NONEQUILIBRIUM EFFECTS ON SLOW DYNAMICS IN CONCENTRATED COLLOIDAL SUSPENSIONS

An alternative stochastic diffusion equation is proposed to study the dynamics of nonequilibrium density fluctuations in concentrated hard-s phere suspensions of interacting Brownian particles with both hydrodyn amic and direct interactions among particles. The singularity of the c orrelation effect of the many-body hydrodynamic interactions is shown to drastically influence the qualitative behavior of the relaxation of nonequilibrium density, fluctuations, and thus to cause the two diffe rent slow relaxations whose time scales, t(beta) and t(alpha), diverge as the volume fraction of Brownian particles approaches the critical value phi(c)=(4/3)(3)/(7In3-8ln2+2); t(beta)similar to(1-phi/phi(c))(- 1) and t(alpha)similar to(1-phi/phi)(-2).