Non-Gaussian statistics of concentration fluctuations in free liquid diffusion
arXiv:2509.25511 · doi:10.1103/d27z-4fxz
Abstract
We show that the three-point skewness of concentration fluctuations is non-vanishing 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.
References in corpus (15)
- Particles and fields in fluid turbulence
- Macroscopic fluctuation theory
- On solving quantum many-body problems by experiment
- Slow modes in passive advection
- Intermittency in passive scalar advection
- Diffusive mass transfer by non equilibrium fluctuations: Fick's law revisited
- A reversible mesoscopic model of diffusion in liquids: from giant fluctuations to Fick's law
- Lagrangian method for multiple correlations in passive scalar advection
- Anomalous scaling in passive scalar advection: Monte-Carlo Lagrangian trajectories
- Emergence of hydrodynamic spatial long-range correlations in nonequilibrium many-body systems
- Thermal Fluctuations in the Dissipation Range of Homogeneous Isotropic Turbulence
- Enhancement of Diffusive Transport by Nonequilibrium Thermal Fluctuations
- Non-Gaussian diffusive fluctuations in Dirac fluids
- Nonlinear Response in Diffusive Systems
- Emergence of long-range non-equilibrium correlations in free liquid diffusion