Non-Gaussian statistics of concentration fluctuations in free liquid diffusion
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arXiv
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| Main Authors: | , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910048308953088 |
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| author | Bussoletti, Marco Gallo, Mirko Jafari, Amir Eyink, Gregory L. |
| author_facet | Bussoletti, Marco Gallo, Mirko Jafari, Amir Eyink, Gregory L. |
| contents | 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_25511 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Non-Gaussian statistics of concentration fluctuations in free liquid diffusion Bussoletti, Marco Gallo, Mirko Jafari, Amir Eyink, Gregory L. Statistical Mechanics Fluid Dynamics 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. |
| title | Non-Gaussian statistics of concentration fluctuations in free liquid diffusion |
| topic | Statistical Mechanics Fluid Dynamics |
| url | https://arxiv.org/abs/2509.25511 |