FREE COOLING AND HIGH-ENERGY TAILS OF GRANULAR GASES WITH VARIABLE RESTITUTION COEFFICIENT

We prove the so-called generalized Haff's law yielding the optimal algebraic cooling rate of the temperature of a granular gas described by the homogeneous Boltzmann equation for inelastic interactions with nonconstant restitution coefficient. Our analysis is carried through a careful study of the infinite system of moments of the solution to the Boltzmann equation for granular gases and precise L(p) estimates in the self-similar variables. In the process, we generalize several results on the Boltzmann collision operator obtained recently for homogeneous granular gases with constant restitution coefficient to a broader class of physical restitution coefficients that depend on the collision impact velocity. This generalization leads to the so-called L(1)-exponential tails theorem for this model.