  An adsorption-desorption (or parking-lot) model can reproduce qualitatively
the densification kinetics and other features of a weakly vibrated granular
material. Here we study the the two-time correlation and response functions of
the model and demonstrate that their behavior is consistent with recently
observed memory effects in granular materials. Although the densification
kinetics and hysteresis are robust properties, we show that the aging behavior
of the adsorption-desorption model is different from other models of granular
compaction. We propose an experimental test to distinguish the possible aging
behaviors.
