Renormalization of drift and diffusivity in random gradient flows
| Autor: | R. R. Horgan, David S. Dean, I T Drummond |
|---|---|
| Rok vydání: | 1996 |
| Předmět: |
Physics
Random field Field (physics) Condensed Matter (cond-mat) Isotropy FOS: Physical sciences General Physics and Astronomy Statistical and Nonlinear Physics Condensed Matter White noise Renormalization group Thermal diffusivity Gaussian random field Renormalization Statistical physics Mathematical Physics |
| Zdroj: | Journal of Physics A: Mathematical and General. 29:7867-7879 |
| ISSN: | 1361-6447 0305-4470 |
| DOI: | 10.1088/0305-4470/29/24/012 |
| Popis: | We investigate the relationship between the effective diffusivity and effective drift of a particle moving in a random medium. The velocity of the particle combines a white noise diffusion process with a local drift term that depends linearly on the gradient of a gaussian random field with homogeneous statistics. The theoretical analysis is confirmed by numerical simulation. For the purely isotropic case the simulation, which measures the effective drift directly in a constant gradient background field, confirms the result previously obtained theoretically, that the effective diffusivity and effective drift are renormalized by the same factor from their local values. For this isotropic case we provide an intuitive explanation, based on a {\it spatial} average of local drift, for the renormalization of the effective drift parameter relative to its local value. We also investigate situations in which the isotropy is broken by the tensorial relationship of the local drift to the gradient of the random field. We find that the numerical simulation confirms a relatively simple renormalization group calculation for the effective diffusivity and drift tensors. Comment: Latex 16 pages, 5 figures eps |
| Databáze: | OpenAIRE |
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