Fluctuation theorems for an asymmetric rotor in a granular gas

TL;DR

This paper examines the applicability of fluctuation theorems to an asymmetric rotor in a granular gas, demonstrating their validity in different dynamical states and revealing insights into symmetry breaking and entropy production.

Contribution

It provides experimental validation of fluctuation theorems in granular systems and explores their robustness amid spontaneous symmetry breaking.

Findings

Fluctuation theorems hold for injected work and entropy production.

A Gaussian velocity distribution fits the first state.

Symmetry relations predict peak ratios in the double-peaked distribution.

Abstract

We investigate the validity of fluctuation theorems for an asymmetric rotor experiment in a granular gas. A first state, with a Gaussian distribution of the angular velocity, is found to be well described by a first order Langevin equation. We show that fluctuation theorems are valid for the injected work and for the total entropy production. In a second state the angular velocity distribution is double-peaked due to a spontaneous symmetry breaking: A convection roll develops in the granular gas, which strongly couples to the rotor. Surprisingly, in this case similar symmetry relations hold, which lead to a good prediction for the height ratio of the two peaks.