D. Brogioli et A. Vailati, Diffusive mass transfer by nonequilibrium fluctuations: Fick's law revisited - art. no. 012105, PHYS REV E, 6301(1), 2001, pp. 2105
Recent experimental and theoretical works have shown that giant Fluctuation
s are present during diffusion in liquid systems. We use linearized fluctua
ting hydrodynamics to calculate the net mass transfer due to these nonequil
ibrium fluctuations. Remarkably, the mass flow turns out to coincide with t
he usual Fick's one. The renormalization of the hydrodynamic equations allo
ws us to quantify the gravitational modifications of the diffusion coeffici
ent induced by the gravitational stabilization of long wavelength fluctuati
ons.