Microscopic Interactions and Flow in Heavy Ion Collisions

Relativistic heavy ion collisions have been extensively investigated to determine the equation-of-state (eos) of nuclear matter using phenomenological e ective elds of the non-relativistic Skyrme or the relativistic Walecka type. It is found generally that a soft eos with momentum dependence can decribe much of the data in the SIS energy range. It is, however, of fundamental interest to test also microscopic elds derived from NNinteractions by manybody theory. We have previously used self energies from relativistic Brueckner calculations (DB) and have shown that these satisfactorily explain the data for ow observables [1], however, only if non-equlibrium e ects are considered, i.e. taking into account that the momentum distribution is not equilibrated during a large part of an energetic heavy ion collision, which changes the e ective elds. The non-equlibrium e ects e ectively soften the eos.