Equilibrium stochastic dynamics of a Brownian particle in inhomogeneous space: derivation of an alternative model

Abstract

An alternative equilibrium stochastic dynamics for a Brownian particle in inhomogeneous space is derived. Such a dynamics can model the motion of a complex molecule in its conformation space when in equilibrium with a uniform heat bath. The derivation is done by a simple generalization of the formulation due to Zwanzig for a Brownian particle in homogeneous heat bath. We show that if the system couples to different number of bath degrees of freedom at different conformations then the alternative model is derived. We discuss results of an experiment by Faucheux and Libchaber which probably has indicated possible limitation of the Boltzmann distribution as equilibrium distribution of a Brownian particle in inhomogeneous space and propose experimental verification of the present theory using similar methods.

arXiv commentThis revised version more clearly describes the cases of vertical and horizontal diffusivity as could be seen in an experiment as has been previously done by Faucheux and Libchaber. This version also includes proposal of a new experiment involving complex molecules