On the speed of approach to equilibrium for a collisionless gas

Abstract

We investigate the speed of approach to Maxwellian equilibriumfor a collisionless gas enclosed in a vessel whose wall are kept at a uniform, constant temperature, assuming diffuse reection of gas molecules on the vesselwall. We establish lower bounds for potential decay rates assuming uniform Lpbounds on the initial distribution function. We also obtain a decay estimate in the spherically symmetric case. We discuss with particular care the inuenceof low-speed particles on thermalization by the wall. © American Institute of Mathematical Sciences.