Violation of Molecular Chaos in dissipative gases
  Numerical simulations of a dissipative hard sphere gas reveal a dependence of the cooling rate on correlation of the particle velocities due to inelastic collisions. We propose a coefficient which characterizes the velocity correlations in the two-particle velocity distribution function and express the temperature decay rate in terms of this coefficient. The analytical results are compared with numerics. 
Thorsten Poeschel, Nikolai V. Brilliantov, and Thomas Schwager