Anomalous diffusion, structural relaxation and shear thinning in glassy hard sphere fluids

The stochastic nonlinear Langevin equation theory of the single-particle dynamics of glassy hard sphere fluids and suspensions has been applied to address several issues raised by recent experimental and simulation studies. The theoretically predicted degree of non-Fickian behaviour at intermediate times, and the slow structural relaxation component of the small wavevector incoherent dynamic structure factor, are compared quantitatively with recent measurements and reveal good agreement. A roughly power law growth, with a common exponent, of the classic and alternative non-Gaussian parameter amplitudes with mean alpha relaxation time is predicted, and qualitative similarities with a multi-point susceptibility that quantifies dynamic heterogeneity effects are noted. The nonlinear rheology version of the theory has been quantitatively applied to explain recent measurements of shear-induced acceleration of the single-particle relaxation time on the local cage scale. The resulting no adjustable parameter calculations are in remarkable agreement with the experimental observations for the absolute magnitude, volume fraction dependence and fractional power law scaling aspects of the shear thinning phenomenon.