theory in all\ndimensions between two and four and as a function of the temperature. The\naccurate description of the momentum dependence of the two-point function,\nrequired to get the spectrum of the theory, is provided by means of the\nBlaizot--M\\'endez-Galain--Wschebor approximation scheme. We confirm the\nexistence of a bound state in dimension three, with a mass within 1% of\nprevious Monte-Carlo and numerical diagonalization values.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Crossovers in the dynamics of supercooled liquids probed by an amorphous\n  wall: We study the relaxation dynamics of a binary Lennard-Jones liquid in the\npresence of an amorphous wall generated from equilibrium particle\nconfigurations. In qualitative agreement with the results presented in Nature\nPhys. {\\bf 8}, 164 (2012) for a liquid of harmonic spheres, we find that our\nbinary mixture shows a saturation of the dynamical length scale close to the\nmode-coupling temperature $T_c$. Furthermore we show that, due to the broken\nsymmetry imposed by the wall, signatures of an additional change in dynamics\nbecome apparent at a temperature well above $T_c$. We provide evidence that\nthis modification in the relaxation dynamics occurs at a recently proposed\ndynamical crossover temperature $T_s > T_c$, which is related to the breakdown\nof the Stokes-Einstein relation. We find that this dynamical crossover at $T_s$\nis also observed for a system of harmonic spheres as well as a WCA liquid,\nshowing that it may be a general feature of glass-forming systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The influence of absorbing boundary conditions on the transition path\n  times statistics: We derive an analytical expression for the transition path time (TPT)\ndistribution for a one-dimensional particle crossing a parabolic barrier. The\nsolution is expressed in terms of the eigenfunctions and eigenvalues of the\nassociated Fokker-Planck equation. The particle performs an anomalous dynamics\ngenerated by a power-law memory kernel, which includes memoryless Markovian\ndynamics as a limiting case. Our result takes into account absorbing boundary\nconditions, extending existing results obtained for free boundaries. We show\nthat TPT distributions obtained from numerical simulations are in excellent\nagreement with analytical results, while the typically employed free boundary\nconditions lead to a systematic overestimation of the barrier height. These\nfindings may be useful in the analysis of experimental results on transition\npath times. A web tool to perform this analysis is freely available.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Internal energy and condensate fraction of a trapped interacting Bose\n  gas: We present a semiclassical two-fluid model for an interacting Bose gas\nconfined in an anisotropic harmonic trap and solve it in the experimentally\nrelevant region for a spin-polarized gas of Rb-87 atoms, obtaining the\ntemperature dependence of the internal energy and of the condensate fraction.\nOur results are in agreement with recent experimental observations by Ensher et\nal.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Probability distributions for polymer translocation: We study the passage (translocation) of a self-avoiding polymer through a\nmembrane pore in two dimensions. In particular, we numerically measure the\nprobability distribution Q(T) of the translocation time T, and the distribution\nP(s,t) of the translocation coordinate s at various times t. When scaled with\nthe mean translocation time <T>, Q(T) becomes independent of polymer length,\nand decays exponentially for large T. The probability P(s,t) is well described\nby a Gaussian at short times, with a variance that grows sub-diffusively as\nt^{\\alpha} with \\alpha~0.8. For times exceeding <T>, P(s,t) of the polymers\nthat have not yet finished their translocation has a non-trivial stable shape.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding conserved amino acids in proteins: It has been conjectured that evolution exerted pressure to preserve amino\nacids bearing thermodynamic, kinetic, and functional roles. In this letter we\nshow that the physical requirement to maintain protein stability gives rise to\na sequence conservatism pattern that is in remarkable agreement with that found\nin natural proteins. Based on the physical properties of amino acids, we\npropose a model of evolution that explains conserved amino acids across protein\nfamilies sharing the same fold.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relativistic diffusion of particles with a continuous mass spectrum: We discuss general positivity conditions necessary for a definition of a\nrelativistic diffusion on the phase space. We show that Lorentz covariant\nrandom vector fields on the forward cone $p^{2}\\geq 0$ lead to a definition of\na generator of Lorentz covariant diffusions. We discuss in more detail\ndiffusions arising from particle dynamics in a random electromagnetic field\napproximating the quantum field at finite temperature. We develop statistical\nmechanics of a gas of diffusing particles. We discuss viscosity of such a gas\nin an expansion in gradients of the fluid velocity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic Equationins in the Theory of Normal Fermi Liquid: On the bases of the improved approximation for the spectral function of\none-particle states the Landau-Silin kinetic equations for the normal Fermi\nliquids of neutral and electrically charged particles are shown to be valid at\nfinite temperature above the temperature of superfluid transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Transition state theory applied to self-diffusion of hard spheres: A description in terms of transition rates among cells is used to analyze\nself-diffusion of hard spheres in the fluid phase. Cell size is assumed much\nlarger than the mean free path. Transition state theory is used to obtain an\nequation that matches numerical results previously obtained by other authors.\nTwo regimes are identified. For small packing fraction $\\xi$, diffusion is\nlimited by free volume; and, for large $\\xi$, diffusion is limited by velocity\nautocorrelation. The expressions obtained in each regime do not require\nadjustable parameters.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Log-Poisson Statistics and Extended Self-Similarity in Driven\n  Dissipative Systems: The Bak-Chen-Tang forest fire model was proposed as a toy model of turbulent\nsystems, where energy (in the form of trees) is injected uniformly and\nglobally, but is dissipated (burns) locally. We review our previous results on\nthe model and present our new results on the statistics of the higher-order\nmoments for the spatial distribution of fires. We show numerically that the\nspatial distribution of dissipation can be described by Log-Poisson statistics\nwhich leads to extended self-similarity (ESS). Similar behavior is also found\nin models based on directed percolation; this suggests that the concept of\nLog-Poisson statistics of (appropriately normalized) variables can be used to\ndescribe scaling not only in turbulence but also in a wide range of driven\ndissipative systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase statistics and the Hamiltonian: Modern statistical thermodynamics retains the concepts employed by Landau of\nthe order parameter and a functional depending on it, now called the\nHamiltonian. The present paper investigates the limits of validity for the use\nof the functional to describe the statistical correlations of a thermodynamic\nphase, particularly in connection with the experimentally accessible scattering\nof X-rays, electrons and neutrons. Guggenheim's definition for the functional\nis applied to a generalized system and the associated paradoxes are analyzed.\nIn agreement with Landau's original hypothesis, it is demonstrated that the\nminimum is equal to the thermodynamic free energy, requiring no fluctuation\ncorrection term. Although the fluctuation amplitude becomes large in the\nvicinity of a second-order phase transition in low dimensionalities, it does\nnot diverge and the equilibrium order parameter remains well defined.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Structure and Randomness of Continuous-Time Discrete-Event Processes: Loosely speaking, the Shannon entropy rate is used to gauge a stochastic\nprocess' intrinsic randomness; the statistical complexity gives the cost of\npredicting the process. We calculate, for the first time, the entropy rate and\nstatistical complexity of stochastic processes generated by finite unifilar\nhidden semi-Markov models---memoryful, state-dependent versions of renewal\nprocesses. Calculating these quantities requires introducing novel mathematical\nobjects ({\\epsilon}-machines of hidden semi-Markov processes) and new\ninformation-theoretic methods to stochastic processes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Enhanced stochastic oscillations in autocatalytic reactions: We study a simplified scheme of $k$ coupled autocatalytic reactions,\npreviously introduced by Togashi and Kaneko. The role of stochastic\nfluctuations is elucidated through the use of the van Kampen system-size\nexpansion and the results compared with direct stochastic simulations. Regular\ntemporal oscillations are predicted to occur for the concentration of the\nvarious chemical constituents, with an enhanced amplitude resulting from a\nresonance which is induced by the intrinsic graininess of the system. The\nassociated power spectra are determined and have a different form depending on\nthe number of chemical constituents, $k$. We make detailed comparisons in the\ntwo cases $k=4$ and $k=8$. Agreement between the theoretical and numerical\nresults for the power spectrum are good in both cases. The resulting spectrum\nis especially interesting in the $k=8$ system, since it has two peaks, which\nthe system-size expansion is still able to reproduce accurately.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Blocking temperature in magnetic nano-clusters: A recent study of nonextensive phase transitions in nuclei and nuclear\nclusters needs a probability model compatible with the appropriate Hamiltonian.\nFor magnetic molecules a representation of the evolution by a Markov process\nachieves the required probability model that is used to study the probability\ndensity function (PDF) of the order parameter, i.e. the magnetization. The\nexistence of one or more modes in this PDF is an indication for the\nsuperparamagnetic transition of the cluster. This allows us to determine the\nfactors that influence the blocking temperature, i.e. the temperature related\nto the change of the number of modes in the density. It turns out that for our\nmodel, rather than the evolution of the system implied by the Hamiltonian, the\nhigh temperature density of the magnetization is the important factor for the\ntemperature of the transition. We find that an initial probability density\nfunction with a high entropy leads to a magnetic cluster with a high blocking\ntemperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Classical and Quantum Fluctuation Theorems for Heat Exchange: The statistics of heat exchange between two classical or quantum finite\nsystems initially prepared at different temperatures are shown to obey a\nfluctuation theorem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Cluster Expansion for Dipole Gases: We give a new proof of the well-known upper bound on the correlation function\nof a gas of non-overlapping dipoles of fixed length and discrete orientation\nworking directly in the charge representation, instead of the more usual\nsine-Gordon representation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical signatures of molecular symmetries in nonequilibrium quantum\n  transport: Symmetries play a crucial role in ubiquitous systems found in Nature. In this\nwork, we propose an elegant approach to detect symmetries by measuring quantum\ncurrents. Our detection scheme relies on initiating the system in an\nanti-symmetric initial condition, with respect to the symmetric sites, and\nusing a probe that acts like a local noise. Depending on the position of the\nprobe the currents exhibit unique signatures such as a quasi-stationary plateau\nindicating the presence of meta-stability and multi-exponential decays in case\nof multiple symmetries. The signatures are sensitive to the probe and vanish\ncompletely when the timescale of the coherent system dynamics is much longer\nthan the timescale of the probe. These results are demonstrated using a\n$4$-site model and an archetypal example of the para-benzene ring and are shown\nto be robust under a weak disorder.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Progressive quenching --- Ising chain models: Of the Ising spin chain with the nearest neighbor or up to the second nearest\nneighbor interactions, we fixed progressively either a single spin or a pair of\nneighboring spins at the value they took. Before the subsequent fixation, the\nunquenched part of the system is equilibrated. We found that, in all four\ncombinations of the cases, the ensemble of quenched spin configurations is the\nequilibrium ensemble.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic Theory and Hydrodynamics for a Low Density Gas: Many features of real granular fluids under rapid flow are exhibited as well\nby a system of smooth hard spheres with inelastic collisions. For such a\nsystem, it is tempting to apply standard methods of kinetic theory and\nhydrodynamics to calculate properties of interest. The domain of validity for\nsuch methods is a priori uncertain due to the inelasticity, but recent\nsystematic studies continue to support the utility of kinetic theory and\nhydrodynamics as both qualitative and quantitative descriptions for many\nphysical states. The basis for kinetic theory and hydrodynamic descriptions is\ndiscussed briefly for the special case of a low density gas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimization and Growth in First-Passage Resetting: We combine the processes of resetting and first-passage to define\n\\emph{first-passage resetting}, where the resetting of a random walk to a fixed\nposition is triggered by a first-passage event of the walk itself. In an\ninfinite domain, first-passage resetting of isotropic diffusion is\nnon-stationary, with the number of resetting events growing with time as\n$\\sqrt{t}$. We calculate the resulting spatial probability distribution of the\nparticle analytically, and also obtain this distribution by a geometric path\ndecomposition. In a finite interval, we define an optimization problem that is\ncontrolled by first-passage resetting; this scenario is motivated by\nreliability theory. The goal is to operate a system close to its maximum\ncapacity without experiencing too many breakdowns. However, when a breakdown\noccurs the system is reset to its minimal operating point. We define and\noptimize an objective function that maximizes the reward (being close to\nmaximum operation) minus a penalty for each breakdown. We also investigate\nextensions of this basic model to include delay after each reset and to two\ndimensions. Finally, we study the growth dynamics of a domain in which the\ndomain boundary recedes by a specified amount whenever the diffusing particle\nreaches the boundary after which a resetting event occurs. We determine the\ngrowth rate of the domain for the semi-infinite line and the finite interval\nand find a wide range of behaviors that depend on how much the recession occurs\nwhen the particle hits the boundary.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Mean trapping time for an arbitrary node on regular hyperbranched\n  polymers: The regular hyperbranched polymers (RHPs), also known as Vicsek fractals, are\nan important family of hyperbranched structures which have attracted a wide\nspread attention during the past several years. In this paper, we study the\nfirst-passage properties for random walks on the RHPs. Firstly, we propose a\nway to label all the different nodes of the RHPs and derive exact formulas to\ncalculate the mean first-passage time (MFPT) between any two nodes and the mean\ntrapping time (MTT) for any trap node. Then, we compare the trapping efficiency\nbetween any two nodes of the RHPs by using the MTT as the measures of trapping\nefficiency. We find that the central node of the RHPs is the best trapping site\nand the nodes which are the farthest nodes from the central node are the worst\ntrapping sites. Furthermore, we find that the maximum of the MTT is about $4$\ntimes more than the minimum of the MTT. The result is similar to the results in\nthe recursive fractal scale-free trees and T-fractal, but it is quite different\nfrom that in the recursive non-fractal scale-free trees. These results can help\nunderstanding the influences of the topological properties and trap location on\nthe trapping efficiency.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic model for the glass transition: deeply supercooled liquids\n  as mixtures of solid-like and liquid-like micro-regions: For a deeply supercooled liquid just above its glass transition temperature,\nwe present a simple thermodynamic model, where the deeply supercooled liquid is\nassumed to be a mixture of solid-like and liquid-like micro regions. The mole\nfraction of the liquid-like regions controls the thermodynamic properties of\nthe supercooled liquid while that of the solid-like regions controls its\nrelaxation time or viscosity. From the universal temperature dependence of the\nmolar excess entropy for the deeply supercooled liquids, we derive the\ntemperature dependence of the mole fraction of the liquid-like regions to\nobtain the universal temperature dependence of the relaxation time or the\nviscosity for the deeply supercooled liquids. A central parameter of our model\nis then shown to be a measure for the fragility of a supercooled liquid. We\nalso suggest a way to test our physical picture of deeply supercooled liquids\nby means of molecular dynamics simulations of model liquids.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Systematic perturbation approach for a dynamical scaling law in a\n  kinetically constrained spin model: The dynamical behaviours of a kinetically constrained spin model\n(Fredrickson-Andersen model) on a Bethe lattice are investigated by a\nperturbation analysis that provides exact final states above the nonergodic\ntransition point. It is observed that the time-dependent solutions of the\nderived dynamical systems obtained by the perturbation analysis become\nsystematically closer to the results obtained by Monte Carlo simulations as the\norder of a perturbation series is increased. This systematic perturbation\nanalysis also clarifies the existence of a dynamical scaling law, which\nprovides a implication for a universal relation between a size scale and a time\nscale near the nonergodic transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical mechanical approach of complex networks with weighted links: Systems which consist of many localized constituents interacting with each\nother can be represented by complex networks. Consistently, network science has\nbecome highly popular in vast fields focusing on natural, artificial and social\nsystems. We numerically analyze the growth of $d$-dimensional geographic\nnetworks (characterized by the index $\\alpha_G\\geq0$; $d = 1, 2, 3, 4$) whose\nlinks are weighted through a predefined random probability distribution, namely\n$P(w) \\propto e^{-|w - w_c|/\\tau}$, $w$ being the weight $ (w_c \\geq 0; \\; \\tau\n> 0)$. In this model, each site has an evolving degree $k_i$ and a local energy\n$\\varepsilon_i \\equiv \\sum_{j=1}^{k_i} w_{ij}/2$ ($i = 1, 2, ..., N$) that\ndepend on the weights of the links connected to it. Each newly arriving site\nlinks to one of the pre-existing ones through preferential attachment given by\nthe probability $\\Pi_{ij}\\propto \\varepsilon_{i}/d^{\\,\\alpha_A}_{ij}\n\\;\\;(\\alpha_A \\ge 0)$, where $d_{ij}$ is the Euclidean distance between the\nsites. Short- and long-range interactions respectively correspond to\n$\\alpha_A/d>1$ and $0\\leq \\alpha_A/d \\leq 1$; $\\alpha_A/d \\to \\infty$\ncorresponds to interactions between close neighbors, and $\\alpha_A/d \\to 0$\ncorresponds to infinitely-ranged interactions. The site energy distribution\n$p(\\varepsilon)$ corresponds to the usual degree distribution $p(k)$ as the\nparticular instance $(w_c,\\tau)=(2,0)$. We numerically verify that the\ncorresponding connectivity distribution $p(\\varepsilon)$ converges, when\n$\\alpha_A/d\\to\\infty$, to the weight distribution $P(w)$ for infinitely narrow\ndistributions (i.e., $\\tau \\to \\infty, \\,\\forall w_c$) as well as for $w_c\\to0,\n\\, \\forall\\tau$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effective interaction between guest charges immersed in 2D jellium: The model under study is an infinite 2D jellium of pointlike particles with\nelementary charge $e$, interacting via the logarithmic potential and in thermal\nequilibrium at the inverse temperature $\\beta$. Two cases of the coupling\nconstant $\\Gamma\\equiv \\beta e^2$ are considered: the Debye-H\\\"uckel limit\n$\\Gamma\\to 0$ and the free-fermion point $\\Gamma=2$. In the most general\nformulation, two guest particles, the one with charge $q e$ (the valence $q$\nbeing an arbitrary integer) and the hard core of radius $\\sigma>0$ and the\npointlike one with elementary charge $e$, are immersed in the bulk of the\njellium at distance $d\\ge \\sigma$. Two problems are of interest: the asymptotic\nlarge-distance behavior of the excess charge density induced in the jellium and\nthe effective interaction between the guest particles. Technically, the induced\ncharge density and the effective interaction are expressed in terms of\nmulti-particle correlations of the pure (translationally invariant) jellium\nsystem. It is shown that the separation form of the induced charge density onto\nits radial and angle parts, observed previously in the limit $\\Gamma\\to 0$, is\nnot reproduced at the coupling $\\Gamma=2$. Based on an exact expression for the\neffective interaction between guest particles at $\\Gamma=2$, oppositely\n($q=0,-1,-2,\\ldots$) charged guest particles always attract one another while\nlikely ($q=1,2,\\ldots$) charged guest particles repeal one another up to a\ncertain distance $d$ between them and then the mutual attraction takes place up\nto asymptotically large (finite) distances.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ballistic aggregation: a solvable model of irreversible many particles\n  dynamics: The adhesive dynamics of a one-dimensional aggregating gas of point particles\nis rigorously described. The infinite hierarchy of kinetic equations for the\ndistributions of clusters of nearest neighbours is shown to be equivalent to a\nsystem of two coupled equations for a large class of initial conditions. The\nsolution to these nonlinear equations is found by a direct construction of the\nrelevant probability distributions in the limit of a continuous initial mass\ndistribution. We show that those limiting distributions are identical to those\nof the statistics of shocks in the Burgers turbulence. The analysis relies on a\nmapping on a Brownian motion problem with parabolic constraints.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Vicinal surface growth: bunching and meandering instabilities: The morphology of a growing crystal surface is studied in the case of an\nunstable two-dimensional step flow. Competition between bunching and meandering\nof steps leads to a variety of patterns characterized by their respective\ninstability growth rates. The roughness exponent is shown to go from 1/2 to 1,\nbetween the pure bunching to the meandering regimes. Using numerical\nsimulations, we observe that generically, a transition between the two regimes\noccurs. We find surface shapes and roughness time evolution in quantitative\nagreement with experiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entropies for complex systems: generalized-generalized entropies: Many complex systems are characterized by non-Boltzmann distribution\nfunctions of their statistical variables. If one wants to -- justified or not\n-- hold on to the maximum entropy principle for complex statistical systems\n(non-Boltzmann) we demonstrate how the corresponding entropy has to look like,\ngiven the form of the corresponding distribution functions. By two natural\nassumptions that (i) the maximum entropy principle should hold and that (ii)\nentropy should describe the correct thermodynamics of a system (which produces\nnon-Boltzmann distributions) the existence of a class of fully consistent\nentropies can be deduced. Classical Boltzmann-Gibbs entropy is recovered as a\nspecial case for the observed distribution being the exponential, Tsallis\nentropy is the special case for q-exponential observations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Open statistical ensemble and surface phenomena: In the present work we investigate a new statistical ensemble, which seems\nlogical to be entitled the open one, for the case of a one-component system of\nordinary particles. Its peculiarity is in complementing the consideration of a\nsystem with the inclusion of a certain surrounding area. The calculations\nindicate the necessity of taking into account the surface that delimits a given\nsystem even in the case when the latter is a part of a uniform medium and is\nnot singled out one way or another.\n  The surface tension coefficient behaves unlike two-phase systems in\nequilibrium and depends on two variables - pressure as well as temperature -\nand belongs to the boundary separating a hard solid from a fluid. As for the\nmathematical mechanism ensuring the fulfillment of thermodynamic relations, the\nemphasis is shifted from operating with series, like in the grand canonical\nensemble, towards employing the recurrence relations of a new class of\nfunctions that incorporate Boltzmann and Ursell factors as their extreme cases\nand towards utilizing generating functions.\n  The second topic of discussion that the present article deals with is the\nconsideration of the surface tension and adsorption observed at the boundary of\na solid body and a liquid or gas carried out on the basis of the analysis of\nthe classical system found in a field of force of general type. The surface\nterms are calculated with the aid of field functions and the correlation\nfunctions of an unperturbed volume phase and behave somewhat vaguely;\nparticularly, as a function of activity, they may start with a linear or\nquadratic term.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "An Explicit Form of the Equation of Motion of the Interface in\n  Bicontinuous Phases: The explicit form of the interface equation of motion derived assuming a\nminimal surface is extended to general bicontinuous interfaces that appear in\nthe diffusion limited stage of the phase separation process of binary mixtures.\nThe derivation is based on a formal solution of the equivalent simple layer for\nthe Dirichlet problem of the Laplace equation with an arbitrary boundary\nsurface. It is shown that the assumption of a minimal surface used in the\nprevious linear theory is not necessary, but its bicontinuous nature is the\nessential condition required for us to rederive the explicit form of the simple\nlayer. The de- rived curvature flow equation has a phenomenological cut-off\nlength, i.e., an `electro-static' screening length. That is re- lated to the\nwell-known scaling length characterizing the spatial pattern size of a\nhomogeneously growing bicontinuous phase. The corresponding equation of the\nlevel function in this scheme is given in a one-parameter form also.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The thermal denaturation of DNA studied with neutron scattering: The melting transition of deoxyribonucleic acid (DNA), whereby the strands of\nthe double helix structure completely separate at a certain temperature, has\nbeen characterized using neutron scattering. A Bragg peak from B-form fibre DNA\nhas been measured as a function of temperature, and its widths and integrated\nintensities have been interpreted using the Peyrard-Bishop-Dauxois (PBD) model\nwith only one free parameter. The experiment is unique, as it gives spatial\ncorrelation along the molecule through the melting transition where other\ntechniques cannot.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact Density Functionals in One Dimension: We propose a new and general method for deriving exact density functionals in\none dimension for lattice gases with finite-range pairwise interactions.\nCorresponding continuum functionals are derived by applying a proper limiting\nprocedure. The method is based on a generalised Markov property, which allows\nus to set up a rather transparent scheme that covers all previously known exact\nfunctionals for one-dimensional lattice gas or fluid systems. Implications for\na systematic construction of approximate density functionals in higher\ndimensions are pointed out.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum critical systems with dissipative boundaries: We study the effects of dissipative boundaries in many-body systems at\ncontinuous quantum transitions, when the parameters of the Hamiltonian driving\nthe unitary dynamics are close to their critical values. As paradigmatic\nmodels, we consider fermionic wires subject to dissipative interactions at the\nboundaries, associated with pumping or loss of particles. They are induced by\ncouplings with a Markovian baths, so that the evolution of the system density\nmatrix can be described by a Lindblad master equation. We study the quantum\nevolution arising from variations of the Hamiltonian and dissipation\nparameters, starting at t=0 from the ground state of the critical Hamiltonian.\nTwo different dynamic regimes emerge: (i) an early-time regime for times t ~ L,\nwhere the competition between coherent and incoherent drivings develops a\ndynamic finite-size scaling, obtained by extending the scaling framework\ndescribing the coherent critical dynamics of the closed system, to allow for\nthe boundary dissipation; (ii) a large-time regime for t ~ L^3 whose dynamic\nscaling describes the late quantum evolution leading to the t->infty stationary\nstates.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ripening and Focusing of Aggregate Size Distributions with Overall\n  Volume Growth: We explore the evolution of the aggregate size distribution in systems where\naggregates grow by diffusive accretion of mass. Supersaturation is controlled\nin such a way that the overall aggregate volume grows linearly in time.\nClassical Ostwald ripening, which is recovered in the limit of vanishing\noverall growth, constitutes an unstable solution of the dynamics. In the\npresence of overall growth evaporation of aggregates always drives the dynamics\ninto a new, qualitatively different growth regime where ripening ceases, and\ngrowth proceeds at a constant number density of aggregates. We provide a\ncomprehensive description of the evolution of the aggregate size distribution\nin the constant density regime: the size distribution does not approach a\nuniversal shape, and even for moderate overall growth rates the standard\ndeviation of the aggregate radius decays monotonically. The implications of\nthis theory for the focusing of aggregate size distributions are discussed for\na range of different settings including the growth of tiny rain droplets in\nclouds, as long as they do not yet feel gravity, and the synthesis of\nnano-particles and quantum dots.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Irreversible mesoscale fluctuations herald the emergence of dynamical\n  phases: We study fluctuating field models with spontaneously emerging dynamical\nphases. We consider two typical transition scenarios associated with\nparity-time symmetry breaking: oscillatory instabilities and critical\nexceptional points. An analytical investigation of the low-noise regime reveals\na drastic increase of the mesoscopic entropy production toward the transitions.\nFor an illustrative model of two nonreciprocally coupled Cahn-Hilliard fields,\nwe find physical interpretations in terms of actively propelled interfaces and\na coupling of modes near the critical exceptional point.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonadditivity in Quasiequilibrium States of Spin Systems with Lattice\n  Distortion: It is pointed out that there exists a short-range interacting system, i.e.\nthe elastic spin model, which is extensive but nonadditive. It is numerically\nshown that, depending on the statistical ensemble, the specific heat or the\nsusceptibility becomes negative in a certain parameter region, which shows\nensemble inequivalence in this model. Further, we numerically estimate the\neffective Hamiltonian for spin variables, and it is clarified that the\neffective interaction among spin variables is long-ranged. Remarkably, the so\ncalled Kac's prescription, which is usually regarded as a mathematical\noperation to make the system extensive, naturally holds in the effective\ninteraction.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Majority Rule Dynamics in Finite Dimensions: We investigate the long-time behavior of a majority rule opinion dynamics\nmodel in finite spatial dimensions. Each site of the system is endowed with a\ntwo-state spin variable that evolves by majority rule. In a single update\nevent, a group of spins with a fixed (odd) size is specified and all members of\nthe group adopt the local majority state. Repeated application of this update\nstep leads to a coarsening mosaic of spin domains and ultimate consensus in a\nfinite system. The approach to consensus is governed by two disparate time\nscales, with the longer time scale arising from realizations in which spins\norganize into coherent single-opinion bands. The consequences of this\ngeometrical organization on the long-time kinetics are explored.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Macroscopic Fluctuation Theory and Current Fluctuations in Active\n  Lattice Gases: We study the current large deviations for a lattice model of interacting\nactive particles displaying a motility-induced phase separation (MIPS). To do\nthis, we first derive the exact fluctuating hydrodynamics of the model in the\nlarge system limit. On top of the usual Gaussian noise terms the theory also\npresents Poissonian noise terms, that we fully account for. We find a dynamical\nphase transition between flat density profiles and sharply phase-separated\ntraveling waves, and we derive the associated phase diagram together with the\nlarge deviation function for all phases, including the one displaying MIPS. We\nshow how the results can be obtained using methods similar to those of\nequilibrium phase separation, in spite of the nonequilibrium nature of the\nproblem.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "From regular to growing small-world networks: We propose a growing model which interpolates between one-dimensional regular\nlattice and small-world networks. The model undergoes an interesting phase\ntransition from large to small world. We investigate the structural properties\nby both theoretical predictions and numerical simulations. Our growing model is\na complementarity for the famous static WS network model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reference Distribution Functions for Magnetically Confined Plasmas from\n  the Minimum Entropy Production Theorem and the MaxEnt Principle, subject to\n  the Scale-Invariant Restrictions: We derive the expression of the reference distribution function for\nmagnetically confined plasmas far from the thermodynamic equilibrium. The local\nequilibrium state is fixed by imposing the minimum entropy production theorem\nand the maximum entropy (MaxEnt) principle, subject to scale invariance\nrestrictions. After a short time, the plasma reaches a state close to the local\nequilibrium. This state is referred to as the reference state. The aim of this\nletter is to determine the reference distribution function (RDF) when the local\nequilibrium state is defined by the above mentioned principles. We prove that\nthe RDF is the stationary solution of a generic family of stochastic processes\ncorresponding to an universal Landau-type equation with white parametric noise.\nAs an example of application, we consider a simple, fully ionized, magnetically\nconfined plasmas, with auxiliary Ohmic heating. The free parameters are linked\nto the transport coefficients of the magnetically confined plasmas, by the\nkinetic theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Division of Labor as the Result of Phase Transition: The emergence of labor division in multi-agent system is analyzed by the\nmethod of statistical physics. Considering a system consists of N homogeneous\nagents. Their behaviors are determined by the returns from their production.\nUsing the Metropolis method in statistical physics, which in this model can\nbeen regarded as a kind of uncertainty in decision making, we constructed a\nMaster equation model to describe the evolution of the agents distribution.\nWhen we introduce the mechanism of learning by doing to describe the effect of\ntechnical progress and a formula for the competitive cooperation, the model\ngives us the following interesting results: (1) As the results of long term\nevolution, the system can reach a steady state. (2) When the parameters exceed\na critical point, the labor division emerges as the result of phase transition.\n(3) Although the technical progress decides whether or not phase transition\noccurs, the critical point is strongly effected by the competitive cooperation.\n  From the above physical model and the corresponding results, we can get a\nmore deeply understanding about the labor division.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum Stochastic Synchronization: We study within the spin-boson dynamics the synchronization of quantum\ntunneling with an external periodic driving signal. As a main result we find\nthat at a sufficiently large system-bath coupling strength (Kondo parameter\na>1) the thermal noise plays a constructive role in yielding both a frequency\nand a phase synchronization in a symmetric two-level system. Such riveting\nsynchronization occurs when the driving frequency supersedes the zero\ntemperature tunneling rate. As an application evidencing the effect, we\nconsider a charge transfer dynamics in molecular complexes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reply to Comment on Nonlocal quartic interactions and universality\n  classes in perovskite manganites: Comment [arXiv:cond-mat.stat.mech., 1602.02087v1 (2016)] has raised questions\nclaiming that the nonlocal model Hamiltonian presented in [Phys. Rev. E 92,\n012123 (2015)] is equivalent to the standard (short-ranged) \\Phi^4 theory.\nThese claims are based on a low momentum expansion of the interaction vertex\nthat cannot be applied to the vertex factors containing both low and high\nmomenta inside the loop-integrals. Elaborating upon the important steps of the\nmomentum shell decimation scheme, employed in the renormalization-group\ncalculation, we explicitly show the interplay of internal (high) and external\n(low) momenta determining the loop integrals for self-energy and vertex\nfunctions giving rise to corrections (to the bare parameters) different from\nthose of the standard (short-ranged) \\Phi^4 theory. Employing explicit\nmathematical arguments, we show that this difference persists when the range of\ninteraction is assumed to be long (short) ranged with respect to the lattice\nconstant (correlation-length), yielding the critical exponents as given in the\noriginal paper.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on ``Fragmented Condensate Ground State of Trapped Weakly\n  Interacting Bosons in Two Dimensions\": Recently Liu et al. [PRL 87, 030404 (2001)] examined the lowest state of a\nweakly-interacting Bose-Einstein condensate. In addition to other interesting\nresults, using the method of the pair correlation function, they questioned the\nvalidity of the mean-field picture of the formation of vortices and stated that\nthe vortices are generated at the center of the cloud. This is in apparent\ncontradiction to the Gross-Pitaevskii approach, which predicts that the\nvortices successively enter the cloud from its outer parts as L/N (where N is\nthe number of atoms in the trap and hbar(L) is the angular momentum of the\nsystem) increases. We have managed to reproduce the results of Liu et al.\nhowever a more careful analysis presented below confirms the validity of the\nmean-field approach.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A comprehensive scenario of the thermodynamic anomalies of water using\n  the TIP4P/2005 model: The striking behavior of water has deserved it to be referred to as an\n\"anomalous\" liquid. The water anomalies are greatly amplified in metastable\n(supercooled/stretched) regions. This makes difficult a complete experimental\ndescription since, beyond certain limits, the metastable phase necessarily\ntransforms into the stable one. Theoretical interpretation of the water\nanomalies could then be based on simulation results of well validated water\nmodels. But the analysis of the simulations has not yet reached a consensus. In\nparticular, one of the most popular theoretical scenarios -involving the\nexistence of a liquid-liquid critical point (LLCP)- is disputed by several\nauthors. In this work we propose to use a number of exact thermodynamic\nrelations which can be tested in a region of the phase diagram outside the LLCP\nthus avoiding the problems associated to the coexistence region. The central\nproperty connected to other water anomalies is the locus of temperatures at\nwhich the density along isobars attain a maximum (TMD line) or a minimum (TmD),\ncomputed via simulations for a successful water model, TIP4P/2005. Next, we\nhave evaluated the vapor-liquid spinodal in the region of large negative\npressures. The shape of these curves and their connection to the extrema of\nresponse functions (isothermal compressibility and heat capacity at constant\npressure) may help to elucidate the validity of the theoretical proposals. In\nthis way we are able to present for the first time a comprehensive scenario of\nthe thermodynamic water anomalies for TIP4P/2005 and their relation to the\nvapor-liquid spinodal. The overall picture shows a remarkable similarity with\nthe corresponding one for the ST2 water model, for which the existence of a\nLLCP has been demonstrated in recent years. It also provides a hint as to where\nthe long-sought for extrema in response functions might become accessible to\nexperiments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonstandard entropy production in the standard map: We investigate the time evolution of the entropy for a paradigmatic\nconservative dynamical system, the standard map, for different values of its\ncontrolling parameter $a$. When the phase space is sufficiently ``chaotic''\n(i.e., for large $|a|$), we reproduce previous results. For small values of\n$|a|$, when the phase space becomes an intricate structure with the coexistence\nof chaotic and regular regions, an anomalous regime emerges. We characterize\nthis anomalous regime with the generalized nonextensive entropy, and we observe\nthat for values of $a$ approaching zero, it lasts for an increasingly large\ntime. This scenario displays a striking analogy with recent observations made\nin isolated classical long-range $N$-body Hamiltonians, where, for a large\nclass of initial conditions, a metastable state (whose duration diverges with\n$1/N\\to 0$) is observed before it crosses over to the usual, Boltzmann-Gibbs\nregime.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamics of emergent structure in active matter: Active matter is rapidly becoming a key paradigm of out-of-equilibrium soft\nmatter exhibiting complex collective phenomena, yet the thermodynamics of such\nsystems remain poorly understood. In this letter we study the nonequilbrium\nthermodynamics of large scale active systems capable of mobility-induced phase\nseparation and polar alignment, using a fully under-damped model which exhibits\nhidden entropy productions not previously reported in the literature. We\nquantify steady state entropy production at each point in the phase diagram,\nrevealing characteristic dissipation rates associated with the distinct phases\nand configurational structure. This reveals sharp discontinuities in the\nentropy production at phase transitions and facilitates identification of the\nthermodynamics of micro-features, such as defects in the emergent structure.\nThe interpretation of the time reversal symmetry in the dynamics of the\nparticles is found to be crucial.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonlinear integral equations for thermodynamics of the sl(r+1)\n  Uimin-Sutherland model: We derive traditional thermodynamic Bethe ansatz (TBA) equations for the\nsl(r+1) Uimin-Sutherland model from the T-system of the quantum transfer\nmatrix. These TBA equations are identical to the ones from the string\nhypothesis. Next we derive a new family of nonlinear integral equations (NLIE).\nIn particular, a subset of these NLIE forms a system of NLIE which contains\nonly a finite number of unknown functions. For r=1, this subset of NLIE reduces\nto Takahashi's NLIE for the XXX spin chain. A relation between the traditional\nTBA equations and our new NLIE is clarified. Based on our new NLIE, we also\ncalculate the high temperature expansion of the free energy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram and structural diversity of the densest binary sphere\n  packings: The densest binary sphere packings have historically been very difficult to\ndetermine. The only rigorously known packings in the alpha-x plane of sphere\nradius ratio alpha and relative concentration x are at the Kepler limit alpha =\n1, where packings are monodisperse. Utilizing an implementation of the\nTorquato-Jiao sphere-packing algorithm [S. Torquato and Y. Jiao, Phys. Rev. E\n82, 061302 (2010)], we present the most comprehensive determination to date of\nthe phase diagram in (alpha,x) for the densest binary sphere packings.\nUnexpectedly, we find many distinct new densest packings.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Size Segregation of Granular Matter in Silo Discharges: We present an experimental study of segregation of granular matter in a\nquasi-two dimensional silo emptying out of an orifice. Size separation is\nobserved when multi-sized particles are used with the larger particles found in\nthe center of the silo in the region of fastest flow. We use imaging to study\nthe flow inside the silo and quantitatively measure the concentration profiles\nof bi-disperse beads as a function of position and time. The angle of the\nsurface is given by the angle of repose of the particles, and the flow occurs\nin a few layers only near the top of this inclined surface. The flowing region\nbecomes deeper near the center of the silo and is confined to a parabolic\nregion centered at the orifice which is approximately described by the\nkinematic model. The experimental evidence suggests that the segregation occurs\non the surface and not in the flow deep inside the silo where velocity\ngradients also are present. We report the time development of the\nconcentrations of the bi-disperse particles as a function of size ratios, flow\nrate, and the ratio of initial mixture. The qualitative aspects of the observed\nphenomena may be explained by a void filling model of segregation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Size effects on generation recombination noise: We carry out an analytical theory of generation-recombination noise for a two\nlevel resistor model which goes beyond those presently available by including\nthe effects of both space charge fluctuations and diffusion current. Finite\nsize effects are found responsible for the saturation of the low frequency\ncurrent spectral density at high enough applied voltages. The saturation\nbehaviour is controlled essentially by the correlations coming from the long\nrange Coulomb interaction. It is suggested that the saturation of the current\nfluctuations for high voltage bias constitutes a general feature of\ngeneration-recombination noise.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "General Structural Results for Potts Model Partition Functions on\n  Lattice Strips: We present a set of general results on structural features of the $q$-state\nPotts model partition function $Z(G,q,v)$ for arbitrary $q$ and temperature\nBoltzmann variable $v$ for various lattice strips of arbitrarily great width\n$L_y$ vertices and length $L_x$ vertices, including (i) cyclic and M\\\"obius\nstrips of the square and triangular lattice, and (ii) self-dual cyclic strips\nof the square lattice. We also present an exact solution for the chromatic\npolynomial for the cyclic and M\\\"obius strips of the square lattice with width\n$L_y=5$ (the greatest width for which an exact solution has been obtained so\nfar for these families). In the $L_x \\to \\infty$ limit, we calculate the\nground-state degeneracy per site, $W(q)$ and determine the boundary ${\\cal B}$\nacross which $W(q)$ is singular in the complex $q$ plane.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Feynman effective classical potential in the Schr\u00f6dinger\n  formulation: New physical insight into the correspondence between path integral concepts\nand the Schr\\\"odinger formulation is gained by the analysis of the effective\nclassical potential, that is defined within the Feynman path integral\nformulation of statistical mechanics. This potential is related to the\nquasi-static response of the equilibrium system to an external force. These\nfindings allow for a comprehensive formulation of dynamical approximations\nbased on this potential.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum phase transitions of the extended isotropic XY model with\n  long-range interactions: The one-dimensional extended isotropic XY model (s=1/2) in a transverse field\nwith uniform long-range interactions among the \\textit{z} components of the\nspin is considered. The model is exactly solved by introducing the gaussian and\nJordan-Wigner transformations, which map it in a non-interacting fermion\nsystem. The partition function can be determined in closed form at arbitrary\ntemperature and for arbitrary multiplicity of the multiple spin interaction.\n  From this result all relevant thermodynamic functions are obtained and, due\nto the long-range interactions, the model can present classical and quantum\ntransitions of first- and second-order. The study of its critical behavior is\nrestricted for the quantum transitions, which are induced by the transverse\nfield at $T=0.$ The phase diagram is explicitly obtained for multiplicities\n$p=2,3,4$ and $\\infty ,$ as a function of the interaction parameters, and, in\nthese cases, the critical behavior of the model is studied\\textbf{\\}in detail.\nExplicit results are also presented for the induced magnetization and\nisothermal susceptibility $\\chi_{T}^{zz}$, and a detailed analysis is also\ncarried out for the static longitudinal $<S_{j}^{z}S_{l}^{z}>$ and transversal\n$<S_{j}^{x}S_{l}^{x}>$ correlation functions. The different phases presented by\nthe model can be characterized by the spatial decay of the these correlations,\nand from these results some of these can be classified as quantum spin liquid\nphases. The static critical exponents and the dynamic one, $z,$ have also been\ndetermined, and it is shown that, besides inducing first order phase\ntransition, the long-range interaction also changes the universality class the\nmodel.-range interaction also changes the universality class the model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Many-particle dephasing after a quench: After a quench in a quantum many-body system, expectation values tend to\nrelax towards long-time averages. However, in any finite-size system, temporal\nfluctuations remain. It is crucial to study the suppression of these\nfluctuations with system size. The particularly important case of\nnon-integrable models has been addressed so far only by numerics and\nconjectures based on analytical bounds. In this work, we are able to derive\nanalytical predictions for the temporal fluctuations in a non-integrable model\n(the transverse Ising chain with extra terms). Our results are based on\nidentifying a dynamical regime of 'many-particle dephasing', where\nquasiparticles do not yet relax but fluctuations are nonetheless suppressed\nexponentially by weak integrability breaking.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Essentially Ergodic Behaviour: I prove a theorem on the precise connection of the time and phase space\naverage of the Boltzmann equilibrium showing that the behaviour of a dynamical\nsystem with a stationary measure and a dominant equilibrium state is\nqualitatively ergodic.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Accuracy of energy measurement and reversible operation of a\n  microcanonical Szilard engine: In a recent paper [Vaikuntanathan and Jarzynski, Phys. Rev. E {\\bf 83},\n061120 (2011), arXiv:1105.1744] a model was introduced whereby work could be\nextracted from a thermal bath by measuring the energy of a particle that was\nthermalized by the bath and manipulating the potential of the particle in the\nappropriate way, depending on the measurement outcome. If the extracted work is\n$W_1$ and the work $W_{\\text{er}}$ needed to be dissipated in order to erase\nthe measured information in accordance with Landauer's principle, it was shown\nthat $W_1\\leq W_{\\text{er}}$ in accordance with the second law of\nthermodynamics. Here we extend this work in two directions: First, we discuss\nhow accurately the energy should be measured. By increasing the accuracy one\ncan extract more work, but at the same time one obtains more information that\nhas to be deleted. We discuss what are the appropriate ways of optimizing the\nbalance between the two and find optimal solutions. Second, whenever $W_1$ is\nstrictly less than $W_{\\text{er}}$ it means that an irreversible step has been\nperformed. We identify the irreversible step and propose a protocol that will\nachieve the same transition in a reversible way, increasing $W_1$ so that $W_1\n= W_{\\text{er}}$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non mean-field behaviour of critical wetting transition for short-range\n  forces: Critical wetting transition for short-range forces in three dimensions\n($d=3$) is reinvestigated by means of Monte Carlo simulation. Using anisotropic\nfinite size scaling approach, as well as approaches that do not rely on finite\nsize scaling, we show that the critical wetting transition shows clear\ndeviation from mean-field behaviour. We estimate that the effective critical\nexponent $\\nu_{\\|}^{\\textrm{eff}}=1.76\\pm 0.08$ for $J/kT=0.35$ and\n$\\nu_{\\|}^{\\textrm{eff}}=1.85\\pm 0.07$ for $J/kT=0.25$. These values are in\naccord with predictions of Parry {\\it et al.} [Phys. Rev. Lett. {\\bf 100},\n136105 (2008)]. We also point out that the anisotropic finite size scaling\napproach in $d=3$ requires additional modification in order to reach full\nconsistency of simulational results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamic Mean-Field Glass Model with Reversible Mode Coupling and Trivial\n  Hamiltonian: Often the current mode coupling theory (MCT) of glass transitions is compared\nwith mean field theories. We explore this possible correspondence. After\nshowing a simple-minded derivation of MCT with some difficulties we give a\nconcise account of our toy model developed to gain more insight into MCT. We\nthen reduce this toy model by adiabatically eliminating rapidly varying\nvelocity-like variables to obtain a Fokker-Planck equation for the slowly\nvarying density-like variables where diffusion matrix can be singular. This\ngives a room for nonergodic stationary solutions of the above equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Separation of spin and charge in the continuum Schr\u00f6dinger equation: I describe here the attempt to introduce spin-charge separation in\nSchrodinger equation. The construction we present here gives a decomposed\nSchrodinger spinor that has one problem: Its absolute value can only have value\nbetween 0 and ${1}{2}$. The problem we solve is to expand and generalize this\nconstruction so that one can have a Schrodinger spinor with absolute value that\nare arbitrary non-negative numbers. It may be that one has to introduce a set\nof different decompositions to cover all nonnegative values, that is to\nintroduce patches over $\\mathbb{R}_{+}^{3}$ so that in each patch one has a\ndifferent representation. It seems that the decomposition has a direct relation\nto so called entangled states that have been discussed very much in connection\nof e.g. quantum computing, and we would like to find this relation and discuss\nit in detail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling laws for diffusion on (trans)fractal scale-free networks: Fractal (or transfractal) features are common in real-life networks and are\nknown to influence the dynamic processes taking place in the network itself.\nHere we consider a class of scale-free deterministic networks, called\n$(u,v)$-flowers, whose topological properties can be controlled by tuning the\nparameters $u$ and $v$; in particular, for $u>1$, they are fractals endowed\nwith a fractal dimension $d_f$, while for $u=1$, they are transfractal endowed\nwith a transfractal dimension $\\tilde{d}_f$. In this work we investigate\ndynamic processes (i.e., random walks) and topological properties (i.e., the\nLaplacian spectrum) and we show that, under proper conditions, the same\nscalings (ruled by the related dimensions), emerge for both fractal and\ntransfractal.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic relations at the coupling boundary in adaptive resolution\n  simulations for open systems: The adaptive resolution simulation (AdResS) technique couples regions with\ndifferent molecular resolutions and allows the exchange of molecules between\ndifferent regions in an adaptive fashion. The latest development of the\ntechnique allows to abruptly couple the atomistically resolved region with a\nregion of non-interacting point-like particles. The abrupt set-up was derived\nhaving in mind the idea of the atomistically resolved region as an open system\nembedded in a large reservoir at a given macroscopic state. In this work,\nstarting from the idea of open system, we derive thermodynamic relations for\nAdResS which justify conceptually and numerically the claim of AdResS as a\ntechnique for simulating open systems. In particular, we derive the relation\nbetween the chemical potential of the AdResS set-up and that of its reference\nfully atomistic simulation. The implication of this result is that the grand\npotential of AdResS can be explicitly written and thus, from a statistical\nmechanics point of view, the atomistically resolved region of AdResS can be\nidentified with a well defined open system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimal inference strategies and their implications for the linear noise\n  approximation: We study the information loss of a class of inference strategies that is\nsolely based on time averaging. For an array of independent binary sensors\n(e.g., receptors, single electron transistors) measuring a weak random signal\n(e.g., ligand concentration, gate voltage) this information loss is up to 0.5\nbit per measurement irrespective of the number of sensors. We derive a\ncondition related to the local detailed balance relation that determines\nwhether or not such a loss of information occurs. Specifically, if the free\nenergy difference arising from the signal is symmetrically distributed among\nthe forward and backward rates, time integration mechanisms will capture the\nfull information about the signal. As an implication, for the linear noise\napproximation, we can identify the same loss of information, arising from its\ninherent simplification of the dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Special flow model for passive particle transport considering internal\n  noise: We have generalized the semi-analytic approach of special flow to the\ndescription of flows of passive particles taking into account internal noise.\nThe model is represented by a series of recurrence relations. The recurrence\nrelations are constructed by numerically solving the Langevin equations in the\npresence of a random force, for an ensemble of passive particles during\ntransport through a secluded cell. This approach allows us to estimate the\ntransit time dependence near stagnation points for fluid elements carried by\nthe flow. Such estimates are obtained for the most important types of\nstagnation points. It is shown that macroscopic transport of an ensemble of\nparticles through such a lattice is possible only when internal noise is taken\ninto account. For Gaussian and non-Gaussian noise at low intensity the transit\ntime has one peak, which is a consequence of the existence of vortices of one\nstagnation point. Increase of noise intensity leads to slowing down of particle\ntransport.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite-size scaling as a way to probe near-criticality in natural swarms: Collective behaviour in biological systems is often accompanied by strong\ncorrelations. The question has therefore arisen of whether correlation is\namplified by the vicinity to some critical point in the parameters space.\nBiological systems, though, are typically quite far from the thermodynamic\nlimit, so that the value of the control parameter at which correlation and\nsusceptibility peak depend on size. Hence, a system would need to readjust its\ncontrol parameter according to its size in order to be maximally correlated.\nThis readjustment, though, has never been observed experimentally. By gathering\nthree-dimensional data on swarms of midges in the field we find that swarms\ntune their control parameter and size so as to maintain a scaling behaviour of\nthe correlation function. As a consequence, correlation length and\nsusceptibility scale with the system's size and swarms exhibit a near-maximal\ndegree of correlation at all sizes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Numerical Study on the Evolution of Portfolio Rules: Is CAPM Fit for\n  Nasdaq?: In this paper we test computationally the performance of CAPM in an\nevolutionary setting. In particular we study the stability of wealth\ndistribution in a financial market where some traders invest as prescribed by\nCAPM and others behave according to different portfolio rules. Our study is\nmotivated by recent analytical results that show that, whenever a logarithmic\nutility maximiser enters the market, traders who either ``believe'' in CAPM and\nuse it as a rule of thumb for their portfolio decisions, or are endowed with\ngenuine mean-variance preferences, vanish in the long run. Our analysis\nprovides further insights and extends these results. We simulate a sequence of\ntrades in a financial market and: first, we address the issue of how long is\nthe long run in different parametric settings; second, we study the effect of\nheterogeneous savings behaviour on asymptotic wealth shares. We find that CAPM\nis particularly ``unfit'' for highly risky environments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Anomalous cooling and heating - the Mpemba effect and its inverse: Under certain conditions, it takes a shorter time to cool a hot system than\nto cool the same system initiated at a lower temperature. This phenomenon - the\n\"Mpemba Effect\" - is well known in water, and has recently been observed in\nother systems as well. However, there is no single generic mechanism that\nexplains this counter-intuitive behavior. Using the theoretical framework of\nnon-equilibrium thermodynamics, we present a widely applicable mechanism for\nthis effect, derive a sufficient condition for its appearance in Markovian\ndynamics, and predict an inverse Mpemba effect in heating: under proper\nconditions, a cold system can heat up faster than the same system initiated at\na higher temperature. Our results suggest that it should be possible to observe\nthe Mpemba effect and its inverse in a variety of systems, where they have\nnever been demonstrated before.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the microscopic foundation of thermodynamics and kinetics. Current\n  status and prospects: A comparative analysis of two concepts aimed at microscopic substantiation of\nthermodynamics and kinetics has been performed. The first concept is based on\nthe idea of microscopic reversibility of the dynamics of a system of particles,\nwhile macroscopic irreversibility is of statistical origin. The second concept\nis based on the idea of the initial microscopic irreversibility of dynamics,\none of the mechanisms of which is the relativistic retardation of interactions\nbetween particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spectral properties of three-dimensional Anderson model: The three-dimensional Anderson model represents a paradigmatic model to\nunderstand the Anderson localization transition. In this work we first review\nsome key results obtained for this model in the past 50 years, and then study\nits properties from the perspective of modern numerical approaches. Our main\nfocus is on the quantitative comparison between the level sensitivity\nstatistics and the level statistics. While the former studies the sensitivity\nof Hamiltonian eigenlevels upon inserting a magnetic flux, the latter studies\nthe properties of unperturbed eigenlevels. We define two versions of\ndimensionless conductance, the first corresponding to the width of the level\ncurvature distribution relative to the mean level spacing, and the second\ncorresponding to the ratio of the Heisenberg and the Thouless time obtained\nfrom the spectral form factor. We show that both conductances look remarkably\nsimilar around the localization transition, in particular, they predict a\nnearly identical critical point consistent with other measures of the\ntransition. We then study some further properties of those quantities: for\nlevel curvatures, we discuss particular similarities and differences between\nthe width of the level curvature distribution and the characteristic energy\nstudied by Edwards and Thouless in their pioneering work [J. Phys. C. 5, 807\n(1972)]. In the context of the spectral form factor, we show that at the\ncritical point it enters a broad time-independent regime, in which its value is\nconsistent with the level compressibility obtained from the level variance.\nFinally, we test the scaling solution of the average level spacing ratio in the\ncrossover regime using the cost function minimization approach introduced in\n[Phys. Rev. B. 102, 064207 (2020)]. We find that the extracted transition point\nand the scaling coefficient agree with those from the literature to high\nnumerical accuracy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dichotomous acceleration process in one dimension: Position fluctuations: We study the motion of a one-dimensional particle which reverses its\ndirection of acceleration stochastically. We focus on two contrasting\nscenarios, where the waiting-times between two consecutive acceleration\nreversals are drawn from (i) an exponential distribution and (ii) a power-law\ndistribution $\\rho(\\tau)\\sim \\tau^{-(1+\\alpha)}$. We compute the mean, variance\nand short-time distribution of the position $x(t)$ using a trajectory-based\napproach. We show that, while for the exponential waiting-time, $\\langle\nx^2(t)\\rangle\\sim t^3$ at long times, for the power-law case, a non-trivial\nalgebraic growth $\\langle x^2(t)\\rangle \\sim t^{2\\phi(\\alpha)}$ emerges, where\n$\\phi(\\alpha)=2$, $(5-\\alpha)/2,$ and $3/2$ for $\\alpha<1,~1<\\alpha\\leq 2$ and\n$\\alpha>2$, respectively.\n  Interestingly, we find that the long-time position distribution in case (ii)\nis a function of the scaled variable $x/t^{\\phi(\\alpha)}$ with an\n$\\alpha$-dependent scaling function, which has qualitatively very different\nshapes for $\\alpha<1$ and $\\alpha>1$. In contrast, for case (i), the typical\nlong-time fluctuations of position are Gaussian.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Latent Heat Calculation of the 3D q=3, 4, and 5 Potts models by Tensor\n  Product Variational Approach: Three-dimensional (3D) $q$-state Potts models ($q$=3, 4, and 5) are studied\nby the tensor product variational approach (TPVA), which is a recently\ndeveloped variational method for 3D classical lattice models. The variational\nstate is given by a two-dimensional (2D) product of local factors, and is\nimproved by way of self-consistent calculations assisted by the corner transfer\nmatrix renormalization group (CTMRG). It should be noted that no a priori\ncondition is imposed for the local factor. Transition temperatures and latent\nheats are calculated from the observations of thermodynamic functions in both\nordered and disordered phases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact analytic multi-quanta states of the Davydov Dimer: The Davydov model describes amide I energy transfer in proteins without\ndispersion or dissipation. In spite of five decades of study, there are few\nexact analytical results, especially for the discrete version of this model.\nHere we develop two methods to determine the exact orthonormal, multi-quanta,\neigenstates of the Davydov dimer. The first method involves the integration of\na system of ordinary differential equations and the second method applies\npurely algebraic methods to this problem. We obtain the general expression of\nthe eigenvalues for any number of quanta and also, as examples, apply the\nmethods to the detailed derivation of the eigenvectors for one to four quanta,\nplus a brief example in the case of $n=5$ and $n=6$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of Fluctuating Bose-Einstein Condensates: We present a generalized Gross-Pitaevskii equation that describes also the\ndissipative dynamics of a trapped partially Bose condensed gas. It takes the\nform of a complex nonlinear Schr\\\"odinger equation with noise. We consider an\napproximation to this Langevin field equation that preserves the correct\nequilibrium for both the condensed and the noncondensed parts of the gas. We\nthen use this formalism to describe the reversible formation of a\none-dimensional Bose condensate, and compare with recent experiments. In\naddition, we determine the frequencies and the damping of collective modes in\nthis case.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Voter Model with Time dependent Flip-rates: We introduce time variation in the flip-rates of the Voter Model. This type\nof generalisation is relevant to models of ageing in language change, allowing\nthe representation of changes in speakers' learning rates over their lifetime\nand may be applied to any other similar model in which interaction rates at the\nmicroscopic level change with time. The mean time taken to reach consensus\nvaries in a nontrivial way with the rate of change of the flip-rates, varying\nbetween bounds given by the mean consensus times for static homogeneous (the\noriginal Voter Model) and static heterogeneous flip-rates. By considering the\nmean time between interactions for each agent, we derive excellent estimates of\nthe mean consensus times and exit probabilities for any time scale of flip-rate\nvariation. The scaling of consensus times with population size on complex\nnetworks is correctly predicted, and is as would be expected for the ordinary\nvoter model. Heterogeneity in the initial distribution of opinions has a strong\neffect, considerably reducing the mean time to consensus, while increasing the\nprobability of survival of the opinion which initially occupies the most slowly\nchanging agents. The mean times to reach consensus for different states are\nvery different. An opinion originally held by the fastest changing agents has a\nsmaller chance to succeed, and takes much longer to do so than an evenly\ndistributed opinion.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Rayleigh-Benard convection in a hard disk system: We do a generic study of the behavior of a hard disk system under the action\nof a thermal gradient in presence of an uniform gravity field. We observe the\nconduction-convection transition and measure the main system observables and\nfields as the thermal current, global pressure, velocity field, temperature\nfield,... We can highlight two of the main results of this overall work: (1)\nfor large enough thermal gradients and a given gravity, we show that the\nhydrodynamic fields (density, temperature and velocity) have a natural scaling\nform with the gradient. And (2) we show that local equilibrium holds if the\nmechanical pressure and the thermodynamic one are not equal, that is, the\nStoke's assumption does not hold in this case. Moreover we observe that the\nbest fit to the data is obtained when the bulk viscosity depends on the\nmechanical pressure.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On Dynamics and Optimal Number of Replicas in Parallel Tempering\n  Simulations: We study the dynamics of parallel tempering simulations, also known as the\nreplica exchange technique, which has become the method of choice for\nsimulation of proteins and other complex systems. Recent results for the\noptimal choice of the control parameter discretization allow a treatment\nindependent of the system in question. Analyzing mean first passage times\nacross control parameter space, we find an expression for the optimal number of\nreplicas in simulations covering a given temperature range. Our results suggest\na particular protocol to optimize the number of replicas in actual simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Note on Phase Space Contraction and Entropy Production in Thermostatted\n  Hamiltonian Systems: The phase space contraction and the entropy production rates of Hamiltonian\nsystems in an external field, thermostatted to obtain a stationary state are\nconsidered. While for stationary states with a constant kinetic energy the two\nrates are formally equal for all numbers of particles N, for stationary states\nwith constant total (kinetic and potential) energy this only obtains for large\nN. However, in both cases a large number of particles is required to obtain\nequality with the entropy production rate of Irreversible Thermodynamics.\nConsequences of this for the positivity of the transport coefficients and for\nthe Onsager relations are discussed. Numerical results are presented for the\nspecial case of the Lorentz gas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Engineering statistical transmutation of identical quantum particles: A fundamental pillar of quantum mechanics concerns indistinguishable quantum\nparticles. In three dimensions they may be classified into fermions or bosons,\nhaving, respectively, antisymmetric or symmetric wave functions under particle\nexchange. One of numerous manifestations of this quantum statistics is the\ntendency of fermions (bosons) to anti-bunch (bunch). In a two-particle\nscattering experiment with two possible outgoing channels, the probability of\nthe two particles to arrive each at a different terminal is enhanced (with\nrespect to classical particles) for fermions, and reduced for bosons. Here we\nshow that by entangling the particles with an external degree of freedom, we\ncan engineer quantum statistical transmutation, e.g. causing fermions to bunch.\nOur analysis may have consequences on the observed fractional statistics of\nanyons, including non-Abelian statistics, with serious implications on quantum\ncomputing operations in the presence of external degrees of freedom.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A mechanism to synchronize fluctuations in scale free networks using\n  growth models: In this paper we study the steady state of the fluctuations of the surface\nfor a model of surface growth with relaxation to any of its lower nearest\nneighbors (SRAM) [F. Family, J. Phys. A {\\bf 19}, L441 (1986)] in scale free\nnetworks. It is known that for Euclidean lattices this model belongs to the\nsame universality class as the model of surface relaxation to the minimum\n(SRM). For the SRM model, it was found that for scale free networks with\nbroadness $\\lambda$, the steady state of the fluctuations scales with the\nsystem size $N$ as a constant for $\\lambda \\geq 3$ and has a logarithmic\ndivergence for $\\lambda < 3$ [Pastore y Piontti {\\it et al.}, Phys. Rev. E {\\bf\n76}, 046117 (2007)]. It was also shown [La Rocca {\\it et al.}, Phys. Rev. E\n{\\bf 77}, 046120 (2008)] that this logarithmic divergence is due to non-linear\nterms that arises from the topology of the network. In this paper we show that\nthe fluctuations for the SRAM model scale as in the SRM model. We also derive\nanalytically the evolution equation for this model for any kind of complex\ngraphs and find that, as in the SRM model, non-linear terms appear due to the\nheterogeneity and the lack of symmetry of the network. In spite of that, the\ntwo models have the same scaling, but the SRM model is more efficient to\nsynchronize systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Sub-Gaussian and subexponential fluctuation-response inequalities: Sub-Gaussian and subexponential distributions are introduced and applied to\nstudy the fluctuation-response relation out of equilibrium. A bound on the\ndifference in expected values of an arbitrary sub-Gaussian or subexponential\nphysical quantity is established in terms of its sub-Gaussian or subexponential\nnorm. Based on that, we find that the entropy difference between two states is\nbounded by the energy fluctuation in these states. Moreover, we obtain\ngeneralized versions of the thermodynamic uncertainty relation in different\nregimes. Operational issues concerning the application of our results in an\nexperimental setting are also addressed, and nonasymptotic bounds on the errors\nincurred by using the sample mean instead of the expected value in our\nfluctuation-response inequalities are derived.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Noise-intensity fluctuation in Langevin model and its higher-order\n  Fokker-Planck equation: In this paper, we investigate a Langevin model subjected to stochastic\nintensity noise (SIN), which incorporates temporal fluctuations in\nnoise-intensity. We derive a higher-order Fokker-Planck equation (HFPE) of the\nsystem, taking into account the effect of SIN by the adiabatic elimination\ntechnique. Stationary distributions of the HFPE are calculated by using the\nperturbation expansion. We investigate the effect of SIN in three cases: (a)\nparabolic and quartic bistable potentials with additive noise, (b) a quartic\npotential with multiplicative noise, and (c) a stochastic gene expression\nmodel. We find that the existence of noise intensity fluctuations induces an\nintriguing phenomenon of a bimodal-to-trimodal transition in probability\ndistributions. These results are validated with Monte Carlo simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram of the restricted solid-on-solid model coupled to the\n  Ising model: We study the phase transitions of a restricted solid-on-solid model coupled\nto an Ising model, which can be derived from the coupled XY-Ising model. There\nare two kinds of phase transition lines. One is a Ising transition line and the\nother is surface roughening transition line. The latter is a KT transition line\nfrom the viewpoint of the XY model. Using a microcanonical Monte Carlo\ntechnique, we obtain a very accurate two dimensional phase diagram. The two\ntransition lines are separate in all the parameter space we study. This result\nis strong evidence that the fully frustrated XY model orders by two separate\ntransitions and that roughening and reconstruction transitions of crystal\nsurfaces occur separately.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal entanglement and correlation measure in two-dimensional\n  conformal field theories: We calculate the amount of entanglement shared by two intervals in the ground\nstate of a (1+1)-dimensional conformal field theory (CFT), quantified by an\nentanglement measure $\\mathcal{E}$ based on the computable cross norm (CCNR)\ncriterion. Unlike negativity or mutual information, we show that $\\mathcal{E}$\nhas a universal expression even for two disjoint intervals, which depends only\non the geometry, the central charge c, and the thermal partition function of\nthe CFT. We prove this universal expression in the replica approach, where the\nRiemann surface for calculating $\\mathcal{E}$ at each order n is always a torus\ntopologically. By analytic continuation, result of n=1/2 gives the value of\n$\\mathcal{E}$. Furthermore, the results of other values of n also yield\nmeaningful conclusions: The n=1 result gives a general formula for the\ntwo-interval purity, which enables us to calculate the Renyi-2 N-partite\ninformation for N<=4 intervals; while the $n=\\infty$ result bounds the\ncorrelation function of the two intervals. We verify our findings numerically\nin the spin-1/2 XXZ chain, whose ground state is described by the Luttinger\nliquid.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling in a Nonconservative Earthquake Model of Self-Organised\n  Criticality: We numerically investigate the Olami-Feder-Christensen model for earthquakes\nin order to characterise its scaling behaviour. We show that ordinary finite\nsize scaling in the model is violated due to global, system wide events.\nNevertheless we find that subsystems of linear dimension small compared to the\noverall system size obey finite (subsystem) size scaling, with universal\ncritical coefficients, for the earthquake events localised within the\nsubsystem. We provide evidence, moreover, that large earthquakes responsible\nfor breaking finite size scaling are initiated predominantly near the boundary.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-Newtonian Poiseuille flow of a gas in a pipe: The Bhatnagar-Gross-Krook kinetic model of the Boltzmann equation is solved\nfor the steady cylindrical Poiseuille flow fed by a constant gravity field. The\nsolution is obtained as a perturbation expansion in powers of the field\n(through fourth order) and for a general class of repulsive potentials. The\nresults, which are hardly sensitive to the interaction potential, suggest that\nthe expansion is only asymptotic. A critical comparison with the profiles\npredicted by the Navier-Stokes equations shows that the latter fail over\ndistances comparable to the mean free path. In particular, while the\nNavier-Stokes description predicts a monotonically decreasing temperature as\none moves apart from the cylinder axis, the kinetic theory description shows\nthat the temperature has a local minimum at the axis and reaches a maximum\nvalue at a distance of the order of the mean free path. Within that distance,\nthe radial heat flows from the colder to the hotter points, in contrast to what\nis expected from the Fourier law. Furthermore, a longitudinal component of the\nheat flux exists in the absence of gradients along the longitudinal direction.\nNon-Newtonian effects, such as a non uniform hydrostatic pressure and normal\nstress differences, are also present.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relevant spontaneous magnetization relations for the triangular and the\n  cubic lattice Ising model: The spontaneous magnetization relations for the 2D triangular and the 3D\ncubic lattices of the Ising model are derived by a new tractable easily\ncalculable mathematical method. The result obtained for the triangular lattice\nis compared with the already available result to test and investigate the\nrelevance the new mathematical method. From this comparison, it is seen that\nthe agreement of our result is almost the same or almost equivalent to the\npreviously obtained exact result. The new approach is, then, applied to the\nlong-standing 3D cubic lattice, and the corresponding expression for the\nspontaneous magnetism is derived. The relation obtained is compared with the\nalready existing numerical results for the 3D lattice. The essence of the\nmethod going to used in this paper is based on exploiting the main\ncharacteristic of the order parameter of a second order phase transition which\nprovides a more direct physical insight into the calculation of the spontaneous\nmagnetization of the Ising model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Percolation on correlated networks: We reconsider the problem of percolation on an equilibrium random network\nwith degree-degree correlations between nearest-neighboring vertices focusing\non critical singularities at a percolation threshold. We obtain criteria for\ndegree-degree correlations to be irrelevant for critical singularities. We\npresent examples of networks in which assortative and disassortative mixing\nleads to unusual percolation properties and new critical exponents.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact solution of the geometrically frustrated spin-1/2 Ising-Heisenberg\n  model on the triangulated Kagome (triangles-in-triangles) lattice: The geometric frustration of the spin-1/2 Ising-Heisenberg model on the\ntriangulated Kagome (triangles-in-triangles) lattice is investigated within the\nframework of an exact analytical method based on the generalized star-triangle\nmapping transformation. Ground-state and finite-temperature phase diagrams are\nobtained along with other exact results for the partition function, Helmholtz\nfree energy, internal energy, entropy, and specific heat, by establishing a\nprecise mapping relationship to the corresponding spin-1/2 Ising model on the\nKagome lattice. It is shown that the residual entropy of the disordered spin\nliquid phase is for the quantum Ising-Heisenberg model significantly lower than\nfor its semi-classical Ising limit (S_0/N_T k_B = 0.2806 and 0.4752,\nrespectively), which implies that quantum fluctuations partially lift a\nmacroscopic degeneracy of the ground-state manifold in the frustrated regime.\nThe investigated model system has an obvious relevance to a series of polymeric\ncoordination compounds Cu_9X_2(cpa)_6 (X=F, Cl, Br and cpa=carboxypentonic\nacid) for which we made a theoretical prediction about the temperature\ndependence of zero-field specific heat.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "How to Quantify and Avoid Finite Size Effects in Computational Studies\n  of Crystal Nucleation: The Case of Heterogeneous Ice Nucleation: Computational studies of crystal nucleation can be impacted by finite size\neffects, primarily due to unphysical interactions between crystalline nuclei\nand their periodic images. It is, however, not always feasible to\nsystematically investigate the sensitivity of nucleation kinetics and mechanism\nto system size due to large computational costs of nucleation studies. Here, we\nuse jumpy forward flux sampling to accurately compute the rates of\nheterogeneous ice nucleation in the vicinity of square-shaped model\nstructureless ice nucleating particles (INPs) of different sizes, and identify\nthree distinct regimes for the dependence of rate on the INP dimension, $L$.\nFor small INPs, the rate is a strong function of $L$ due to artificial spanning\nof critical nuclei across the periodic boundary. Intermediate-sized INPs,\nhowever, give rise to the emergence of non-spanning 'proximal` nuclei that are\nclose enough to their periodic images to fully structure the intermediary\nliquid. While such proximity can facilitate nucleation, its effect is offset by\nthe higher density of the intermediary liquid, leading to artificially small\nnucleation rates overall. The critical nuclei formed at large INPs are neither\nspanning nor proximal. Yet, the rate is a weak function of $L$, with its\nlogarithm scaling linearly with $1/L$. The key heuristic emerging from these\nobservations is that finite size effects will be minimal if critical nuclei are\nneither spanning nor proximal, and if the intermediary liquid has a region that\nis structurally indistinguishable from the supercooled liquid under the same\nconditions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Equilibrium statistics of an inelastically bouncing ball, subject to\n  gravity and a random force: We consider a particle moving on the half line $x>0$ and subject to a\nconstant force in the $-x$ direction plus a delta-correlated random force. At\n$x=0$ the particle is reflected inelastically. The velocities just after and\nbefore reflection satisfy $v_f=-rv_i$, where $r$ is the coefficient of\nrestitution. This simple model is of interest in connection with studies of\ndriven granular matter in a gravitational field. With an exact analytical\napproach and simulations we study the steady state distribution function\n$P(x,v)$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Screening of classical Casimir forces by electrolytes in semi-infinite\n  geometries: We study the electrostatic Casimir effect and related phenomena in\nequilibrium statistical mechanics of classical (non-quantum) charged fluids.\nThe prototype model consists of two identical dielectric slabs in empty space\n(the pure Casimir effect) or in the presence of an electrolyte between the\nslabs. In the latter case, it is generally believed that the long-ranged\nCasimir force due to thermal fluctuations in the slabs is screened by the\nelectrolyte into some residual short-ranged force. The screening mechanism is\nbased on a \"separation hypothesis\": thermal fluctuations of the electrostatic\nfield in the slabs can be treated separately from the pure image effects of the\n\"inert\" slabs on the electrolyte particles. In this paper, by using a\nphenomenological approach under certain conditions, the separation hypothesis\nis shown to be valid. The phenomenology is tested on a microscopic model in\nwhich the conducting slabs and the electrolyte are modelled by the symmetric\nCoulomb gases of point-like charges with different particle fugacities. The\nmodel is solved in the high-temperature Debye-H\\\"uckel limit (in two and three\ndimensions) and at the free fermion point of the Thirring representation of the\ntwo-dimensional Coulomb gas. The Debye-H\\\"uckel theory of a Coulomb gas between\ndielectric walls is also solved.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Q-factor: A measure of competition between the topper and the average in\n  percolation and in SOC: We define the $Q$-factor in the percolation problem as the quotient of the\nsize of the largest cluster and the average size of all clusters. As the\noccupation probability $p$ is increased, the $Q$-factor for the system size $L$\ngrows systematically to its maximum value $Q_{max}(L)$ at a specific value\n$p_{max}(L)$ and then gradually decays. Our numerical study of site percolation\nproblems on the square, triangular and the simple cubic lattices exhibits that\nthe asymptotic values of $p_{max}$ though close, are distinctly different from\nthe corresponding percolation thresholds of these lattices. We have also shown\nusing the scaling analysis that at $p_{max}$ the value of $Q_{max}(L)$ diverges\nas $L^d$ ($d$ denoting the dimension of the lattice) as the system size\napproaches to their asymptotic limit. We have further extended this idea to the\nnon-equilibrium systems such as the sandpile model of self-organized\ncriticality. Here, the $Q(\\rho,L)$-factor is the quotient of the size of the\nlargest avalanche and the cumulative average of the sizes of all the\navalanches; $\\rho$ being the drop density of the driving mechanism. This study\nhas been prompted by some observations in Sociophysics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on ``Renormalization-group picture of the Lifshitz critical\n  behavior'': We show that the recent renormalization-group analysis of Lifshitz critical\nbehavior presented by Leite [Phys. Rev. B {\\bf 67}, 104415 (2003)] suffers from\na number of severe deficiencies. In particular, we show that his approach does\nnot give an ultraviolet finite renormalized theory, is plagued by\ninconsistencies, misses the existence of a nontrivial anisotropy exponent\n$\\theta\\ne 1/2$, and therefore yields incorrect hyperscaling relations. His\n$\\epsilon$-expansion results to order $\\epsilon^2$ for the critical exponents\nof $m$-axial Lifshitz points are incorrect both in the anisotropic ($0<m<d$)\nand the isotropic cases ($m=d$). The inherent inconsistencies and the lack of a\nsound basis of the approach makes its results unacceptable even if they are\ninterpreted in the sense of approximations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding and Controlling Regime Switching in Molecular Diffusion: Diffusion can be strongly affected by ballistic flights (long jumps) as well\nas long-lived sticking trajectories (long sticks). Using statistical inference\ntechniques in the spirit of Granger causality, we investigate the appearance of\nlong jumps and sticks in molecular-dynamics simulations of diffusion in a\nprototype system, a benzene molecule on a graphite substrate. We find that\nspecific fluctuations in certain, but not all, internal degrees of freedom of\nthe molecule can be linked to either long jumps or sticks. Furthermore, by\nchanging the prevalence of these predictors with an outside influence, the\ndiffusion of the molecule can be controlled. The approach presented in this\nproof of concept study is very generic, and can be applied to larger and more\ncomplex molecules. Additionally, the predictor variables can be chosen in a\ngeneral way so as to be accessible in experiments, making the method feasible\nfor control of diffusion in applications. Our results also demonstrate that\ndata-mining techniques can be used to investigate the phase-space structure of\nhigh-dimensional nonlinear dynamical systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diffusion in a logarithmic potential: scaling and selection in the\n  approach to equilibrium: The equation which describes a particle diffusing in a logarithmic potential\narises in diverse physical problems such as momentum diffusion of atoms in\noptical traps, condensation processes, and denaturation of DNA molecules. A\ndetailed study of the approach of such systems to equilibrium via a scaling\nanalysis is carried out, revealing three surprising features: (i) the solution\nis given by two distinct scaling forms, corresponding to a diffusive (x ~\n\\sqrt{t}) and a subdiffusive (x >> \\sqrt{t}) length scales, respectively; (ii)\nthe scaling exponents and scaling functions corresponding to both regimes are\nselected by the initial condition; and (iii) this dependence on the initial\ncondition manifests a \"phase transition\" from a regime in which the scaling\nsolution depends on the initial condition to a regime in which it is\nindependent of it. The selection mechanism which is found has many similarities\nto the marginal stability mechanism which has been widely studied in the\ncontext of fronts propagating into unstable states. The general scaling forms\nare presented and their practical and theoretical applications are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Analytical theory of mesoscopic Bose-Einstein condensation in ideal gas: We find universal structure and scaling of BEC statistics and thermodynamics\nfor mesoscopic canonical-ensemble ideal gas in a trap for any parameters,\nincluding critical region. We identify universal constraint-cut-off mechanism\nthat makes BEC fluctuations non-Gaussian and is responsible for critical\nphenomena. Main result is analytical solution to problem of critical phenomena.\nIt is derived by calculating universal distribution of noncondensate occupation\n(Landau function) and then universal functions for physical quantities. We find\nasymptotics of that solution and its approximations which describe universal\nstructure of critical region in terms of parabolic cylinder or confluent\nhypergeometric functions. Results for order parameter, statistics, and\nthermodynamics match known asymptotics outside critical region. We suggest\n2-level and 3-level trap models and find their exact solutions in terms of\ncut-off negative binomial distribution (that tends to cut-off gamma\ndistribution in continuous limit) and confluent hypergeometric distribution. We\nintroduce a regular refinement scheme for condensate statistics approximations\non the basis of infrared universality of higher-order cumulants and method of\nsuperposition and show how to model BEC statistics in actual traps. We find\nthat 3-level trap model with matching the first 4 or 5 cumulants is enough to\nyield remarkably accurate results in whole critical region. We derive exact\nmultinomial expansion for noncondensate occupation distribution and find its\nhigh temperature asymptotics (Poisson distribution). We demonstrate that\ncritical exponents and a few known terms of Taylor expansion of universal\nfunctions, calculated previously from fitting finite-size simulations within\nrenorm-group theory, can be obtained from presented solutions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Coulomb-Higgs phase transition of three-dimensional lattice\n  Abelian-Higgs gauge models with noncompact gauge variables and gauge fixing: We study the critical behavior of three-dimensional (3D) lattice\nAbelian-Higgs (AH) gauge models with noncompact gauge variables and\nmulticomponent complex scalar fields, along the transition line between the\nCoulomb and Higgs phases. Previous works that focused on gauge-invariant\ncorrelations provided evidence that, for a sufficiently large number of scalar\ncomponents, these transitions are continuous and associated with the stable\ncharged fixed point of the renormalization-group flow of the 3D AH field theory\n(scalar electrodynamics), in which charged scalar matter is minimally coupled\nwith an electromagnetic field. Here we extend these studies by considering\ngauge-dependent correlations of the gauge and matter fields, in the presence of\ntwo different gauge fixings, the Lorenz and the axial gauge fixing. Our results\nfor N=25 are definitely consistent with the predictions of the AH field theory\nand therefore provide additional evidence for the characterization of the 3D AH\ntransitions along the Coulomb-Higgs line as charged transitions in the AH\nfield-theory universality class. Moreover, our results give additional insights\non the role of the gauge fixing at charged transitions. In particular, we show\nthat scalar correlations are critical only if a hard Lorenz gauge fixing is\nimposed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Asymptotic front behavior in an $A+B\\rightarrow 2A$ reaction under\n  subdiffusion: We discuss the front propagation in the $A+B\\rightarrow 2A$ reaction under\nsubdiffusion which is described by continuous time random walks with a\nheavy-tailed power law waiting time probability density function. Using a\ncrossover argument, we discuss the two scaling regimes of the front\npropagation: an intermediate asymptotic regime given by the front solution of\nthe corresponding continuous equation, and the final asymptotics, which is\nfluctuation-dominated and therefore lays out of reach of the continuous scheme.\nWe moreover show that the continuous reaction subdiffusion equation indeed\npossesses a front solution that decelerates and becomes narrow in the course of\ntime. This continuous description breaks down for larger times when the front\ngets atomically sharp. We show that the velocity of such fronts decays in time\nfaster than in the continuous regime.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Consistent Lattice Boltzmann Method: The problem of energy conservation in the lattice Boltzmann method is solved.\nA novel model with energy conservation is derived from Boltzmann's kinetic\ntheory. It is demonstrated that the full thermo-hydrodynamics pertinent to the\nBoltzmann equation is recovered in the domain where variations around the\nreference temperature are small. Simulation of a Poiseuille micro-flow is\nperformed in a quantitative agreement with exact results for low and moderate\nKnudsen numbers. The new model extends in a natural way the standard lattice\nBoltzmann method to a thermodynamically consistent simulation tool for\nnearly-incompressible flows.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kondo signature in heat transfer via a local two-state system: We study the Kondo effect in heat transport via a local two-state system.\nThis system is described by the spin-boson Hamiltonian with Ohmic dissipation,\nwhich can be mapped onto the Kondo model with anisotropic exchange coupling. We\ncalculate thermal conductance by the Monte Carlo method based on the exact\nformula. Thermal conductance has a scaling form \\kappa = (k_B^2 T_K/\\hbar)\nf(\\alpha,T/T_K ), where T_K and \\alpha indicate the Kondo temperature and\ndimensionless coupling strength, respectively. Temperature dependence of\nconductance is classified by the Kondo temperature as \\kappa\\propto (T/T_K )^3\nfor T\\ll T_K and \\kappa\\propto (k_B T / \\hbar\\omega_c)^{2\\alpha-1} for T\\gg\nT_K. Similarities to the Kondo signature in electric transport are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Microcanonical Thermostatistical Investigation of the Blackbody\n  Radiation: In this work is presented the microcanonical analysis of the blackbody\nradiation. In our model the electromagnetic radiation is confined in an\nisolated container with volume V in which the radiation can not escape,\nconserving this way its total energy, E. Our goal is to precise the meaning of\nthe Thermodynamic Limit for this system as well as the description of the\nnonextensive effects of the generalized Planck formula for the spectral density\nof energy. Our analysis shows the sterility of the intents of finding\nnonnextensive effects in normal conditions: the traditional description of the\nblackbody radiation is extraordinarily exact. The nonextensive effects only\nappear in the low temperature region, however, they are extremely difficult to\ndetect.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Informational and Causal Architecture of Continuous-time Renewal and\n  Hidden Semi-Markov Processes: We introduce the minimal maximally predictive models ({\\epsilon}-machines) of\nprocesses generated by certain hidden semi-Markov models. Their causal states\nare either hybrid discrete-continuous or continuous random variables and\ncausal-state transitions are described by partial differential equations.\nClosed-form expressions are given for statistical complexities, excess\nentropies, and differential information anatomy rates. We present a complete\nanalysis of the {\\epsilon}-machines of continuous-time renewal processes and,\nthen, extend this to processes generated by unifilar hidden semi-Markov models\nand semi-Markov models. Our information-theoretic analysis leads to new\nexpressions for the entropy rate and the rates of related information measures\nfor these very general continuous-time process classes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Negative Specific Heat in a Quasi-2D Generalized Vorticity Model: Negative specific heat is a dramatic phenomenon where processes decrease in\ntemperature when adding energy. It has been observed in gravo-thermal collapse\nof globular clusters. We now report finding this phenomenon in bundles of\nnearly parallel, periodic, single-sign generalized vortex filaments in the\nelectron magnetohydrodynamic (EMH) model for the unbounded plane under strong\nmagnetic confinement. We derive the specific heat using a steepest descent\nmethod and a mean field property. Our derivations show that as temperature\nincreases, the overall size of the system increases exponentially and the\nenergy drops. The implication of negative specific heat is a runaway reaction,\nresulting in a collapsing inner core surrounded by an expanding halo of\nfilaments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Analytical approximation for reaction-diffusion processes in rough pores: The concept of an active zone in Laplacian transport is used to obtain an\nanalytical approximation for the reactive effectiveness of a pore with an\narbitrary rough geometry. We show that this approximation is in very good\nagreement with direct numerical simulations performed over a wide range of\ndiffusion-reaction conditions (i.e., with or without screening effects). In\nparticular, we find that in most practical situations, the effect of roughness\nis to increase the intrinsic reaction rate by a geometrical factor, namely, the\nratio between the real and the apparent surface area. We show that this simple\ngeometrical information is sufficient to characterize the reactive\neffectiveness of a pore, in spite of the complex morphological features it\nmight possess.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Out-of-equilibrium scaling behavior arising during round-trip protocols\n  across a quantum first-order transition: We investigate the nonequilibrium dynamics of quantum spin chains during a\nround-trip protocol that slowly drives the system across a quantum first-order\ntransition. Out-of-equilibrium scaling behaviors \\`a la Kibble-Zurek for the\nsingle-passage protocol across the first-order transition have been previously\ndetermined. Here, we show that such scaling relations persist when the driving\nprotocol is inverted and the transition is approached again by a\nfar-from-equilibrium state. This results in a quasi-universality of the scaling\nfunctions, which keep some dependence on the details of the protocol at the\ninversion time. We explicitly determine such quasi-universal scaling functions\nby employing an effective two-level description of the many-body system near\nthe transition. We discuss the validity of this approximation and how this\nrelates to the observed scaling regime. Although our results apply to generic\nsystems, we focus on the prototypical example of a $1D$ transverse field Ising\nmodel in the ferromagnetic regime, which we drive across the first-order\ntransitions through a time-dependent longitudinal field.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact Solution of a Vertex Model with Unlimited Number of States Per\n  Bond: The exact solution is obtained for the eigenvalues and eigenvectors of the\nrow-to-row transfer matrix of a two-dimensional vertex model with unlimited\nnumber of states per bond. This model is a classical counterpart of a quantum\nspin chain with an unlimited value of spin. This quantum chain is studied using\ngeneral predictions of conformal field theory. The long-distance behaviour of\nsome ground-state correlation functions is derived from a finite-size analysis\nof the gapless excitations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the velocity distributions of the one-dimensional inelastic gas: We consider the single-particle velocity distribution of a one-dimensional\nfluid of inelastic particles. Both the freely evolving (cooling) system and the\nnon-equilibrium stationary state obtained in the presence of random forcing are\ninvestigated, and special emphasis is paid to the small inelasticity limit. The\nresults are obtained from analytical arguments applied to the Boltzmann\nequation along with three complementary numerical techniques (Molecular\nDynamics, Direct Monte Carlo Simulation Methods and iterative solutions of\nintegro-differential kinetic equations). For the freely cooling fluid, we\ninvestigate in detail the scaling properties of the bimodal velocity\ndistribution emerging close to elasticity and calculate the scaling function\nassociated with the distribution function. In the heated steady state, we find\nthat, depending on the inelasticity, the distribution function may display two\ndifferent stretched exponential tails at large velocities. The inelasticity\ndependence of the crossover velocity is determined and it is found that the\nextremely high velocity tail may not be observable at ``experimentally\nrelevant'' inelasticities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Characterization of relaxation processes in interacting vortex matter\n  through a time-dependent correlation length: Vortex lines in type-II superconductors display complicated relaxation\nprocesses due to the intricate competition between their mutual repulsive\ninteractions and pinning to attractive point or extended defects. We perform\nextensive Monte Carlo simulations for an interacting elastic line model with\neither point-like or columnar pinning centers. From measurements of the space-\nand time-dependent height-height correlation function for lateral flux line\nfluctuations, we extract a characteristic correlation length that we use to\ninvestigate different non-equilibrium relaxation regimes. The specific time\ndependence of this correlation length for different disorder configurations\ndisplays characteristic features that provide a novel diagnostic tool to\ndistinguish between point-like pinning centers and extended columnar defects.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "High-precision Estimate of the Critical Exponents for the Directed Ising\n  Universality Class: With extensive Monte Carlo simulations, we present high-precision estimates\nof the critical exponents of branching annihilating random walks with two\noffspring, a prototypical model of the directed Ising universality class in one\ndimension. To estimate the exponents accurately, we propose a systematic method\nto find corrections to scaling whose leading behavior is supposed to take the\nform $t^{-\\chi}$ in the long-time limit at the critical point. Our study shows\nthat $\\chi\\approx 0.75$ for the number of particles in defect simulations and\n$\\chi \\approx 0.5$ for other measured quantities, which should be compared with\nthe widely used value of $\\chi = 1$. Using $\\chi$ so obtained, we analyze the\neffective exponents to find that $\\beta/\\nu_\\| = 0.2872(2)$, $z = 1.7415(5)$,\n$\\eta = 0.0000(2)$, and accordingly, $\\beta /\\nu_\\perp = 0.5000(6)$. Our\nnumerical results for $\\beta/\\nu_\\|$ and $z$ are clearly different from the\nconjectured rational numbers $\\beta/\\nu_\\| = \\frac{2}{7} \\approx 0.2857$, $z =\n\\frac{7}{4}= 1.75$ by Jensen [Phys. Rev. E, {\\bf 50}, 3623 (1994)]. Our result\nfor $\\beta/\\nu_\\perp$, however, is consistent with $\\frac{1}{2}$, which is\nbelieved to be exact.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetics of Vapor-Solid Phase Transitions: Structure, growth and\n  mechanism: Kinetics of separation between the low and high density phases in a single\ncomponent Lennard-Jones model has been studied via molecular dynamics\nsimulations, at a very low temperature, in the space dimension $d=2$. For\ndensities close to the vapor (low density) branch of the coexistence curve,\ndisconnected clusters of the high density phase exhibit ballistic motion, the\nkinetic energy distribution of the clusters being closely Maxwellian. Starting\nfrom nearly circular shapes, at the time of nucleation, these clusters grow via\nsticky collisions, gaining filament-like nonequilibrium structure at late\ntimes, with a very low fractal dimensionality. The origin of the latter is\nshown to lie in the low mobility of the constituent particles, in the\ncorresponding cluster reference frame, due to the (quasi-long-range)\ncrystalline order. Standard self-similarity in the domain pattern, typically\nobserved in kinetics of phase transitions, is found to be absent in this growth\nprocess. This invalidates the common method, that provides a growth law same as\nin immiscible solid mixtures, of quantifying growth. An appropriate alternative\napproach, involving the fractality in the structure, quantifies the growth of\nthe characteristic \"length\" to be a power-law with time, the exponent being\nsurprisingly high. The observed growth law has been derived via a\nnonequilibrium kinetic theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Time evolution of entanglement entropy after quenches in two-dimensional\n  free fermion systems: a dimensional reduction treatment: We study the time evolution of the R\\'enyi entanglement entropies following a\nquantum quench in a two-dimensional (2D) free-fermion system. By employing\ndimensional reduction, we effectively transform the 2D problem into decoupled\nchains, a technique applicable when the system exhibits translational\ninvariance in one direction. Various initial configurations are examined,\nrevealing that the behavior of entanglement entropies can often be explained by\nadapting the one-dimensional quasiparticle picture. However, intriguingly, for\nspecific initial states the entanglement entropy saturates to a finite value\nwithout the reduced density matrix converging to a stationary state. We discuss\nthe conditions necessary for a stationary state to exist and delve into the\nnecessary modifications to the quasiparticle picture when such a state is\nabsent.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Far-from-equilibrium growth of thin films in a temperature gradient: The irreversible growth of thin films under far-from-equilibrium conditions\nis studied in $(2+1)-$dimensional strip geometries. Across one of the\ntransverse directions, a temperature gradient is applied by thermal baths at\nfixed temperatures between $T_1$ and $T_2$, where $T_1<T_c^{hom}<T_2$ and\n$T_c^{hom}=0.69(1)$ is the critical temperature of the system in contact with\nan homogeneous thermal bath. By using standard finite-size scaling methods, we\ncharacterized a continuous order-disorder phase transition driven by the\nthermal bath gradient with critical temperature $T_c=0.84(2)$ and critical\nexponents $\\nu=1.53(6)$, $\\gamma=2.54(11)$, and $\\beta=0.26(8)$, which belong\nto a different universality class from that of films grown in an homogeneous\nbath. Furthermore, the effects of the temperature gradient are analyzed by\nmeans of a bond model that captures the growth dynamics. The interplay of\ngeometry and thermal bath asymmetries leads to growth bond flux asymmetries and\nthe onset of transverse ordering effects that explain qualitatively the shift\nin the critical temperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Aging and fluctuation-dissipation ratio for the diluted Ising Model: We consider the out-of-equilibrium, purely relaxational dynamics of a weakly\ndiluted Ising model in the aging regime at criticality. We derive at first\norder in a $\\sqrt{\\epsilon}$ expansion the two-time response and correlation\nfunctions for vanishing momenta. The long-time limit of the critical\nfluctuation-dissipation ratio is computed at the same order in perturbation\ntheory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling, Multiscaling, and Nontrivial Exponents in Inelastic Collision\n  Processes: We investigate velocity statistics of homogeneous inelastic gases using the\nBoltzmann equation. Employing an approximate uniform collision rate, we obtain\nanalytic results valid in arbitrary dimension. In the freely evolving case, the\nvelocity distribution is characterized by an algebraic large velocity tail,\nP(v,t) ~ v^{-sigma}. The exponent sigma(d,epsilon), a nontrivial root of an\nintegral equation, varies continuously with the spatial dimension, d, and the\ndissipation coefficient, epsilon. Although the velocity distribution follows a\nscaling form, its moments exhibit multiscaling asymptotic behavior.\nFurthermore, the velocity autocorrelation function decays algebraically with\ntime, A(t)=<v(0)v(t)> ~ t^{-alpha}, with a non-universal dissipation-dependent\nexponent alpha=1/epsilon. In the forced case, the steady state Fourier\ntransform is obtained via a cumulant expansion. Even in this case, velocity\ncorrelations develop and the velocity distribution is non-Maxwellian.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Large-n conditional facedness m_n of 3D Poisson-Voronoi cells: We consider the three-dimensional Poisson-Voronoi tessellation and study the\naverage facedness m_n of a cell known to neighbor an n-faced cell. Whereas\nAboav's law states that m_n=A+B/n, theoretical arguments indicate an asymptotic\nexpansion m_n = 8 + k_1 n^{-1/6} +.... Recent new Monte Carlo data due to Lazar\net al., based on a very large data set, now clearly rule out Aboav's law. In\nthis work we determine the numerical value of k_1 and compare the expansion to\nthe Monte Carlo data. The calculation of k_1 involves an auxiliary planar\ncellular structure composed of circular arcs, that we will call the\nPoisson-Moebius diagram. It is a special case of more general Moebius diagrams\n(or multiplicatively weighted power diagrams) and is of interest for its own\nsake. We obtain exact results for the total edge length per unit area, which is\na prerequisite for the coefficient k_1, and a few other quantities in this\ndiagram.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "1/f Noise and Extreme Value Statistics: We study the finite-size scaling of the roughness of signals in systems\ndisplaying Gaussian 1/f power spectra. It is found that one of the extreme\nvalue distributions (Gumbel distribution) emerges as the scaling function when\nthe boundary conditions are periodic. We provide a realistic example of\nperiodic 1/f noise, and demonstrate by simulations that the Gumbel distribution\nis a good approximation for the case of nonperiodic boundary conditions as\nwell. Experiments on voltage fluctuations in GaAs films are analyzed and\nexcellent agreement is found with the theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Magnetic properties of exactly solvable doubly decorated\n  Ising-Heisenberg planar models: Applying the decoration-iteration procedure, we introduce a class of exactly\nsolvable doubly decorated planar models consisting both of the Ising- and\nHeisenberg-type atoms. Exact solutions for the ground state, phase diagrams and\nbasic physical quantities are derived and discussed. The detailed analysis of\nthe relevant quantities suggests the existence of an interesting quantum\nantiferromagnetic phase in the system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Monte Carlo Study of the Axial Next-Nearest-Neighbor Ising Model: The equilibrium phase behavior of microphase-forming substances and models is\nnotoriously difficult to obtain because of the extended metastability of the\nmodulated phases. We develop a simulation method based on thermodynamic\nintegration that avoids this problem and with which we obtain the phase diagram\nof the canonical three-dimensional axial next-nearest-neighbor Ising model. The\nequilibrium devil's staircase, magnetization, and susceptibility are obtained.\nThe critical exponents confirm the XY nature of the disorder-modulated phase\ntransition beyond the Lifshitz point. The results identify the limitations of\nvarious approximation schemes used to analyze this basic microphase-forming\nmodel.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the Truncation of Systems with Non-Summable Interactions: In this note we consider long range $q$-states Potts models on\n$\\mathbf{Z}^d$, $d\\geq 2$. For various families of non-summable ferromagnetic\npair potentials $\\phi(x)\\geq 0$, we show that there exists, for all inverse\ntemperature $\\beta>0$, an integer $N$ such that the truncated model, in which\nall interactions between spins at distance larger than $N$ are suppressed, has\nat least $q$ distinct infinite-volume Gibbs states. This holds, in particular,\nfor all potentials whose asymptotic behaviour is of the type $\\phi(x)\\sim\n\\|x\\|^{-\\alpha}$, $0\\leq\\alpha\\leq d$. These results are obtained using simple\npercolation arguments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Emergence of oscillations in fixed energy sandpile models on complex\n  networks: Fixed-energy sandpile (FES) models, introduced to understand the\nself-organized criticality, show a continuous phase transition between\nabsorbing and active phases. In this work, we study the dynamics of the\ndeterministic FES models on random networks. We observe that close to absorbing\ntransition the density of active nodes oscillates and nodes topple in\nsynchrony. The deterministic toppling rule and the small-world property of\nrandom networks lead to the emergence of sustained oscillations. The amplitude\nof oscillations becomes larger with increasing the value of network randomness.\nThe bifurcation diagram for the density of active nodes is obtained. We use the\nactivity-dependent rewiring rule and show that the interplay between the\nnetwork structure and the FES dynamics leads to the emergence of a bistable\nregion with a first-order transition between the absorbing and active states.\nFurthermore during the rewiring, the ordered activation pattern of the nodes is\nbroken, which causes the oscillations to disappear.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Self-Organized Criticality in the Olami-Feder-Christensen model: A system is in a self-organized critical state if the distribution of some\nmeasured events (avalanche sizes, for instance) obeys a power law for as many\ndecades as it is possible to calculate or measure. The finite-size scaling of\nthis distribution function with the lattice size is usually enough to assume\nthat any cut off will disappear as the lattice size goes to infinity. This\napproach, however, can lead to misleading conclusions. In this work we analyze\nthe behavior of the branching rate sigma of the events to establish whether a\nsystem is in a critical state. We apply this method to the\nOlami-Feder-Christensen model to obtain evidences that, in contrast to previous\nresults, the model is critical in the conservative regime only.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Geometrical interpretation of fluctuating hydrodynamics in diffusive\n  systems: We discuss geometric formulations of hydrodynamic limits in diffusive\nsystems. Specifically, we describe a geometrical construction in the space of\ndensity profiles --- the Wasserstein geometry --- which allows the\ndeterministic hydrodynamic evolution of the systems to be related to steepest\ndescent of the free energy, and show how this formulation can be related to\nmost probable paths of mesoscopic dissipative systems. The geometric viewpoint\nis also linked to fluctuating hydrodynamics of these systems via a saddle point\nargument.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Interface growth in two dimensions: A Loewner-equation approach: The problem of Laplacian growth in two dimensions is considered within the\nLoewner-equation framework. Initially the problem of fingered growth recently\ndiscussed by Gubiec and Szymczak [T. Gubiec and P. Szymczak, Phys. Rev. E 77,\n041602 (2008)] is revisited and a new exact solution for a three-finger\nconfiguration is reported. Then a general class of growth models for an\ninterface growing in the upper-half plane is introduced and the corresponding\nLoewner equation for the problem is derived. Several examples are given\nincluding interfaces with one or more tips as well as multiple growing\ninterfaces. A generalization of our interface growth model in terms of\n``Loewner domains,'' where the growth rule is specified by a time evolving\nmeasure, is briefly discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Slow relaxation, dynamic transitions and extreme value statistics in\n  disordered systems: We show that the dynamics of simple disordered models, like the directed Trap\nModel and the Random Energy Model, takes place at a coexistence point between\nactive and inactive dynamical phases. We relate the presence of a dynamic phase\ntransition in these models to the extreme value statistics of the associated\nrandom energy landscape.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Conductance in diffusive quasi-one-dimensional periodic waveguides: a\n  semiclassical and random matrix study: We study quantum transport properties of finite periodic\nquasi-one-dimensional waveguides whose classical dynamics is diffusive. The\nsystem we consider is a scattering configuration, composed of a finite periodic\nchain of $L$ identical (classically chaotic and finite-horizon) unit cells,\nwhich is connected to semi-infinite plane leads at its extremes. Particles\ninside the cavity are free and only interact with the boundaries through\nelastic collisions; this means waves are described by the Helmholtz equation\nwith Dirichlet boundary conditions on the waveguide walls. The equivalent to\nthe disorder ensemble is an energy ensemble, defined over a classically small\nrange but many mean level spacings wide. The number of propagative channels in\nthe leads is $N$. We have studied the (adimensional) Landauer conductance $g$\nas a function of $L$ and $N$ in the cosine-shaped waveguide and by means of our\nRMT periodic chain model. We have found that $<g(L)>$ exhibit two regimes.\nFirst, for chains of length $L\\lesssim\\sqrt{N}$ the dynamics is diffusive just\nlike in the disordered wire in the metallic regime, where the typic ohmic\nscaling is observed with $<g(L)> = N/(L+1)$. In this regime, the conductance\ndistribution is a Gaussian with small variance but which grows linearly with\n$L$. Then, in longer systems with $L\\gg\\sqrt{N}$, the periodic nature becomes\nrelevant and the conductance reaches a constant asymptotic value\n$<g(L\\to\\infty)> \\sim <N_B>$. The variance approaches a constant value\n$\\sim\\sqrt{N}$ as $L\\to\\infty$. Comparing the conductance using the unitary and\northogonal circular ensembles we observed that a weak localization effect is\npresent in the two regimes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hidden Criticality of Counterion Condensation Near a Charged Cylinder: We study the condensation transition of counterions on a charged cylinder via\nMonte Carlo simulations. Varying the cylinder radius systematically in relation\nto the system size, we find that all counterions are bound to the cylinder and\nthe heat capacity shows a drop at a finite Manning parameter. A finite-size\nscaling analysis is carried out to confirm the criticality of the complete\ncondensation transition, yielding the same critical exponents with the Manning\ntransition. We show that the existence of the complete condensation is\nessential to explain how the condensation nature alters from continuous to\ndiscontinuous transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Colossal Brownian yet non-Gaussian diffusion induced by nonequilibrium\n  noise: We report on novel Brownian, yet non-Gaussian diffusion, in which the mean\nsquare displacement of the particle grows linearly with time, the probability\ndensity for the particle spreading is Gaussian-like, however, the probability\ndensity for its position increments possesses an exponentially decaying tail.\nIn contrast to recent works in this area, this behaviour is not a consequence\nof either a space or time-dependent diffusivity, but is induced by external\nnon-thermal noise acting on the particle dwelling in a periodic potential. The\nexistence of the exponential tail in the increment statistics leads to colossal\nenhancement of diffusion, surpassing drastically the previously researched\nsituation known under the label of \"giant\" diffusion. This colossal diffusion\nenhancement crucially impacts a broad spectrum of the first arrival problems,\nsuch as diffusion limited reactions governing transport in living cells.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Improved upper and lower energy bounds for antiferromagnetic Heisenberg\n  spin systems: Large spin systems as given by magnetic macromolecules or two-dimensional\nspin arrays rule out an exact diagonalization of the Hamiltonian. Nevertheless,\nit is possible to derive upper and lower bounds of the minimal energies, i.e.\nthe smallest energies for a given total spin S.\n  The energy bounds are derived under additional assumptions on the topology of\nthe coupling between the spins. The upper bound follows from \"n-cyclicity\",\nwhich roughly means that the graph of interactions can be wrapped round a ring\nwith n vertices. The lower bound improves earlier results and follows from\n\"n-homogeneity\", i.e. from the assumption that the set of spins can be\ndecomposed into n subsets where the interactions inside and between spins of\ndifferent subsets fulfill certain homogeneity conditions. Many Heisenberg spin\nsystems comply with both concepts such that both bounds are available.\n  By investigating small systems which can be numerically diagonalized we find\nthat the upper bounds are considerably closer to the true minimal energies than\nthe lower ones.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Triangular arbitrage as an interaction among foreign exchange rates: We first show that there are in fact triangular arbitrage opportunities in\nthe spot foreign exchange markets, analyzing the time dependence of the\nyen-dollar rate, the dollar-euro rate and the yen-euro rate. Next, we propose a\nmodel of foreign exchange rates with an interaction. The model includes effects\nof triangular arbitrage transactions as an interaction among three rates. The\nmodel explains the actual data of the multiple foreign exchange rates well.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Triangle Distribution and Equation of State for Classical Rigid Disks: The triangle distribution function f^(3) for three mutual nearest neighbors\nin the plane describes basic aspects of short-range order and statistical\nthermodynamics in two-dimensional many-particle systems. This paper examines\nprospects for constructing a self-consistent calculation for the rigid-disk\nsystem f^(3). We present several identities obeyed by f^(3). A rudimentary\nclosure suggested by scaled-particle theory is introduced. In conjunction with\nthree of the basic identities, this closure leads to a unique f^(3) over the\nentire density range. The pressure equation of state exhibits qualitatively\ncorrect behavior in both the low density and the close-packed limits, but no\nintervening phase transition appears. We discuss extensions to improved disk\nclosures, and to the three-dimensional rigid sphere system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Metal - non-metal transition and the second critical point in expanded\n  metals: Based on the non-relativistic Coulomb model within which the matter is a\nsystem of interacting electrons and nuclei, using the quantum field theory and\nlinear response theory methods, opportunity for the existence of the second\ncritical point in expanded metals, which is directly related to the\nmetal--nonmetal transition, predicted by Landau and Zeldovitch, is\ntheoretically justified. It is shown that the matter at the second critical\npoint is in the state of true dielectric with zero static conductivity. The\nresults obtained are in agreement with recent experiments for expanded metals.\nThe existence of the second critical point is caused by the initial\nmulti-component nature of the matter consisting of electrons and nuclei and the\nlong-range character of the Coulomb interaction. (Accepted in PTEP)",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A simple one-dimensional model of heat conduction which obeys Fourier's\n  law: We present the computer simulation results of a chain of hard point particles\nwith alternating masses interacting on its extremes with two thermal baths at\ndifferent temperatures. We found that the system obeys Fourier's law at the\nthermodynamic limit. This result is against the actual belief that one\ndimensional systems with momentum conservative dynamics and nonzero pressure\nhave infinite thermal conductivity. It seems that thermal resistivity occurs in\nour system due to a cooperative behavior in which light particles tend to\nabsorb much more energy than the heavier ones.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random graphs containing arbitrary distributions of subgraphs: Traditional random graph models of networks generate networks that are\nlocally tree-like, meaning that all local neighborhoods take the form of trees.\nIn this respect such models are highly unrealistic, most real networks having\nstrongly non-tree-like neighborhoods that contain short loops, cliques, or\nother biconnected subgraphs. In this paper we propose and analyze a new class\nof random graph models that incorporates general subgraphs, allowing for\nnon-tree-like neighborhoods while still remaining solvable for many fundamental\nnetwork properties. Among other things we give solutions for the size of the\ngiant component, the position of the phase transition at which the giant\ncomponent appears, and percolation properties for both site and bond\npercolation on networks generated by the model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Crossing the bottleneck of rain formation: The demixing of a binary fluid mixture, under gravity, is a two stage\nprocess. Initially droplets, or in general aggregates, grow diffusively by\ncollecting supersaturation from the bulk phase. Subsequently, when the droplets\nhave grown to a size, where their Peclet number is of order unity, buoyancy\nsubstantially enhances droplet growth. The dynamics approaches a finite-time\nsingularity where the droplets are removed from the system by precipitation.\nThe two growth regimes are separated by a bottleneck of minimal droplet growth.\nHere, we present a low-dimensional model addressing the time span required to\ncross the bottleneck, and we hence determine the time, \\Delta t, from initial\ndroplet growth to rainfall. Our prediction faithfully captures the dependence\nof \\Delta t on the ramp rate of the droplet volume fraction, \\xi, the droplet\nnumber density, the interfacial tension, the mass diffusion coefficient, the\nmass density contrast of the coexisting phases, and the viscosity of the bulk\nphase. The agreement of observations and the prediction is demonstrated for\nmethanol/hexane and isobutoxyethanol/water mixtures where we determined \\Delta\nt for a vast range of ramp rates, \\xi, and temperatures. The very good\nquantitative agreement demonstrates that it is sufficient for binary mixtures\nto consider (i) droplet growth by diffusive accretion that relaxes\nsupersaturation, and (ii) growth by collisions of sedimenting droplets. An\nanalytical solution of the resulting model provides a quantitative description\nof the dependence of \\Delta t on the ramp rate and the material constants.\nExtensions of the model that will admit a quantitative prediction of \\Delta t\nin other settings are addressed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Two-bath model for activated surface diffusion of interacting adsorbates: The diffusion and low vibrational motions of adsorbates on surfaces can be\nwell described by a purely stochastic model, the so-called interacting single\nadsorbate model, for low-moderate coverages (\\theta \\lesssim 0.12). Within this\nmodel, the effects of thermal surface phonons and adsorbate-adsorbate\ncollisions are accounted for by two uncorrelated noise functions which arise in\na natural way from a two-bath model based on a generalization of the one-bath\nCaldeira-Leggett Hamiltonian. As an illustration, the model is applied to the\ndiffusion of Na atoms on a Cu(001) surface with different coverages.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Glassy dynamics: effective temperatures and intermittencies from a\n  two-state model: We show the existence of intermittent dynamics in one of the simplest model\nof a glassy system: the two-state model, which has been used to explain the\norigin of the violation of the fluctuation-dissipation theorem. The dynamics is\nanalyzed through a Langevin equation for the evolution of the state of the\nsystem through its energy landscape. The results obtained concerning the\nviolation factor and the non-Gaussian nature of the fluctuations are in good\nqualitative agreement with experiments measuring the effective temperature and\nthe voltage fluctuations in gels and in polymer glasses. The method proposed\ncan be useful to study the dynamics of other slow relaxation systems in which\nnon-Gaussian fluctuations have been observed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Minimal knotted polygons in cubic lattices: An implementation of BFACF-style algorithms on knotted polygons in the simple\ncubic, face centered cubic and body centered cubic lattice is used to estimate\nthe statistics and writhe of minimal length knotted polygons in each of the\nlattices. Data are collected and analysed on minimal length knotted polygons,\ntheir entropy, and their lattice curvature and writhe.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comment on `Monte Carlo simulation study of the two-stage percolation\n  transition in enhanced binary trees': The enhanced binary tree (EBT) is a nontransitive graph which has two\npercolation thresholds $p_{c1}$ and $p_{c2}$ with $p_{c1}<p_{c2}$. Our Monte\nCarlo study implies that the second threshold $p_{c2}$ is significantly lower\nthan a recent claim by Nogawa and Hasegawa (J. Phys. A: Math. Theor. {\\bf 42}\n(2009) 145001). This means that $p_{c2}$ for the EBT does not obey the duality\nrelation for the thresholds of dual graphs $p_{c2}+\\overline{p}_{c1}=1$ which\nis a property of a transitive, nonamenable, planar graph with one end. As in\nregular hyperbolic lattices, this relation instead becomes an inequality\n$p_{c2}+\\overline{p}_{c1}<1$. We also find that the critical behavior is well\ndescribed by the scaling form previously found for regular hyperbolic lattices.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Most probable path of an active Brownian particle: In this study, we investigate the transition path of a free active Brownian\nparticle (ABP) on a two-dimensional plane between two given states. The\nextremum conditions for the most probable path connecting the two states are\nderived using the Onsager--Machlup integral and its variational principle. We\nprovide explicit solutions to these extremum conditions and demonstrate their\nnonuniqueness through an analogy with the pendulum equation indicating possible\nmultiple paths. The pendulum analogy is also employed to characterize the shape\nof the globally most probable path obtained by explicitly calculating the path\nprobability for multiple solutions. We comprehensively examine a translation\nprocess of an ABP to the front as a prototypical example. Interestingly, the\nnumerical and theoretical analyses reveal that the shape of the most probable\npath changes from an I to a U shape and to the $\\ell$ shape with an increase in\nthe transition process time. The Langevin simulation also confirms this shape\ntransition. We also discuss further method applications for evaluating a\ntransition path in rare events in active matter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Finite Temperature Treatment of Ultracold Atoms in a 1-D Optical\n  Lattice: We consider the effects of temperature upon the superfluid phase of\nultracold, weakly interacting bosons in a one dimensional optical lattice. We\nuse a finite temperature treatment of the Bose-Hubbard model based upon the\nHartree-Fock-Bogoliubov formalism, considering both a translationally invariant\nlattice and one with additional harmonic confinement. In both cases we observe\nan upward shift in the critical temperature for Bose condensation. For the case\nwith additional harmonic confinement, this is in contrast with results for the\nuniform gas.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Zero-temperature glass transition in two dimensions: The nature of the glass transition is theoretically understood in the\nmean-field limit of infinite spatial dimensions, but the problem remains\ntotally open in physical dimensions. Nontrivial finite-dimensional fluctuations\nare hard to control analytically, and experiments fail to provide conclusive\nevidence regarding the nature of the glass transition. Here, we use Monte Carlo\nsimulations that fully bypass the glassy slowdown, and access equilibrium\nstates in two-dimensional glass-forming liquids at low enough temperatures to\ndirectly probe the transition. We find that the liquid state terminates at a\nthermodynamic glass transition at zero temperature, which is associated with an\nentropy crisis and a diverging static correlation length.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Visibility Graphs of Correlated Time Series Violate the Barthelemy's\n  Conjecture for Degree and Betweenness Centralities: The problem of betweenness centrality remains a fundamental unsolved problem\nin complex networks. After a pioneering work by Barthelemy, it has been\nwell-accepted that the maximal betweenness-degree ($b$-$k$) exponent for\nscale-free (SF) networks is $\\eta_{\\text{max}}=2$, belonging to scale-free\ntrees (SFTs), based on which one concludes $\\delta\\ge\\frac{\\gamma+1}{2}$, where\n$\\gamma$ and $\\delta$ are the scaling exponents of the distribution functions\nof the degree and betweenness centrality, respectively. Here we present\nevidence for violation of this conjecture for SF visibility graphs (VGs). To\nthis end, we consider the VG of three models: two-dimensional (2D)\nBak-Tang-Weisenfeld (BTW) sandpile model, 1D fractional Brownian motion (FBM)\nand, 1D Levy walks, the two later cases are controlled by the Hurst exponent\n$H$ and step-index $\\alpha$, respectively. Specifically, for the BTW model and\nFBM with $H\\lesssim 0.5$, $\\eta$ is greater than $2$, and also\n$\\delta<\\frac{\\gamma+1}{2}$ for the BTW model, while Barthelemy's conjecture\nremains valid for the Levy process. We argue that this failure of Barthelemy's\nconjecture is due to large fluctuations in the scaling $b$-$k$ relation\nresulting in the violation of hyperscaling relation\n$\\eta=\\frac{\\gamma-1}{\\delta-1}$ and emergent anomalous behaviors for the BTW\nmodel and FBM. A super-universal behavior is found for the distribution\nfunction for a generalized degree function identical to the Barabasi-Albert\nnetwork model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Symmetry enriched phases of quantum circuits: Quantum circuits consisting of random unitary gates and subject to local\nmeasurements have been shown to undergo a phase transition, tuned by the rate\nof measurement, from a state with volume-law entanglement to an area-law state.\nFrom a broader perspective, these circuits generate a novel ensemble of quantum\nmany-body states at their output. In this paper, we characterize this ensemble\nand classify the phases that can be established as steady states. Symmetry\nplays a nonstandard role in that the physical symmetry imposed on the circuit\nelements does not on its own dictate the possible phases. Instead, it is\nextended by dynamical symmetries associated with this ensemble to form an\nenlarged symmetry. Thus, we predict phases that have no equilibrium counterpart\nand could not have been supported by the physical circuit symmetry alone. We\ngive the following examples. First, we classify the phases of a circuit\noperating on qubit chains with $\\mathbb{Z}_2$ symmetry. One striking\nprediction, corroborated with numerical simulation, is the existence of\ndistinct volume-law phases in one dimension, which nonetheless support true\nlong-range order. We furthermore argue that owing to the enlarged symmetry,\nthis system can in principle support a topological area-law phase, protected by\nthe combination of the circuit symmetry and a dynamical permutation symmetry.\nSecond, we consider a Gaussian fermionic circuit that only conserves fermion\nparity. Here the enlarged symmetry gives rise to a $U(1)$ critical phase at\nmoderate measurement rates and a Kosterlitz-Thouless transition to area-law\nphases. We comment on the interpretation of the different phases in terms of\nthe capacity to encode quantum information. We discuss close analogies to the\ntheory of spin glasses pioneered by Edwards and Anderson as well as crucial\ndifferences that stem from the quantum nature of the circuit ensemble.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistics of quantum transmission in one dimension with broad disorder: We study the statistics of quantum transmission through a one-dimensional\ndisordered system modelled by a sequence of independent scattering units. Each\nunit is characterized by its length and by its action, which is proportional to\nthe logarithm of the transmission probability through this unit. Unit actions\nand lengths are independent random variables, with a common distribution that\nis either narrow or broad. This investigation is motivated by results on\ndisordered systems with non-stationary random potentials whose fluctuations\ngrow with distance.\n  In the statistical ensemble at fixed total sample length four phases can be\ndistinguished, according to the values of the indices characterizing the\ndistribution of the unit actions and lengths. The sample action, which is\nproportional to the logarithm of the conductance across the sample, is found to\nobey a fluctuating scaling law, and therefore to be non-self-averaging, in\nthree of the four phases. According to the values of the two above mentioned\nindices, the sample action may typically grow less rapidly than linearly with\nthe sample length (underlocalization), more rapidly than linearly\n(superlocalization), or linearly but with non-trivial sample-to-sample\nfluctuations (fluctuating localization).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Competition between relaxation and external driving in the dissipative\n  Landau-Zener problem: We study Landau-Zener transitions in a dissipative environment by means of\nthe quasiadiabatic propagator path-integral scheme. It allows to obtain\nnumerically exact results for the full range of the involved parameters. We\ndiscover a nonmonotonic dependence of the Landau-Zener transition probability\non the sweep velocity which is explained in terms of a simple physical picture.\nThis feature results from a nontrivial competition between relaxation processes\nand the external sweep and is not captured by perturbative approaches. In\naddition to the Landau-Zener transition probability, we study the excitation\nsurvival probability and also provide a qualitative understanding of the\ninvolved competition of time scales.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Probabilistic analysis of the phase space flow for linear programming: The phase space flow of a dynamical system leading to the solution of Linear\nProgramming (LP) problems is explored as an example of complexity analysis in\nan analog computation framework. An ensemble of LP problems with $n$ variables\nand $m$ constraints ($n>m$), where all elements of the vectors and matrices are\nnormally distributed is studied. The convergence time of a flow to the fixed\npoint representing the optimal solution is computed. The cumulative\ndistribution ${\\cal F}^{(n,m)}(\\Delta)$ of the convergence rate $\\Delta_{min}$\nto this point is calculated analytically, in the asymptotic limit of large\n$(n,m)$, in the framework of Random Matrix Theory. In this limit ${\\cal\nF}^{(n,m)}(\\Delta)$ is found to be a scaling function, namely it is a function\nof one variable that is a combination of $n$, $m$ and $\\Delta$ rather then a\nfunction of these three variables separately. From numerical simulations also\nthe distribution of the computation times is calculated and found to be a\nscaling function as well.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Farey Graphs as Models for Complex Networks: Farey sequences of irreducible fractions between 0 and 1 can be related to\ngraph constructions known as Farey graphs. These graphs were first introduced\nby Matula and Kornerup in 1979 and further studied by Colbourn in 1982 and they\nhave many interesting properties: they are minimally 3-colorable, uniquely\nHamiltonian, maximally outerplanar and perfect. In this paper we introduce a\nsimple generation method for a Farey graph family, and we study analytically\nrelevant topological properties: order, size, degree distribution and\ncorrelation, clustering, transitivity, diameter and average distance. We show\nthat the graphs are a good model for networks associated with some complex\nsystems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Real-Time Wavelet-transform spectrum analyzer for the investigation of\n  1/f^\u03b1noise: A wavelet transform spectrum analyzer operating in real time within the\nfrequency range 3X10^(-5) - 1.3X10^5 Hz has been implemented on a low-cost\nDigital Signal Processing board operating at 150MHz. The wavelet decomposition\nof the signal allows to efficiently process non-stationary signals dominated by\nlarge amplitude events fairly well localized in time, thus providing the\nnatural tool to analyze processes characterized by 1/f^alpha power spectrum.\nThe parallel architecture of the DSP allows the real-time processing of the\nwavelet transform of the signal sampled at 0.3MHz. The bandwidth is about\n220dB, almost ten decades. The power spectrum of the scattered intensity is\nprocessed in real time from the mean square value of the wavelet coefficients\nwithin each frequency band. The performances of the spectrum analyzer have been\ninvestigated by performing Dynamic Light Scattering experiments on colloidal\nsuspensions and by comparing the measured spectra with the correlation\nfunctions data obtained with a traditional multi tau correlator. In order to\nasses the potentialities of the spectrum analyzer in the investigation of\nprocesses involving a wide range of timescales, we have performed measurements\non a model system where fluctuations in the scattered intensities are generated\nby the number fluctuations in a dilute colloidal suspension illuminated by a\nwide beam. This system is characterized by a power-law spectrum with exponent\n-3/2 in the scattered intensity fluctuations. The spectrum analyzer allows to\nrecover the power spectrum with a dynamic range spanning about 8 decades. The\nadvantages of wavelet analysis versus correlation analysis in the investigation\nof processes characterized by a wide distribution of time scales and\nnon-stationary processes are briefly discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Onsager coefficients of a finite-time Carnot cycle: We study a finite-time Carnot cycle of a weakly interacting gas which we can\nregard as a nearly ideal gas in the limit of $T_\\mathrm{h}-T_\\mathrm{c}\\to 0$\nwhere $T_\\mathrm{h}$ and $T_\\mathrm{c}$ are the temperatures of the hot and\ncold heat reservoirs, respectively. In this limit, we can assume that the cycle\nis working in the linear-response regime and can calculate the Onsager\ncoefficients of this cycle analytically using the elementary molecular kinetic\ntheory. We reveal that these Onsager coefficients satisfy the so-called\ntight-coupling condition and this fact explains why the efficiency at the\nmaximal power $\\eta_\\mathrm{max}$ of this cycle can attain the Curzon-Ahlborn\nefficiency from the viewpoint of the linear-response theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Overdamped dynamics of particles with repulsive power-law interactions: We investigate the dynamics of overdamped $D$-dimensional systems of\nparticles repulsively interacting through short-ranged power-law potentials,\n$V(r)\\sim r^{-\\lambda}\\;(\\lambda/D>1)$. We show that such systems obey a\nnon-linear diffusion equation, and that their stationary state extremizes a\n$q$-generalized nonadditive entropy. Here we focus on the dynamical evolution\nof these systems. Our first-principle $D=1,2$ many-body numerical simulations\n(based on Newton's law) confirm the predictions obtained from the\ntime-dependent solution of the non-linear diffusion equation, and show that the\none-particle space-distribution $P(x,t)$ appears to follow a compact-support\n$q$-Gaussian form, with $q=1-\\lambda/D$. We also calculate the velocity\ndistributions $P(v_x,t)$ and, interestingly enough, they follow the same\n$q$-Gaussian form (apparently precisely for $D=1$, and nearly so for $D=2$).\nThe satisfactory match between the continuum description and the molecular\ndynamics simulations in a more general, time-dependent, framework neatly\nconfirms the idea that the present dissipative systems indeed represent\nsuitable applications of the $q$-generalized thermostatistical theory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Superchemistry: dynamics of coupled atomic and molecular Bose-Einstein\n  condensates: We analyze the dynamics of a dilute, trapped Bose-condensed atomic gas\ncoupled to a diatomic molecular Bose gas by coherent Raman transitions. This\nsystem is shown to result in a new type of `superchemistry', in which giant\ncollective oscillations between the atomic and molecular gas can occur. The\nphenomenon is caused by stimulated emission of bosonic atoms or molecules into\ntheir condensate phases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Resilience of the topological phases to frustration: Recently it was highlighted that one-dimensional antiferromagnetic spin\nmodels with frustrated boundary conditions, i.e. periodic boundary conditions\nin a ring with an odd number of elements, may show very peculiar behavior.\nIndeed the presence of frustrated boundary conditions can destroy the local\nmagnetic orders presented by the models when different boundary conditions are\ntaken into account and induce novel phase transitions. Motivated by these\nresults, we analyze the effects of the introduction of frustrated boundary\nconditions on several models supporting (symmetry protected) topological\norders, and compare our results with the ones obtained with different boundary\nconditions. None of the topological order phases analyzed are altered by this\nchange. This observation leads naturally to the conjecture that topological\nphases of one-dimensional systems are in general not affected by topological\nfrustration.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The relaxation dynamics of a viscous silica melt: II The intermediate\n  scattering functions: We use molecular dynamics computer simulations to study the relaxation\ndynamics of a viscous melt of silica. The coherent and incoherent intermediate\nscattering functions, F_d(q,t) and F_s(q,t), show a crossover from a nearly\nexponential decay at high temperatures to a two-step relaxation at low\ntemperatures. Close to the critical temperature of mode-coupling theory (MCT)\nthe correlators obey in the alpha-regime the time temperature superposition\nprinciple (TTSP) and show a weak stretching. We determine the wave-vector\ndependence of the stretching parameter and find that for F_d(q,t) it shows\noscillations which are in phase with the static structure factor. The\ntemperature dependence of the alpha- relaxation times tau shows a crossover\nfrom an Arrhenius law at low temperatures to a weaker T-dependence at\nintermediate and high temperatures. At the latter temperatures the T-dependence\nis described well by a power law. We find that the exponent gamma of the power\nlaw for tau are significantly larger than the one for the diffusion constant.\nThe q-dependence of the alpha-relaxation times for F_d(q,t) oscillates around\ntau(q) for F_s(q,t) and is in phase with the structure factor. Due to the\nstrong vibrational component of the dynamics at short times the TTSP is not\nvalid in the beta- relaxation regime. We show, however, that in this time\nwindow the shape of the curves is independent of the correlator and is given by\na functional form proposed by MCT. We find that the value of the von Schweidler\nexponent and the value of gamma for finite q are compatible with the expression\nproposed by MCT. We conclude that, in the temperature regime where the\nrelaxation times are mesoscopic, many aspects of the dynamics of this strong\nglass former can be rationalized very well by MCT.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Attractive and repulsive polymer-mediated forces between scale-free\n  surfaces: We consider forces acting on objects immersed in, or attached to, long\nfluctuating polymers. The confinement of the polymer by the obstacles results\nin polymer-mediated forces that can be repulsive (due to loss of entropy) or\nattractive (if some or all surfaces are covered by adsorbing layers). The\nstrength and sign of the force in general depends on the detailed shape and\nadsorption properties of the obstacles, but assumes simple universal forms if\ncharacteristic length scales associated with the objects are large. This occurs\nfor scale-free shapes (such as a flat plate, straight wire, or cone), when the\npolymer is repelled by the obstacles, or is marginally attracted to it (close\nto the depinning transition where the absorption length is infinite). In such\ncases, the separation $h$ between obstacles is the only relevant macroscopic\nlength scale, and the polymer mediated force equals ${\\cal A} \\, k_{B}T/h$,\nwhere $T$ is temperature. The amplitude ${\\cal A}$ is akin to a critical\nexponent, depending only on geometry and universality of the polymer system.\nThe value of ${\\cal A}$, which we compute for simple geometries and ideal\npolymers, can be positive or negative. Remarkably, we find ${\\cal A}=0$ for\nideal polymers at the adsorption transition point, irrespective of shapes of\nthe obstacles, i.e. at this special point there is no polymer-mediated force\nbetween obstacles (scale-free or not).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cooperative Transport of Brownian Particles: We consider the collective motion of finite-sized, overdamped Brownian\nparticles (e.g., motor proteins) in a periodic potential. Simulations of our\nmodel have revealed a number of novel cooperative transport phenomena,\nincluding (i) the reversal of direction of the net current as the particle\ndensity is increased and (ii) a very strong and complex dependence of the\naverage velocity on both the size and the average distance of the particles.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On controlling simple dynamics by a disagreement function: We introduce a formula for the disagreement function which is used to control\na recently proposed dynamics of the Ising spin system. This leads to four\ndifferent phases of the Ising spin chain in a zero temperature. One of these\nphases is doubly degenerated (anti- and ferromagnetic states are equally\nprobable). On the borders between the phases two types of transitions are\nobserved: infinite degeneration and instability lines. The relaxation of the\nsystem depends strongly on the phase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistics of the work done by splitting a one-dimensional\n  quasi-condensate: Motivated by experiments on splitting one-dimensional quasi-condensates, we\nstudy the statistics of the work done by a quantum quench in a bosonic system.\nWe discuss the general features of the probability distribution of the work and\nfocus on its behaviour at the lowest energy threshold, which develops an edge\nsingularity. A formal connection between this probability distribution and the\ncritical Casimir effect in thin classical films shows that certain features of\nthe edge singularity are universal as the post-quench gap tends to zero. Our\nresults are quantitatively illustrated by an exact calculation for\nnon-interacting bosonic systems. The effects of finite system size,\ndimensionality, and non-zero initial temperature are discussed in detail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Domain-wall structure of a classical Heisenberg ferromagnet on a Mobius\n  strip: We study theoretically the structure of domain walls in ferromagnetic states\non Mobius strips. A two-dimensional classical Heisenberg ferromagnet with\nsingle-site anisotropy is treated within a mean-field approximation by taking\ninto account the boundary condition to realize the Mobius geometry. It is found\nthat two types of domain walls can be formed, namely, parallel or perpendicular\nto the circumference, and that the relative stability of these domain walls is\nsensitive to the change in temperature and an applied magnetic field. The\nmagnetization has a discontinuity as a function of temperature and the external\nfield.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Legendre transform structure and extremal properties of the relative\n  Fisher information: Variational extremization of the relative Fisher information (RFI, hereafter)\nis performed. Reciprocity relations, akin to those of thermodynamics are\nderived, employing the extremal results of the RFI expressed in terms of\nprobability amplitudes. A time independent Schr\\\"{o}dinger-like equation\n(Schr\\\"{o}dinger-like link) for the RFI is derived. The concomitant Legendre\ntransform structure (LTS, hereafter) is developed by utilizing a generalized\nRFI-Euler theorem, which shows that the entire mathematical structure of\nthermodynamics translates into the RFI framework, both for equilibrium and\nnon-equilibrium cases. The qualitatively distinct nature of the present results\n\\textit{vis-\\'{a}-vis} those of prior studies utilizing the Shannon entropy\nand/or the Fisher information measure (FIM, hereafter) is discussed. A\nprincipled relationship between the RFI and the FIM frameworks is derived. The\nutility of this relationship is demonstrated by an example wherein the energy\neigenvalues of the Schr\\\"{o}dinger-like link for the RFI is inferred solely\nusing the quantum mechanical virial theorem and the LTS of the RFI.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Counterintuitive effect of gravity on the heat capacity of a metal\n  sphere: re-examination of a well-known problem: A well-known high-school problem asking the final temperature of two spheres\nthat are given the same amount of heat, one lying on a table and the other\nhanging from a thread, is re-examined. The conventional solution states that\nthe sphere on the table ends up colder, since thermal expansion raises its\ncenter of mass. It is found that this solution violates the second law of\nthermodynamics and is therefore incorrect. Two different new solutions are\nproposed. The first uses statistical mechanics, while the second is based on\npurely classical thermodynamical arguments. It is found that gravity produces a\ncounterintuitive effect on the heat capacity, and the new answer to the problem\ngoes in the opposite direction of what traditionally thought.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Randomly dilute Ising model: A nonperturbative approach: The N-vector cubic model relevant, among others, to the physics of the\nrandomly dilute Ising model is analyzed in arbitrary dimension by means of an\nexact renormalization-group equation. This study provides a unified picture of\nits critical physics between two and four dimensions. We give the critical\nexponents for the three-dimensional randomly dilute Ising model which are in\ngood agreement with experimental and numerical data. The relevance of the cubic\nanisotropy in the O(N) model is also treated.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimal tuning of a confined Brownian information engine: A Brownian information engine is a device extracting a mechanical work from a\nsingle heat bath by exploiting the information on the state of a Brownian\nparticle immersed in the bath. As for engines, it is important to find the\noptimal operating condition that yields the maximum extracted work or power.\nThe optimal condition for a Brownian information engine with a finite cycle\ntime $\\tau$ has been rarely studied because of the difficulty in finding the\nnonequilibrium steady state. In this study, we introduce a model for the\nBrownian information engine and develop an analytic formalism for its steady\nstate distribution for any $\\tau$. We find that the extracted work per engine\ncycle is maximum when $\\tau$ approaches infinity, while the power is maximum\nwhen $\\tau$ approaches zero.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Correlation functions of the integrable spin-s chain: We study the correlation functions of su(2) invariant spin-s chains in the\nthermodynamic limit. We derive non-linear integral equations for an auxiliary\ncorrelation function $\\omega$ for any spin s and finite temperature T. For the\nspin-3/2 chain for arbitrary temperature and zero magnetic field we obtain\nalgebraic expressions for the reduced density matrix of two-sites. In the zero\ntemperature limit, the density matrix elements are evaluated analytically and\nappear to be given in terms of Riemann's zeta function values of even and odd\narguments.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Investigation of the seismicity after the initiation of a Seismic\n  Electric Signal activity until the main shock: The behavior of seismicity in the area candidate to suffer a main shock is\ninvestigated after the observation of the Seismic Electric Signal activity\nuntil the impending mainshock. This makes use of the concept of natural time\n$\\chi$ and reveals that the probability density function of the variance\n$\\kappa_1(=< \\chi^2 > -< \\chi > ^2)$ exhibits distinct features before the\noccurrence of the mainshock. Examples are presented, which refer to magnitude\nclass 6.0 earthquakes that occurred in Greece during the first two months in\n2008.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical dynamics of nonconserved $N$-vector model with anisotropic\n  nonequilibrium perturbations: We study dynamic field theories for nonconserving $N$-vector models that are\nsubject to spatial-anisotropic bias perturbations. We first investigate the\nconditions under which these field theories can have a single length scale.\nWhen N=2 or $N \\ge 4$, it turns out that there are no such field theories, and,\nhence, the corresponding models are pushed by the bias into the Ising class. We\nfurther construct nontrivial field theories for N=3 case with certain bias\nperturbations and analyze the renormalization-group flow equations. We find\nthat the three-component systems can exhibit rich critical behavior belonging\nto two different universality classes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Single-vehicle data of highway traffic: microscopic description of\n  traffic phases: We present a detailed analysis of single-vehicle data which sheds some light\non the microscopic interaction of the vehicles. Besides the analysis of free\nflow and synchronized traffic the data sets especially provide information\nabout wide jams which persist for a long time. The data have been collected at\na location far away from ramps and in the absence of speed limits which allows\na comparison with idealized traffic simulations. We also resolve some open\nquestions concerning the time-headway distribution.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Coil-Globule transition of a single short polymer chain - an exact\n  enumeration study: We present an exact enumeration study of short SAWs in two as well as three\ndimensions that addresses the question, `what is the shortest walk for which\nthe existence of all the three phases - coil, globule and the {\\it theta} -\ncould be demonstrated'. Even though we could easily demonstrate the coil and\nthe globule phases from Free Energy considerations, we could demonstrate the\nexistence of a {\\it theta} phase only by using a scaling form for the\ndistribution of gyration radius. That even such short walks have a scaling\nbehavior is an unexpected result of this work.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "How cooperatively folding are homopolymer molecular knots?: Detailed thermodynamic analysis of complex systems with multiple stable\nconfigurational states allows for insight into the cooperativity of each\nindividual transition. In this work we derive a heat capacity decomposition\ncomprising contributions from each individual configurational state, which\ntogether sum to a baseline heat capacity, and contributions from each\nstate-to-state transition. We apply this analysis framework to a series of\nreplica exchange molecular dynamics simulations of linear and 1-1\ncoarse-grained homo-oligomer models which fold into stable, configurationally\nwell-defined molecular knots, in order to better understand the parameters\nleading to stable and cooperative folding of these knots. We find that a stiff\nharmonic backbone bending angle potential is key to achieving knots with\nspecific 3D structures. Tuning the backbone equilibrium angle in small\nincrements yields a variety of knot topologies, including $3_1$, $5_1$, $7_1$,\nand $8_{19}$ types. Populations of different knotted states as functions of\ntemperature can also be manipulated by tuning backbone torsion stiffness or by\nadding side chain beads. We find that sharp total heat capacity peaks for the\nhomo-oligomer knots are largely due to a coil-to-globule transition, rather\nthan a cooperative knotting step. However, in some cases the cooperativity of\nglobule-to-knot and coil-to-globule transitions are comparable, suggesting that\nhighly cooperative folding to knotted structures can be achieved by refining\nthe model parameters or adding sequence specificity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite-time scaling for kinetic rough interfaces: We consider discrete models of kinetic rough interfaces that exhibit\nspace-time scale-invariance in height-height correlation. A generic scaling\ntheory implies that the dynamical structure factor of the height profile can\nuniquely characterize the underlying dynamics. We provide a finite-time scaling\nthat systematically allows an estimation of the critical exponents and the\nscaling functions, eventually establishing the universality class accurately.\nAs an illustration, we investigate a class of self-organized interface models\nin random media with extremal dynamics. The isotropic version shows a faceted\npattern and belongs to the same universality class (as shown numerically) as\nthe Sneppen (model A). We also introduce an anisotropic version of the Sneppen\n(model A) and suggest that the model belongs to the universality class of the\ntensionless one-dimensional Kardar-Parisi-Zhang equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fermionic theory of nonequilibrium steady states: As the quantification of metabolism, nonequilibrium steady states play a\ncentral role in living matter, but are beyond the purview of equilibrium\nstatistical mechanics. Here we develop a fermionic theory of nonequilibrium\nsteady states in continuous-time Markovian systems. The response to an\narbitrary perturbation is computed, and simplified in canonical cases. Beyond\nresponse, we consider ensembles of NESS and derive a fluctuation-response\nrelation over a non-equilibrium ensemble. Some connections to quantum gravity\nare pointed out, and the formulation is extended to a supersymmetric integral\none, which may form the basis of nontrivial solvable models of nonequilibrium\nsteady states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phases fluctuations, self-similarity breaking and anomalous scalings in\n  driven nonequilibrium critical phenomena: We study in detail the dynamic scaling of the three-dimensional (3D) Ising\nmodel driven through its critical point on finite-size lattices and show that a\nseries of new critical exponents are needed to account for the anomalous\nscalings originating from breaking of self-similarity of the so-called phases\nfluctuations. Our results demonstrate that new exponents are generally required\nfor scaling in the whole driven process once the lattice size or an externally\napplied field are taken into account. These open a new door in critical\nphenomena and suggest that much is yet to be explored in driven nonequilibrium\ncritical phenomena.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Shearing of loose granular materials: A statistical mesoscopic model: A two-dimensional lattice model for the formation and evolution of shear\nbands in granular media is proposed. Each lattice site is assigned a random\nvariable which reflects the local density. At every time step, the strain is\nlocalized along a single shear-band which is a spanning path on the lattice\nchosen through an extremum condition. The dynamics consists of randomly\nchanging the `density' of the sites only along the shear band, and then\nrepeating the procedure of locating the extremal path and changing it. Starting\nfrom an initially uncorrelated density field, it is found that this dynamics\nleads to a slow compaction along with a non-trivial patterning of the system,\nwith high density regions forming which shelter long-lived low-density valleys.\nFurther, as a result of these large density fluctuations, the shear band which\nwas initially equally likely to be found anywhere on the lattice, gets\nprogressively trapped for longer and longer periods of time. This state is\nhowever meta-stable, and the system continues to evolve slowly in a manner\nreminiscent of glassy dynamics. Several quantities have been studied\nnumerically which support this picture and elucidate the unusual system-size\neffects at play.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Understanding how both the partitions of a bipartite network affect its\n  one-mode projection: It is a well-known fact that the degree distribution (DD) of the nodes in a\npartition of a bipartite network influences the DD of its one-mode projection\non that partition. However, there are no studies exploring the effect of the DD\nof the other partition on the one-mode projection. In this article, we show\nthat the DD of the other partition, in fact, has a very strong influence on the\nDD of the one-mode projection. We establish this fact by deriving the exact or\napproximate closed-forms of the DD of the one-mode projection through the\napplication of generating function formalism followed by the method of\niterative convolution. The results are cross-validated through appropriate\nsimulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase-ordering dynamics in itinerant quantum ferromagnets: The phase-ordering dynamics that result from domain coarsening are considered\nfor itinerant quantum ferromagnets. The fluctuation effects that invalidate the\nHertz theory of the quantum phase transition also affect the phase ordering.\nFor a quench into the ordered phase a transient regime appears, where the\ndomain growth follows a different power law than in the classical case, and for\nasymptotically long times the prefactor of the t^{1/2} growth law has an\nanomalous magnetization dependence. A quench to the quantum critical point\nresults in a growth law that is not a power-law function of time. Both\nphenomenological scaling arguments and renormalization-group arguments are\ngiven to derive these results, and estimates of experimentally relevant length\nand time scales are presented.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A detailed investigation into near degenerate exponential random graphs: The exponential family of random graphs has been a topic of continued\nresearch interest. Despite the relative simplicity, these models capture a\nvariety of interesting features displayed by large-scale networks and allow us\nto better understand how phases transition between one another as tuning\nparameters vary. As the parameters cross certain lines, the model\nasymptotically transitions from a very sparse graph to a very dense graph,\ncompletely skipping all intermediate structures. We delve deeper into this near\ndegenerate tendency and give an explicit characterization of the asymptotic\ngraph structure as a function of the parameters.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entropy Production of Open Quantum System in Multi-Bath Environment: We study the entropy production of an open quantum system surrounded by a\ncomplex environment consisting of several heat baths at different temperatures.\nThe detailed balance is elaborated in view of the distinguishable channels\nprovided by the couplings to different heat baths, and a refined entropy\nproduction rate is derived accordingly. It is demonstrated that the entropy\nproduction rates can characterize the quantum statistical property of the\nbaths: the bosonic and fermionic baths display different behaviors in the\nhigh-temperature limit while they have the same asymptotic behavior at low\ntemperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Jamming and pattern formation in models of segregation: We investigate the Schelling model of social segregation, formulated as an\nintrinsically non-equilibrium system, in which the agents occupy districts (or\npatches) rather than sites on a grid. We show that this allows the equations\ngoverning the dynamical behaviour of the model to be derived. Analysis of these\nequations reveals a jamming transition in the regime of low-vacancy density,\nand inclusion of a spatial dimension in the model leads to a pattern forming\ninstability. Both of these phenomena exhibit unusual characteristics which may\nbe studied through our approach.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exploration of Order in Chaos with Replica Exchange Monte Carlo: A method for exploring unstable structures generated by nonlinear dynamical\nsystems is introduced. It is based on the sampling of initial conditions and\nparameters by Replica Exchange Monte Carlo (REM), and efficient both for the\nsearch of rare initial conditions and for the combined search of rare initial\nconditions and parameters. Examples discussed here include the sampling of\nunstable periodic orbits in chaos and search for the stable manifold of\nunstable fixed points, as well as construction of the global bifurcation\ndiagram of a map.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nanoswimmers in a ratchet potential: Effects of a transverse rocking\n  force: We study the dynamics of a chemical nanoswimmer in a ratchet potential, which\nis periodically rocked in the transverse direction. As a result of the\nmechanochemical coupling, the self-propulsion velocity becomes force-dependent\nand particle trajectories are rectified in the direction of the ratchet\nmodulation. The magnitude and direction of the nanoswimmer mean velocity depend\nupon both the rocking amplitude and the frequency. Remarkably, for frequencies\nlarger than the inverse correlation time of the rotational diffusion, the\nvelocity exhibits oscillatory behaviour as a function of the amplitude and the\nfrequency with multiple reversals of the sign. These findings suggest that\nmechanochemical coupling can be utilized for controlling the motion of\nchemically active particles at the nanoscale.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Detecting fuzzy community structures in complex networks with a Potts\n  model: A fast community detection algorithm based on a q-state Potts model is\npresented. Communities in networks (groups of densely interconnected nodes that\nare only loosely connected to the rest of the network) are found to coincide\nwith the domains of equal spin value in the minima of a modified Potts spin\nglass Hamiltonian. Comparing global and local minima of the Hamiltonian allows\nfor the detection of overlapping (``fuzzy'') communities and quantifying the\nassociation of nodes to multiple communities as well as the robustness of a\ncommunity. No prior knowledge of the number of communities has to be assumed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ultracold Fermion Cooling Cycle using Heteronuclear Feshbach Resonances: We consider an ideal gas of Bose and Fermi atoms in a harmonic trap, with a\nFeshbach resonance in the interspecies atomic scattering that can lead to\nformation of fermionic molecules. We map out the phase diagram for this\nthree-component mixture in chemical and thermal equilibrium. Considering\nadiabatic association and dissociation of the molecules, we identify a possible\ncooling cycle, which in ideal circumstances can yield an exponential increase\nof the phase-space density.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low self-affine exponents of fracture surfaces of glass ceramics: The geometry of post mortem rough fracture surfaces of porous glass ceramics\nmade of sintered glass beads is shown experimentally to be self-affine with an\nexponent zeta=0.40 (0.04) remarkably lower than the 'universal' value zeta=0.8\nfrequently measured for many materials. This low value of zeta is similar to\nthat found for sandstone samples of similar micro structure and is also\npractically independent on the porosity phi in the range investigated (3% < phi\n< 26%) as well as on the bead diameter d and of the crack growth velocity. In\ncontrast, the roughness amplitude normalized by d increases linearly with phi\nwhile it is still independent, within experimental error, of d and of the crack\npropagation velocity. An interpretation of this variation is suggested in terms\nof a transition from transgranular to intergranular fracture propagation with\nno influence, however, on the exponent zeta.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Glassy behavior of the site frustrated percolation model: The dynamical properties of the site frustrated percolation model are\ninvestigated and compared with those of glass forming liquids. When the density\nof the particles on the lattice becomes high enough, the dynamics of the model\nbecomes very slow, due to geometrical constraints, and rearrangement on large\nscales is needed to allow relaxation. The autocorrelation functions, the\nspecific volume for different cooling rates, and the mean square displacement\nare evaluated, and are found to exhibit glassy behavior.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Variational HFB Equations in the Thomas-Fermi Limit for Ultracold\n  Trapped Gases: We derive variationally the HFB equations for a trapped self-interacting Bose\ngas at finite temperature. In the Thomas-Fermi limit, we obtain simple\nexpressions for the condensate, the non condensate and the anomalous densities.\nTheir behavior in terms of the condensate fraction meets qualitatively the\nexperimental data. In particular, the non condensate and the anomalous\ndensities are peaked at the center of the trap and not at the edges as\npredicted by the self-consistent HFB calculations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Parameters of state in the global thermodynamics of binary ideal gas\n  mixtures in a stationary heat flow: We formulate the first law of global thermodynamics for stationary states of\nthe binary ideal gas mixture subjected to heat flow. We map the non-uniform\nsystem onto the uniform one and show that the internal energy\n$U(S^*,V,N_1,N_2,f_1^*,f_2^*)$ is the function of the following parameters of\nstate: a non-equilibrium entropy $S^*$, volume $V$, number of particles of the\nfirst component, $N_1$, number of particles of the second component $N_2$ and\nthe renormalized degrees of freedom. The parameters $f_1^*,f_2^*$, $N_1, N_2$\nsatisfy the relation $x_1f_1^*/f_1+x_2f_2^*/f_2=1$ ($f_1$, where $x_i$ is the\nfraction of $i$ component, and $f_2$ are the degrees of freedom for each\ncomponent respectively). Thus only 5 parameters of state describe the\nnon-equilibrium state of the binary mixture in the heat flow. We calculate the\nnon-equilibrium entropy $S^{*}$ and new thermodynamic parameters of state\n$f_1^*, f_2^*$ explicitly. The latter are responsible for heat generation due\nto the concentration gradients. The theory reduces to equilibrium\nthermodynamics, when the heat flux goes to zero. As in equilibrium\nthermodynamics, the steady-state fundamental equation also leads to the\nthermodynamic Maxwell relations for measurable steady-state properties.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Single-particle excitations and the order parameter for a trapped\n  superfluid Fermi gas: We reveal a strong influence of a superfluid phase transition on the\ncharacter of single-particle excitations of a trapped neutral-atom Fermi gas.\nBelow the transition temperature the presence of a spatially inhomogeneous\norder parameter (gap) shifts up the excitation eigenenergies and leads to the\nappearance of in-gap excitations localized in the outer part of the gas sample.\nThe eigenenergies become sensitive to the gas temperature and are no longer\nmultiples of the trap frequencies. These features should manifest themselves in\na strong change of the density oscillations induced by modulations of the trap\nfrequencies and can be used for identifying the superfluid phase transition.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Pricing Derivatives by Path Integral and Neural Networks: Recent progress in the development of efficient computational algorithms to\nprice financial derivatives is summarized. A first algorithm is based on a path\nintegral approach to option pricing, while a second algorithm makes use of a\nneural network parameterization of option prices. The accuracy of the two\nmethods is established from comparisons with the results of the standard\nprocedures used in quantitative finance.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relativistic Nonextensive Thermodynamics: Starting from the basic prescriptions of the Tsallis' nonextensive\nthermostatistics, i.e. generalized entropy and normalized q-expectation values,\nwe study the relativistic nonextensive thermodynamics and derive a Boltzmann\ntransport equation that implies the validity of the H-theorem where a local\nnonextensive four-entropy density is considered. Macroscopic thermodynamic\nfunctions and the equation of state for a perfect gas are derived at the\nequilibrium.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Coulomb Systems with Ideal Dielectric Boundaries: Free Fermion Point and\n  Universality: A two-component Coulomb gas confined by walls made of ideal dielectric\nmaterial is considered. In two dimensions at the special inverse temperature\n$\\beta = 2$, by using the Pfaffian method, the system is mapped onto a\nfour-component Fermi field theory with specific boundary conditions. The exact\nsolution is presented for a semi-infinite geometry of the dielectric wall (the\ndensity profiles, the correlation functions) and for the strip geometry (the\nsurface tension, a finite-size correction of the grand potential). The\nuniversal finite-size correction of the grand potential is shown to be a\nconsequence of the good screening properties, and its generalization is derived\nfor the conducting Coulomb gas confined in a slab of arbitrary dimension $\\ge\n2$ at any temperature.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Magnetic Eden Model: In the magnetic Eden model (MEM), particles have a spin and grow in contact\nwith a thermal bath. Although Ising-like interactions affect the growth\ndynamics, deposited spins are frozen and not allowed to flip. This review\narticle focuses on recent developments and future prospects, such as\nspontaneous switching phenomena, critical behavior associated with fractal,\nwetting, and order-disorder phase transitions, the equilibrium/nonequilibrium\ncorrespondence conjecture, as well as dynamical and critical features of the\nMEM defined on complex network substrates.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Constructing effective free energies for dynamical quantum phase\n  transitions in the transverse-field Ising chain: The theory of dynamical quantum phase transitions represents an attempt to\nextend the concept of phase transitions to the far from equilibrium regime.\nWhile there are many formal analogies to conventional transitions, it is a\nmajor question to which extent it is possible to formulate a nonequilibrium\ncounterpart to a Landau-Ginzburg theory. In this work we take a first step in\nthis direction by constructing an effective free energy for continuous\ndynamical quantum phase transitions appearing after quantum quenches in the\ntransverse-field Ising chain. Due to unitarity of quantum time evolution this\neffective free energy becomes a complex quantity transforming the conventional\nminimization principle of the free energy into a saddle-point equation in the\ncomplex plane of the order parameter, which as in equilibrium is the\nmagnetization. We study this effective free energy in the vicinity of the\ndynamical quantum phase transition by performing an expansion in terms of the\ncomplex magnetization and discuss the connections to the equilibrium case.\nFurthermore, we study the influence of perturbations and signatures of these\ndynamical quantum phase transitions in spin correlation functions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Symmetries and zero modes in sample path large deviations: Sharp large deviation estimates for stochastic differential equations with\nsmall noise, based on minimizing the Freidlin-Wentzell action functional under\nappropriate boundary conditions, can be obtained by integrating certain matrix\nRiccati differential equations along the large deviation minimizers or\ninstantons, either forward or backward in time. Previous works in this\ndirection often rely on the existence of isolated minimizers with positive\ndefinite second variation. By adopting techniques from field theory and\nexplicitly evaluating the large deviation prefactors as functional determinant\nratios using Forman's theorem, we extend the approach to general systems where\ndegenerate submanifolds of minimizers exist. The key technique for this is a\nboundary-type regularization of the second variation operator. This extension\nis particularly relevant if the system possesses continuous symmetries that are\nbroken by the instantons. We find that removing the vanishing eigenvalues\nassociated with the zero modes is possible within the Riccati formulation and\namounts to modifying the initial or final conditions and evaluation of the\nRiccati matrices. We apply our results in multiple examples including a\ndynamical phase transition for the average surface height in short-time large\ndeviations of the one-dimensional Kardar-Parisi-Zhang equation with flat\ninitial profile.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the spatially periodic ordering in the system of electrons above the\n  surface of liquid helium in an external electric field: A theory of equilibrium states of electrons above a liquid helium surface in\nthe presence of an external clamping field is built based on the first\nprinciples of quantum statistics for the system of many identical\nFermi-particles. The approach is based on the variation principle modified for\nthe considered system and on Thomas-Fermi model. In terms of the developed\ntheory we obtain the self-consistency equations that connect the parameters of\nthe system description, i.e., the potential of a static electric field, the\ndistribution function of electrons and the surface profile of a liquid\ndielectric. The equations are used to study the phase transition of the system\nto a spatially periodic state. To demonstrate the capabilities of the proposed\nmethod, the characteristics of the phase transition of the system to a\nspatially periodic state of a trough type are analyzed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random Matrix Theory approach to Mesoscopic Fluctuations of Heat Current: We consider an ensemble of fully connected networks of N oscillators coupled\nharmonically with random springs and show, using Random Matrix Theory\nconsiderations, that both the average phonon heat current and its variance are\nscale-invariant and take universal values in the large N-limit. These anomalous\nmesoscopic uctuations is the hallmark of strong correlations between normal\nmodes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Asymptotic Dynamics of Breathers in Fermi-Pasta-Ulam Chains: We study the asymptotic dynamics of breathers in finite Fermi-Pasta-Ulam\nchains at zero and non-zero temperatures. While such breathers are essentially\nstationary and very long-lived at zero temperature, thermal fluctuations tend\nto lead to breather motion and more rapid decay.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Active XY model on a substrate: Density fluctuations and phase ordering: We explore the generic long wavelength properties of an active XY model on a\nsubstrate, consisting of collection of nearly phase-ordered active XY spins in\ncontact with a diffusing, conserved species, as a representative system of\nactive spinners with a conservation law. The spins rotate actively in response\nto the local density fluctuations and local phase differences, on a solid\nsubstrate. We investigate this system by Monte-Carlo simulations of an\nagent-based model, which we set up, complemented by the hydrodynamic theory for\nthe system. We demonstrate that this system can phase-synchronize without any\nhydrodynamic interactions. Our combined numerical and analytical studies show\nthat this model, when stable, displays hitherto unstudied scaling behavior: As\na consequence of the interplay between the mobility, active rotation and number\nconservation, such a system can be stable over a wide range of the model\nparameters characterized by a novel correspondence between the phase and\ndensity fluctuations. In different regions of the phase space where the\nphase-ordered system is stable, it shows phase ordering which is generically\neither logarithmically stronger than the conventional quasi long range order\n(QLRO) found in its equilibrium limit, together with \"miniscule number\nfluctuations\", or logarithmically weaker than QLRO along with \"giant number\nfluctuations\", showing a novel one-to-one correspondence between phase ordering\nand density fluctuations in the ordered states. Intriguingly, these scaling\nexponents are found to depend explicitly on the model parameters. We further\nshow that in other parameter regimes there are no stable, ordered phases.\nInstead, two distinct types of disordered states with short range phase-order\nare found, characterized by the presence or absence of stable clusters of\nfinite sizes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ballistic spin transport in a periodically driven integrable quantum\n  system: We demonstrate ballistic spin transport of an integrable unitary quantum\ncircuit, which can be understood either as a paradigm of an integrable\nperiodically driven (Floquet) spin chain, or as a Trotterized anisotropic\n($XXZ$) Heisenberg spin-1/2 model. We construct an analytic family of\nquasi-local conservation laws that break the spin-reversal symmetry and compute\na lower bound on the spin Drude weight which is found to be a fractal function\nof the anisotropy parameter. Extensive numerical simulations of spin transport\nsuggest that this fractal lower bound is in fact tight.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Collision densities and mean residence times for $d$-dimensional\n  exponential flights: In this paper we analyze some aspects of {\\em exponential flights}, a\nstochastic process that governs the evolution of many random transport\nphenomena, such as neutron propagation, chemical/biological species migration,\nor electron motion. We introduce a general framework for $d$-dimensional\nsetups, and emphasize that exponential flights represent a deceivingly simple\nsystem, where in most cases closed-form formulas can hardly be obtained. We\nderive a number of novel exact (where possible) or asymptotic results, among\nwhich the stationary probability density for 2d systems, a long-standing issue\nin Physics, and the mean residence time in a given volume. Bounded or\nunbounded, as well as scattering or absorbing domains are examined, and Monte\nCarlo simulations are performed so as to support our findings.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Simple Model of Superconducting Vortex Avalanches: We introduce a simple lattice model of superconducting vortices driven by\nrepulsive interactions through a random pinning potential. The model describes\nthe behavior at the scale of the London length lambda or larger. It\nself-organizes to a critical state, characterized by a constant flux density\ngradient, where the activity takes place in terms of avalanches spanning all\nlength scales up to the system size. We determine scaling relations as well as\nfour universal critical exponents for avalanche moments and durations: tau =\n1.63 +/- 0.02, D = 2.7 +/- 0.1, z = 1.5 +/- 0.1, and tau_t = 2.13 +/- 0.14, for\nthe system driven at the boundary.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Information Geometry, Phase Transitions, and Widom Lines : Magnetic and\n  Liquid Systems: We study information geometry of the thermodynamics of first and second order\nphase transitions, and beyond criticality, in magnetic and liquid systems. We\nestablish a universal microscopic characterization of such phase transitions\nvia the equality of correlation lengths $\\xi$ in coexisting phases, where $\\xi$\nis related to the scalar curvature of the equilibrium thermodynamic state\nspace. The 1-D Ising model, and the mean-field Curie-Weiss model are discussed,\nand we show that information geometry correctly describes the phase behavior\nfor the latter. The Widom lines for these systems are also established. We\nfurther study a simple model for the thermodynamics of liquid-liquid phase\nco-existence, and show that our method provides a simple and direct way to\nobtain its phase behavior and the locations of the Widom lines. Our analysis\npoints towards multiple Widom lines in liquid systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Entanglement in Far From Equilibrium Stationary States: We present four estimators of the entanglement (or interdepency) of\nground-states in which the coefficients are all real nonnegative and therefore\ncan be interpreted as probabilities of configurations. Such ground-states of\nhermitian and non-hermitian Hamiltonians can be given, for example, by\nsuperpositions of valence bond states which can describe equilibrium but also\nstationary states of stochastic models. We consider in detail the last case.\nUsing analytical and numerical methods we compare the values of the estimators\nin the directed polymer and the raise and peel models which have massive,\nconformal invariant and non-conformal invariant massless phases. We show that\nlike in the case of the quantum problem, the estimators verify the area law and\ncan therefore be used to signal phase transitions in stationary states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Rejoinder to the Response arXiv:0812.2330 to 'Comment on a recent\n  conjectured solution of the three-dimensional Ising model': We comment on Z. D. Zhang's Response [arXiv:0812.2330] to our recent Comment\n[arXiv:0811.3876] addressing the conjectured solution of the three-dimensional\nIsing model reported in [arXiv:0705.1045].",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Injected Power Fluctuations in 1D Dissipative Systems: Using fermionic techniques, we compute exactly the large deviation function\n(ldf) of the time-integrated injected power in several one-dimensional\ndissipative systems of classical spins. The dynamics are T=0 Glauber dynamics\nsupplemented by an injection mechanism, which is taken as a Poissonian flipping\nof one particular spin. We discuss the physical content of the results,\nspecifically the influence of the rate of the Poisson process on the properties\nof the ldf.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Vertex dynamics during domain growth in three-state models: Topological aspects of interfaces are studied by comparing quantitatively the\nevolving three-color patterns in three different models, such as the\nthree-state voter, Potts and extended voter models. The statistical analysis of\nsome geometrical features allows to explore the role of different elementary\nprocesses during distinct coarsening phenomena in the above models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase transition of $q$-state clock models on heptagonal lattices: We study the $q$-state clock models on heptagonal lattices assigned on a\nnegatively curved surface. We show that the system exhibits three classes of\nequilibrium phases; in between ordered and disordered phases, an intermediate\nphase characterized by a diverging susceptibility with no magnetic order is\nobserved at every $q \\ge 2$. The persistence of the third phase for all $q$ is\nin contrast with the disappearance of the counterpart phase in a planar system\nfor small $q$, which indicates the significance of nonvanishing surface-volume\nratio that is peculiar in the heptagonal lattice. Analytic arguments based on\nGinzburg-Landau theory and generalized Cayley trees make clear that the\ntwo-stage transition in the present system is attributed to an energy gap of\nspin-wave excitations and strong boundary-spin contributions. We further\ndemonstrate that boundary effects breaks the mean-field character in the bulk\nregion, which establishes the consistency with results of clock models on\nboundary-free hyperbolic lattices.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram of S=1/2 XXZ chain with NNN interaction: We study the ground state properties of one-dimensional XXZ model with\nnext-nearest neighbor coupling alpha and anisotropy Delta. We find the direct\ntransition between the ferromagnetic phase and the spontaneously dimerized\nphase. This is surprising, because the ferromagnetic phase is classical,\nwhereas the dimer phase is a purely quantum and nonmagnetic phase. We also\ndiscuss the effect of bond alternation which arises in realistic systems due to\nlattice distortion. Our results mean that the direct transition between the\nferromagnetic and spin-Peierls phase occur.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Efficiency of autonomous soft nano-machines at maximum power: We consider nano-sized artificial or biological machines working in steady\nstate enforced by imposing non-equilibrium concentrations of solutes or by\napplying external forces, torques or electric fields. For unicyclic and\nstrongly coupled multicyclic machines, efficiency at maximum power is not\nbounded by the linear response value 1/2. For strong driving, it can even\napproach the thermodynamic limit 1. Quite generally, such machines fall in\nthree different classes characterized, respectively, as \"strong and efficient\",\n\"strong and inefficient\", and \"balanced\". For weakly coupled multicyclic\nmachines, efficiency at maximum power has lost any universality even in the\nlinear response regime.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Finite Size Effect on Bose-Einstein Condensation: We show various aspects of finite size effects on Bose-Einstein\ncondensation(BEC). In the first section we introduce very briefly the BEC of\nharmonically trapped ideal Bose gas. In the second section we theoretically\nargued that Bose-Einstein(B-E) statistics needs a correction for finite system\nat ultralow temperatures. As a corrected statistics we introduced a Tsallis\ntype of generalized B-E statistics. The condensate fraction calculated with\nthis generalized B-E statistics, is satisfied well with the experimental\nresult. In the third section we show how to apply the scaling theory in an\ninhomogeneous system like harmonically trapped Bose condensate at finite\ntemperatures. We calculate the temperature dependence of the critical number of\nparticles by a scaling theory within the Hartree-Fock approximation and find\nthat there is a dramatic increase in the critical number of particles as the\ncondensation point is approached. Our results support the experimental result\nwhich was obtained well below the condensation temperature. In the fourth\nsection we concentrate on the thermodynamic Casimir force on the Bose-Einstein\ncondensate. We explored the temperature dependence of the Casimir force.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase diagram of two-lane driven diffusive systems: We consider a large class of two-lane driven diffusive systems in contact\nwith reservoirs at their boundaries and develop a stability analysis as a\nmethod to derive the phase diagrams of such systems. We illustrate the method\nby deriving phase diagrams for the asymmetric exclusion process coupled to\nvarious second lanes: a diffusive lane; an asymmetric exclusion process with\nadvection in the same direction as the first lane, and an asymmetric exclusion\nprocess with advection in the opposite direction. The competing currents on the\ntwo lanes naturally lead to a very rich phenomenology and we find a variety of\nphase diagrams. It is shown that the stability analysis is equivalent to an\n`extremal current principle' for the total current in the two lanes. We also\npoint to classes of models where both the stability analysis and the extremal\ncurrent principle fail.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Z_2-vortex ordering of the triangular-lattice Heisenberg antiferromagnet: Ordering of the classical Heisenberg antiferromagnet on the triangular\nlattice is studied by means of a mean-field calculation, a scaling argument and\na Monte Carlo simulation, with special attention to its vortex degree of\nfreedom. The model exhibits a thermodynamic transition driven by the Z_2-vortex\nbinding-unbinding, at which various thermodynamic quantities exhibit an\nessential singularity. The low-temperature state is a \"spin-gel\" state with a\nlong but finite spin correlation length where the ergodicity is broken\ntopologically. Implications to recent experiments on triangular-lattice\nHeisenberg antiferromagnets are discussed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Complementary aspects of non-equilibrium thermodynamics: Bio-molecules are active agents in that they consume energy to perform tasks.\nThe standard theoretical description, however, considers only a system-external\nwork agent. Fluctuation theorems, for example, do not allow work-exchange\nbetween fluctuating molecules. This tradition leaves `action through work', an\nessential characteristic of an active agent, out of proper thermodynamic\nconsideration. Here, we investigate thermodynamics that considers\ninternal-work. We find a complementary set of relations that capture the\nproduction of free energy in molecular interactions while obeying the second\nlaw of thermodynamics. This thermodynamic description is in stark contrast to\nthe traditional one. A choice of an axiom whether one treats a portion of\nHamiltonian as `internal-work' or `internal-energy' decides which of the two\ncomplementary descriptions manifests among the dual. We illustrate, by\nexamining an allosteric transition and a single-molecule\nfluorescence-resonance-energy-transfer measurement of proteins, that the\ncomplementary set is useful in identifying work content by experimental and\nnumerical observation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Complex-valued second difference as a measure of stabilization of\n  complex dissipative statistical systems: Girko ensemble: A quantum statistical system with energy dissipation is studied. Its\nstatistics is governed by random complex-valued non-Hermitean Hamiltonians\nbelonging to complex Ginibre ensemble. The eigenenergies are shown to form\nstable structure. Analogy of Wigner and Dyson with system of electrical charges\nis drawn.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Master equation approach to the stochastic accumulation dynamics of\n  bacterial cell cycle: The mechanism of bacterial cell size control has been a mystery for decades,\nwhich involves the well-coordinated growth and division in the cell cycle. The\nrevolutionary modern techniques of microfluidics and the advanced live imaging\nanalysis techniques allow long term observations and high-throughput analysis\nof bacterial growth on single cell level, promoting a new wave of quantitative\ninvestigations on this puzzle. Taking the opportunity, this theoretical study\naims to clarify the stochastic nature of bacterial cell size control under the\nassumption of the accumulation mechanism, which is favoured by recent\nexperiments on species of bacteria. Via the master equation approach with\nproperly chosen boundary conditions, the distributions concerned in cell size\ncontrol are estimated and are confirmed by experiments. In this analysis, the\ninter-generation Green's function is analytically evaluated as the key to\nbridge two kinds of statistics used in batch-culture and mother machine\nexperiments. This framework allows us to quantify the noise level in growth and\naccumulation according to experimental data. As a consequence of non-Gaussian\nnoises of the added sizes, the non-equilibrium nature of bacterial cell size\nhomeostasis is predicted, of which the biological meaning requires further\ninvestigation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Occupation times on a comb with ramified teeth: We investigate occupation time statistics for random walks on a comb with\nramified teeth. This is achieved through the relation between the occupation\ntime and the first passage times. Statistics of occupation times in half space\nfollows Lamperti's distribution, i.e. the generalized arcsine law holds.\nTransitions between different behaviors are observed, which are controlled by\nthe size of the backbone and teeth of the comb, as well as bias. Occupation\ntime on a non-simply connected domain is analyzed with a mean-field theory and\nnumerical simulations. In that case, the generalized arcsine law isn't valid.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Firms Growth Dynamics, Competition and Power Law Scaling: We study the growth dynamics of the size of manufacturing firms considering\ncompetition and normal distribution of competency. We start with the fact that\nall components of the system struggle with each other for growth as happened in\nreal competitive bussiness world. The detailed quantitative agreement of the\ntheory with empirical results of firms growth based on a large economic\ndatabase spanning over 20 years is good .Further we find that this basic law of\ncompetition leads approximately a power law scaling over a wide range of\nparameters. The empirical datas are in accordance with present theory rather\nthan a simple power law.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Self-Similar Factor Approximants: The problem of reconstructing functions from their asymptotic expansions in\npowers of a small variable is addressed by deriving a novel type of\napproximants. The derivation is based on the self-similar approximation theory,\nwhich presents the passage from one approximant to another as the motion\nrealized by a dynamical system with the property of group self-similarity. The\nderived approximants, because of their form, are named the self-similar factor\napproximants. These complement the obtained earlier self-similar exponential\napproximants and self-similar root approximants. The specific feature of the\nself-similar factor approximants is that their control functions, providing\nconvergence of the computational algorithm, are completely defined from the\naccuracy-through-order conditions. These approximants contain the Pade\napproximants as a particular case, and in some limit they can be reduced to the\nself-similar exponential approximants previously introduced by two of us. It is\nproved that the self-similar factor approximants are able to reproduce exactly\na wide class of functions which include a variety of transcendental functions.\nFor other functions, not pertaining to this exactly reproducible class, the\nfactor approximants provide very accurate approximations, whose accuracy\nsurpasses significantly that of the most accurate Pade approximants. This is\nillustrated by a number of examples showing the generality and accuracy of the\nfactor approximants even when conventional techniques meet serious\ndifficulties.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Numerical validation of the Complex Swift-Hohenberg equation for lasers: Order parameter equations, such as the complex Swift-Hohenberg (CSH)\nequation, offer a simplified and universal description that hold close to an\ninstability threshold. The universality of the description refers to the fact\nthat the same kind of instability produces the same order parameter equation.\nIn the case of lasers, the instability usually corresponds to the emitting\nthreshold, and the CSH equation can be obtained from the Maxwell-Bloch (MB)\nequations for a class C laser with small detuning. In this paper we numerically\ncheck the validity of the CSH equation as an approximation of the MB equations,\ntaking into account that its terms are of different asymptotic order, and that,\ndespite of having been systematically overlooked in the literature, this fact\nis essential in order to correctly capture the weakly nonlinear dynamics of the\nMB. The approximate distance to threshold range for which the CSH equation\nholds is also estimated.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Improved Lower Bounds on the Ground-State Entropy of the\n  Antiferromagnetic Potts Model: We present generalized methods for calculating lower bounds on the\nground-state entropy per site, $S_0$, or equivalently, the ground-state\ndegeneracy per site, $W=e^{S_0/k_B}$, of the antiferromagnetic Potts model. We\nuse these methods to derive improved lower bounds on $W$ for several lattices.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermal buckling and symmetry breaking in thin ribbons under compression: Understanding thin sheets, ranging from the macro to the nanoscale, can allow\ncontrol of mechanical properties such as deformability. Out-of-plane buckling\ndue to in-plane compression can be a key feature in designing new materials.\nWhile thin-plate theory can predict critical buckling thresholds for thin\nframes and nanoribbons at very low temperatures, a unifying framework to\ndescribe the effects of thermal fluctuations on buckling at more elevated\ntemperatures presents subtle difficulties. We develop and test a theoretical\napproach that includes both an in-plane compression and an out-of-plane\nperturbing field to describe the mechanics of thermalised ribbons above and\nbelow the buckling transition. We show that, once the elastic constants are\nrenormalised to take into account the ribbon's width (in units of the thermal\nlength scale), we can map the physics onto a mean-field treatment of buckling,\nprovided the length is short compared to a ribbon persistence length. Our\ntheoretical predictions are checked by extensive molecular dynamics simulations\nof thin thermalised ribbons under axial compression.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Accuracy and Efficiency of Simplified Tensor Network Codes: We examine in detail the accuracy, efficiency and implementation issues that\narise when a simplified code structure is employed to evaluate the partition\nfunction of the two-dimensional square Ising model on periodic lattices though\nrepeated tensor contractions.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nontrivial critical crossover between directed percolation models:\n  Effect of infinitely many absorbing states: At non-equilibrium phase transitions into absorbing (trapped) states, it is\nwell known that the directed percolation (DP) critical scaling is shared by two\nclasses of models with a single (S) absorbing state and with infinitely many\n(IM) absorbing states. We study the crossover behavior in one dimension,\narising from a considerable reduction of the number of absorbing states\n(typically from the IM-type to the S-type DP models), by following two\ndifferent (excitatory or inhibitory) routes which make the auxiliary field\ndensity abruptly jump at the crossover. Along the excitatory route, the system\nbecomes overly activated even for an infinitesimal perturbation and its\ncrossover becomes discontinuous. Along the inhibitory route, we find continuous\ncrossover with the universal crossover exponent $\\phi\\simeq 1.78(6)$, which is\nargued to be equal to $\\nu_\\|$, the relaxation time exponent of the DP\nuniversality class on a general footing. This conjecture is also confirmed in\nthe case of the directed Ising (parity-conserving) class. Finally, we discuss\nthe effect of diffusion to the IM-type models and suggest an argument why\ndiffusive models with some hybrid-type reactions should belong to the DP class.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Feedback and Fluctuations in a Totally Asymmetric Simple Exclusion\n  Process with Finite Resources: We revisit a totally asymmetric simple exclusion process (TASEP) with open\nboundaries and a global constraint on the total number of particles [Adams, et.\nal. 2008 J. Stat. Mech. P06009]. In this model, the entry rate of particles\ninto the lattice depends on the number available in the reservoir. Thus, the\ntotal occupation on the lattice feeds back into its filling process. Although a\nsimple domain wall theory provided reasonably good predictions for Monte Carlo\nsimulation results for certain quantities, it did not account for the\nfluctuations of this feedback. We generalize the previous study and find\ndramatically improved predictions for, e.g., the density profile on the lattice\nand provide a better understanding of the phenomenon of \"shock localization.\"",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spectral fingerprints of non-equilibrium dynamics: The case of a\n  Brownian gyrator: The same system can exhibit a completely different dynamical behavior when it\nevolves in equilibrium conditions or when it is driven out-of-equilibrium by,\ne.g., connecting some of its components to heat baths kept at different\ntemperatures. Here we concentrate on an analytically solvable and\nexperimentally-relevant model of such a system -- the so-called Brownian\ngyrator -- a two-dimensional nanomachine that performs a systematic, on\naverage, rotation around the origin under non-equilibrium conditions, while no\nnet rotation takes place in equilibrium. On this example, we discuss a question\nwhether it is possible to distinguish between two types of a behavior judging\nnot upon the statistical properties of the trajectories of components, but\nrather upon their respective spectral densities. The latter are widely used to\ncharacterize diverse dynamical systems and are routinely calculated from the\ndata using standard built-in packages. From such a perspective, we inquire\nwhether the power spectral densities possess some \"fingerprint\" properties\nspecific to the behavior in non-equilibrium. We show that indeed one can\nconclusively distinguish between equilibrium and non-equilibrium dynamics by\nanalyzing the cross-correlations between the spectral densities of both\ncomponents in the short frequency limit, or from the spectral densities of both\ncomponents evaluated at zero frequency. Our analytical predictions,\ncorroborated by experimental and numerical results, open a new direction for\nthe analysis of a non-equilibrium dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of node position on diffusion and trapping efficiency for random\n  walks on fractal scale-free trees: We study unbiased discrete random walks on the FSFT based on the its\nself-similar structure and the relations between random walks and electrical\nnetworks. First, we provide new methods to derive analytic solutions of the\nMFPT for any pair of nodes, the MTT for any target node and MDT for any\nstarting node. And then, using the MTT and the MDT as the measures of trapping\nefficiency and diffusion efficiency respectively, we analyze the effect of\ntrap's position on trapping efficiency and the effect of starting position on\ndiffusion efficiency. Comparing the trapping efficiency and diffusion\nefficiency among all nodes of FSFT, we find the best (or worst) trapping sites\nand the best (or worst) diffusing sites. Our results show that: the node which\nis at the center of FSFT is the best trapping site, but it is also the worst\ndiffusing site. The nodes which are the farthest nodes from the two hubs are\nthe worst trapping sites, but they are also the best diffusion sites. Comparing\nthe maximum and minimum of MTT and MDT, we found that the maximum of MTT is\nalmost $\\frac{20m^2+32m+12}{4m^2+4m+1}$ times of the minimum of MTT, but the\nthe maximum of MDT is almost equal to the minimum of MDT. These results shows\nthat the position of target node has big effect on trapping efficiency, but the\nposition of starting node almost has no effect on diffusion efficiency. We also\nconducted numerical simulation to test the results we have derived, the results\nwe derived are consistent with those obtained by numerical simulation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Diffusive transport on networks with stochastic resetting to multiple\n  nodes: We study the diffusive transport of Markovian random walks on arbitrary\nnetworks with stochastic resetting to multiple nodes. We deduce analytical\nexpressions for the stationary occupation probability and for the mean and\nglobal first passage times. This general approach allows us to characterize the\neffect of resetting on the capacity of random walk strategies to reach a\nparticular target or to explore the network. Our formalism holds for ergodic\nrandom walks and can be implemented from the spectral properties of the random\nwalk without resetting, providing a tool to analyze the efficiency of search\nstrategies with resetting to multiple nodes. We apply the methods developed\nhere to the dynamics with two reset nodes and derive analytical results for\nnormal random walks and L\\'evy flights on rings. We also explore the effect of\nresetting to multiple nodes on a comb graph, L\\'evy flights that visit specific\nlocations in a continuous space, and the Google random walk strategy on regular\nnetworks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Path statistics, memory, and coarse-graining of continuous-time random\n  walks on networks: Continuous-time random walks (CTRWs) on discrete state spaces, ranging from\nregular lattices to complex networks, are ubiquitous across physics, chemistry,\nand biology. Models with coarse-grained states, for example those employed in\nstudies of molecular kinetics, and models with spatial disorder can give rise\nto memory and non-exponential distributions of waiting times and first-passage\nstatistics. However, existing methods for analyzing CTRWs on complex energy\nlandscapes do not address these effects. We therefore use statistical mechanics\nof the nonequilibrium path ensemble to characterize first-passage CTRWs on\nnetworks with arbitrary connectivity, energy landscape, and waiting time\ndistributions. Our approach is valuable for calculating higher moments (beyond\nthe mean) of path length, time, and action, as well as statistics of any\nconservative or non-conservative force along a path. For homogeneous networks\nwe derive exact relations between length and time moments, quantifying the\nvalidity of approximating a continuous-time process with its discrete-time\nprojection. For more general models we obtain recursion relations, reminiscent\nof transfer matrix and exact enumeration techniques, to efficiently calculate\npath statistics numerically. We have implemented our algorithm in PathMAN, a\nPython script that users can easily apply to their model of choice. We\ndemonstrate the algorithm on a few representative examples which underscore the\nimportance of non-exponential distributions, memory, and coarse-graining in\nCTRWs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamic Phase Transition in the Kinetic Spin-3/2 Blume-Capel Model:\n  Phase Diagrams in the Temperature and Crystal-Field Interaction Plane: We analyze, within a mean-field approach, the stationary states of the\nkinetic spin-3/2 Blume-Capel model by the Glauber-type stochastic dynamics and\nsubject to a time-dependent oscillating external magnetic field. The dynamic\nphase transition points are obtained by investigating the behavior of the\ndynamic magnetization as a function of temperature and as well as calculating\nthe Liapunov exponent. Phase diagrams are constructed in the temperature and\ncrystal-field interaction plane. We find five fundamental types of phase\ndiagrams for the different values of the reduced magnetic field amplitude\nparameter (h) in which they present a disordered, two ordered phases and the\ncoexistences phase regions. The phase diagrams also exhibit a dynamic double\ncritical end point for 0<h<1.44, one dynamic tricritical point for 1.44<h<5.06\nand two dynamic tricritical points for h>5.06.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal bridge functional for infinitely diluted solutions: a case\n  study for Lennard-Jones spheres of different diameter: In the paper we propose an universal bridge functional for the closure of the\nOrnstein-Zernike (OZ) equation for the case of infinitely diluted solutions of\nLennard-Jones shperes of different size in the Lennard-Jones fluid. Bridge\nfunctional is paprameterized using the data of the Molecular Dynamics (MD)\nsimulations. We show that for all investigated systems the bridge functional\ncan be efficiently papameterized with the exponential function which depends\nonly on the ratio of sizes of the solute and solvent atoms. To check the\nparameterization we solve the OZ equation with the closure which includes the\nparametrized functional and with the closure without the bridge functional\n(Hyper-netted chain closure). We show that introducing the bridge functional\nallows to obtain radial distribution functions (RDFs), which are close to the\nMD results and essentially improve predictions of the location and height of\nthe first peak of the RDF.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamics of Ising models coupled microscopically to bath systems: Based on the Robertson theory the nonlinear dynamics of general Ising systems\ncoupled microscopically to bath systems is investigated leading to two\ncomplimentary approaches. Within the master equation approach microscopically\nfounded transition rates are presented which essentially differ from the usual\nphenological rates. The second approach leads to coupled equations of motion\nfor the local magnetizations and the exchange energy. Simple examples are\ndiscussed and the general results are applied to the Sherrington-Kirkpatrick\nspin glass model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase Transitions in a Forest-Fire Model: We investigate a forest-fire model with the density of empty sites as control\nparameter. The model exhibits three phases, separated by one first-order phase\ntransition and one 'mixed' phase transition which shows critical behavior on\nonly one side and hysteresis. The critical behavior is found to be that of the\nself-organized critical forest-fire model [B. Drossel and F. Schwabl, Phys.\nRev. Lett. 69, 1629 (1992)], whereas in the adjacent phase one finds the spiral\nwaves of the Bak et al. forest-fire model [P. Bak, K. Chen and C. Tang, Phys.\nLett. A 147, 297 (1990)]. In the third phase one observes clustering of trees\nwith the fire burning at the edges of the clusters. The relation between the\ndensity distribution in the spiral state and the percolation threshold is\nexplained and the implications for stationary states with spiral waves in\narbitrary excitable systems are discussed. Furthermore, we comment on the\npossibility of mapping self-organized critical systems onto 'ordinary' critical\nsystems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Renewal equations for single-particle diffusion through a semipermeable\n  interface: Diffusion through semipermeable interfaces has a wide range of applications,\nranging from molecular transport through biological membranes to reverse\nosmosis for water purification using artificial membranes. At the\nsingle-particle level, one-dimensional diffusion through a barrier with\nconstant permeability $\\kappa_0$ can be modeled in terms of so-called snapping\nout Brownian motion (BM). The latter sews together successive rounds of\npartially reflecting BMs that are restricted to either the left or right of the\nbarrier. Each round is killed (absorbed) at the barrier when its Brownian local\ntime exceeds an exponential random variable parameterized by $\\kappa_0$. A new\nround is then immediately started in either direction with equal probability.\nIt has recently been shown that the probability density for snapping out BM\nsatisfies a renewal equation that relates the full density to the probability\ndensities of partially reflected BM on either side of the barrier. Moreover,\ngeneralized versions of the renewal equation can be constructed that\nincorporate non-Markovian, encounter-based models of absorption. In this paper\nwe extend the renewal theory of snapping out BM to single-particle diffusion in\nbounded domains and higher spatial dimensions. We also consider an example of\nan asymmetric interface in which the directional switching after each\nabsorption event is biased. Finally, we show how to incorporate an\nencounter-based model of absorption for single-particle diffusion through a\nspherically symmetric interface. We find that, even when the same non-Markovian\nmodel of absorption applies on either side of the interface, the resulting\npermeability is an asymmetric time-dependent function with memory. Moreover,\nthe permeability functions tend to be heavy-tailed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Some universal trends of the Mie(n,m) fluid thermodynamics: By using canonical Monte Carlo simulation, the liquid-vapor phase diagram,\nsurface tension, interface width, and pressure for the Mie(n,m) model fluids\nare calculated for six pairs of parameters $m$ and $n$. It is shown that after\ncertain re-scaling of fluid density the corresponding states rule can be\napplied for the calculations of the thermodynamic properties of the Mie model\nfluids, and for some real substances",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Innovative insights into which statements the third law of\n  thermodynamics includes exactly: It is found from textbooks and literature that the third law of\nthermodynamics has three different statements, i.e., the Nernst theorem,\nunattainability statement of absolute zero temperature, and heat capacity\nstatement. It is pointed out that such three statements correspond to three\nthermodynamic parameters, which are, respectively, the entropy, temperature,\nand heat capacity, and can be obtained by extrapolating the experimental\nresults of different parameters at ultra-low temperatures to absolute zero. It\nis expounded that because there's no need for additional assumptions in the\nderivation of the Nernst equation, the Nernst theorem should be renamed as the\nNernst statement. Moreover, it is proved that both the Nernst statement and the\nheat capacity statement are mutually deducible and equivalent, while the\nunattainability of absolute zero temperature is only a corollary of the Nernst\nstatement or the heat capacity statement so that it is unsuitably referred to\nas one statement of the third law of thermodynamics. The conclusion is that the\nNernst statement and the heat capacity statement are two equivalent statements\nof the third law of thermodynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cardy states, defect lines and chiral operators of coset CFTs on the\n  lattice: We construct Cardy states, defect lines and chiral operators for rational\ncoset conformal field theories on the lattice. The bulk theory is obtained by\ntaking the overlap between tensor network representations of different\nstring-nets, while the primary fields emerge from using the topological\nsuperselection sectors of the anyons in the original topological theory. This\nmapping provides an explicit manifestation of the equivalence between conformal\nfield theories in two dimensions and topological field theories in three\ndimensions: their groundstates and elementary excitations are represented by\nexactly the same tensors.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Random-cluster multi-histogram sampling for the q-state Potts model: Using the random-cluster representation of the $q$-state Potts models we\nconsider the pooling of data from cluster-update Monte Carlo simulations for\ndifferent thermal couplings $K$ and number of states per spin $q$. Proper\ncombination of histograms allows for the evaluation of thermal averages in a\nbroad range of $K$ and $q$ values, including non-integer values of $q$. Due to\nrestrictions in the sampling process proper normalization of the combined\nhistogram data is non-trivial. We discuss the different possibilities and\nanalyze their respective ranges of applicability.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Properties of pattern formation and selection processes in\n  nonequilibrium systems with external fluctuations: We extend the phase field crystal method for nonequilibrium patterning to\nstochastic systems with external source where transient dynamics is essential.\nIt was shown that at short time scales the system manifests pattern selection\nprocesses. These processes are studied by means of the structure function\ndynamics analysis. Nonequilibrium pattern-forming transitions are analyzed by\nmeans of numerical simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Coherent Averaging: an Alternative to the Average Hamiltonian Theory: Line-narrowing by periodic modulation of nuclear spin interaction\nHamiltonians is the central element of various experimental techniques in NMR\nspectroscopy. In this study, we present a theoretical formulation of coherent\naveraging to calculate the heights of narrowed spectral peaks. This concept is\nexperimentally demonstrated using proton spectra of solids obtained under fast\nmagic-angle spinning.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Sluggish Kinetics in the Parking Lot Model: We investigate, both analytically and by computer simulation, the kinetics of\na microscopic model of hard rods adsorbing on a linear substrate. For a small,\nbut finite desorption rate, the system reaches the equilibrium state very\nslowly, and the long-time kinetics display three successive regimes: an\nalgebraic one where the density varies as $1/t$, a logarithmic one where the\ndensity varies as $1/ln(t)$, followed by a terminal exponential approach. A\nmean-field approach fails to predict the relaxation rate associated with the\nlatter. We show that the correct answer can only be provided by using a\nsystematic description based on a gap-distribution approach.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Bi-Critical Central Point Of J FN -J SN Ising Model Phase Diagram: When interfaces between ordered domains are ordered clusters, frustration\ndisappears. A phase with mixed ordered structures emerges but no length scale\ncan be associated to. We show that sum of densities of each structure plays the\nrole of order parameter. For, we consider a regular half full lattice with\nrepulsive interaction extended to second neighboring particles. Ordered\nstructures are p(2X2) when ratio between second and first neighboring\ninteraction energies R=J SN /J FN <0.5 and degenerate p(2X1)/p(1X2) for R>0.5.\nThe ground states coexist with another named p(4X2)/p(2X4) at central\nbi-critical point: a state to cross when passing between non-frustrated ordered\nphases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermal noise of a cryo-cooled silicon cantilever locally heated up to\n  its melting point: The Fluctuation-Dissipation Theorem (FDT) is a powerful tool to estimate the\nthermal noise of physical systems in equilibrium. In general however, thermal\nequilibrium is an approximation, or cannot be assumed at all. A more general\nformulation of the FDT is then needed to describe the behavior of the\nfluctuations. In our experiment we study a micro-cantilever brought\nout-ofequilibrium by a strong heat flux generated by the absorption of the\nlight of a laser. While the base is kept at cryogenic temperatures, the tip is\nheated up to the melting point, thus creating the highest temperature\ndifference the system can sustain. We independently estimate the temperature\nprofile of the cantilever and its mechanical fluctuations, as well as its\ndissipation. We then demonstrate how the thermal fluctuations of all the\nobserved degrees of freedom, though increasing with the heat flux, are much\nlower than what is expected from the average temperature of the system. We\ninterpret these results thanks to a minimal extension of the FDT: this dearth\nof thermal noise arises from a dissipation shared between clamping losses and\ndistributed damping.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Short-range Ising spin glasses: the metastate interpretation of replica\n  symmetry breaking: Parisi's formal replica-symmetry--breaking (RSB) scheme for mean-field spin\nglasses has long been interpreted in terms of many pure states organized\nultrametrically. However, the early version of this interpretation, as applied\nto the short-range Edwards-Anderson model, runs into problems because as shown\nby Newman and Stein (NS) it does not allow for chaotic size dependence, and\npredicts non-self-averaging that cannot occur. NS proposed the concept of the\nmetastate (a probability distribution over infinite-size Gibbs states in a\ngiven sample that captures the effects of chaotic size dependence) and a\nnon-standard interpretation of the RSB results in which the metastate is\nnon-trivial and is responsible for what was called non-self-averaging. Here we\nuse the effective field theory of RSB, in conjunction with the rigorous\ndefinitions of pure states and the metastate in infinite-size systems, to show\nthat the non-standard picture follows directly from the RSB mean-field theory.\nIn addition, the metastate-averaged state possesses power-law correlations\nthroughout the low temperature phase; the corresponding exponent $\\zeta$ takes\nthe value $4$ according to the field theory in high dimensions $d$, and\ndescribes the effective fractal dimension of clusters of spins. Further, the\nlogarithm of the number of pure states in the decomposition of the\nmetastate-averaged state that can be distinguished if only correlations in a\nwindow of size $W$ can be observed is of order $W^{d-\\zeta}$. These results\nextend the non-standard picture quantitatively; we show that arguments against\nthis scenario are inconclusive.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Tsallis nonextensive statistical mechanics of El Nino Southern\n  Oscillation Index: The shape and tails of partial distribution functions (PDF) for a\nclimatological signal, i.e. the El Nino SOI and the turbulent nature of the\nocean-atmosphere variability are linked through a model encompassing Tsallis\nnonextensive statistics and leading to evolution equations of the Langevin and\nFokker-Planck type. A model originally proposed to describe the intermittent\nbehavior of turbulent flows describes the behavior of the normalized\nvariability for such a climatological index, for small and large time windows,\nboth for small and large variability. This normalized variabil- ity\ndistributions can be sufficiently well fitted with a chi-square-distribution.\nThe transition between the small time scale model of nonextensive, intermittent\nprocess and the large scale Gaussian exten- sive homogeneous fluctuation\npicture is found to occur at above ca. a 48 months time lag. The intermittency\nexponent ($\\kappa$) in the framework of the Kolmogorov log-normal model is\nfound to be related to the scaling exponent of the PDF moments. The value of\n$\\kappa$ (= 0.25) is in agreement with the intermittency exponent recently\nobtained for other atmospheric data.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Exact solution for a sample space reducing stochastic process: Stochastic processes wherein the size of the state space is changing as a\nfunction of time offer models for the emergence of scale-invariant features\nobserved in complex systems. I consider such a sample-space reducing (SSR)\nstochastic process that results in a random sequence of strictly decreasing\nintegers $\\{x(t)\\}$, $0\\le t \\le \\tau$, with boundary conditions $x(0) = N$ and\n$x(\\tau)$ = 1. This model is shown to be exactly solvable:\n$\\mathcal{P}_N(\\tau)$, the probability that the process survives for time\n$\\tau$ is analytically evaluated. In the limit of large $N$, the asymptotic\nform of this probability distribution is Gaussian, with mean and variance both\nvarying logarithmically with system size: $\\langle \\tau \\rangle \\sim \\ln N$ and\n$\\sigma_{\\tau}^{2} \\sim \\ln N$. Correspondence can be made between survival\ntime statistics in the SSR process and record statistics of i.i.d. random\nvariables.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling laws for single-file diffusion of adhesive particles: Single-file diffusion refers to the Brownian motion in narrow channels where\nparticles cannot pass each other. In such processes, the diffusion of a tagged\nparticle is typically normal at short times and becomes subdiffusive at long\ntimes. For hard-sphere interparticle interaction, the time-dependent mean\nsquared displacement of a tracer is well understood. Here we develop a scaling\ntheory for adhesive particles. It provides a full description of the\ntime-dependent diffusive behavior with a scaling function that depends on an\neffective strength of adhesive interaction. Particle clustering induced by the\nadhesive interaction slows down the diffusion at short times, while it enhances\nsubdiffusion at long times. The enhancement effect can be quantified in\nmeasurements irrespective of how tagged particles are injected into the system.\nCombined effects of pore structure and particle adhesiveness should speed up\ntranslocation of molecules through narrow pores.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Sensitivity of solid phase stability to the interparticle potential\n  range: studies of a new Lennard-Jones like model: In a recent article, Wang et al (Phys. Chem. Chem. Phys., 22, 10624 (2020))\nintroduced a new class of interparticle potential for molecular simulations.\nThe potential is defined by a single range parameter, eliminating the need to\ndecide how to truncate truly long-range interactions like the Lennard-Jones\n(LJ) potential. The authors explored the phase diagram for a particular value\nof the range parameter for which their potential is similar in shape to the LJ\n12-6 potential. We have reevaluated the solid phase behaviour of this model\nusing both Lattice Switch Monte Carlo and thermodynamic integration. In\naddition to finding that the boundary between hexagonal close packed (hcp) and\nface centred cubic (fcc) phases presented by Wang et al was calculated\nincorrectly, we show that owing to its finite range, the new potential exhibits\nseveral 'artifact' reentrant transitions between hcp and fcc phases. The\nartifact phases, which do not occur in the full (untruncated) LJ system, are\nalso found for typically adopted forms of the truncated and shifted LJ\npotential. However, whilst in the latter case one can systematically\ninvestigate and correct for the effects of the finite range on the calculated\nphase behaviour, this is not possible for the new potential because the choice\nof range parameter affects the entire potential shape. Our results highlight\nthat potentials with finite range may fail to represent the crystalline phase\nbehaviour of systems with long-range dispersion interactions, even\nqualitatively.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Introduction to Markov Chain Monte Carlo Simulations and their\n  Statistical Analysis: This article is a tutorial on Markov chain Monte Carlo simulations and their\nstatistical analysis. The theoretical concepts are illustrated through many\nnumerical assignments from the author's book on the subject. Computer code (in\nFortran) is available for all subjects covered and can be downloaded from the\nweb.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quantum Films Adsorbed on Graphite: Third and Fourth Helium Layers: Using a path-integral Monte Carlo method for simulating superfluid quantum\nfilms, we investigate helium layers adsorbed on a substrate consisting of\ngraphite plus two solid helium layers. Our results for the promotion densities\nand the dependence of the superfluid density on coverage are in agreement with\nexperiment. We can also explain certain features of the measured heat capacity\nas a function of temperature and coverage.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Memory and irreversibility on two-dimensional overdamped Brownian\n  dynamics: We consider the effects of memory on the stationary behavior of a\ntwo-dimensional Langevin dynamics in a confining potential. The system is\ntreated in an overdamped approximation and the degrees of freedom are under the\ninfluence of distinct kinds of stochastic forces, described by Gaussian white\nand colored noises, as well as different effective temperatures. The joint\ndistribution function is calculated by time-averaging approaches, and the\nlong-term behavior is analyzed. We determine the influence of noise temporal\ncorrelations on the steady-state behavior of heat flux and entropy production.\nNon-Markovian effects lead to a decaying heat exchange with spring force\nparameter, which is in contrast to the usual linear dependence when only\nGaussian white noises are presented in overdamped treatments. Also, the model\nexhibits non-equilibrium states characterized by a decreasing entropy\nproduction with memory time-scale.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cascading Dynamics in Modular Networks: In this paper we study a simple cascading process in a structured\nheterogeneous population, namely, a network composed of two loosely coupled\ncommunities. We demonstrate that under certain conditions the cascading\ndynamics in such a network has a two--tiered structure that characterizes\nactivity spreading at different rates in the communities. We study the dynamics\nof the model using both simulations and an analytical approach based on\nannealed approximation, and obtain good agreement between the two. Our results\nsuggest that network modularity might have implications in various\napplications, such as epidemiology and viral marketing.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Asymmetric temperature equilibration with heat flow from cold to hot in\n  a quantum thermodynamic system: A model computational quantum thermodynamic network is constructed with two\nvariable temperature baths coupled by a linker system, with an asymmetry in the\ncoupling of the linker to the two baths. It is found in computational\nsimulations that the baths come to \"thermal equilibrium\" at different bath\nenergies and temperatures. In a sense, heat is observed to flow from cold to\nhot. A description is given in which a recently defined quantum entropy\n$S^Q_{univ}$ for a pure state \"universe\" continues to increase after passing\nthrough the classical equilibrium point of equal temperatures, reaching a\nmaximum at the asymmetric equilibrium. Thus, a second law account $\\Delta\nS^Q_{univ} \\ge 0$ holds for the asymmetric quantum process. In contrast, a von\nNeumann entropy description fails to uphold the entropy law, with a maximum\nnear when the two temperatures are equal, then a decrease $\\Delta S^{vN} < 0$\non the way to the asymmetric equilibrium.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reaction Front in an A+B -> C Reaction-Subdiffusion Process: We study the reaction front for the process A+B -> C in which the reagents\nmove subdiffusively. Our theoretical description is based on a fractional\nreaction-subdiffusion equation in which both the motion and the reaction terms\nare affected by the subdiffusive character of the process. We design numerical\nsimulations to check our theoretical results, describing the simulations in\nsome detail because the rules necessarily differ in important respects from\nthose used in diffusive processes. Comparisons between theory and simulations\nare on the whole favorable, with the most difficult quantities to capture being\nthose that involve very small numbers of particles. In particular, we analyze\nthe total number of product particles, the width of the depletion zone, the\nproduction profile of product and its width, as well as the reactant\nconcentrations at the center of the reaction zone, all as a function of time.\nWe also analyze the shape of the product profile as a function of time, in\nparticular its unusual behavior at the center of the reaction zone.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Constructing smooth potentials of mean force, radial, distribution\n  functions and probability densities from sampled data: In this paper a method of obtaining smooth analytical estimates of\nprobability densities, radial distribution functions and potentials of mean\nforce from sampled data in a statistically controlled fashion is presented. The\napproach is general and can be applied to any density of a single random\nvariable. The method outlined here avoids the use of histograms, which require\nthe specification of a physical parameter (bin size) and tend to give noisy\nresults. The technique is an extension of the Berg-Harris method [B.A. Berg and\nR.C. Harris, Comp. Phys. Comm. 179, 443 (2008)], which is typically inaccurate\nfor radial distribution functions and potentials of mean force due to a\nnon-uniform Jacobian factor. In addition, the standard method often requires a\nlarge number of Fourier modes to represent radial distribution functions, which\ntends to lead to oscillatory fits. It is shown that the issues of poor sampling\ndue to a Jacobian factor can be resolved using a biased resampling scheme,\nwhile the requirement of a large number of Fourier modes is mitigated through\nan automated piecewise construction approach. The method is demonstrated by\nanalyzing the radial distribution functions in an energy-discretized water\nmodel. In addition, the fitting procedure is illustrated on three more\napplications for which the original Berg-Harris method is not suitable, namely,\na random variable with a discontinuous probability density, a density with long\ntails, and the distribution of the first arrival times of a diffusing particle\nto a sphere, which has both long tails and short-time structure. In all cases,\nthe resampled, piecewise analytical fit outperforms the histogram and the\noriginal Berg-Harris method.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Spontaneous Breaking of Translational Invariance and Spatial\n  Condensation in Stationary States on a Ring: II. The Charged System and the\n  Two-component Burgers Equations: We further study the stochastic model discussed in Ref.[2] in which positive\nand negative particles diffuse in an asymmetric, CP invariant way on a ring.\nThe positive particles hop clockwise, the negative counter-clockwise and\noppositely-charged adjacent particles may swap positions. We extend the\nanalysis of this model to the case when the densities of the charged particles\nare not the same. The mean-field equations describing the model are coupled\nnonlinear differential equations that we call the two-component Burgers\nequations. We find roundabout weak solutions of these equations. These\nsolutions are used to describe the properties of the stationary states of the\nstochastic model. The values of the currents and of various two-point\ncorrelation functions obtained from Monte-Carlo simulations are compared with\nthe mean-field results. Like in the case of equal densities, one finds a pure\nphase, a mixed phase and a disordered phase.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical Properties of Contact Maps: A contact map is a simple representation of the structure of proteins and\nother chain-like macromolecules. This representation is quite amenable to\nnumerical studies of folding. We show that the number of contact maps\ncorresponding to the possible configurations of a polypeptide chain of N amino\nacids, represented by (N-1)-step self avoiding walks on a lattice, grows\nexponentially with N for all dimensions D>1. We carry out exact enumerations in\nD=2 on the square and triangular lattices for walks of up to 20 steps and\ninvestigate various statistical properties of contact maps corresponding to\nsuch walks. We also study the exact statistics of contact maps generated by\nwalks on a ladder.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The weighted random graph model: We introduce the weighted random graph (WRG) model, which represents the\nweighted counterpart of the Erdos-Renyi random graph and provides fundamental\ninsights into more complicated weighted networks. We find analytically that the\nWRG is characterized by a geometric weight distribution, a binomial degree\ndistribution and a negative binomial strength distribution. We also\ncharacterize exactly the percolation phase transitions associated with edge\nremoval and with the appearance of weighted subgraphs of any order and\nintensity. We find that even this completely null model displays a percolation\nbehavior similar to what observed in real weighted networks, implying that edge\nremoval cannot be used to detect community structure empirically. By contrast,\nthe analysis of clustering successfully reveals different patterns between the\nWRG and real networks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Truncations of Random Orthogonal Matrices: Statistical properties of non--symmetric real random matrices of size $M$,\nobtained as truncations of random orthogonal $N\\times N$ matrices are\ninvestigated. We derive an exact formula for the density of eigenvalues which\nconsists of two components: finite fraction of eigenvalues are real, while the\nremaining part of the spectrum is located inside the unit disk symmetrically\nwith respect to the real axis. In the case of strong non--orthogonality,\n$M/N=$const, the behavior typical to real Ginibre ensemble is found. In the\ncase $M=N-L$ with fixed $L$, a universal distribution of resonance widths is\nrecovered.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Stochastic thermodynamics and modes of operation of a ribosome: a\n  network theoretic perspective: The ribosome is one of the largest and most complex macromolecular machines\nin living cells. It polymerizes a protein in a step-by-step manner as directed\nby the corresponding nucleotide sequence on the template messenger RNA (mRNA)\nand this process is referred to as `translation' of the genetic message encoded\nin the sequence of mRNA transcript. In each successful chemo-mechanical cycle\nduring the (protein) elongation stage, the ribosome elongates the protein by a\nsingle subunit, called amino acid, and steps forward on the template mRNA by\nthree nucleotides called a codon. Therefore, a ribosome is also regarded as a\nmolecular motor for which the mRNA serves as the track, its step size is that\nof a codon and two molecules of GTP and one molecule of ATP hydrolyzed in that\ncycle serve as its fuel. What adds further complexity is the existence of\ncompeting pathways leading to distinct cycles, branched pathways in each cycle\nand futile consumption of fuel that leads neither to elongation of the nascent\nprotein nor forward stepping of the ribosome on its track. We investigate a\nmodel formulated in terms of the network of discrete chemo-mechanical states of\na ribosome during the elongation stage of translation. The model is analyzed\nusing a combination of stochastic thermodynamic and kinetic analysis based on a\ngraph-theoretic approach. We derive the exact solution of the corresponding\nmaster equations. We represent the steady state in terms of the cycles of the\nunderlying network and discuss the energy transduction processes. We identify\nthe various possible modes of operation of a ribosome in terms of its average\nvelocity and mean rate of GTP hydrolysis. We also compute entropy production as\nfunctions of the rates of the interstate transitions and the thermodynamic cost\nfor accuracy of the translation process.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the existence of supersolid helium-4 monolayer films: Extensive Monte Carlo simulations of helium-4 monolayer films adsorbed on\nweak substrates have been carried out, aimed at ascertaining the possible\noccurrence of a quasi-two-dimensional supersolid phase. Only crystalline films\nnot registered with underlying substrates are considered. Numerical results\nyield strong evidence that helium-4 will not form a supersolid film on {any}\nsubstrate strong enough to stabilize a crystalline layer. On weaker substrates,\ncontinuous growth of a liquid film takes place.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Non-Equilibrium Steady State of the Lieb-Liniger model: exact treatment\n  of the Tonks Girardeau limit: Aiming at studying the emergence of Non-Equilibrium Steady States (NESS) in\nquantum integrable models by means of an exact analytical method, we focus on\nthe Tonks-Girardeau or hard-core boson limit of the Lieb-Liniger model. We\nconsider the abrupt expansion of a gas from one half to the entire confining\nbox, a prototypical case of inhomogeneous quench, also known as \"geometric\nquench\". Based on the exact calculation of quench overlaps, we develop an\nanalytical method for the derivation of the NESS by rigorously treating the\nthermodynamic and large time and distance limit. Our method is based on complex\nanalysis tools for the derivation of the asymptotics of the many-body\nwavefunction, does not make essential use of the effectively non-interacting\ncharacter of the hard-core boson gas and is sufficiently robust for\ngeneralisation to the genuinely interacting case.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dissipative maps at the chaos threshold: Numerical results for the\n  single-site map: We numerically study, at the edge of chaos, the behaviour of the sibgle-site\nmap $x_{t+1}=x_t-x_t/(x_t^2+\\gamma^2)$, where $\\gamma$ is the map parameter.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A perturbative path integral study of active and passive tracer\n  diffusion in fluctuating fields: We study the effective diffusion constant of a Brownian particle linearly\ncoupled to a thermally fluctuating scalar field. We use a path integral method\nto compute the effective diffusion coefficient perturbatively to lowest order\nin the coupling constant. This method can be applied to cases where the field\nis affected by the particle (an active tracer), and cases where the tracer is\npassive. Our results are applicable to a wide range of physical problems, from\na protein diffusing in a membrane to the dispersion of a passive tracer in a\nrandom potential. In the case of passive diffusion in a scalar field, we show\nthat the coupling to the field can, in some cases, speed up the diffusion\ncorresponding to a form of stochastic resonance. Our results on passive\ndiffusion are also confirmed via a perturbative calculation of the probability\ndensity function of the particle in a Fokker-Planck formulation of the problem.\nNumerical simulations on simplified systems corroborate our results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Virtual potentials for feedback traps: The recently developed feedback trap can be used to create arbitrary virtual\npotentials, to explore the dynamics of small particles or large molecules in\ncomplex situations. Experimentally, feedback traps introduce several finite\ntime scales: there is a delay between the measurement of a particle's position\nand the feedback response; the feedback response is applied for a finite update\ntime; and a finite camera exposure integrates motion. We show how to\nincorporate such timing effects into the description of particle motion. For\nthe test case of a virtual quadratic potential, we give the first accurate\ndescription of particle dynamics, calculating the power spectrum and variance\nof fluctuations as a function of feedback gain, testing against simulations. We\nshow that for small feedback gains, the motion approximates that of a particle\nin an ordinary harmonic potential. Moreover, if the potential is varied in\ntime, for example by varying its stiffness, the work that is calculated\napproximates that done in an ordinary changing potential. The quality of the\napproximation is set by the ratio of the update time of the feedback loop to\nthe relaxation time of motion in the virtual potential.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Potts-Percolation-Gauss Model of a Solid: We study a statistical mechanics model of a solid. Neighboring atoms are\nconnected by Hookian springs. If the energy is larger than a threshold the\n\"spring\" is more likely to fail, while if the energy is lower than the\nthreshold the spring is more likely to be alive. The phase diagram and\nthermodynamic quantities, such as free energy, numbers of bonds and clusters,\nand their fluctuations, are determined using renormalization-group and\nMonte-Carlo techniques.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Jamming versus Glass Transitions: Recent ideas based on the properties of assemblies of frictionless particles\nin mechanical equilibrium provide a perspective of amorphous systems different\nfrom that offered by the traditional approach originating in liquid theory. The\nrelation, if any, between these two points of view, and the relevance of the\nformer to the glass phase, has been difficult to ascertain. In this paper we\nintroduce a model for which both theories apply strictly: it exhibits on the\none hand an ideal glass transition and on the other `jamming' features\n(fragility, soft modes) virtually identical to that of real systems. This\nallows us to disentangle the different contents and domains of applicability of\nthe two physical phenomena.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Computing solution space properties of combinatorial optimization\n  problems via generic tensor networks: We introduce a unified framework to compute the solution space properties of\na broad class of combinatorial optimization problems. These properties include\nfinding one of the optimum solutions, counting the number of solutions of a\ngiven size, and enumeration and sampling of solutions of a given size. Using\nthe independent set problem as an example, we show how all these solution space\nproperties can be computed in the unified approach of generic tensor networks.\nWe demonstrate the versatility of this computational tool by applying it to\nseveral examples, including computing the entropy constant for hardcore lattice\ngases, studying the overlap gap properties, and analyzing the performance of\nquantum and classical algorithms for finding maximum independent sets.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Higgs and Goldstone modes in crystalline solids: In crystalline solids the acoustic phonon is known to be the\nfrequency-gapless Goldstone boson emerging from the spontaneous breaking of the\ncontinuous Galilean symmetry induced by the crystal lattice. It has also been\ndescribed as the gauge boson that appears when the free electrons' Lagrangian\nin the crystal is requested to be locally gauge invariant with respect to T(3),\nthe group of the infinitesimal spatial translations. However, the\nnon-Abelianity of T(3) makes the acoustic phonon a frequency-gapped mode, in\ncontradiction with its description as Goldstone boson. A different perspective\novercomes this contradiction. In fact, we show that both the acoustic and\noptical phonon - the latter never appearing following the other two approaches\n- emerge respectively as the gapless Goldstone (phase) and the gapped Higgs\n(amplitude) fluctuation mode of an order parameter arising from the spontaneous\nbreaking of a global symmetry, without invoking the gauge principle. The\noptical phonon's frequency-gap is present in all regimes, and it arises from a\nmass-like term in the Lagrangian due to the Higgs mechanism itself. Instead, an\neventual acoustic phonon's frequency-gap appears only in the strong nonlinear\nregime, and it is due to an anharmonic term, the same term arising from the\ngauging of T(3), an approach which did not provide any description of the\noptical phonon, though. In addition, the Higgs mechanism describes all the\nphonon-phonon interactions, including a possible perturbation on the acoustic\nphonon's frequency dispersion relation induced by the eventual optical phonon,\na peculiar behavior not described so far in these terms.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Thermodynamic cost of external control: Artificial molecular machines are often driven by the periodic variation of\nan external parameter. This external control exerts work on the system of which\na part can be extracted as output if the system runs against an applied load.\nUsually, the thermodynamic cost of the process that generates the external\ncontrol is ignored. Here, we derive a refined second law for such small\nmachines that include this cost, which is, for example, generated by free\nenergy consumption of a chemical reaction that modifies the energy landscape\nfor such a machine. In the limit of irreversible control, this refined second\nlaw becomes the standard one. Beyond this ideal limiting case, our analysis\nshows that due to a new entropic term unexpected regimes can occur: The control\nwork can be smaller than the extracted work and the work required to generate\nthe control can be smaller than this control work. Our general inequalities are\nillustrated by a paradigmatic three-state system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Component sizes in networks with arbitrary degree distributions: We give an exact solution for the complete distribution of component sizes in\nrandom networks with arbitrary degree distributions. The solution tells us the\nprobability that a randomly chosen node belongs to a component of size s, for\nany s. We apply our results to networks with the three most commonly studied\ndegree distributions -- Poisson, exponential, and power-law -- as well as to\nthe calculation of cluster sizes for bond percolation on networks, which\ncorrespond to the sizes of outbreaks of SIR epidemic processes on the same\nnetworks. For the particular case of the power-law degree distribution, we show\nthat the component size distribution itself follows a power law everywhere\nbelow the phase transition at which a giant component forms, but takes an\nexponential form when a giant component is present.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuation-dissipation theorem for thermo-refractive noise: We introduce a simple prescription for calculating the spectra of thermal\nfluctuations of temperature-dependent quantities of the form $\\hat{\\delta\nT}(t)=\\int d^3\\vec{r} \\delta T(\\vec{r},t) q(\\vec{r})$. Here $T(\\vec{r}, t)$ is\nthe local temperature at location $\\vec{r}$ and time $t$, and $q(\\vec{r})$ is\nan arbitrary function. As an example of a possible application, we compute the\nspectrum of thermo-refractive coating noise in LIGO, and find a complete\nagreement with the previous calculation of Braginsky, Gorodetsky and\nVyatchanin. Our method has computational advantage, especially for non-regular\nor non-symmetric geometries, and for the cases where $q(\\vec{r})$ is\nnon-negligible in a significant fraction of the total volume.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Biochemical machines for the interconversion of mutual information and\n  work: We propose a physically-realisable biochemical device that is coupled to a\nbiochemical reservoir of mutual information, fuel molecules and a chemical\nbath. Mutual information allows work to be done on the bath even when the fuel\nmolecules appear to be in equilibrium; alternatively, mutual information can be\ncreated by driving from the fuel or the bath. The system exhibits diverse\nbehaviour, including a regime in which the information, despite increasing\nduring the reaction, enhances the extracted work. We further demonstrate that a\nmodified device can function without the need for external manipulation,\neliminating the need for a complex and potentially costly control.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Computation of the Kolmogorov-Sinai entropy using statistitical\n  mechanics: Application of an exchange Monte Carlo method: We propose a method for computing the Kolmogorov-Sinai (KS) entropy of\nchaotic systems. In this method, the KS entropy is expressed as a statistical\naverage over the canonical ensemble for a Hamiltonian with many ground states.\nThis Hamiltonian is constructed directly from an evolution equation that\nexhibits chaotic dynamics. As an example, we compute the KS entropy for a\nchaotic repeller by evaluating the thermodynamic entropy of a system with many\nground states.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kardar-Parisi-Zhang universality from soft gauge modes: The emergence of superdiffusive spin dynamics in integrable classical and\nquantum magnets is well established by now, but there is no generally valid\ntheoretical explanation for this phenomenon. A fundamental difficulty is that\nthe hydrodynamic fluctuations of conserved quasiparticle modes are purely\ndiffusive. We argue that in isotropic integrable magnets, a complete\nhydrodynamic description must include soft \"gauge\" degrees of freedom, that\narise from spontaneous breaking of the Bethe pseudovacuum symmetry. We show\nthat the coarse-grained time evolution of these modes lies in the\nKardar-Parisi-Zhang universality class of dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Soft modes in Fermi liquids at arbitrary temperatures: We use kinetic-theory methods to analyze Landau Fermi-liquid theory, and in\nparticular to investigate the number and nature of soft modes in Fermi liquids,\nboth in the hydrodynamic and the collisionless regimes. In the hydrodynamic\nregime we show that Fermi-liquid theory is consistent with Navier-Stokes\nhydrodynamics at all temperatures. The soft modes are the ones familiar from\nclassical hydrodynamics that are controlled by the five conservation laws;\nnamely, two first-sound modes, two shear diffusion modes, and one heat\ndiffusion mode. These modes have a particle-like spectrum and are soft, or\nscale invariant, at all temperatures. In the collisionless regime we show that\nthe entire single-particle distribution function is soft with a continuous part\nof the spectrum. This continuous soft mode, which is well known but often not\nemphasized, has important physical consequences, e.g., for certain quantum\nphase transitions. In addition, there are the well known soft zero-sound\nexcitations that describe angular fluctuations of the Fermi surface; their\nspectra are particle-like. They are unrelated to conservation laws, acquire a\nmass at any nonzero temperature, and their number depends on the strength of\nthe quasiparticle interaction. We also discuss the fates of these two families\nof soft modes as the temperature changes. With increasing temperature the size\nof the collisionless regime shrinks, the damping of the modes grows, and\neventually all of the collisionless modes become overdamped. In their stead the\nfive hydrodynamic modes appear in the hydrodynamic regime at asymptotically low\nfrequencies. The two families of soft modes are unrelated and have very\ndifferent physical origins.In charged Fermi liquids the first-sound modes in\nthe hydrodynamic regime and the l=0 zero-sound modes in the collisionless\nregime get replaced by plasmons, all other modes remain soft.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Cahn-Hilliard Theory for Unstable Granular Flows: A Cahn-Hilliard-type theory for hydrodynamic fluctuations is proposed that\ngives a quantitative description of the slowly evolving spatial correlations\nand structures in density and flow fields in the early stages of evolution of\nfreely cooling granular fluids. Two mechanisms for pattern selection and\nstructure formation are identified: unstable modes leading to density\nclustering (compare spinodal decomposition), and selective noise reduction\n(compare peneplanation in structural geology) leading to vortex structures. As\ntime increases, the structure factor for the density field develops a maximum,\nwhich shifts to smaller wave numbers. This corresponds to an approximately\ndiffusively growing length scale for density clusters. The spatial velocity\ncorrelations exhibit algebraic decay $\\sim r^{-d}$ on intermediate length\nscales. The theoretical predictions for spatial correlation functions and\nstructure factors agree well with molecular dynamics simulations of a system of\ninelastic hard disks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal scaling relations for logarithmic-correction exponents: By the early 1960's advances in statistical physics had established the\nexistence of universality classes for systems with second-order phase\ntransitions and characterized these by critical exponents which are different\nto the classical ones. There followed the discovery of (now famous) scaling\nrelations between the power-law critical exponents describing second-order\ncriticality. These scaling relations are of fundamental importance and now form\na cornerstone of statistical mechanics. In certain circumstances, such scaling\nbehaviour is modified by multiplicative logarithmic corrections. These are also\ncharacterized by critical exponents, analogous to the standard ones. Recently\nscaling relations between these logarithmic exponents have been established.\nHere, the theories associated with these advances are presented and expanded\nand the status of investigations into logarithmic corrections in a variety of\nmodels is reviewed.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Slowest relaxation mode of the partially asymmetric exclusion process\n  with open boundaries: We analyze the Bethe ansatz equations describing the complete spectrum of the\ntransition matrix of the partially asymmetric exclusion process on a finite\nlattice and with the most general open boundary conditions. We extend results\nobtained recently for totally asymmetric diffusion [J. de Gier and F.H.L.\nEssler, J. Stat. Mech. P12011 (2006)] to the case of partial symmetry. We\ndetermine the finite-size scaling of the spectral gap, which characterizes the\napproach to stationarity at large times, in the low and high density regimes\nand on the coexistence line. We observe boundary induced crossovers and discuss\npossible interpretations of our results in terms of effective domain wall\ntheories.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Taming chaos to sample rare events: the effect of weak chaos: Rare events in non-linear dynamical systems are difficult to sample because\nof the sensitivity to perturbations of initial conditions and of complex\nlandscapes in phase space. Here we discuss strategies to control these\ndifficulties and succeed in obtainining an efficient sampling within a\nMetropolis-Hastings Monte Carlo framework. After reviewing previous successes\nin the case of strongly chaotic systems, we discuss the case of weakly chaotic\nsystems. We show how different types of non-hyperbolicities limit the\nefficiency of previously designed sampling methods and we discuss strategies\nhow to account for them. We focus on paradigmatic low-dimensional chaotic\nsystems such as the logistic map, the Pomeau-Maneville map, and area-preserving\nmaps with mixed phase space.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Rotating Vicsek Model: Pattern Formation and Enhanced Flocking in\n  Chiral Active Matter: We generalize the Vicsek model to describe the collective behaviour of polar\ncircle swimmers with local alignment interactions. While the phase transition\nleading to collective motion in 2D (flocking) occurs at the same interaction to\nnoise ratio as for linear swimmers, as we show, circular motion enhances the\npolarization in the ordered phase (enhanced flocking) and induces secondary\ninstabilities leading to structure formation. Slow rotations result in phase\nseparation whereas fast rotations generate patterns which consist of phase\nsynchronized microflocks of controllable self-limited size. Our results defy\nthe viewpoint that monofrequent rotations form a rather trivial extension of\nthe Vicsek model and establish a generic route to pattern formation in chiral\nactive matter with possible applications to control coarsening and to design\nrotating microflocks.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "From Boltzmann-Gibbs ensemble to generalized ensembles: We reconsider the Boltzmann-Gibbs statistical ensemble in thermodynamics\nusing the multinomial coefficient approach. We show that an ensemble is defined\nby the determination of four statistical quantities, the element probabilities\n$p_i$, the configuration probabilities $P_j$, the entropy $S$ and the extremum\nconstraints (EC). This distinction is of central importance for the\nunderstanding of the conditions under which a microcanonical, canonical and\nmacrocanonical ensemble is defined. These three ensembles are characterized by\nthe conservation of their sizes. A variation of the ensemble size creates\ndifficulties in the definitions of the quadruplet $\\{p_i, P_j, S, \\mt{EC}\\}$,\ngiving rise for a generalization of the Boltzmann-Gibbs formalism, such one as\nintroduced by Tsallis. We demonstrate that generalized thermodynamics represent\na transformation of ordinary thermodynamics in such a way that the energy of\nthe system remains conserved.\n  From our results it becomes evident that Tsallis's formalism is a very\nspecific generalization, however, not the only one. We also revisit the\nJaynes's Maximum Entropy Principle, showing that in general it can lead to\nincorrect results and consider the appropriate corrections.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Different critical behaviors in cubic to trigonal and tetragonal\n  perovskites: Perovskites like LaAlO3 (or SrTiO3) undergo displacive structural phase\ntransitions from a cubic crystal to a trigonal (or tetragonal) structure. For\nmany years, the critical exponents in both these types of transitions have been\nfitted to those of the isotropic three-components Heisenberg model. However,\nfield theoretical calculations showed that the isotropic fixed point of the\nrenormalization group is unstable, and renormalization group iterations flow\neither to a cubic fixed point or to a fluctuation-driven first-order\ntransition. Here we show that these two scenarios correspond to the cubic to\ntrigonal and to the cubic to tetragonal transitions, respectively. In both\ncases, the critical behavior is described by slowly varying effective critical\nexponents, which exhibit universal features. For the trigonal case, we predict\na crossover of the effective exponents from their Ising values to their cubic\nvalues (which are close to the isotropic ones). For the tetragonal case, the\neffective exponents can have the isotropic values over a wide temperature\nrange, before exhibiting large changes en route to the first-order transition.\nNew renormalization group calculations near the isotropic fixed point in three\ndimensions are presented and used to estimate the effective exponents, and\ndedicated experiments to test these predictions are proposed. Similar\npredictions apply to cubic magnetic and ferroelectric systems.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Minimal Off-Lattice Model for Alpha-helical Proteins: A minimal off-lattice model for alpha-helical proteins is presented. It is\nbased on hydrophobicity forces and sequence independent local interactions. The\nlatter are chosen so as to favor the formation of alpha-helical structure. They\nmodel chirality and alpha-helical hydrogen bonding. The global structures\nresulting from the competition between these forces are studied by means of an\nefficient Monte Carlo method. The model is tested on two sequences of length\nN=21 and 33 which are intended to form 2- and 3-helix bundles, respectively.\nThe local structure of our model proteins is compared to that of real\nalpha-helical proteins, and is found to be very similar. The two sequences\ndisplay the desired numbers of helices in the folded phase. Only a few\ndifferent relative orientations of the helices are thermodynamically allowed.\nOur ability to investigate the thermodynamics relies heavily upon the\nefficiency of the used algorithm, simulated tempering; in this Monte Carlo\napproach, the temperature becomes a fluctuating variable, enabling the crossing\nof free-energy barriers.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Tagged Particle Correlations in the Asymmetric Simple Exclusion Process:\n  Finite Size Effects: We study finite size effects in the variance of the displacement of a tagged\nparticle in the stationary state of the Asymmetric Simple Exclusion Process\n(ASEP) on a ring of size $L$. The process involves hard core particles\nundergoing stochastic driven dynamics on a lattice. The variance of the\ndisplacement of the tagged particle, averaged with respect to an initial\nstationary ensemble and stochastic evolution, grows linearly with time at both\nsmall and very large times. We find that at intermediate times, it shows\noscillations with a well defined size-dependent period. These oscillations\narise from sliding density fluctuations (SDF) in the stationary state with\nrespect to the drift of the tagged particle, the density fluctuations being\ntransported through the system by kinematic waves. In the general context of\ndriven diffusive systems, both the Edwards-Wilkinson (EW) and the\nKardar-Parisi-Zhang (KPZ) fixed points are unstable with respect to the SDF\nfixed point, a flow towards which is generated on adding a gradient term to the\nEW and the KPZ time-evolution equation. We also study tagged particle\ncorrelations for a fixed initial configuration, drawn from the stationary\nensemble, following earlier work by van Beijeren. We find that the time\ndependence of this correlation is determined by the dissipation of the density\nfluctuations. We show that an exactly solvable linearized model captures the\nessential qualitative features seen in the finite size effects of the tagged\nparticle correlations in the ASEP. Moreover, this linearized model also\nprovides an exact coarse-grained description of two other microscopic models.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Specific heat anomalies of small quantum systems subjected to finite\n  baths: We have studied the specific heat of the $(N_S+N_B)$ model for an $N_S$-body\nharmonic oscillator (HO) system which is strongly coupled to an $N_B$-body HO\nbath without dissipation. The system specific heat of $C_S(T)$ becomes $N_S\nk_B$ at $T \\rightarrow \\infty$ and vanishes at $T = 0$ in accordance with the\nthird law of thermodynamics. The calculated $C_S(T)$ at low temperatures is not\nproportional to $N_S$ and shows an anomalous temperature dependence, strongly\ndepending on $N_S$, $N_B$ and the system-bath coupling. In particular at very\nlow (but finite) temperatures, it may become {\\it negative} for a strong\nsystem-bath coupling, which is in contrast with {\\it non-negative} specific\nheat of an HO system with $N_S=1$ reported by G-L. Ingold, P. H\\\"{a}nggi and P.\nTalkner [Phys. Rev. E {\\bf 79}, 061105 (2005)]. Our calculation indicates an\nimportance of taking account of finite $N_S$ in studying open quantum systems\nwhich may include an arbitrary number of particles in general.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Estimating differential entropy using recursive copula splitting: A method for estimating the Shannon differential entropy of multidimensional\nrandom variables using independent samples is described. The method is based on\ndecomposing the distribution into a product of the marginal distributions and\nthe joint dependency, also known as the copula. The entropy of marginals is\nestimated using one-dimensional methods. The entropy of the copula, which\nalways has a compact support, is estimated recursively by splitting the data\nalong statistically dependent dimensions. Numerical examples demonstrate that\nthe method is accurate for distributions with compact and non-compact supports,\nwhich is imperative when the support is not known or of mixed type (in\ndifferent dimensions). At high dimensions (larger than 20), our method is not\nonly more accurate, but also significantly more efficient than existing\napproaches.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Dynamical density functional theory for circle swimmers: The majority of studies on self-propelled particles and microswimmers\nconcentrates on objects that do not feature a deterministic bending of their\ntrajectory. However, perfect axial symmetry is hardly found in reality, and\nshape-asymmetric active microswimmers tend to show a persistent curvature of\ntheir trajectories. Consequently, we here present a particle-scale statistical\napproach of circle-swimmer suspensions in terms of a dynamical density\nfunctional theory. It is based on a minimal microswimmer model and,\nparticularly, includes hydrodynamic interactions between the swimmers. After\nderiving the theory, we numerically investigate a planar example situation of\nconfining the swimmers in a circularly symmetric potential trap. There, we find\nthat increasing curvature of the swimming trajectories can reverse the\nqualitative effect of active drive. More precisely, with increasing curvature,\nthe swimmers less effectively push outwards against the confinement, but\ninstead form high-density patches in the center of the trap. We conclude that\nthe circular motion of the individual swimmers has a localizing effect, also in\nthe presence of hydrodynamic interactions. Parts of our results could be\nconfirmed experimentally, for instance, using suspensions of L-shaped circle\nswimmers of different aspect ratio.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Singular relaxation of a random walk in a box with a Metropolis Monte\n  Carlo dynamics: We study analytically the relaxation eigenmodes of a simple Monte Carlo\nalgorithm, corresponding to a particle in a box which moves by uniform random\njumps. Moves outside of the box are rejected. At long times, the system\napproaches the equilibrium probability density, which is uniform inside the\nbox. We show that the relaxation towards this equilibrium is unusual: for a\njump length comparable to the size of the box, the number of relaxation\neigenmodes can be surprisingly small, one or two. We provide a complete\nanalytic description of the transition between these two regimes. When only a\nsingle relaxation eigenmode is present, a suitable choice of the symmetry of\nthe initial conditions gives a localizing decay to equilibrium. In this case,\nthe deviation from equilibrium concentrates at the edges of the box where the\nrejection probability is maximal. Finally, in addition to the relaxation\nanalysis of the master equation, we also describe the full eigen-spectrum of\nthe master equation including its sub-leading eigen-modes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Critical behaviour of annihilating random walk of two species with\n  exclusion in one dimension: The $A+A\\to 0$, $B+B\\to 0 $ process with exclusion between the different\nkinds is investigated here numerically. Before treating this model explicitly,\nwe study the generalized Domany-Kinzel cellular automaton model of Hinrichsen\non the line of the parameter space where only compact clusters can grow. The\nsimplest version is treated with two absorbing phases in addition to the active\none. The two kinds of kinks which arise in this case do not react, leading to\nkinetics differing from standard annihilating random walk of two species. Time\ndependent simulations are presented here to illustrate the differences caused\nby exclusion in the scaling properties of usually discussed characteristic\nquantities. The dependence on the density and composition of the initial state\nis most apparent. Making use of the parallelism between this process and\ndirected percolation limited by a reflecting parabolic surface we argue that\nthe two kinds of kinks exert marginal perturbation on each other leading to\ndeviations from standard annihilating random walk behavior.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Ashkin-Teller phase transition and multicritical behavior in a classical\n  monomer-dimer model: We use Monte Carlo simulations and tensor network methods to study a\nclassical monomer-dimer model on the square lattice with a hole (monomer)\nfugacity $z$, an aligning dimer-dimer interaction $u$ that favors columnar\norder, and an attractive dimer-dimer interaction $v$ between two adjacent\ndimers that lie on the same principal axis of the lattice. The Monte Carlo\nsimulations of finite size systems rely on our grand-canonical generalization\nof the dimer worm algorithm, while the tensor network computations are based on\na uniform matrix product ansatz for the eigenvector of the row-to-row transfer\nmatrix that work directly in the thermodynamic limit. The phase diagram has\nnematic, columnar order and fluid phases, and a nonzero temperature\nmulticritical point at which all three meet. For any fixed $v/u < \\infty$, we\nargue that this multicritical point continues to be located at a nonzero hole\nfugacity $z_{\\rm mc}(v/u) > 0$; our numerical results confirm this theoretical\nexpectation but find that $z_{\\rm mc}(v/u) \\to 0$ very rapidly as $v/u \\to\n\\infty$. Our numerical results also confirm the theoretical expectation that\nthe corresponding multicritical behavior is in the universality class of the\nfour-state Potts multicritical point on critical line of the two-dimensional\nAshkin-Teller model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Magnetization plateaus and phase diagrams of the extended Ising model on\n  the Shastry-Sutherland lattice: Effects of long-range interactions: Magnetization plateaus and phase diagrams of the extended Ising model on the\nShastry-Sutherland lattice with the first $(J_1)$, second $(J_2)$, third\n$(J_3)$ fourth $(J_4)$ and fifth $(J_5)$ nearest-neighbour spin couplings are\nstudied by the classical Monte Carlo method. It is shown that switching on\n$J_4$ and $J_5$ interactions (in addition to usually considered $J_1, J_2$ and\n$J_3$ interactions) changes significantly the picture of magnetization\nprocesses found for $J_4=J_5=0$ and leads to stabilization of new macroscopic\nmagnetic phases (plateaus) with fractional magnetization. In particular, it is\nfound that combined effects of $J_4$ and $J_5$ interactions generate the\nfollowing sequence of plateaus with the fractional magnetization: $m/m_s$=1/9,\n1/6, 2/9, 1/3, 4/9, 1/2, 5/9 and 2/3. The results obtained are consistent with\nexperimental measurements of magnetization curves in selected rare-earth\ntetraborides.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling Theories of Kosterlitz-Thouless Phase Transitions: We propose scaling theories for Kosterlitz-Thouless (KT) phase transitions on\nthe basis of the hallmark exponential growth of their correlation length.\nFinite-size scaling, finite-entanglement scaling, short-time critical dynamics,\nand finite-time scaling, as well as some of their combinations are studied.\nRelaxation times of both a usual power-law and an unusual power-law with a\nlogarithmic factor are considered. Finite-size and finite-entanglement scaling\nforms somehow similar to a frequently employed ansatz are presented. The\nKibble-Zurek scaling of topological defect density for a linear driving across\nthe KT transition point is investigated in detail. An implicit equation for a\nrate exponent in the theory is derived and the exponent varies with the\ndistance from the critical point and the driving rate consistent with relevant\nexperiments. To verify the theories, we utilize the KT phase transition of a\none-dimensional Bose-Hubbard model. The infinite time-evolving-block-decimation\nalgorithm is employed to solve numerically the model for finite bond\ndimensions. Both a correlation length and an entanglement entropy in imaginary\ntime and only the entanglement entropy in real-time driving are computed. Both\nthe short-time critical dynamics in imaginary time and the finite-time scaling\nin real-time driving, both including the finite bond dimension, for the\nmeasured quantities are found to describe the numerical results quite well via\nsurface collapses. The critical point is also estimated and confirmed to be\n$0.302(1)$ at the infinite bond dimension on the basis of the scaling form.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Numerical Study of the Thermodynamic Uncertainty Relation for the\n  KPZ-Equation: A general framework for the field-theoretic thermodynamic uncertainty\nrelation was recently proposed and illustrated with the $(1+1)$ dimensional\nKardar-Parisi-Zhang equation. In the present paper, the analytical results\nobtained there in the weak coupling limit are tested via a direct numerical\nsimulation of the KPZ equation with good agreement. The accuracy of the\nnumerical results varies with the respective choice of discretization of the\nKPZ non-linearity. Whereas the numerical simulations strongly support the\nanalytical predictions, an inherent limitation to the accuracy of the\napproximation to the total entropy production is found. In an analytical\ntreatment of a generalized discretization of the KPZ non-linearity, the origin\nof this limitation is explained and shown to be an intrinsic property of the\nemployed discretization scheme.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "On the von Neumann entropy of a bath linearly coupled to a driven\n  quantum system: The change of the von Neumann entropy of a set of harmonic oscillators\ninitially in thermal equilibrium and interacting linearly with an externally\ndriven quantum system is computed by adapting the Feynman-Vernon influence\nfunctional formalism. This quantum entropy production has the form of the\nexpectation value of three functionals of the forward and backward paths\ndescribing the system history in the Feynman-Vernon theory. In the classical\nlimit of Kramers-Langevin dynamics (Caldeira-Leggett model) these functionals\ncombine to three terms, where the first is the entropy production functional of\nstochastic thermodynamics, the classical work done by the system on the\nenvironment in units of $k_BT$, the second another functional with no analogue\nin stochastic thermodynamics, and the third is a boundary term.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Pipe network model for scaling of dynamic interfaces in porous media: We present a numerical study on the dynamics of imbibition fronts in porous\nmedia using a pipe network model. This model quantitatively reproduces the\nanomalous scaling behavior found in imbibition experiments [Phys. Rev. E {\\bf\n52}, 5166 (1995)]. Using simple scaling arguments, we derive a new identity\namong the scaling exponents in agreement with the experimental results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Communication and optimal hierarchical networks: We study a general and simple model for communication processes. In the\nmodel, agents in a network (in particular, an organization) interchange\ninformation packets following simple rules that take into account the limited\ncapability of the agents to deal with packets and the cost associated to the\nexistence of open communication channels. Due to the limitation in the\ncapability, the network collapses under certain conditions. We focus on when\nthe collapse occurs for hierarchical networks and also on the influence of the\nflatness or steepness of the structure. We find that the need for hierarchy is\nrelated to the existence of costly connections.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Radial marginal perturbation of two-dimensional systems and conformal\n  invariance: The conformal mapping w=(L/2\\pi)\\ln z transforms the critical plane with a\nradial perturbation \\alpha\\rho^{-y} into a cylinder with width L and a constant\ndeviation \\alpha(2\\pi/L)^y from the bulk critical point when the decay exponent\ny is such that the perturbation is marginal. From the known behavior of the\nhomogeneous off-critical system on the cylinder, one may deduce the correlation\nfunctions and defect exponents on the perturbed plane. The results are\nsupported by an exact solution for the Gaussian model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Jamming and Stress Propagation in Particulate Matter: We present simple models of particulate materials whose mechanical integrity\narises from a jamming process. We argue that such media are generically\n\"fragile\", that is, they are unable to support certain types of incremental\nloading without plastic rearrangement. In such models, fragility is naturally\nlinked to the marginal stability of force chain networks (granular skeletons)\nwithin the material. Fragile matter exhibits novel mechanical responses that\nmay be relevant to both jammed colloids and cohesionless assemblies of poured,\nrigid grains.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A non perturbative approach of the principal chiral model between two\n  and four dimensions: We investigate the principal chiral model between two and four dimensions by\nmeans of a non perturbative Wilson-like renormalization group equation. We are\nthus able to follow the evolution of the effective coupling constants within\nthis whole range of dimensions without having recourse to any kind of small\nparameter expansion. This allows us to identify its three dimensional critical\nphysics and to solve the long-standing discrepancy between the different\nperturbative approaches that characterizes the class of models to which the\nprincipal chiral model belongs.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Macroscopically measurable force induced by temperature discontinuities\n  at solid-gas interfaces: We consider a freely movable solid that separates a long tube into two\nregions, each of which is filled with a dilute gas. The gases in each region\nare initially prepared at the same pressure but different temperatures. Under\nthe assumption that the pressure and temperatures of gas particles before\ncolliding with the solid are kept constant over time, we show that temperature\ngaps appearing on the solid surface generate a force. We provide a quantitative\nestimation of the force, which turns out to be large enough to be observed by a\nmacroscopic measurement.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Burr, Levy, Tsallis: The purpose of this short paper dedicated to the 60th anniversary of\nProf.Constantin Tsallis is to show how the use of mathematical tools and\nphysical concepts introduced by Burr, L\\.{e}vy and Tsallis open a new line of\nanalysis of the old problem of non-Debye decay and universality of relaxation.\nWe also show how a finite characteristic time scale can be expressed in terms\nof a $q$-expectation using the concept of $q$- escort probability.The\ncomparison with the Weron et al. probabilistic theory of relaxation leads to a\nbetter understanding of the stochastic properties underlying the Tsallis\nentropy concept.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Phase Diagrams and Crossover in Spatially Anisotropic d=3 Ising, XY\n  Magnetic and Percolation Systems: Exact Renormalization-Group Solutions of\n  Hierarchical Models: Hierarchical lattices that constitute spatially anisotropic systems are\nintroduced. These lattices provide exact solutions for hierarchical models and,\nsimultaneously, approximate solutions for uniaxially or fully anisotropic d=3\nphysical models. The global phase diagrams, with d=2 and d=1 to d=3 crossovers,\nare obtained for Ising, XY magnetic models and percolation systems, including\ncrossovers from algebraic order to true long-range order.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Relativistic antifragility: It is shown that the barbell distribution of a gas of relativistic molecules\nabove its critical temperature, can be interpreted as an antifragile response\nto the relativistic constraint of subluminal propagation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Generalized arcsine laws for fractional Brownian motion: The three arcsine laws for Brownian motion are a cornerstone of extreme-value\nstatistics. For a Brownian $B_t$ starting from the origin, and evolving during\ntime $T$, one considers the following three observables: (i) the duration $t_+$\nthe process is positive, (ii) the time $t_{\\rm last}$ the process last visits\nthe origin, and (iii) the time $t_{\\rm max}$ when it achieves its maximum (or\nminimum). All three observables have the same cumulative probability\ndistribution expressed as an arcsine function, thus the name of arcsine laws.\nWe show how these laws change for fractional Brownian motion $X_t$, a\nnon-Markovian Gaussian process indexed by the Hurst exponent $H$. It\ngeneralizes standard Brownian motion (i.e. $H=\\tfrac{1}{2}$). We obtain the\nthree probabilities using a perturbative expansion in $\\epsilon =\nH-\\tfrac{1}{2}$. While all three probabilities are different, this distinction\ncan only be made at second order in $\\epsilon$. Our results are confirmed to\nhigh precision by extensive numerical simulations.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Symmetry and species segregation in diffusion-limited pair annihilation: We consider a system of q diffusing particle species A_1,A_2,...,A_q that are\nall equivalent under a symmetry operation. Pairs of particles may annihilate\naccording to A_i + A_j -> 0 with reaction rates k_{ij} that respect the\nsymmetry, and without self-annihilation (k_{ii} = 0). In spatial dimensions d >\n2 mean-field theory predicts that the total particle density decays as n(t) ~\n1/t, provided the system remains spatially uniform. We determine the conditions\non the matrix k under which there exists a critical segregation dimension\nd_{seg} below which this uniformity condition is violated; the symmetry between\nthe species is then locally broken. We argue that in those cases the density\ndecay slows down to n(t) ~ t^{-d/d_{seg}} for 2 < d < d_{seg}. We show that\nwhen d_{seg} exists, its value can be expressed in terms of the ratio of the\nsmallest to the largest eigenvalue of k. The existence of a conservation law\n(as in the special two-species annihilation A + B -> 0), although sufficient\nfor segregation, is shown not to be a necessary condition for this phenomenon\nto occur. We work out specific examples and present Monte Carlo simulations\ncompatible with our analytical results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of turbulent mixing on critical behaviour: Renormalization group\n  analysis of the Potts model: Critical behaviour of a system, subjected to strongly anisotropic turbulent\nmixing, is studied by means of the field theoretic renormalization group.\nSpecifically, relaxational stochastic dynamics of a non-conserved\nmulticomponent order parameter of the Ashkin-Teller-Potts model, coupled to a\nrandom velocity field with prescribed statistics, is considered. The velocity\nis taken Gaussian, white in time, with correlation function of the form\n$\\propto \\delta(t-t') /|{\\bf k}_{\\bot}|^{d-1+\\xi}$, where ${\\bf k}_{\\bot}$ is\nthe component of the wave vector, perpendicular to the distinguished direction\n(\"direction of the flow\") --- the $d$-dimensional generalization of the\nensemble introduced by Avellaneda and Majda [1990 {\\it Commun. Math. Phys.}\n{\\bf 131} 381] within the context of passive scalar advection. This model can\ndescribe a rich class of physical situations. It is shown that, depending on\nthe values of parameters that define self-interaction of the order parameter\nand the relation between the exponent $\\xi$ and the space dimension $d$, the\nsystem exhibits various types of large-scale scaling behaviour, associated with\ndifferent infrared attractive fixed points of the renormalization-group\nequations. In addition to known asymptotic regimes (critical dynamics of the\nPotts model and passively advected field without self-interaction), existence\nof a new, non-equilibrium and strongly anisotropic, type of critical behaviour\n(universality class) is established, and the corresponding critical dimensions\nare calculated to the leading order of the double expansion in $\\xi$ and\n$\\epsilon=6-d$ (one-loop approximation). The scaling appears strongly\nanisotropic in the sense that the critical dimensions related to the directions\nparallel and perpendicular to the flow are essentially different.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "One-dimensional fluids with positive potentials: We study a class of one-dimensional classical fluids with penetrable\nparticles interacting through positive, purely repulsive, pair-potentials.\nStarting from some lower bounds to the total potential energy, we draw results\non the thermodynamic limit of the given model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Reply to Comment on `Monte-Carlo simulation study of the two-stage\n  percolation transition in enhanced binary trees': We discuss the nature of the two-stage percolation transition on the enhanced\nbinary tree in order to explain the disagreement in the estimation of the\nsecond transition probability between the one in our recent paper (J. Phys.\nA:Math. Theor. 42 (2009) 145001) and the one in the comment to it from Baek,\nMinnhagen and Kim. We point out some reasons that the finite size scaling\nanalysis used by them is not proper for the enhanced tree due to its\nnonamenable nature, which is verified by some numerical results.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Comments on Generalization of thermodynamics in of fractional-order\n  derivatives and calculation of heat transfer properties of noble gases,\n  Journal of Thermal Analysis and Calorimetry 2018 133, 1189 1194: It is shown that the equations for pressure, entropy and the isochoric heat\ncapacity obtained by using generalization of the equilibrium thermodynamics in\nfractional derivatives in the paper mentioned above are approximate, the\ncomparison of the equations with the experimental (tabulated) data for Neon and\nArgon made in the paper is incorrect, and the conclusions of the paper made on\nthe basis of the comparison could be incorrect. The conditions for validity of\nthe equations are established. It is also established that the question about a\nphysical sense of the exponent of the derivative of a fractional order is still\nopen.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Attractive energy and entropy or particle size: the yin and yang of\n  physical and biological science: It is well known that equilibrium in a thermodynamic system results from a\ncompetition or balance between lowering the energy and increasing the entropy,\nor at least the product of the temperature and entropy. This is remarkably\nsimilar to the Taoist concept of yin, a downward influence, and yang, an upward\ninfluence, where harmony is established by balancing yin and yang. Entropy is\ndue to structure, which is largely determined by core repulsions or particle\nsize whereas energy is largely determined by longer range attractive\ninteractions. Here, this balance between energy and entropy or particle size is\ntraced through the theory of simple fluids, beginning with Andrews and van der\nWaals, the subsequent developments of perturbation theory, theories of\ncorrelation functions that are based on the Ornstein-Zernike relation and the\nmean spherical approximation, electrolytes, and recent work on ion channels in\nbiological membranes, where the competition between energy and size gives an\nintuitively attractive explanation of the selectivity of cation channels.\nSimulations of complex systems, including proteins in aqueous solution, should\nbe studied to determine the extent to which these concepts are useful for such\nsituations",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Percolation on a Feynman Diagram: In a recent paper hep-lat/9704020 we investigated Potts models on ``thin''\nrandom graphs -- generic Feynman diagrams, using the idea that such models may\nbe expressed as the N --> 1 limit of a matrix model. The models displayed first\norder transitions for all q greater than 2, giving identical behaviour to the\ncorresponding Bethe lattice.\n  We use here one of the results of hep-lat/9704020 namely a general saddle\npoint solution for a q state Potts model expressed as a function of q, to\ninvestigate some peculiar features of the percolative limit q -> 1 and compare\nthe results with those on the Bethe lattice.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Second-order phase transition in the Heisenberg model on a triangular\n  lattice with competing interactions: We discover an example where the dissociation of the Z2 vortices occurs at\nthe second-order phase transition point. We investigate the nature of phase\ntransition in a classical Heisenberg model on a distorted triangular lattice\nwith competing interactions. The order parameter space of the model is\nSO(3)xZ2. The dissociation of the Z2 vortices which comes from SO(3) and a\nsecond-order phase transition with Z2 symmetry breaking occur at the same\ntemperature. We also find that the second-order phase transition belongs to the\nuniversality class of the two-dimensional Ising model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Linear response subordination to intermittent energy release in\n  off-equilibrium aging dynamics: The interpretation of experimental and numerical data describing\noff-equilibrium aging dynamics crucially depends on the connection between\nspontaneous and induced fluctuations. The hypothesis that linear response\nfluctuations are statistically subordinated to irreversible outbursts of\nenergy, so-called quakes, leads to predictions for averages and fluctuations\nspectra of physical observables in reasonable agreement with experimental\nresults [see e.g. Sibani et al., Phys. Rev. B74:224407, 2006]. Using\nsimulational data from a simple but representative Ising model with plaquette\ninteractions, direct statistical evidence supporting the hypothesis is\npresented and discussed in this work.\n  A strict temporal correlation between quakes and intermittent magnetization\nfluctuations is demonstrated. The external magnetic field is shown to bias the\npre-existent intermittent tails of the magnetic fluctuation distribution, with\nlittle or no effect on the Gaussian part of the latter. Its impact on energy\nfluctuations is shown to be negligible.\n  Linear response is thus controlled by the quakes and inherits their temporal\nstatistics. These findings provide a theoretical basis for analyzing\nintermittent linear response data from aging system in the same way as thermal\nenergy fluctuations, which are far more difficult to measure.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Some general features of matrix product states in stochastic systems: We will prove certain general relations in Matrix Product Ansatz for one\ndimensional stochastic systems, which are true in both random and sequential\nupdates. We will derive general MPA expressions for the currents and current\ncorrelators and find the conditions in the MPA formalism, under which the\ncorrelators are site-independent or completely vanishing.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Effects of turbulent mixing on the nonequilibrium critical behaviour: We study effects of turbulent mixing on the critical behaviour of a\nnonequilibrium system near its second-order phase transition between the\nabsorbing and fluctuating states. The model describes the spreading of an agent\n(e.g., infectious disease) in a reaction-diffusion system and belongs to the\nuniversality class of the directed bond percolation process, also known as\nsimple epidemic process, and is equivalent to the Reggeon field theory. The\nturbulent advecting velocity field is modelled by the Obukhov--Kraichnan's\nrapid-change ensemble: Gaussian statistics with the correlation function < vv>\n\\propto \\delta(t-t') k^{-d-\\xi}, where k is the wave number and 0<\\xi<2 is a\nfree parameter. Using the field theoretic renormalization group we show that,\ndepending on the relation between the exponent \\xi and the space dimensionality\nd, the system reveals different types of large-scale asymptotic behaviour,\nassociated with four possible fixed points of the renormalization group\nequations. In addition to known regimes (ordinary diffusion, ordinary directed\npercolation process, and passively advected scalar field), existence of a new\nnonequilibrium universality class is established, and the corresponding\ncritical dimensions are calculated to first order of the double expansion in\n\\xi and \\varepsilon=4-d (one-loop approximation). It turns out, however, that\nthe most realistic values \\xi=4/3 (Kolmogorov's fully developed turbulence) and\nd=2 or 3 correspond to the case of passive scalar field, when the nonlinearity\nof the Reggeon model is irrelevant and the spreading of the agent is completely\ndetermined by the turbulent transfer.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Wet Sand flows better than dry sand: We investigated the yield stress and the apparent viscosity of sand with and\nwithout small amounts of liquid. By pushing the sand through a tube with an\nenforced Poiseuille like profile we minimize the effect of avalanches and shear\nlocalization. We find that the system starts to flow when a critical shear of\nthe order of one particle diameter is exceeded. In contrast to common believe,\nwe observe that the resistance against the flow of wet sand is much smaller\nthan that of dry sand. For the dissipative flow we propose a non-equilibrium\nstate equation for granular fluids.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Characterization of Sleep Stages by Correlations of Heartbeat Increments: We study correlation properties of the magnitude and the sign of the\nincrements in the time intervals between successive heartbeats during light\nsleep, deep sleep, and REM sleep using the detrended fluctuation analysis\nmethod. We find short-range anticorrelations in the sign time series, which are\nstrong during deep sleep, weaker during light sleep and even weaker during REM\nsleep. In contrast, we find long-range positive correlations in the magnitude\ntime series, which are strong during REM sleep and weaker during light sleep.\nWe observe uncorrelated behavior for the magnitude during deep sleep. Since the\nmagnitude series relates to the nonlinear properties of the original time\nseries, while the signs series relates to the linear properties, our findings\nsuggest that the nonlinear properties of the heartbeat dynamics are more\npronounced during REM sleep. Thus, the sign and the magnitude series provide\ninformation which is useful in distinguishing between the sleep stages.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Frequency clustering and disaggregation in idealized fractal tree: The pattern of formation of resonant frequency clusters in idealized\nsympodial dichasium trees is revealed by numerical modeling and analysis. The\nlarger cluster's cardinality correlates with that of a Small World Network,\nwhich share the same adjacency matrix. Topology and inherent symmetry of the\nstructure dictate compartmentalization of the modal characteristics and\nrobustness to perturbations to the limb geometry, and are not limited to a\nspecific allometry. When the spatial symmetry of the limb geometry is perturbed\nabove a certain level, we see percolation of the largest cluster.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Wind on the boundary for the Abelian sandpile model: We continue our investigation of the two-dimensional Abelian sandpile model\nin terms of a logarithmic conformal field theory with central charge c=-2, by\nintroducing two new boundary conditions. These have two unusual features: they\ncarry an intrinsic orientation, and, more strangely, they cannot be imposed\nuniformly on a whole boundary (like the edge of a cylinder). They lead to seven\nnew boundary condition changing fields, some of them being in highest weight\nrepresentations (weights -1/8, 0 and 3/8), some others belonging to\nindecomposable representations with rank 2 Jordan cells (lowest weights 0 and\n1). Their fusion algebra appears to be in full agreement with the fusion rules\nconjectured by Gaberdiel and Kausch.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low-temperature behavior of the $O(N)$ models below two dimensions: We investigate the critical behavior and the nature of the low-temperature\nphase of the $O(N)$ models treating the number of field components $N$ and the\ndimension $d$ as continuous variables with a focus on the $d\\leq 2$ and $N\\leq\n2$ quadrant of the $(d,N)$ plane. We precisely chart a region of the $(d,N)$\nplane where the low-temperature phase is characterized by an algebraic\ncorrelation function decay similar to that of the Kosterlitz-Thouless phase but\nwith a temperature-independent anomalous dimension $\\eta$. We revisit the\nCardy-Hamber analysis leading to a prediction concerning the nonanalytic\nbehavior of the $O(N)$ models' critical exponents and emphasize the previously\nnot broadly appreciated consequences of this approach in $d<2$. In particular,\nwe discuss how this framework leads to destabilization of the long-range order\nin favour of the quasi long-range order in systems with $d<2$ and $N<2$.\nSubsequently, within a scheme of the nonperturbative renormalization group we\nidentify the low-temperature fixed points controlling the quasi long-range\nordered phase and demonstrate a collision between the critical and the\nlow-temperature fixed points upon approaching the lower critical dimension. We\nevaluate the critical exponents $\\eta(d,N)$ and $\\nu^{-1}(d,N)$ and demonstrate\na very good agreement between the predictions of the Cardy-Hamber type analysis\nand the nonperturbative renormalization group in $d<2$.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "From the density functional to the single-particle Green function: An analysis shows that the ground state of the inhomogeneous system of\ninteracting electrons in the static external field, which satisfies the\nthermodynamic limit, can be consistently described only using the Green\nfunction theory based on the quantum field theory methods (perturbation theory\ndiagram technique). In this case, the ground state energy and inhomogeneous\nelectron density in such a system can be determined only after calculating the\nsingle-particle Green function.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A Biologically Motivated Asymmetric Exclusion Process: interplay of\n  congestion in RNA polymerase traffic and slippage of nascent transcript: We develope a theoretical framework, based on exclusion process, that is\nmotivated by a biological phenomenon called transcript slippage (TS). In this\nmodel a discrete lattice represents a DNA strand while each of the particles\nthat hop on it unidirectionally, from site to site, represents a RNA polymerase\n(RNAP). While walking like a molecular motor along a DNA track in a\nstep-by-step manner, a RNAP simultaneously synthesizes a RNA chain; in each\nforward step it elongates the nascent RNA molecule by one unit, using the DNA\ntrack also as the template. At some special \"slippery\" position on the DNA,\nwhich we represent as a defect on the lattice, a RNAP can lose its grip on the\nnascent RNA and the latter's consequent slippage results in a final product\nthat is either longer or shorter than the corresponding DNA template. We\ndevelope an exclusion model for RNAP traffic where the kinetics of the system\nat the defect site captures key features of TS events. We demonstrate the\ninterplay of the crowding of RNAPs and TS. A RNAP has to wait at the defect\nsite for longer period in a more congested RNAP traffic, thereby increasing the\nlikelihood of its suffering a larger number of TS events. The qualitative\ntrends of some of our results for a simple special case of our model are\nconsistent with experimental observations. The general theoretical framework\npresented here will be useful for guiding future experimental queries and for\nanalysis of the experimental data with more detailed versions of the same\nmodel.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "50 years of correlations with Michael Fisher and the renormalization\n  group: This paper will be published in ``50 years of the renormalization group\",\ndedicated to the memory of Michael E. Fisher, edited by Amnon Aharony, Ora\nEntin-Wohlman, David Huse, and Leo Radzihovsky, World Scientific. I start with\na review of my personal and scientific interactions with Michael E. Fisher, who\nwas my post-doc mentor in 1972-1974. I then describe several recent\nrenormalization group studies, which started during those years, and still\nraise some open issues. These include the magnets with dipole-dipole\ninteractions, the puzzle of the bicritical points and the random field Ising\nmodel.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonergodic Brownian oscillator: Low-frequency response: An undisturbed Brownian oscillator may not reach thermal equilibrium with the\nthermal bath due to the formation of a localized normal mode. The latter may\nemerge when the spectrum of the thermal bath has a finite upper bound\n$\\omega_0$ and the oscillator natural frequency exceeds a critical value\n$\\omega_c$, which depends on the specific form of the bath spectrum. We\nconsider the response of the oscillator with and without a localized mode to\nthe external periodic force with frequency $\\Omega$ lower than $\\omega_0$. The\nresults complement those obtained earlier for the high-frequency response at\n$\\Omega\\ge \\omega_0$ and require a different mathematical approach. The\nsignature property of the high-frequency response is resonance when the\nexternal force frequency $\\Omega$ coincides with the frequency of the localized\nmode $\\omega_*$. In the low-frequency domain $\\Omega<\\omega_0$ the condition of\nresonance $\\Omega=\\omega_*$ cannot be met (since $\\omega_*>\\omega_0$). Yet, in\nthe limits $\\omega\\to\\omega_c$ and $\\Omega\\to\\omega_0^-$, the oscillator shows\na peculiar quasi-resonance response with an amplitude increasing with time\nsublinearly.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Fluctuations and Criticality of a Granular Solid-Liquid-like Phase\n  Transition: We present an experimental study of density and order fluctuations in the\nvicinity of the solid-liquid-like transition that occurs in a vibrated\nquasi-two-dimensional granular system. The two-dimensional projected static and\ndynamic correlation functions are studied. We show that density fluctuations,\ncharacterized through the structure factor, increase in size and intensity as\nthe transition is approached, but they do not change significantly at the\ntransition itself. The dense, metastable clusters, which present square\nsymmetry, also increase their local order in the vicinity of the transition.\nThis is characterized through the bond-orientational order parameter $Q_4$,\nwhich in Fourier space obeys an Ornstein-Zernike behavior. Depending on filling\ndensity and vertical height, the transition can be of first or second order\ntype. In the latter case, the associated correlation length $\\xi_4$, relaxation\ntime $\\tau_4$, zero $k$ limit of $Q_4$ fluctuations (static susceptibility),\nthe pair correlation function of $Q_4$, and the amplitude of the order\nparameter obey critical power laws, with saturations due to finite size\neffects. Their respective critical exponents are $\\nu_{\\bot} = 1$, $\\nu_{||} =\n2$, $\\gamma = 1$, $\\eta=0.67$, and $\\beta=1/2$, whereas the dynamical critical\nexponent $z = \\nu_{||}/\\nu_{\\bot} = 2$. These results are consistent with model\nC of dynamical critical phenomena, valid for a non-conserved critical order\nparameter (bond-orientation order) coupled to a conserved field (density).",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Nonequilibrium thermodynamics as a gauge theory: We assume that markovian dynamics on a finite graph enjoys a gauge symmetry\nunder local scalings of the probability density, derive the transformation law\nfor the transition rates and interpret the thermodynamic force as a gauge\npotential. A widely accepted expression for the total entropy production of a\nsystem arises as the simplest gauge-invariant completion of the time derivative\nof Gibbs's entropy. We show that transition rates can be given a simple\nphysical characterization in terms of locally-detailed-balanced heat\nreservoirs. It follows that Clausius's measure of irreversibility along a\ncyclic transformation is a geometric phase. In this picture, the gauge symmetry\narises as the arbitrariness in the choice of a prior probability. Thermostatics\ndepends on the information that is disposable to an observer; thermodynamics\ndoes not.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Gauge Invariant Formulations of Dicke-Preparata Super-Radiant Models: In a gauge invariant formulation of the molecular electric dipole-photon\ninteraction, the rigorous coupling is strictly linear in the photon creation\nand photon annihilation operators. The linear coupling allows for a\nsuper-radiant phase transition as in the Hepp-Lieb formulation. A previous\nnotion of a quadratic-coupling ``no-go theorem'' for super-radiance is\nincorrect. Also incorrect is a previous assertion that the dipole-photon\ncoupling has absolutely no effect on the thermal equations of state. These\ndubious assertions were based on incorrect canonical transformations which\neliminated the electric field (and thereby eliminated the dipole-photon\ninteraction) which is neither mathematically nor physically consistent. The\ncorrect form of the canonical transformations are given in this work which\nallows for the physical reality of super-radiant condensed matter phases.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Aging and fluctuation-dissipation ratio for the diluted Ising Model: We consider the out-of-equilibrium, purely relaxational dynamics of a weakly\ndiluted Ising model in the aging regime at criticality. We derive at first\norder in a $\\sqrt{\\epsilon}$ expansion the two-time response and correlation\nfunctions for vanishing momenta. The long-time limit of the critical\nfluctuation-dissipation ratio is computed at the same order in perturbation\ntheory.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Organic nanowires and chiral patterns of tetracyanoquinodimethane (TCNQ)\n  grown by vacuum vapor deposition: Organic nanowires and quasi-two-dimensional chiral patterns of\ntetracyanoquinodimethane have been successfully generated by vacuum thermal\nevaporation. The nanowires and patterns were characterized by using atomic\nforce microscopy and transmission electron microscopy. The influence of\nelectric charged clusters, deposition rate, and substrate temperature were\nexperimentally investigated. Contrary to previous reports, charged clusters are\nfound to be unnecessary to the chiral pattern formation. It was shown that the\nnanowire and pattern formation should be mainly dominated by its special\ncrystallization properties, though the effect of the growth conditions cannot\nbe neglected.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Survival Analysis, Master Equation, Efficient Simulation of Path-Related\n  Quantities, and Hidden State Concept of Transitions: This paper presents and derives the interrelations between survival analysis\nand master equation. Survival analysis deals with modeling the transitions\nbetween succeeding states of a system in terms of hazard rates. Questions\nrelated with this are the timing and sequencing of the states of a time series.\nThe frequency and characteristics of time series can be investigated by\nMonte-Carlo simulations. If one is interested in cross-sectional data connected\nwith the stochastic process under consideration, one needs to know the temporal\nevolution of the distribution of states. This can be obtained by simulation of\nthe associated master equation. Some new formulas allow the determination of\npath-related (i.e. longitudinal) quantities like the occurence probability, the\noccurence time distribution, or the effective cumulative life-time distribution\nof a certain sequencing of states (path). These can be efficiently evaluated\nwith a recently developed simulation tool (EPIS). The effective cumulative\nlife-time distribution facilitates the formulation of a hidden state concept of\nbehavioral changes which allows an interpretation of the respective\ntime-dependence of hazard rates. Hidden states represent states which are\neither not phenomenological distinguishable from other states, not externally\nmeasurable, or simply not detected.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Analytical calculations of the Quantum Tsallis thermodynamic variables: In this article, we provide an account of analytical results related to the\nTsallis thermodynamics that have been the subject matter of a lot of studies in\nthe field of high-energy collisions. After reviewing the results for the\nclassical case in the massless limit and for arbitrarily massive classical\nparticles, we compute the quantum thermodynamic variables. For the first time,\nthe analytical formula for the pressure of a Tsallis-like gas of massive bosons\nhas been obtained. Hence, this article serves both as a brief review of the\nknowledge gathered in this area, and as an original research that forwards the\nexisting scholarship. The results of the present paper will be important in a\nplethora of studies in the field of high-energy collisions including the\npropagation of non-linear waves generated by the traversal of high-energy\nparticles inside the quark-gluon plasma medium showing the features of\nnon-extensivity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Coagulation kinetics beyond mean field theory using an optimised Poisson\n  representation: Binary particle coagulation can be modelled as the repeated random process of\nthe combination of two particles to form a third. The kinetics can be\nrepresented by population rate equations based on a mean field assumption,\naccording to which the rate of aggregation is taken to be proportional to the\nproduct of the mean populations of the two participants. This can be a poor\napproximation when the mean populations are small. However, using the Poisson\nrepresentation it is possible to derive a set of rate equations that go beyond\nmean field theory, describing pseudo-populations that are continuous, noisy and\ncomplex, but where averaging over the noise and initial conditions gives the\nmean of the physical population. Such an approach is explored for the simple\ncase of a size-independent rate of coagulation between particles. Analytical\nresults are compared with numerical computations and with results derived by\nother means. In the numerical work we encounter instabilities that can be\neliminated using a suitable 'gauge' transformation of the problem [P. D.\nDrummond, Eur. Phys. J. B38, 617 (2004)] which we show to be equivalent to the\napplication of the Cameron-Martin-Girsanov formula describing a shift in a\nprobability measure. The cost of such a procedure is to introduce additional\nstatistical noise into the numerical results, but we identify an optimised\ngauge transformation where this difficulty is minimal for the main properties\nof interest. For more complicated systems, such an approach is likely to be\ncomputationally cheaper than Monte Carlo simulation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universal free energy correction for the two-dimensional one-component\n  plasma: The universal finite-size correction to the free energy of a two-dimensional\nCoulomb system is checked in the special case of a one-component plasma on a\nsphere. The correction is related to the known second moment of the short-range\npart of the direct correlation function for a planar system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Eliminating the cuspidal temperature profile of a non-equilibrium chain: In 1967, Z. Rieder, J. L. Lebowitz and E. Lieb (RLL) introduced a model of\nheat conduction on a crystal that became a milestone problem of non-equilibrium\nstatistical mechanics. Along with its inability to reproduce Fourier's Law -\nwhich subsequent generalizations have been trying to amend - the RLL model is\nalso characterized by awkward cusps at the ends of the non-equilibrium chain,\nan effect that has endured all these years without a satisfactory answer. In\nthis paper, we first show that such trait stems from the insufficiency of\npinning interactions between the chain and the substrate. Assuming the\npossibility of pinning the chain, the analysis of the temperature profile in\nthe space of parameters reveals that for a proper combination of the border and\nbulk pinning values, the temperature profile may shift twice between the RLL\ncuspidal behavior and the expected monotonic local temperature evolution along\nthe system, as a function of the pinning. At those inversions, the temperature\nprofile along the chain is characterized by perfect plateaux: at the first\nthreshold, the cumulants of the heat flux reach their maxima and the vanishing\nof the two-point velocity correlation function for all sites of the chain so\nthat the system behaves similarly to a \"phonon box\". On the other hand, at the\nsecond change of the temperature profile, we still have the vanishing of the\ntwo-point correlation function but only for the bulk, which explains the\nemergence of the temperature plateau and thwarts the reaching of the maximal\nvalues of the cumulants of the heat flux.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Evolutionary design of non-frustrated networks of phase-repulsive\n  oscillators: Evolutionary optimisation algorithm is employed to design networks of\nphase-repulsive oscillators that achieve an anti-phase synchronised state. By\nintroducing the link frustration, the evolutionary process is implemented by\nrewiring the links with probability proportional to their frustration, until\nthe final network displaying a unique non-frustrated dynamical state is\nreached. Resulting networks are bipartite and with zero clustering. In\naddition, the designed non-frustrated anti-phase synchronised networks display\na clear topological scale. This contrasts usually studied cases of networks\nwith phase-attractive dynamics, whose performance towards full synchronisation\nis typically enhanced by the presence of a topological hierarchy.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Quasi-elastic solutions to the nonlinear Boltzmann equation for\n  dissipative gases: The solutions of the one-dimensional homogeneous nonlinear Boltzmann equation\nare studied in the QE-limit (Quasi-Elastic; infinitesimal dissipation) by a\ncombination of analytical and numerical techniques. Their behavior at large\nvelocities differs qualitatively from that for higher dimensional systems. In\nour generic model, a dissipative fluid is maintained in a non-equilibrium\nsteady state by a stochastic or deterministic driving force. The velocity\ndistribution for stochastic driving is regular and for infinitesimal\ndissipation, has a stretched exponential tail, with an unusual stretching\nexponent $b_{QE} = 2b$, twice as large as the standard one for the\ncorresponding $d$-dimensional system at finite dissipation. For deterministic\ndriving the behavior is more subtle and displays singularities, such as\nmulti-peaked velocity distribution functions. We classify the corresponding\nvelocity distributions according to the nature and scaling behavior of such\nsingularities.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Scaling of the glassy dynamics of soft repulsive particles: a\n  mode-coupling approach: We combine the hyper-netted chain approximation of liquid state theory with\nthe mode-coupling theory of the glass transition to analyze the structure and\ndynamics of soft spheres interacting via harmonic repulsion. We determine the\nlocus of the fluid-glass dynamic transition in a temperature -- volume fraction\nphase diagram. The zero-temperature (hard sphere) glass transition influences\nthe dynamics at finite temperatures in its vicinity. This directly implies a\nform of dynamic scaling for both the average relaxation time and dynamic\nsusceptibilities quantifying dynamic heterogeneity. We discuss several\nqualitative disagreements between theory and existing simulations at\nequilibrium. Our theoretical results are, however, very similar to numerical\nresults for the driven athermal dynamics of repulsive spheres, suggesting that\n`mean-field' mode-coupling approaches might be good starting points to describe\nthese nonequilibrium dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Low temperature ratchet current: In [3], the low temperature ratchet current in a multilevel system is\nconsidered. In this note, we give an explicit expression for it and find its\nnumerical value as the number of states goes to infinity.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Series Expansion of the Percolation Threshold on Hypercubic Lattices: We study proper lattice animals for bond- and site-percolation on the\nhypercubic lattice $\\mathbb{Z}^d$ to derive asymptotic series of the\npercolation threshold $p_c$ in $1/d$, The first few terms of these series were\ncomputed in the 1970s, but the series have not been extended since then. We add\ntwo more terms to the series for $\\pcsite$ and one more term to the series for\n$\\pcbond$, using a combination of brute-force enumeration, combinatorial\nidentities and an approach based on Pad\\'e approximants, which requires much\nfewer resources than the classical method. We discuss why it took 40 years to\ncompute these terms, and what it would take to compute the next ones. En\npassant, we present new perimeter polynomials for site and bond percolation and\nnumerical values for the growth rate of bond animals.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Statistical origin of Legendre invariant metrics: Legendre invariant metrics have been introduced in Geometrothermodynamics to\ntake into account the important fact that the thermodynamic properties of\nphysical systems do not depend on the choice of thermodynamic potential from a\ngeometric perspective. In this work, we show that these metrics also have a\nstatistical origin which can be expressed in terms of the average and variance\nof the differential of the microscopic entropy. To show this, we use a\nparticular reparametrization of the coordinates of the corresponding\nthermodynamic phase space.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Permutation Phase and Gentile Statistics: This paper presents a new way to construct single-valued many-body\nwavefunctions of identical particles with intermediate exchange phases between\nFermi and Bose statistics. It is demonstrated that the exchange phase is not a\nrepresentation character but the \\textit{word metric} of the permutation group,\nbeyond the anyon phase from the braiding group in two dimensions. By\nconstructing this type of wavefunction from the direct product of\nsingle-particle states, it is shown that a finite \\textit{capacity q} -- the\nmaximally allowed particle occupation of each quantum state, naturally arises.\nThe relation between the permutation phase and capacity is given, interpolating\nbetween fermions and bosons in the sense of both exchange phase and occupation\nnumber. This offers a quantum mechanics foundation for \\textit{Gentile\nstatistics} and new directions to explore intermediate statistics and anyons.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Kinetic theory of collisionless relaxation for systems with long-range\n  interactions: We develop the kinetic theory of collisionless relaxation for systems with\nlong-range interactions in relation to the statistical theory of Lynden-Bell.\nWe treat the multi-level case. We make the connection between the kinetic\nequation obtained from the quasilinear theory of the Vlasov equation and the\nrelaxation equation obtained from a maximum entropy production principle. We\npropose a method to close the infinite hierarchy of kinetic equations for the\nphase level moments and obtain a kinetic equation for the coarse-grained\ndistribution function in the form of a generalized Landau, Lenard-Balescu or\nKramers equation associated with a generalized form of entropy [P.H. Chavanis,\nPhysica A {\\bf 332}, 89 (2004)]. This allows us to go beyond the two-level case\nassociated with a Fermi-Dirac-type entropy. We discuss the numerous analogies\nwith two-dimensional turbulence. We also mention possible applications of the\npresent formalism to fermionic and bosonic dark matter halos.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Optimal protocols for Hamiltonian and Schr\u00f6dinger dynamics: For systems in an externally controllable time-dependent potential, the\noptimal protocol minimizes the mean work spent in a finite-time transition\nbetween given initial and final values of a control parameter. For an initially\nthermalized ensemble, we consider both Hamiltonian evolution for classical\nsystems and Schr\\\"odinger evolution for quantum systems. In both cases, we show\nthat for harmonic potentials, the optimal work is given by the adiabatic work\neven in the limit of short transition times. This result is counter-intuitive\nbecause the adiabatic work is substantially smaller than the work for an\ninstantaneous jump. We also perform numerical calculations of the optimal\nprotocol for Hamiltonian dynamics in an anharmonic quartic potential. For a\ntwo-level spin system, we give examples where the adiabatic work can be reached\nin either a finite or an arbitrarily short transition time depending on the\nallowed parameter space.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Explicit formula of energy-conserving Fokker-Planck type collision term\n  for single species point vortex systems with weak mean flow: This paper derives a kinetic equation for a two-dimensional single species\npoint vortex system. We consider a situation (different from the ones\nconsidered previously) of weak mean flow where the time scale of the\nmacroscopic motion is longer than the decorrelation time so that the trajectory\nof the point vortices can be approximated by a straight line on the\ndecorrelation time scale. This may be the case when the number $N$ of point\nvortices is not too large. Using a kinetic theory based on the Klimontovich\nformalism, we derive a collision term consisting of a diffusion term and a\ndrift term, whose structure is similar to the Fokker-Planck equation. The\ncollision term exhibits several important properties: (a) it includes a\nnonlocal effect; (b) it conserves the mean field energy; (c) it satisfies the H\ntheorem; (d) its effect vanishes in each local equilibrium region with the same\ntemperature. When the system reaches a global equilibrium state, the collision\nterm completely converges to zero all over the system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Universality and criticality of a second-order granular\n  solid-liquid-like phase transition: We experimentally study the critical properties of the non-equilibrium\nsolid-liquid-like transition that takes place in vibrated granular matter. The\ncritical dynamics is characterized by the coupling of the density field with\nthe bond-orientational order parameter $Q_4$, which measures the degree of\nlocal crystallization. Two setups are compared, which present the transition at\ndifferent critical accelerations as a a result of modifying the energy\ndissipation parameters. In both setups five independent critical exponents are\nmeasured, associated to different properties of $Q_4$: the correlation length,\nrelaxation time, vanishing wavenumber limit (static susceptibility), the\nhydrodynamic regime of the pair correlation function, and the amplitude of the\norder parameter. The respective critical exponents agree in both setups and are\ngiven by $\\nu_{\\perp} = 1$, $\\nu_{\\parallel} = 2$, $\\gamma = 1$, $\\eta \\approx\n0.6 - 0.67$, and $\\beta=1/2$, whereas the dynamical critical exponent is $z =\n\\nu_{\\parallel}/\\nu_{\\perp} = 2$. The agreement on five exponents is an exigent\ntest for the universality of the transition. Thus, while dissipation is\nstrictly necessary to form the crystal, the path the system undergoes towards\nthe phase separation is part of a well defined universality class. In fact, the\nlocal order shows critical properties while density does not. Being the later\nconserved, the appropriate model that couples both is model C in the Hohenberg\nand Halperin classification. The measured exponents are in accord with the\nnon-equilibrium extension to model C if we assume that $\\alpha$, the exponent\nassociated in equilibrium to the specific heat divergence but with no\ncounterpart in this non-equilibrium experiment, vanishes.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Equilibrium sampling of hard spheres up to the jamming density and\n  beyond: We implement and optimize a particle-swap Monte-Carlo algorithm that allows\nus to thermalize a polydisperse system of hard spheres up to\nunprecedentedly-large volume fractions, where \\revise{previous} algorithms and\nexperiments fail to equilibrate. We show that no glass singularity intervenes\nbefore the jamming density, which we independently determine through two\ndistinct non-equilibrium protocols. We demonstrate that equilibrium fluid and\nnon-equilibrium jammed states can have the same density, showing that the\njamming transition cannot be the end-point of the fluid branch.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "The Mixed Spin 3 - Spin 3/2 Ferrimagnetic Ising Model on Cellular\n  Automaton: The mixed spin 3- spin 3/2 Ising model has been simulated using cooling\nalgorithm on cellular automaton (CA). The simulations have been made in the\ninterval -6<=D<=6 for J=1 for the square lattices with periodic boundary\nconditions. The ground state phase diagram of the model has different type\nferrimagnetic orderings. Through D/J=2 line, compensation points occurs at\nkT/J=0. The values of the critical exponents ( {\\nu}, {\\alpha}, {\\beta} and\n{\\gamma}) are estimated within the framework of the finite-size scaling theory\nand power law relations for selected D/J values (-2, 0, 1, 2 and 4). The\nestimated critical exponent values are in a good agreement with their universal\nvalues of the two dimensional Ising model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Hamiltonian dynamics of the two-dimensional lattice phi^4 model: The Hamiltonian dynamics of the classical $\\phi^4$ model on a two-dimensional\nsquare lattice is investigated by means of numerical simulations. The\nmacroscopic observables are computed as time averages. The results clearly\nreveal the presence of the continuous phase transition at a finite energy\ndensity and are consistent both qualitatively and quantitatively with the\npredictions of equilibrium statistical mechanics. The Hamiltonian microscopic\ndynamics also exhibits critical slowing down close to the transition. Moreover,\nthe relationship between chaos and the phase transition is considered, and\ninterpreted in the light of a geometrization of dynamics.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Magnitude-Dependent Omori Law: Empirical Study and Theory: We propose a new physically-based ``multifractal stress activation'' model of\nearthquake interaction and triggering based on two simple ingredients: (i) a\nseismic rupture results from activated processes giving an exponential\ndependence on the local stress; (ii) the stress relaxation has a long memory.\nThe combination of these two effects predicts in a rather general way that\nseismic decay rates after mainshocks follow the Omori law 1/t^p with exponents\np linearly increasing with the magnitude M of the mainshock and the inverse\ntemperature. We carefully test the prediction on the magnitude dependence of p\nby a detailed analysis of earthquake sequences in the Southern California\nEarthquake catalog. We find power law relaxations of seismic sequences\ntriggered by mainshocks with exponents p increasing with the mainshock\nmagnitude by approximately 0.1-0.15 for each magnitude unit increase, from\np(M=3) \\approx 0.6 to p(M=7) \\approx 1.1, in good agreement with the prediction\nof the multifractal model. The results are robust with respect to different\ntime intervals, magnitude ranges and declustering methods. When applied to\nsynthetic catalogs generated by the ETAS (Epidemic-Type Aftershock Sequence)\nmodel constituting a strong null hypothesis with built-in magnitude-independent\n$p$-values, our procedure recovers the correct magnitude-independent p-values.\nOur analysis thus suggests that a new important fact of seismicity has been\nunearthed. We discuss alternative interpretations of the data and describe\nother predictions of the model.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Totally asymmetric limit for models of heat conduction: We consider one dimensional weakly asymmetric boundary driven models of heat\nconduction. In the cases of a constant diffusion coefficient and of a quadratic\nmobility we compute the quasi-potential that is a non local functional obtained\nby the solution of a variational problem. This is done using the dynamic\nvariational approach of the macroscopic fluctuation theory \\cite{MFT}. The case\nof a concave mobility corresponds essentially to the exclusion model that has\nbeen discussed in \\cite{Lag,CPAM,BGLa,ED}. We consider here the convex case\nthat includes for example the Kipnis-Marchioro-Presutti (KMP) model and its\ndual (KMPd) \\cite{KMP}. This extends to the weakly asymmetric regime the\ncomputations in \\cite{BGL}. We consider then, both microscopically and\nmacroscopically, the limit of large external fields. Microscopically we discuss\nsome possible totally asymmetric limits of the KMP model. In one case the\ntotally asymmetric dynamics has a product invariant measure. Another possible\nlimit dynamics has instead a non trivial invariant measure for which we give a\nduality representation. Macroscopically we show that the quasi-potentials of\nKMP and KMPd, that for any fixed external field are non local, become local in\nthe limit. Moreover the dependence on one of the external reservoirs\ndisappears. For models having strictly positive quadratic mobilities we obtain\ninstead in the limit a non local functional having a structure similar to the\none of the boundary driven asymmetric exclusion process.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Renormalized Multicanonical Sampling: For a homogeneous system divisible into identical, weakly interacting\nsubsystems, the muticanonical procedure can be accelerated if it is first\napplied to determine of the density of states for a single subsystem. This\nresult is then employed to approximate the state density of a subsystem with\ntwice the size that forms the starting point of a new multicanonical iteration.\nSince this compound subsystem interacts less on average with its environment,\niterating this sequence of steps rapidly generates the state density of the\nfull system.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "A weighted planar stochastic lattice with scale-free, small-world and\n  multifractal properties: We investigate a class of weighted planar stochastic lattice (WPSL1) created\nby random sequential nucleation of seed from which a crack is grown parallel to\none of the sides of the chosen block and ceases to grow upon hitting another\ncrack. It results in the partitioning of the square into contiguous and\nnon-overlapping blocks. Interestingly, we find that the dynamics of WPSL1 is\ngoverned by infinitely many conservation laws and each of the conserved\nquantities, except the trivial conservation of total mass or area, is a\nmultifractal measure. On the other hand, the dual of the lattice is a\nscale-free network as its degree distribution exhibits a power-law $P(k)\\sim\nk^{-\\gamma}$ with $\\gamma=4.13$. The network is also a small-world network as\nwe find that (i) the total clustering coefficient $C$ is high and independent\nof the network size and (ii) the mean geodesic path length grows\nlogarithmically with $N$. Besides, the clustering coefficient $C_k$ of the\nnodes which have degree $k$ decreases exactly as $2/(k-1)$ revealing that it is\nalso a nested hierarchical network.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Transport Equations from Liouville Equations for Fractional Systems: We consider dynamical systems that are described by fractional power of\ncoordinates and momenta. The fractional powers can be considered as a\nconvenient way to describe systems in the fractional dimension space. For the\nusual space the fractional systems are non-Hamiltonian. Generalized transport\nequation is derived from Liouville and Bogoliubov equations for fractional\nsystems. Fractional generalization of average values and reduced distribution\nfunctions are defined. Hydrodynamic equations for fractional systems are\nderived from the generalized transport equation.",
        "category": "cond-mat_stat-mech"
    },
    {
        "text": "Topological squashed entanglement: nonlocal order parameter for\n  one-dimensional topological superconductors: Identifying entanglement-based order parameters characterizing topological\nsystems, in particular topological superconductors and topological insulators,\nhas remained a major challenge for the physics of quantum matter in the last\ntwo decades. Here we show that the end-to-end, long-distance, bipartite\nsquashed entanglement between the edges of a many-body system, defined in terms\nof the edge-to-edge quantum conditional mutual information, is the natural\nnonlocal order parameter for topological superconductors in one dimension as\nwell as in quasi one-dimensional geometries. For the Kitaev chain in the entire\ntopological phase, the edge squashed entanglement is quantized to log(2)/2,\nhalf the maximal Bell-state entanglement, and vanishes in the trivial phase.\nSuch topological squashed entanglement exhibits the correct scaling at the\nquantum phase transition, is stable in the presence of interactions, and is\nrobust against disorder and local perturbations. Edge quantum conditional\nmutual information and edge squashed entanglement defined with respect to\ndifferent multipartitions discriminate topological superconductors from\nsymmetry breaking magnets, as shown by comparing the fermionic Kitaev chain and\nthe spin-1/2 Ising model in transverse field. For systems featuring multiple\ntopological phases with different numbers of edge modes, like the quasi 1D\nKitaev ladder, topological squashed entanglement counts the number of Majorana\nexcitations and distinguishes the different topological phases of the system.\nIn fact, we show that the edge quantum conditional mutual information and the\nedge squashed entanglement remain valid detectors of topological\nsuperconductivity even for systems, like the Kitaev tie with long-range\nhopping, featuring geometrical frustration and a suppressed bulk-edge\ncorrespondence.",
        "category": "cond-mat_stat-mech"
    }
]