BROWNIAN TRANSPORT CONTROLLED BY DICHOTOMIC AND THERMAL FLUCTUATIONS

We study transport of Brownian particles in spatially periodic structu res, driven by both thermal equilibrium fluctuations and dichotomic no ise of zero mean values. Introducing specific scaling, we show that th e dimensionless Newton-Langevin type equation governing the motion of Brownian particles is very well approximated by the overdamped dynamic s; inertial effects can be neglected because for generic systems dimen sionless mass is many orders less than a dimensionless friction coeffi cient. An exact probability current, proportional to the mean drift ve locity of particles, is obtained for a piecewise linear spatially peri odic potential. We analyze in detail properties of the macroscopic ave raged motion of particles. In dependence on statistics of both sources of fluctuations, the directed transport of particles exhibits such di stinctive non-monotonic behavior as: bell-shaped dependence (there exi sts optimal statistics of fluctuations maximizing velocity) and revers al in the direction of macroscopic motion (there exists critical stati stics at which the drift velocity is zero). (C) 1998 Elsevier Science B.V. All rights reserved.