Liquid-gas phase transition in the nuclear equation of state

A canonical ensemble model is used to describe a caloric curve of the nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze-out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze-out densities of all possible initial temperatures for a given total reaction energy, the first order characteristics of the liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low energy and one at high energy, show different caloric behaviors and are discussed. {copyright} {ital 1997} {ital The American Physical Society}