The temperature of a vibrated granular gas

The temperature of a granular medium is defined, in a manner analogous to that of a molecular gas, as the root mean squared kinetic energy of the grains. Using a novel two-layer granular experiment, we have made a systematic study of the granular temperature as a function of driving parameters in order to determine whether the behavior of the granular temperature is truly analogous to the temperature of a molecular gas. By examining the behavior of this particular system in detail, where two fluctuating granular media are in thermal contact, we also suggest general conditions under which such analogies can be extended to other driven systems.