Searcharxiv⌕ Search

SEARCH · Searcharxiv

Results for “cond-mat.stat-mech”

Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
arXiv2014

An assessment of the concept of fragility

The concept of "fragility", which was introduced to characterize the degree of super-Arrhenius temperature dependence of the relaxation time and transport coefficients, has since been taken as a key quantity that seems to correlate with other properties of glass-forming liquids and polymers. With the goal of assessing the usefulness and the robustness of the concept, we address here several questions: How to best quantify fragility? How significant are the observed differences in fragility? Is fragility connected to "cooperativity" and collective behavior?

cond-mat.stat-mech↗
arXiv2014

The $(q,μ,ν)$-Boson process and $(q,μ,ν)$-TASEP

We prove a intertwining relation (or Markov duality) between the $(q,μ,ν)$-Boson process and $(q,μ,ν)$-TASEP, two discrete time Markov chains introduced by Povolotsky. Using this and a variant of the coordinate Bethe ansatz we compute nested contour integral formulas for expectations of a family of observables of the $(q,μ,ν)$-TASEP when started from step initial data. We then utilize these to prove a Fredholm determinant formula for distribution of the location of any given particle.

math.PR↗
arXiv2014

Chaotic behavior of a spin-glass model on a Cayley tree

We investigate the phase diagram of a spin--1 Ising spin-glass model on a Cayley tree. According to early work of Thompson and collaborators, this problem can be formulated in terms of a set of nonlinear discrete recursion relations along the branches of the tree. Physically relevant solutions correspond to the attractors of these mapping equations. In the limit of infinite coordination of the tree, and for some choices of the model parameters, we make contact with findings for the phase diagram of more recently investigated versions of the Blume-Emery-Griffiths spin-glass model. In addition to the anticipated phases, we numerically characterize the existence of modulated and chaotic structures.

cond-mat.stat-mech↗
arXiv2014

Analysis of the stability of stationary boundary friction modes in the framework of a synergetic model

A synergetic model describing the state of an ultrathin lubricant layer squeezed between two atomically smooth solid surfaces operating in the boundary friction mode has been developed further. To explain the presence of different operation modes of the system for various sets of its main parameters, the mathematical analysis of the synergetic model is carried out. The type of functioning a tribological system is described in accordance with the stability character of singular points, and the diagrams distinguishing various operation modes are obtained. Phase portraits corresponding to different stability types are plotted for all diagram areas. A stick-slip mode of motion that is often observed experimentally is described.

cond-mat.mes-hall↗
arXiv2014

Stochastic patterns in a 1D Rock-Paper-Scissor model with mutation

In the framework of a 1D cyclic competition model, the Rock-Paper-Scissor model, where bacteria are allowed to mutate and move in space, we study the formation of stochastic patterns, where all the bacteria species do coexist. We modelled the problem using an individual-based setting and using the system size van Kampen expansion to deal with the Master Equation, we have been able to characterise the spatio-temporal patterns using the power spectrum of the fluctuations. We proved that such patterns are robust against the intrinsic noise and they can be found for parameters values beyond the ones fixed by the deterministic approach. We complement such analytical results with numerical simulations based on the Gillespie's algorithm.

cond-mat.stat-mech↗
arXiv2014

Statistical Physics of Pure Barkhausen Noise

We discuss a model metallic glass in which Barkhausen Noise can be studied in exquisite detail, free of thermal effects and of the rate of ramping of the magnetic field. The mechanism of the jumps in magnetic moment that cause the Barkhausen Noise can be fully understood as consecutive instabilities where an eigenvalue of the Hessian matrix hits zero, leading to a magnetization jump $Δm$ which is simultaneous with a stress and energy changes $Δσ$ and $ΔU$ respectively. Contrary to common belief we find no "movements of magnetic domain boundaries" across pinning sites, no fractal domains, no self-organized criticality and no exact scaling behaviour. We present a careful numerical analysis of the statistical properties of the phenomenon, and show that with every care taken this analysis is tricky, and easily misleading. Without a guiding theory it is almost impossible to get the right answer for the statistics of Barkhausen Noise. We therefore present an analytic theory, showing that the probability distribution function (pdf) of Barkhausen Noise is not a power law times an exponential cutoff.

cond-mat.stat-mech↗
arXiv2014

Dynamical Heterogeneity in the Glassy State

We compare dynamical heterogeneities in equilibrated supercooled liquids and in the nonequilibrium glassy state within the framework of the random first order transition theory. Fluctuating mobility generation and transport in the glass are treated by numerically solving stochastic continuum equations for mobility and fictive temperature fields that arise from an extended mode coupling theory containing activated events. Fluctuating spatiotemporal structures in aging and rejuvenating glasses lead to dynamical heterogeneity in glasses with characteristics distinct from those found in the equilibrium supercooled liquid. The non-Gaussian distribution of activation free energies, the stretching exponent $β$, and the growth of characteristic lengths are studied along with the four-point correlation function. Asymmetric thermodynamic responses upon heating and cooling are predicted to be the results of the heterogeneity and the out-of-equilibrium behavior of glasses below $T_g$. Numerical results agree with experimental calorimetry. We numerically confirm the prediction of Lubchenko and Wolynes in the glass that the dynamical heterogeneity can lead to noticeably bimodal distributions of local fictive temperatures which explains in a unified way recent experimental observations that have been interpreted as coming from two distinct equilibration mechanisms in glasses.

cond-mat.stat-mech↗
arXiv2014

Effect of the fluctuations around mean field for N-body systems with long range interactions

We study the effect of Chandrasekhar and Holstmark's distribution of field fluctuations on the dynamics of N-body systems interacting via Coulomb or Newton gravitational force. We develop an approach based on statistical dynamics first principles whose mathematical framework is similar to the one used by Chandrasekhar and Holstmark for their field fluctuation theory. We use the Picard iteration method to approximate the Hamiltonian dynamics in the short time limit. Neglecting correlations between particles, carrying the thermodynamic limit and assuming that the system is spatially homogeneous, we find a fractional kinetic equation for the velocity distribution. Both, the fractional derivative order and the asymptotic behavior of the solution appear to be directly connected to the $1/r^2$ behavior of the Coulombian or gravitational interaction force over short distances.

physics.class-ph↗
arXiv2014

Numerical Detection of the Ergodicity Breaking in a Lattice Glass Model

We directly detect the ergodicity breaking in a lattice glass model by a numerical simulation. The obtained results nicely agree with those by the cavity method that the model on a regular random graph exhibits a dynamical transition with the ergodicity breaking at an occupation density. The present method invented for a numerical detection of the ergodicity breaking is applicable to glassy systems in finite dimensions.

cond-mat.dis-nn↗
arXiv2014

1D Cahn-Hilliard dynamics : coarsening and interrupted coarsening

Many systems exhibit a phase where the order parameter is spatially modulated. These patterns can be the result of a frustration caused by the competition between interaction forces with opposite effects. In all models with local interactions, these ordered phases disappear in the strong segregation regime (low temperature). It is expected however that these phases should persist in the case of long range interactions, which can't be correctly described by a Ginzburg-Landau type model with only a finite number of spatial derivatives of the order parameter. An alternative approach is to study the dynamics of the phase transition or pattern formation. While, in the usual process of Ostwald ripening, succession of doubling of the domain size leads to a total segregation, or macro-segregation, C. Misbah and P. Politi have shown that long-range interactions could cause an interruption of this coalescence process, stabilizing a pattern which then remains in a micro-structured state or super-crystal. We show that this is the case for a modified Cahn-Hilliard dynamics due to Oono which includes a non local term and which is particularly well suited to describe systems with a modulated phase.

cond-mat.stat-mech↗
arXiv2014

Emergence of a sustained current by coupling equilibrating systems: Making a NESS out of equilibrium

We show that coupling together two closed thermodynamic systems that independently attain equilibrium may give rise to a nonequilibrium stationary state (NESS) with a persistent, non-vanishing current. We study a simple example that is exactly soluble, consisting of random walkers with different biases towards a reflecting boundary, modelling, for example, Brownian particles with different charge states in an electric field. We obtain exact analytical expressions for the (generating functions of) concentrations and currents in the NESS for this model, and exhibit the main features by numerical simulation.

cond-mat.stat-mech↗
arXiv2014

Properties of spatial coupling in compressed sensing

In this paper we address a series of open questions about the construction of spatially coupled measurement matrices in compressed sensing. For hardware implementations one is forced to depart from the limiting regime of parameters in which the proofs of the so-called threshold saturation work. We investigate quantitatively the behavior under finite coupling range, the dependence on the shape of the coupling interaction, and optimization of the so-called seed to minimize distance from optimality. Our analysis explains some of the properties observed empirically in previous works and provides new insight on spatially coupled compressed sensing.

cs.IT↗
arXiv2014

Do dipole correlations exist in two-dimensional spin ice?

Here we study the statistical properties of two-dimensional spin ice in its ground state by the Monte Carlo simulation method. Using a new sampling algorithm, we show that the short-range ice rule in two dimensions gives rise to long-range but not dipole-like correlations, to non-Gaussian probability density function for magnetization and to non-extensive conditional entropy (entropy with given value of magnetization).

cond-mat.stat-mech↗
arXiv2014

Is ergodicity a reasonable hypothesis?

In the physics literature "ergodicity" is taken to mean that a system, including a macroscopic one, visits all microscopic states in a relatively short time. We show that this is an impossibility even if that time is billions of years. We also suggest that this feature does not contradict most physical considerations since those considerations deal with correlations of only a few particles.

cond-mat.stat-mech↗
arXiv2014

New developments for dual methods in lattice field theory at non-zero density

In recent years the complex action problem of lattice field theory at finite density was overcome for several system by mapping them to dual variables (flux lines and surfaces). We illustrate this mapping for the case of the U(1) gauge Higgs system and present some representative physics results for this model. Conceptual challenges such as spectroscopy in the dual approach, as well as algorithmic developments are discussed and related ideas for systems with fermions are addressed. Models where the dual variables approach solves the complex action problem can serve as reference systems for other approaches to finite density lattice field theory and we discuss some examples. Finally we address the strategy of a partial dualization in certain limits, e.g., for strong coupling and large mass.

hep-lat↗
arXiv2017

Comment on Ben-Amotz and Honig, "Average entropy dissipation in irreversible mesoscopic processes," Phys. Rev. Lett. 96, 020602 (2006)

We point out that most of the classical thermodynamics results in the paper have been known in the literature, see Kestin and Woods, for quite some time and are not new, contrary to what the authors imply. As shown by Kestin, these results are valid for quasistatic irreversible processes only and not for arbitrary irreversible processes as suggested in the paper. Thus, the application to the Jarzynski process is limited.

physics.chem-ph↗
arXiv2017

Caliber Corrected Markov Modeling (C2M2): Correcting Equilibrium Markov models

Rate processes are often modeled using Markov-State Models (MSM). Suppose you know a prior MSM, and then learn that your prediction of some particular observable rate is wrong. What is the best way to correct the whole MSM? For example, molecular dynamics simulations of protein folding may sample many microstates, possibly giving correct pathways through them, while also giving the wrong overall folding rate, when compared to experiment. Here, we describe Caliber Corrected Markov Modeling (C2M2): an approach based on the principle of maximum entropy for updating a Markov model by imposing state- and trajectory- based constraints. We show that such corrections are equivalent to asserting position-dependent diffusion coefficients in continuous-time continuous-space Markov processes modeled by a Smoluchowski equation. We derive the functional form of the diffusion coefficient explicitly in terms of the trajectory-based constraints. We illustrate with examples of 2D particle diffusion and an overdamped harmonic oscillator.

cond-mat.stat-mech↗