  We use numerical simulations to investigate the effect of different
dissipative models on the shearing rheology of massive soft-core frictionless
disks in two dimensions. We show that the presence of Newtonian (overdamped) vs
Bagnoldian (inertial) rheology is related to the formation of large connected
clusters of disks, and that sharp transitions may exist between the two as
system parameters vary. In the limit of strongly inelastic collisions, we find
that rheological curves collapse to a well-defined limit when plotted against
an appropriate dimensionless strain rate.
