Characterization of a freezing/melting transition in a vibrated and sheared granular medium

In the regime 0 <˜< 10 and 0 << 6 we observe two distinct granular states of matter: crystallized and disordered. Sample images of these two states are shown in Fig. 2(ab), as viewed from the outer wall. For ˜ 0.1, the phase boundary between the two states roughly corresponds to a line where the characteristic velocities (and hence the kinetic energies) of the two motions are equal: R = 2πfA. Below, we characterize these two states, with further details to be found in (Daniels and Behringer, 2004).