VISUALIZING THE COLLECTIVE MOTIONS RESPONSIBLE FOR THE ALPHA AND BETA RELAXATIONS IN A MODEL GLASS

Maps of the spatial distributions of the relaxation times are obtained from Monte Carlo simulations of the facilitated kinetic Ising model. The beta relaxation, acting over short and intermediate time scales, is observed to occur in localized pockets. The slow alpha a relaxation is governed by the fraction of these pockets which are free to move. This physical picture is able to account for the non-Arrhenius temperature dependence of the time scales of the alpha process, the scaling of the relaxation function in the beta region, and the value of the relaxation function at the crossover time.