Linear response in aging glassy systems, intermittency and the Poisson statistics of record fluctuations

摘要

We study the intermittent behavior of the energy decay and linear magneticresponse of a glassy system during isothermal aging after a deep thermal quenchusing the Edward-Anderson spin glass model as a paradigmatic example. The largeintermittent changes in the two observables are found to occur in a correlatedfashion and through irreversible bursts, `quakes', which punctuate reversibleand equilibrium-like fluctuations of zero average. The temporal distribution ofthe quakes it found to be a Poisson distribution with an average growinglogarithmically on time, indicating that the quakes are triggered by recordsized fluctuations. As the drift of an aging system is to a good approximationsubordinated to the quakes, simple analytical expressions (Sibani et al. PhysRev B 74, 224407, 2006) are available for the time and age dependence of theaverage response and average energy. These expressions are shown to capture thetime dependencies of the EA simulation results. Finally, we argue that wheneverthe changes of the linear response function and of its conjugateautocorrelation function follow from the same intermittent events afluctuation-dissipation-like relation can arise between the two inoff-equilibrium aging.