To test and to complement the moment method for solving kinetic equations in the space outside of a sphere that absorbs one component out of a gas mixture, we develop a solution method especially suitable for radii smaller or not much larger than a mean free path. The method is used to calculate...

The transfer of heat between an object not too large compared to a mean free path and a gas surrounding it is influenced considerably by the structure of the kinetic boundary layer around the object. We calculate this effect for a spherical object in a dilute gas by applying a recently developed...

We consider the motion of a Brownian particle in a medium with inhomogeneous temperature in the presence of an external potential. We start from the Klein-Kramers equation; in this equation a thermophoretic force, proportional to the temperature gradient, should in general be included to obtain...

Recently we discussed the adiabatic elimination of fast variables from a many-dimensional Fokker-Planck equation linear in the fast variables. Here we show how the same results can be obtained by manipulation of the equivalent set of coupled Langevin equations. At first sight the Langevin...

The motion of a Brownian particle in an external field can be described on two levels: by a Fokker-Planck equation for the joint probability distribution of position and velocity, and by a Smoluchowski equation for the distribution in position space only. We derive the second description, with...

We study stationary solutions of the Fokker-Planck equation for velocity and position of a Brownian particle in the presence of a constant external field and a completely or selectively absorbing plane wall. Adapting a procedure used earlier for the field-free case, we determine analytically a...

The normal mode analysis of systems of linear macroscopic equations in irreversible thermodynamics is extended in several ways. When the characteristics equation has multiple roots, there may appear normal solutions that do not decay purely exponentially, but a closed form for the Green function...

The description using the Smoluchowski equation, on which the traditional theory of diffusion-controlled reactions is based, presupposes local equilibrium. Hence it must break down in the vicinity of an absorbing wall, where a kinetic boundary layer is formed. We explore in this paper the...

We provide a covariant, coordinate-free formulation of the many-dimensional Klein-Kramers equation for the phase space distribution of a Brownian particle. We construct a complete set of eigenfunctions of the collision operator adapted to the coordinate system, which involve covariant tensorial...

The Chapman-Enskog method for the adiabatic elimination of fast variables is applied to a general Fokker-Planck equation linear in the fast variables. This equation is the counterpart of the generalized Haken-Zwanzig model, a system of coupled Langevin equations often encountered in quantum...