Diffusion of Brownian particles with hydrodynamic interaction and hard core repulsion

We study diffusion in a dilute system of Brownian particles with hydrodynamic interaction and hard core repulsion. We assume that the hard core has a radius larger than the hydrodynamic one. The short-time and long-time self-diffusion coefficient, as well as the collective diffusion coefficient, are calculated exactly to first order in the volume fraction. We show that hydrodynamic interactions are important even when the hard core radius is several times larger than the hydrodynamic one.