Density fluctuations in a fluid mixture of hard spheres

Time-dependent phase-space density correlation functions in a fluid mixture of hard spheres are analyzed using a coupled set of generalized Boltzmann equations. The matrix of memory functions is expressed explicitly as static, direct-collision, and cross-collision contributions. Low-order matrix elements of the memory functions are calculated, and the results used to discuss the hydrodynamics of the system and to construct kinetic models. Numerical spectra of density fluctuations are presented to illustrate the effects due to dynamical correlations in a mixture.