Aging in Out-of-Equilibrium Dynamics of Models for Granular Media

In the framework of recently introduced frustrated lattice gas models, we study the out-of-equilibrium dynamical processes during the compaction in granular media. We find irreversible-reversible cycles in agreement with recent experimental observations, along which we can individuate an equivalent ``glass transition,'' Γg. In analogy with the phenomenology of glassy systems 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).