Non-Gaussian statistics of concentration fluctuations in free liquid diffusion
Abstract
We show that the three-point skewness of concentration fluctuations is nonvanishing in free liquid diffusion, even in the limit of vanishingly small mean concentration gradients. We exploit a high-Schmidt reduction of nonlinear Landau-Lifshitz hydrodynamics for a binary fluid, both analytically and by a massively parallel Lagrangian Monte Carlo simulation. Non-Gaussian statistics result from nonlinear coupling of concentration fluctuations to thermal velocity fluctuations, analogous to the turbulent advection of a passive scalar. Concentration fluctuations obey no central limit theorem, counter to the predictions of macroscopic fluctuation theory for generic diffusive systems.
Fields of Study & Subjects
Field-Flow Fractionation Techniques
stochastic dynamics and bifurcation
Theoretical and Computational Physics
Publication details
- Journal / source
- Physical Review Research
- Publisher
- American Physical Society (APS)
- Volume
- 8
- Issue
- 1
- Publication date
- 12 January 2026
- Language
- EN