A local fluctuation theorem for large systems

TL;DR

This paper derives a local fluctuation theorem for small open subsystems within large systems, accounting for correlations with surroundings, supported by analytical derivation and numerical validation.

Contribution

It introduces a correction term to the fluctuation theorem for subsystems, extending the theorem's applicability to large systems with negligible external fluctuations.

Findings

A correction term is necessary for the local fluctuation theorem.

Analytic expression for the correction term is derived.

Numerical simulations confirm the theoretical predictions.

Abstract

The fluctuation theorem characterizes the distribution of the dissipation in nonequilibrium systems and proves that the average dissipation will be positive. For a large system with no external source of fluctuation, fluctuations in properties will become unobservable and details of the fluctuation theorem are unable to be explored. In this letter, we consider such a situation and show how a fluctuation theorem can be obtained for a small open subsystem within the large system. We find that a correction term has to be added to the large system fluctuation theorem due to correlation of the subsystem with the surroundings. Its analytic expression can be derived provided some general assumptions are fulfilled, and its relevance it checked using numerical simulations.