Noise simulations of an Ising model of glassy kinetics

Non-Gaussian properties of equilibrium ‘‘magnetization’’ fluctuations in a two-spin facilitated Ising model of the glass transition were studied by Monte Carlo simulation. The noise had properties unlike parallel distributed kinetics and similar to those expected for hierarchical kinetic schemes. The power spectrum had a region of slightly steeper than 1/f frequency dependence consistent with a highly stretched exponential response function. Fluctuations of noise power in different octaves were found to be correlated over a frequency range much larger than would be expected for systems in which each site contributed noise with one time constant. Further, higher-order non-Gaussian power spectra had a similar 1/f behavior demonstrating an overall order invariance in higher moments of the noise. This behavior might be used to identify similar kinetic cooperativity in real systems.