Elastic energy, fluctuations and temperature for granular materials

We probe, using a model system, elastic and kinetic energies for sheared granular materials. For large enough P/E_y (pressure/Young's modulus) and P/v² (P/kinetic energy density) elastic dominates kinetic energy, and energy fluctuations become primarily elastic in nature. This regime has likely been reached in recent experiments. We consider a generalization of the granular temperature, T_g, with both kinetic and elastic terms and that changes smoothly from one regime to the other. This T_g is roughly consistent with a temperature adapted from equilibrium statistical mechanics.