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Tracer diffusivity in a time or space dependent temperature field

Ramin Golestanian·Armand Ajdari
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Abstract

The conventional assumption that the self-diffusion coefficient of a small tracer can be obtained by a local and instantaneous application of Einstein's relation in a temperature field with spatial and temporal heterogeneity is revisited. It is shown that hydrodynamic fluctuations contribute to the self-diffusion tensor in a universal way, i.e. independent of the size and shape of the tracer. The hydrodynamic contribution is anisotropic--it reflects knowledge of the global anisotropy in the temperature profile, leading to anisotropic self-diffusion tensor for a spherical tracer. It is also retarded--it creates memory effects during the diffusion process due to hydrodynamic interactions.

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Ramin Golestanian, Armand Ajdari. 2002-06-26. Tracer diffusivity in a time or space dependent temperature field. https://doi.org/10.1209/epl/i2002-00113-x

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