Typical and rare fluctuations in nonlinear driven diffusive systems with dissipation

TL;DR

This paper extends macroscopic fluctuation theory to nonlinear driven dissipative systems, analyzing energy dissipation fluctuations and revealing Gaussian behavior for small fluctuations and non-Gaussian large deviations, with implications for fluctuation theorems.

Contribution

It introduces a generalized macroscopic fluctuation framework for dissipative media, deriving explicit equations for fluctuation probabilities and analyzing their scaling behavior.

Findings

Small fluctuations follow Gaussian distribution as per the central limit theorem.

Large fluctuations deviate from Gaussian, violating the Gallavotti-Cohen fluctuation theorem.

Large-deviation functions show simple scaling forms depending on dissipation strength.

Abstract

We consider fluctuations of the dissipated energy in nonlinear driven diffusive systems subject to bulk dissipation and boundary driving. With this aim, we extend the recently-introduced macroscopic fluctuation theory to nonlinear driven dissipative media, starting from the fluctuating hydrodynamic equations describing the system mesoscopic evolution. Interestingly, the action associated to a path in mesoscopic phase-space, from which large-deviation functions for macroscopic observables can be derived, has the same simple form as in non-dissipative systems. This is a consequence of the quasi-elasticity of microscopic dynamics, required in order to have a nontrivial competition between diffusion and dissipation at the mesoscale. Euler-Lagrange equations for the optimal density and current fields that sustain an arbitrary dissipation fluctuation are also derived. A perturbative solution thereof shows that the probability distribution of small fluctuations is always gaussian, as expected from the central limit theorem. On the other hand, strong separation from the gaussian behavior is observed for large fluctuations, with a distribution which shows no negative branch, thus violating the Gallavotti-Cohen fluctuation theorem as expected from the irreversibility of the dynamics. The dissipation large-deviation function exhibits simple and general scaling forms for weakly and strongly dissipative systems, with large fluctuations favored in the former case but heavily supressed in the latter. (...) [see complete abstract by downloading the paper]