Generalized fluctuation relation and effective temperatures in a driven fluid

TL;DR

This study uses numerical simulations to explore the fluctuation relation in a driven Lennard-Jones liquid below the glass transition, introducing an effective temperature that aligns with the fluctuation-dissipation temperature.

Contribution

It demonstrates a generalized fluctuation relation with a numerical factor defining an effective temperature in a driven fluid below T_g.

Findings

The fluctuation relation is valid with a generalized form involving a factor X(T,γ).

The effective temperature from the fluctuation relation agrees qualitatively with that from fluctuation-dissipation.

The effective temperature provides insight into nonequilibrium thermodynamics of driven glasses.

Abstract

By numerical simulation of a Lennard-Jones like liquid driven by a velocity gradient \gamma we test the fluctuation relation (FR) below the (numerical) glass transition temperature T_g. We show that, in this region, the FR deserves to be generalized introducing a numerical factor X(T,\gamma)<1 that defines an ``effective temperature'' T_{FR}=T/X. On the same system we also measure the effective temperature T_{eff}, as defined from the generalized fluctuation-dissipation relation, and find a qualitative agreement between the two different nonequilibrium temperatures.