A NEW QUANTUM PROPAGATOR FOR HARD-SPHERE AND CAVITY SYSTEMS

A new short time propagator for a particle interacting with a hard sphere or with a hard sphere cavity is derived. This new propagator is shown to be a much better approximation than the image approximations used in the literature and should prove useful for path integral or Green function Monte Carlo simulations. The simple example of the radial distribution function of a hard sphere gas is calculated using the new propagator as well as the older image approximation propagator and is shown to converge much more rapidly to the ab initio result.