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,” ${\Gamma }_g$. 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 $C\left({t,t}^{\prime }\right)$ asymptotically scales as a function of the single variable $\ln \left(t^{\prime }\right)/\ln \left(t\right)$.