SPINODAL INSTABILITIES IN EXPANDING FERMI LIQUIDS

In this article we investigate the influence of the expansion on the properties and the dynamical evolution of a piece of unstable nuclear matter. We discuss how the expansion modifies the spinodal decomposition of the system by deriving analytical results, which are confirmed and illustrated by numerical simulations in two dimensions. Moreover, the expansion is introducing a short freeze-out time which allows to unambiguously define the formed fragments. An important result of this study is that for a wide range of expansion velocities the fragmentation is dominated by the same unstable wave lengths, which happen to be weakly dependent on density and temperature provided that the system is lying well inside the spinodal instability region. © 1995 The American Physical Society.