Local correlations and local responses in the aging of a sample

We investigate the relationship between local fluctuations in the correlation and the response in a three dimensional strucural glass model. We perform molecular dynamics simulations of a binary Lennard-Jones mixture and measure local correlations and responses in small regions of the system, after a quench into the glass regime. We compare the joint probability distribution of these local quantities with the out-of-equilibrium fluctuation-dissipation relation of the bulk system. We also compare our results with the results of analogous simulations in short range spin glass systems, which support the presence of a soft mode in the aging dynamics.