SLOW DYNAMICS OF NONEQUILIBRIUM DENSITY-FLUCTUATIONS IN HARD-SPHERE SUSPENSIONS

The coupled diffusion equations recently proposed for concentrated har d-sphere suspensions are numerically solved to investigate the dynamic s of density fluctuations around time-dependent nonequilibrium (spatia lly inhomogeneous) states. As the volume fraction of spheres phi appro aches the critical value phi(g) from below, the self-intermediate scat tering function F-S(k,t) is shown to obey two different slow relaxatio ns whose time scales t(beta) and t(alpha) diverge as the separation pa rameter sigma=(phi-phi(g))/phi(g) approaches zero: t(beta)similar to\s igma\(-beta) and t(alpha)similar to\sigma\(-alpha), where phi(g)=(4/3) (3)/(7 ln3 - 8 ln2+2), Thus, the Importance of nonequilibrium effects on slow dynamics is stressed from a unifying viewpoint.