Aging and multiscaling in out of equilibrium dynamical processes in granular media

In the framework of recently introduced frustrated lattice gas models, we study the out of equilibrium dynamical processes during the compaction process in granular media. We find irreversible-reversible cycles in agreement with recent experimental observations. Moreover in analogy with the phenomenology of the glass transition we find aging effects during the compaction process In particular we find that the two time density correlation function C ( t, t ′ ) asymptotically scales as a function of the single variable ln( t ′ ) / ln( t ). This result is interpreted in terms of multiscaling properties of the system.