Breakdown of the Brownian motion model in ultrafast dynamics

Publisher Website
Google Scholar
Abstract
When the motion of the surrounding heat bath particles is a slow coordinate, a ‘‘system’’ particle and its bath become dynamically coupled. A nonlinear Langevin (Fokker-Planck) equation is required to describe the stochastic process. In general, the steady-state distribution is not canonical. The rapid-motion effect, in association with the dynamical coupling among multimodes of the system, and the combined contributions from nonlinear and non-Markovian processes, cause a breakdown of the conventional Brownian motion theory. The discussion given in this paper puts previous computer-simulation results on a better theoretical foundation.