Interplay of equilibrium and nonequilibrium phenomena in the nuclear liquid-gas phase transition

Energy spectra of protons emitted by the target residue in Au+Au collisions at 1 GeV/u reveal two components with different slopes attributed to preequilibrium and equilibrium emission. The relative contribution of the latter decreases rapidly with excitation energy, so that its presence becomes not apparent for the highest energy bins. It is argued therefore, that equilibrium may not be reached on the gas branch of the caloric curve. The nuclear liquid-gas phase transition thus belongs to the category of nonequilibrium phase transitions for which the concepts developed in synergetics, such as self-organized criticality, provide the proper framework.