The evolution of dynamical perturbations is examined in nuclear
multifragmentation in the frame of Vlasov equation. Both plane wave and bubble
type of perturbations are investigated in the presence of surface (Yukawa)
forces. An energy condition is given for the allowed type of instabilities and
the time scale of the exponential growth of the instabilities is calculated.
The results are compared to the mechanical spinodal region predictions. PACS:
25.70 MnComment: 22 pages, latex, with 5 PS figures, available at
http://www.gsi.de/~papp
