Comment II on J.M. Salazar and L. Brenig's article: ``Computer Simulations and Kinetic Theory of an Inelastic Granular Gas''

Abstract

In two recent articles Salazar and Brenig question the validity of kinetic theory for granular gases and fluids, on the based of a supposedly exact hierarchy of coupled equations for the velocity moments, which the authors derive from the BBGKY-hierarchy. Their derivation contains several errors, which are exposed. Moreover, they support their findings with results from direct monte carlo simulation (DSMC) of the Boltzmann equation, which supposedly show that Haff's homogeneous cooling law only holds for times shorter than one mean free time. However, their DSMC results have no physical significance as they are carried out at a density, twice close packing.