Correlation functions in quantum hard-sphere fluids at short times or high frequencies, and high-energy neutron scattering

The short-time or high-frequency expansions of several dynamical correlation functions in a quantum hard-sphere fluid of spinless bosons are computed. These expansions are shown to be of a different form than those obtained for either a fluid of quantum particles interacting through a smooth potential or for a classical fluid of hard spheres. Assuming that the same dynamical contributions that are important in the short-time expansions are also responsible for dominant final-state interactions in high-energy neutron scattering, we also approximately compute the shape of the dynamic structure factor near the free-particle frequency.