Driven granular media and dissipative gases: correlations and liquid-gas phase transitions

We present lattice and continuum models of a vibrationally excited one- and two-dimensional granular medium in the absence of boundaries or fields. These are the simplest possible models for a granular material. 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.