Large Mpemba-like effect in a gas of inelastic rough hard spheres

A giant Mpemba-like effect emerges in a uniformly heated gas of inelastic rough hard spheres, where the initially hotter sample cools sooner than the colder one, even when the initial temperatures differ by more than one order of magnitude. In order to understand this behavior, it suffices to consider the simplest Maxwellian approximation for the velocity distribution in a kinetic approach. The largeness of the effect stems from the fact that the rotational and translational temperatures, which obey two coupled evolution equations, are comparable, and it increases with higher inelasticity and lower roughness of the particles. Our theoretical predictions agree very well with molecular dynamics and direct simulation Monte Carlo data.