  The numerical solutions of nonlocal and local Boltzmann kinetic equations for
the simulation of central heavy ion reactions are parameterized in terms of
time dependent thermodynamical variables in the Fermi liquid sense. This allows
one to discuss dynamical trajectories in phase space. The nonequilibrium state
is characterized by non-isobaric, non-isochoric etc. conditions, shortly called
iso-nothing conditions. Therefore a combination of thermodynamical observables
is constructed which allows one to locate instabilities and points of possible
phase transition in a dynamical sense. We find two different mechanisms of
instability, a short time surface - dominated instability and later a spinodal
- dominated volume instability. The latter one occurs only if the incident
energies do not exceed significantly the Fermi energy and might be attributed
to spinodal decomposition. In contrast the fast surface explosion occurs far
outside the spinodal region and pertains also in the cases where the system
develops too fast to suffer a spinodal decomposition and where the system
approaches equilibrium outside the spinodal region.
