Abstract
We use X-ray tomography to investigate the translational and rotational dynamical heterogeneitiesof a three dimensional hard ellipsoids granular packing driven by oscillatory shear. We find thatparticles which translate quickly form clusters with a size distribution given by a power-law withan exponent that is independent of the strain amplitude. Identical behavior is found for particles that are translating slowly, rotating quickly, or rotating slowly. The geometrical properties of these four different types of clusters are the same as those of random clusters. Different cluster types are considerably correlated/anticorrelated, indicating a significant coupling between translational androtational degrees of freedom. Surprisingly these clusters are formed already at time scales that aremuch shorter than theα−relaxation time, in stark contrast to the behavior found in glass-forming systems.