Anomalous diffusion of scaled Brownian tracers

Abstract

A model for anomalous transport of tracer particles diffusing in complex media in two dimensions is proposed. The model takes into account the characteristics of persistent motion that active bath transfer to the tracer, thus the model proposed in here extends active Brownian motion, for which the stochastic dynamics of the orientation of the propelling force is described by scale Brownian motion (sBm), identified by a the time dependent diffusivity of the form $D_{\beta }\propto t^{\beta -1}$, $\beta >0$. If $\beta \ne 1$, sBm is highly non-stationary and suitable to describe such a non-equilibrium dynamics induced by complex media. In this paper we provide analytical calculations and computer simulations to show that genuine anomalous diffusion emerge in the long-time regime, with a time scaling of the mean square displacement $t^{2-\beta }$, while ballistic transport $t^2$, characteristic of persistent motion, is found in the short-time one. An analysis of the time dependence of the kurtosis, and intermediate scattering function of the positions distribution, as well as the propulsion auto-correlation function, which defines the effective persistence time, are provided.

8 pages, 5 figures

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