Mpemba effect in an anisotropically driven granular gas

Abstract

The Mpemba effect refers to the counterintuitive relaxation wherein a hotter system equilibrates faster than a cooler system when quenched to a cold temperature. Even though the effect has been illustrated for isotropically driven granular gases, a prototypical system far from equilibrium, its existence requires non-stationary initial states, limiting experimental realisation. In this paper, we demonstrate the existence of the Mpemba effect in anisotropically driven granular gases, even when quenched from initial states that are stationary. Our theoretical predictions, based on kinetic theory, for the regular, inverse and strong Mpemba effects agree well with results of event-driven molecular dynamics simulations of hard discs.