  An isolated mixture of smooth, inelastic hard spheres supports a homogeneous
cooling state with different kinetic temperatures for each species. This
phenomenon is explored here by molecular dynamics simulation of a two component
fluid, with comparison to predictions of the Enskog kinetic theory. The ratio
of kinetic temperatures is studied for two values of the restitution
coefficient, $\alpha =0.95$ and 0.80, as a function of mass ratio, size ratio,
composition, and density. Good agreement between theory and simulation is found
for the lower densities and higher restitution coefficient; significant
disagreement is observed otherwise. The phenomenon of different temperatures is
also discussed for driven systems, as occurs in recent experiments. Differences
between the freely cooling state and driven steady states are illustrated.
