Viscoelastic properties of attractive and repulsive colloidal glasses

We report a numerical study of the shear viscosity and the frequency dependent elastic moduli close to dynamical arrest for a model of short range at tractive colloids, both for the repulsive and the attractive glass transition. Calculating the stress autocorrelation functions, we find that density fluctuations of wavevectors close to the first peak in the structure factor control the viscosity rise on approaching the repulsive glass, while fluctuations of larger wavevectors control the viscosity close to the attractive glass. On approaching the glass transition, the viscosity diverges with a power law with the same exponent as the density autocorrelation time.