Coarse-graining and Thermodynamics in Far-from-equilibrium Systems

Abstract

Lying at the core of statistical physics is the need to reduce the number of degrees of freedom in a system. Coarse-graining is a frequently-used procedure to bridge molecular modeling with experiments. In equilibrium systems, this task can be readily performed; however in systems outside equilibrium, a possible lack of equilibration of the eliminated degrees of freedom may lead to incomplete or even misleading descriptions. Here, we present some examples showing how an improper coarse-graining procedure may result in linear approaches to nonlinear processes, miscalculations of activation rates and violations of the fluctuation-dissipation theorem.

On the Existence and Applicability of Extremal Principles in the Theory of Irreversible Processes: A Critical Review

“…If the local equilibrium approximation becomes inapplicable, then statistical approaches can be applied that use variable decomposition based on relaxation times (for example, the Fokker-Planck equation approach [22].…”