FIG. 1. Top panel: global 1D momentum distribution in the PIC simulation of a shear force acting on an uncharged collection of particles, demonstrating the formation of a nonthermal tail. t Þ relative Bottom panel: change of the Casimir momenta Δ p c; χ ð 0 Þ for the local coarse-grained distribution to the initial value p c; χ ð (solid lines) and for the global distribution (dotted lines); varying χ values are indicated by colors in the legend. For reference, the relative increase in the average momentum Δ h p ið t Þ = h p ið 0 Þ is shown by the black dashed