Unexpected crossovers in correlated random-diffusivity processes. (14th August 2020)

• Record Type: Journal Article
• Authors: Wang, Wei; Seno, Flavio; Sokolov, Igor M; Chechkin, Aleksei V; Metzler, Ralf
• Is Part Of: New journal of physics. Volume 22:Number 8(2020:Aug.)
• Publication Date: 2020-08-14
• Subjects: diffusion -- anomalous diffusion -- non-Gaussianity -- fractional Brownian motion; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aba390
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: The passive and active motion of micron-sized tracer particles in crowded liquids and inside living biological cells is ubiquitously characterised by 'viscoelastic' anomalous diffusion, in which the increments of the motion feature long-ranged negative and positive correlations. While viscoelastic anomalous diffusion is typically modelled by a Gaussian process with correlated increments, so-called fractional Gaussian noise, an increasing number of systems are reported, in which viscoelastic anomalous diffusion is paired with non-Gaussian displacement distributions. Following recent advances in Brownian yet non-Gaussian diffusion we here introduce and discuss several possible versions of random-diffusivity models with long-ranged correlations. While all these models show a crossover from non-Gaussian to Gaussian distributions beyond some correlation time, their mean squared displacements exhibit strikingly different behaviours: depending on the model crossovers from anomalous to normal diffusion are observed, as well as a priori unexpected dependencies of the effective diffusion coefficient on the correlation exponent. Our observations of the non-universality of random-diffusivity viscoelastic anomalous diffusion are important for the analysis of experiments and a better understanding of the physical origins of 'viscoelastic yet non-Gaussian' diffusion.