  Via event driven molecular dynamics simulations and experiments, we study the
packing fraction and shear-rate dependence of single particle fluctuations and
dynamic correlations in hard sphere glasses under shear. At packing fractions
above the glass transition, correlations increase as shear rate decreases: the
exponential tail in the distribution of single particle jumps broadens and
dynamic four-point correlations increase. Interestingly, however, upon
decreasing the packing fraction, a broadening of the exponential tail is also
observed, while dynamic heterogeneity is shown to decrease. An explanation for
this behavior is proposed in terms of a competition between shear and thermal
fluctuations. Building upon our previous studies [Chikkadi et al, Europhys.
Lett. (2012)], we further address the issue of anisotropy of the dynamic
correlations.
