Relaxation of nonequilibrium fluctuations in liquid mixtures above the consolute point

Abstract

We study the relaxation of nonequilibrium concentration fluctuations in binary-liquid mixtures near but above the critical consolute temperature. We show that if the strength of the fluctuations is far enough above the thermal level, hydrodynamic effects cause these fluctuations to migrate towards the smallest wave numbers. They are dissipated only in an exceedingly long time at the largest available scale. The structure factor of the fluctuations obeys a scaling law similar to the one observed in experiments of spinodal decomposition. Experimental tests of our result are suggested and their possible relevance to the theory of spinodal decomposition briefly discussed.