Fig. 2

Mutually exclusive fluctuations. Joint probabilities \(P({\sigma }_{xy}^{-},\delta {v}^{+})\) (left axis, filled symbols) and \(P(\delta {v}^{-},\,{\sigma }_{xy}^{+})\) (right axis, hollow symbols) as functions of packing fraction, ϕ, for various shear rates, \(\dot{\gamma }\). In the fluid state, ϕ < ϕ _J , the dominant mechanism of negative power injection is the reversal of the shear stress. In the jammed state, ϕ > ϕ _J , it is due to the reversion of the velocity gradient. Error bars correspond to square root of variance