Thermal fluctuations of granular gas under HCS using two-point kinetic theory

Thermal fluctuations of the granular gas under the homogeneous cooling state (HCS) are estimated using two-point kinetic theory by Tsuge-Sagara. Thermal fluctuations of the elastic gas are modified for the granular gas by nonequilibrium moments, which defines the distribution function under the HCS. The deviations of thermal fluctuations for the granular gas from those for the elastic gas obtained by the fluctuation-dissipation theorem are calculated as a function of the restitution coefficient.