Canonical structure of dynamical fluctuations in mesoscopic nonequilibrium steady states

TL;DR

This paper derives the explicit canonical form of the fluctuation functional for density and current in mesoscopic nonequilibrium steady states, extending Onsager-Machlup theory to stochastic lattice gases and chemical networks.

Contribution

It provides a generalised fluctuation functional structure for mesoscopic systems in nonequilibrium steady states, including entropy current and traffic terms, and clarifies density-current coupling.

Findings

Identifies the fluctuation functional structure for mesoscopic systems.

Includes entropy current and traffic as key terms in the functional.

Shows decoupling of density and current fluctuations near equilibrium.

Abstract

We give the explicit structure of the functional governing the dynamical density and current fluctuations for a mesoscopic system in a nonequilibrium steady state. Its canonical form determines a generalised Onsager-Machlup theory. We assume that the system is described as a Markov jump process satisfying a local detailed balance condition such as typical for stochastic lattice gases and for chemical networks. We identify the entropy current and the traffic between the mesoscopic states as extra terms in the fluctuation functional with respect to the equilibrium dynamics. The density and current fluctuations are coupled in general, except close to equilibrium where their decoupling explains the validity of entropy production principles.