Multifractal analysis of light scattering-intensity fluctuations.

We provide a simple interpretation of non-Gaussian nature of the light scattering-intensity fluctuations from an aging colloidal suspension of Laponite using the multiplicative cascade model, Markovian method, and volatility correlations. The cascade model and Markovian method enable us to reproduce most of recent empirical findings: long-range volatility correlations and non-Gaussian statistics of intensity fluctuations. We provide evidence that the intensity increments Deltax(tau)=I(t+tau)-I(t), upon different delay time scales tau, can be described as a Markovian process evolving in tau. Thus, the tau dependence of the probability density function p(Deltax,tau) on the delay time scale tau can be described by a Fokker-Planck equation. We also demonstrate how drift and diffusion coefficients in the Fokker-Planck equation can be estimated directly from the data.