Generalized fluctuation relation and effective temperatures in a driven fluid

Abstract

By numerical simulation of a Lennard-Jones like liquid driven by a velocity gradient γwe 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,γ)<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.

Version accepted for publication on Phys.Rev.E; major changes, 1 figure added