Heat fluctuations in an out of equilibrium bath

TL;DR

This study investigates energy fluctuations of a Brownian particle in an aging gelatin bath after a rapid quench, interpreting the fluctuations as heat fluxes and deriving a model that matches experimental data within a fluctuation theorem framework.

Contribution

It provides the first experimental measurement of heat fluctuations in an out-of-equilibrium bath and introduces a simple model that accurately describes the heat distribution.

Findings

Heat fluctuations follow a specific probability distribution.

The model fits experimental data well.

Fluctuation relations are satisfied in the out-of-equilibrium system.

Abstract

We measure the energy fluctuations of a Brownian particle confined by an optical trap in an aging gelatin after a very fast quench (less than 1 ms). The strong nonequilibrium fluctuations due to the assemblage of the gel, are interpreted, within the framework of fluctuation theorem, as a heat flux from the particle towards the bath. We derive, from a simple model, an analytical expression of the heat probability distribution, which fits the experimental data and satisfies a fluctuation relation similar to that of a system in contact with two baths at different temperatures.