MEMORY EFFECTS IN NUCLEAR FRAGMENTATION

A general procedure to identify instability regions which lead to mult ifragmentation events is presented. The dominant mode at the instabili ty point is determined from the knowledge of the mean properties (dens ity and temperature) of the system at that point. For spinodal instabi lities the dependence of fragment structures on the dynamical conditio ns is studied changing the beam energy and the considered equation of state. An important competition between two dynamical effects, expansi on of the system and growth of fluctuations, is revealed. It is shown that in heavy-ion central collisions at medium energies memory effects of the configuration formed at the instability time could be observed in the final fragmentation pattern. Some hints towards a fully dynami cal picture of fragmentation processes are finally suggested.