F. Sciortino et P. Tartaglia, Extension of the fluctuation-dissipation theorem to the physical aging of a model glass-forming liquid, PHYS REV L, 86(1), 2001, pp. 107-110
We present evidence in favor of the possibility of treating an out-of-equil
ibrium super cooled simple liquid as a system in quasiequilibrium. Two diff
erent temperatures, one controlled by the external bath and one internally
selected by the system, characterize the quasiequilibrium state. The value
of the internal temperature is explicitly calculated within the inherent st
ructure thermodynamic formalism. We find that the internal temperature ente
rs the relation between the response to an external perturbation and the lo
ng-time decay of fluctuations in the liquid.