Inhomogeneous cooling in inelastic granular fluids

We present results from a granular dynamics study of the nonequilibrium behavior of a freely evolving inelastic granular gas. The velocity and density fields exhibit complex pattern formation, which is reminiscent of phase-ordering systems. At early times, the density field stays approximately uniform and the system is said to be in a homogeneous cooling state. However, at later times, the density field undergoes clustering, and evolves into an inhomogeneous cooling state (ICS). We characterize the nonlinear evolution of the density and velocity fields in the ICS by invoking analogies from studies of phase ordering dynamics.