Spinodal and two-flow instabilities in nuclear collisions at intermediate energies

The development of instabilities of spinodal and two-flow types arising in collisions of two slabs of nuclear matter is investigated using the Vlasov equation involving a self-consistent nuclear potential. Expansion of nuclear matter formed as a result of fusion of the slabs leads to a strong contraction of the Fermi surface along the direction of a collision. In turn, this contraction leads to an increase in the rate of growth of modes with wave vectors directed along the axis of expansion when the system enters the region of spinodal instability. Instability of the two-flow regime, taking place at the initial stage of the collision, is investigated for the case when an unperturbed distribution function can be parameterized as two separated Fermi spheres. It is shown that, in this case, the increment of longitudinal perturbation modes increases monotonically with increasing magnitude of the wave vector. A mechanism is discussed according to which two-flow instability generates initial perturbations for spinodal instability. 19 refs., 5 figs