Structures and non-equilibrium dynamics in granular media

In granular media, dissipation leads to interesting phenomena like cluster formation in non-equilibrium dynamical states. As an example, the freely cooling system is examined concerning the energy decay and the cluster evolution with time. Furthermore, the probability distribution of the collision frequency is discussed. Uncorrelated events lead to a Poisson distribution for the collision frequencies in the homogeneous system, whereas cooperative phenomena can be related to a power-law decay of the collision probability per unit time.