Intermittency, aging and extremal fluctuationsP. Sibani1, 2 and H. Jeldtoft Jensen2
1 Theoretical Physics - 1 Keble Rd, Oxford OX1 3NP, UK
2 Department of Mathematics, Imperial College London South Kensington Campus, London SW7 2AZ, UK
received 16 September 2004; accepted in final form 7 December 2004
published online 14 January 2005
Aging in spin glasses is analyzed via the probability density function (PDF) of the heat transfer over a short time between system and heat bath. The PDF contains a Gaussian part, describing reversible fluctuations, and an exponential "intermittent" tail. We find that the relative weight of these two parts depends, for fixed , on the ratio of the total sampling time t to the age tw. Fixing this ratio, the intensity of the intermittent events is proportional to and independent of the temperature. The Gaussian part has a variance with the same temperature dependence as the variance of the equilibrium energy in a system with an exponential density of states. All these observations are explained assuming that for any tw, intermittent events are triggered by local energy fluctuations exceeding those previously occurred.
65.60.+a - Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
05.40.-a - Fluctuation phenomena, random processes, noise, and Brownian motion.
75.10.Nr - Spin-glass and other random models.
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