An Enskog repeated-ring kinetic equation; Long-time tails and the Brownian limit

A kinetic equation for the motion of a particle of arbitrary size and mass through a moderately dense gas is derived and discussed. The "long-time tail" of the velocity correlation function is calculated and found to agree with existing results. For a Brownian particle, the theory gives the Stokes-Einstein law for the self-diffusion coefficient, with the shear viscosity given by its Enskog value. © 1983 Plenum Publishing Corporation.