NONEQUILIBRIUM PHASE-TRANSITIONS IN SHEARED COLLOIDS

Colloidal crystals under steady shear flow are known to melt by a firs t order transition. At high shear rates, molecular dynamics simulation s show a reentrant transition by which the system orders back into a f lowing crystalline phase. We describe here a simple two variable model which captures both these phase transitions. In doing so we propose a prescription for identifying the stable phase in nonequilibrium stead y states which should apply to a variety of other problems.