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Paper   IPM / Physic / 6909
School of Physics
  Title:   Tracer Diffusivity in A Time- or Space-Dependent Temperature Field
1.  A. Ajdari
2.  R. Golestanian
  Status:   Published
  Journal: Europhys. Lett.
  No.:  15
  Vol.:  59
  Year:  2002
  Pages:   800-806
  Supported by:  IPM
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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