  The critical rheology of sheared frictional granular materials near jamming
transition is numer- ically investigated. It is confirmed that there exist a
true critical density which characterizes the onset of the yield stress, and
two fictitious critical densities which characterize the scaling laws of
rheological properties. We find the existence of a hysteresis loop between two
of the critical densities for each friction coefficient. It is noteworthy that
the critical scaling law for frictionless jamming transition seems to be still
valid even for frictional jamming despite using fictitious critical density
values.
