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.