Memory effects and entropy production in granular fluids

A non-equilibrium Generalized Langevin Equation with exponential
memory is proposed for the dynamics of a massive intruder in a dense
granular fluid. The source of memory is identified in the coupling of
the tracer velocity with a spontaneous local velocity field in the
surrounding fluid. Such identification allows us to measure the
intruder?s fluctuating entropy production, obtaining a neat
verification of the Fluctuation Relation.