A fluidized granular medium as an instance of the Fluctuation Theorem

TL;DR

This paper investigates the power flux fluctuations in a fluidized granular medium and finds that their statistical behavior aligns with the Fluctuation Theorem, revealing insights into non-equilibrium steady states.

Contribution

It demonstrates that the Fluctuation Theorem applies to a fluidized granular system, providing new experimental evidence of fluctuation symmetry in inelastic particle media.

Findings

Power flux exhibits large fluctuations, including negative ones.

Fluctuation probabilities agree with the Fluctuation Theorem even at short times.

An effective temperature relates to the granular temperature.

Abstract

We study the statistics of the power flux into a collection of inelastic beads maintained in a fluidized steady-state by external mechanical driving. The power shows large fluctuations, including frequent large negative fluctuations, about its average value. The relative probabilities of positive and negative fluctuations in the power flux are in close accord with the Fluctuation Theorem of Gallavotti and Cohen, even at time scales shorter than those required by the theorem. We also compare an effective temperature that emerges from this analysis to the kinetic granular temperature.