CMSP Seminar Series @ICTP - Adriatico Guest House Giambiagi Thursday 6 June 11am - Flavio SENO

[CM Section]

Condensed Matter and Statistical Physics Seminar Series

Kindly note change of Venue:  ADRIATICO Guest House

Thursday 6 June at 11:00 a.m.
Giambiagi Lecture Room, lower level 1, Adriatico Guest House

Flavio SENO (Dept. of Physics, University of Padova)

'Brownian yet not Gaussian Diffusion'

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.