Kinetic models for the generalized Enskog equation

The generalized Enskog equation is used to describe the dynamic structure factor S(k,ω) for a hard-sphere gas. The problem of constructing kinetic models for the calculation of S(k,ω) is considered and the minimum set of matrix elements of the exact collision operator required by hydrodynamics is identified. The source of existing discrepancies between kinetic-model calculations and light-scattering experiments is also found and removed. Sensitivity of S(k,ω) to the parameters of kinetic models is discussed and a simple model proposed. A preliminary comparison of the hard-sphere S(k,ω) calculated from this model with neutron-scattering data from gaseous krypton is given.