Statistical Mechanics of dense granular media

Recently, the hypothesis that dense granular media can be described by the methods of Statistical Mechanics, as originally proposed by Sam Edwards, has been deeply investigated. This is an important issue since granular packs are non-thermal systems and cannot be described by usual Thermodynamics. We review here some pioneering models and Monte Carlo and Molecular Dynamics (MD) simulations, as well as some experiments, supporting the idea that, in some model systems, it is possible to introduce a suitable distribution function for microstates, in analogy to Boltzmann-Gibbs weight of thermal systems, replacing time with ensemble averages. Interestingly, a, comprehensive description of "thermodynamic" and dynamical properties of dense GM is emerging, as a unified picture appears of "jamming" in glasses and granular matter. We discuss, as well, mixing/segregation transitions in binary mixtures.