Please note change of venue to Adriatico Guest House, Giambiagi Lecture Hall

Abstract:
Anomalous diffusion has been known since Richardson’s treatise on turbulent diffusion in 1926. Today the list of systems displaying anomalous dynamical behaviour is quite extensive and hosts, among others systems as charge carrier transport in amorphous semiconductors, collective slip diffusion on solid surface, transport in turbulent plasma and bacterial motion. In this talk I will focus on recent experimental observations of systems which exhibit a new anomalous behaviour with a linear growth of the mean square displacement, yet with a non-Gaussian distribution of increments. Based on the idea of diffusing diffusivitiy, I will illustrate a minimal model framework of diffusion processes with fluctuating diffusivity. In particular, I will demonstrate the equivalence of diffusing diffusivity processes with a superstatistical approach with a distribution of diffusivities, at times shorther than the diffusivity correlation time. At longer times, a crossover to a Gaussian distribution with an effective diffusivity emerges. Specifically, I will establish a subordination picture of Brownian yet not Gaussian diffusion processes, which can be used for a wide class of diffusivity fluctuation statistics. In the last part of the talk, I will show how a simple polymerization process provides a suitable set-up to bridge the diffusing diffusivity approach with a microscopic description.