Driven granular media and dissipative gases: Phase transitions and instabilities

We study a simple model of a granular material or powder where the particles are excited by an external noise source and dissipate energy by inelastic collisions. Due to the inelastic collisions between particles there is an effective interaction between them. In one dimension this leads to long-range correlations between the particles in a gas phase despite the absence of long-range forces between the particles. In two dimensions the dissipative effects cause a very sharp liquid-gas phase transition at which the susceptibility has a pronounced peak. In the presence of a double-welled potential the inelasticity causes a symmetry-breaking instability where all the particles cluster into one of the wells.