Linear response subordination to intermittent energy release in off-equilibrium aging dynamics

TL;DR

This paper provides evidence that in aging systems, linear response fluctuations are governed by intermittent energy release events called quakes, linking spontaneous and induced fluctuations and enabling better analysis of aging dynamics.

Contribution

The study offers direct statistical evidence supporting the hypothesis that linear response fluctuations are subordinated to quakes in off-equilibrium aging systems, using Ising model simulations.

Findings

Quakes are strictly correlated with intermittent magnetization fluctuations.

External magnetic field biases the tail of fluctuation distributions without affecting the Gaussian core.

Linear response inherits the temporal statistics of quakes, linking spontaneous and induced fluctuations.

Abstract

The interpretation of experimental and numerical data describing off-equilibrium aging dynamics crucially depends on the connection between spontaneous and induced fluctuations. The hypothesis that linear response fluctuations are statistically subordinated to irreversible outbursts of energy, so-called quakes, leads to predictions for averages and fluctuations spectra of physical observables in reasonable agreement with experimental results [see e.g. Sibani et al., Phys. Rev. B74:224407, 2006]. Using simulational data from a simple but representative Ising model with plaquette interactions, direct statistical evidence supporting the hypothesis is presented and discussed in this work. A strict temporal correlation between quakes and intermittent magnetization fluctuations is demonstrated. The external magnetic field is shown to bias the pre-existent intermittent tails of the magnetic fluctuation distribution, with little or no effect on the Gaussian part of the latter. Its impact on energy fluctuations is shown to be negligible. Linear response is thus controlled by the quakes and inherits their temporal statistics. These findings provide a theoretical basis for analyzing intermittent linear response data from aging system in the same way as thermal energy fluctuations, which are far more difficult to measure.