Glassy aging dynamics.

We present time-dependent dielectric loss data for various glass formers below the glass temperature. The observed aging dynamics is described using a modified Kohlrausch-Williams-Watts law taking into account the variation of the relaxation time during aging. It leads to values for the aging relaxation time and stretching exponent, fully consistent with the results from equilibrium measurements performed at higher temperatures. Irrespective of the dynamic process prevailing in the investigated frequency region, the aging dynamics is always determined by the structural relaxation process.