From Subaging to Hyperaging in Structural Glasses

We demonstrate nonequilibrium scaling laws for the aging and equilibration dynamics in glass formers that emerge from combining a relaxation equation for the static structure with the equilibrium scaling laws of glassy dynamics. Different scaling regimes are predicted for the evolution of the structural relaxation time ? with age (waiting time tw), depending on the depth of the quench from the liquid into the glass: "simple" aging (?~tw) applies for quenches close to the critical point of mode-coupling theory (MCT) and implies "subaging" (??t?w with ?<1) as a broad equilibration crossover for quenches to nearly arrested equilibrium states; "hyperaging" (or superaging, ?~t??w with ??>1) emerges for quenches deep into the glass. The latter is cut off by non-mean-field fluctuations that we account for within a recent extension of MCT, the stochastic ?-relaxation theory (SBR). We exemplify the scaling laws with a schematic model that quantitatively fits simulation data.