Special CMP Seminar Thursday, March 14, 2002 11:30 am, Room 224 Physics-Astronomy Building Jamming and Glass Transitions Corey S. O'Hern (UCLA and University of Chicago) Abstract: We investigate the proposed jamming phase diagram (A. J. Liu and S. R. Nagel, Nature 396 (1998) 21) by conducting molecular dynamics simulations on quiescent and sheared liquids. Liquids jam (or become amorphous glasses) by rapidly cooling, compressing, or decreasing the applied shear stress. We first show that the distribution of normal force magnitudes P(F) develops a peak as the jammed state is approached along several different routes. We also study in detail the onset of jamming with increasing packing fraction at the special point where temperature and shear stress equal zero. This point is interesting because it resembles a critical point (but is not a critical point) and may control jamming transitions at nonzero temperature and shear stress. Finally, we measure several definitions of effective temperature in a sheared, athermal system. We determine whether these definitions give the same result in our nonequilibrium system as they would in an equilibrium system. This is a first step in developing a statistical mechanics for these driven, dissipative systems.