Long-time tails in freely cooling granular gases.

The long-time behavior of the current autocorrelation functions for the velocity, the shear stress, and the heat flux is investigated in freely cooling granular gases. It is found that the correlation functions for the velocity and the shear stress have the long-time tails obeying tau(-d/2), while the correlation function for heat flux decays as tau(-(d+2)/2) exp(-zeta*tau) with the dimensionless cooling rate zeta*, the spatial dimension d, and the scaled time tau in terms of the collision frequency. The result of our numerical simulation of the freely cooling granular gases is consistent with the theoretical prediction.