Intermittent origin of the large violations of the fluctuation-dissipation relations in an aging polymer glass

The fluctuation-dissipation relation (FDR)is measured on the dielectric prop- erties of a polymer glass (polycarbonate)in the range 20 mHz-100 Hz. It is found that after a quench below the glass transition temperature, the fluctuation-dissipation theorem is strongly violated. The amplitude and the persistence time of this violation are decreasing functions of frequency. At frequencies larger than 1 Hz it persists for about 3 h. The origin of this violation is a highly intermittent dynamics characterized by large fluctuations. The relevance of these results for recent models of aging dynamics is discussed.