MODELS FOR CHRONOLOGY SELECTION

In this paper, we derive an expression for the grand canonical partiti on function for a fluid of hot, rotating massless scalar held particle s in the Einstein universe. We consider the number of states with a gi ven energy as one increases the angular momentum so that the fluid rot ates with an increasing angular velocity. We find that at the critical value when the velocity of the particles furthest from the origin rea ches the speed of light, the number of states tends to zero. We illust rate how one can also interpret this partition function as the effecti ve action for a boosted scalar field configuration in the product of t hree dimensional de Sitter space and S-1. In this case, we consider th e number of states with a fixed linear momentum around the S-1 as the particles are given more and more boost momentum. At the critical poin t when the spacetime is about to develop closed timelike curves, the n umber of states again tends to zero. Thus it seems that quantum mechan ics naturally enforces the chronology protection conjecture by superse lecting the causality violating held configurations from the quantum m echanical phase space.