Latest Papers in Condensed Matter Physics

Statistical Mechanics

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Dynamics in dissipative systems. And, their Maximum Caliber trajectories in a solvable model (1904.11426v1)

Luca Agozzino, Ken A Dill

2019-04-25

Maximum Caliber(Max Cal) is purported to be a general variational principle for Non-EquilibriumStatistical Physics (NESP). But recently, Jack and Evans [1] and Maes [2] have raised concerns about how Max Cal handles dissipative processes. Here, we show that the problem does not lie in Max Cal; the problem is in the use of insufficient constraints. We also present an exactly solvable single-particle model of dissipation, valid far from equilibrium, and its solution by Maximum Caliber. The model illustrates how the influx and efflux of work and heat into a flowing system alters the distribution of trajectories. Maximum Caliber is a viable principle for dissipative systems.

Multimodal stationary states under Cauchy noise (1902.07491v2)

Michał Cieśla, Karol Capała, Bartłomiej Dybiec

2019-02-20

A L'evy noise is an efficient description of out-of-equilibrium systems. The presence of L'evy flights results in a plenitude of noise-induced phenomena. Among others, L'evy flights can produce stationary states with more than one modal value in single-well potentials. Here, we explore stationary states in special double-well potentials demonstrating that a sufficiently high potential barrier separating potential wells can produce bimodal stationary states in each potential well. Furthermore, we explore how the decrease in the barrier height affects the multimodality of stationary states. Finally, we explore a role of the multimodality of stationary states on the noise induced escape over the static potential barrier.

Gaussian statistics as an emergent symmetry of the stochastic Burgers equation (1809.02158v2)

Enrique Rodriguez-Fernandez, Rodolfo Cuerno

2018-09-06

Symmetries play a conspicuous role in the large-scale behavior of critical systems. While in equilibrium they allow to classify asymptotics into different universality classes, out of equilibrium they can emerge, some times unexpectedly, as collective properties which are not explicit in the 'bare' interactions. Here we elucidate the emergence of an up-down symmetry in the asymptotic behavior of the stochastic scalar Burgers equation in one and two dimensions, manifested by the occurrence of Gaussian fluctuations for the physical field. This robustness of Gaussian behavior contradicts naive expectations, due to the detailed relation ---including the same set of symmetries--- between Burgers equation and the Kardar-Parisi-Zhang equation, which paradigmatically displays non-Gaussian fluctuations described by Tracy-Widom distributions. We reach our conclusions via a dynamic renormalization group study of the field statistics, confirmed by direct evaluation of the field probability distribution function from numerical simulations of the dynamical equation. All odd-order cumulants cancel exactly, while the excess kurtosis vanishes for large systems, indeed consistent with Gaussian behavior.

Scaling in the massive antiferromagnetic XXZ spin-1/2 chain near the isotropic point (1904.11324v1)

S. B. Rutkevich

2019-04-25

The scaling limit of the Heisenberg XXZ spin chain at zero magnetic field is studied in the gapped antiferromagnetic phase. For a spin-chain ring having sites, the universal Casimir scaling function, which characterises the leading finite-size correction term in the large- expansion of the ground state energy, is calculated by numerical solution of the nonlinear integral equation of the convolution type. It is shown, that the same scaling function describes the temperature dependence of the free energy of the infinite XXZ chain at low enough temperatures in the gapped scaling regime.

Spontaneous rectification and absolute negative mobility of inertial Brownian particles induced by Gaussian potentials in steady laminar flows (1902.08947v2)

Jian-Chun Wu, Meng An, Wei-Gang Ma

2019-02-24

We study the transport of inertial Brownian particles in steady laminar flows in the presence of two-dimensional Gaussian potentials. Through extensive numerical simulations, it is found that the transport is sensitively dependent on the external constant force and the Gaussian potential. Within tailored parameter regimes, the system exhibits a rich variety of transport behaviors. In the absence of any external driving forces, the spontaneous rectification of the particles can be manipulated by the spatial position of the Gaussian potential. Moreover, when the potential lies at the center of the cellular flow, the system exhibits absolute negative mobility (ANM), i.e., the particles can move in a direction opposite to the constant force. More importantly, the phenomenon of ANM induced by Gaussian potential is robust in a wider range of the system parameters and can be further strengthened with the optimized parameters, which may pave the way to the implementation of related experiments.

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