Corrections to the Smoluchowski equation in the presence of hydrodynamic interactions

The systematic procedure for deriving the Smoluchowski equation and successive corrections to it from the Fokker-Planck equation is modified and extended in such a way that it now also covers the case of several interacting Brownian particles with hydrodynamic interactions. This is done by means of a suitable adaptation of the Chapman-Enskog method. The expression found for the first correction term to the Smoluchowski equation is worked out in full detail for the special case of two identical, spherically symmetric Brownian particles.