Simple models for compartmentalized sand

We study the behavior of inelastically colliding particles moving in a bistable potential, and driven by a stochastic heat bath. The system has the tendency to cluster at low drivings, and to fill completely the available space when vigorously shaked. In the case of just two particles, we show that the hopping over the potential barrier occurs following the Arrhenius rate, if the temperature is replaced by the granular temperature. For systems containing many particles we observe a strong competition between the excluded volume effect, which favors a symmetric distribution between the two wells, and inelasticity which on the contrary induces clustering.