Europhys. Lett.
Volume 69, Number 4, February 2005
Page(s) 563 - 569
Section Condensed matter: structure, mechanical and thermal properties
Published online 14 January 2005
Europhys. Lett., 69 (4), pp. 563-569 (2005)
DOI: 10.1209/epl/i2004-10376-1

Intermittency, aging and extremal fluctuations

P. 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 $\delta t$ 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 $\delta t$, 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 $\delta
t/t_w$ 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.

© EDP Sciences 2005