Growth of spatial correlations in the aging of a simple structural glass.

We present a detailed numerical study of dynamical heterogeneities in the aging regime of a simple binary Lennard-Jones glass former. For most waiting times t_{w} and final times t , both the dynamical susceptibility chi_{4}(t,t_{w}) and the dynamical correlation length xi_{4}(t,t_{w}) can be approximated as products of two factors: (i) a waiting-time-dependent scale that grows as a power of t_{w} , and (ii) a scaling function dependent on t,t_{w} only through the value of the intermediate scattering function C(t,t_{w}) . We find that chi_{4}(t,t_{w}) is determined only in part by the correlation volume.