A model of non-Gaussian diffusion in heterogeneous media

Abstract

Recent progresses in single particle tracking have shown evidences of non-Gaussian distribution of displacements in living cells, both near the cellular membrane and inside the cytoskeleton. A similar behavior has also been observed in granular media, turbulent flows, gels, and colloidal suspensions, suggesting that this is a general feature of diffusion in complex media. A possible interpretation of this phenomenon is that a tracer explores a medium with spatio-temporal fluctuations which result in local changes of diffusivity. We propose and investigate an ergodic, easily interpretable model, which implements the concept of diffusing diffusivity. Depending on the parameters, the distribution of displacements can be either flat or peaked at small displacements with an exponential tail at large displacements. We show that the distribution converges slowly to a Gaussian one. We calculate statistical properties, derive the asymptotic behavior, and discuss some implications and extensions.

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• Resetting by rescaling: exact results for a diffusing particle in one-dimension
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• Super-Gaussian, super-diffusive transport of multi-mode active matter
• Dynamically emergent correlations in a Brownian gas with diffusing diffusivity
• Exact height distribution in one-dimensional Edwards-Wilkinson interface with diffusing diffusivity
• Evaluating Gaussianity of heterogeneous fractional Brownian motion
• First passage time properties of diffusion with a broad class of stochastic diffusion coefficients