Local fluctuations in the aging of a simple glass

The presence of dynamical heterogeneities, i.e. nanometer-scale regions containing molecules rearranging cooperatively at very different rates compared to the bulk, is increasingly being recognized as crucial in our understanding of the glass transition, from the non-exponential nature of relaxation, to the divergence of the relaxation times. Recently, dynamical heterogeneities have been directly observed experimentally. However a clear physical picture for the origin of these heterogeneities is still lacking. Here we investigate a possible physical mechanism for the origin of dynamical heterogeneities in the non-equilibrium dynamics of structural glasses. We test the predictions regarding universal scaling of fluctuations derived from this mechanism against simulation results in a simple binary Lennard-Jones glass model, and find that to a first approximation they are satisfied. We also propose to apply the same kind of analysis to experimental data from confocal microscopy in colloidal glasses.