A theory is developed of Brownian motion in granular gases (systems of many macroscopic parti cles undergoing inelastic collisions), where the energy loss in inelastic collisions is determined by a restitution coefficient ε. Whereas previous studies used a simplified model with ε = const, the present analysis takes into account the dependence of the restitution coefficient on relative impact velocity. The granular temperature and the Brownian diffusion coefficient are calculated for a granular gas in the homogeneous cooling state and a gas driven by a thermostat force, and their variation with grain mass and size and the restitution coefficient is analyzed. Both equipartition principle and fluctuation–dissipation relations are found to break down. One manifestation of this behavior is a new phenomenon of “relative heating” of Brownian particles at the expense of cooling of the ambient granular gas.
展开▼
