Microscopic calculation of expanding nuclear matter

Quantum Molecular Dynamics (QMD) calculations are used to study the expansion phase in central collisions between heavy nuclei. The final state of such a reaction can be understood as the result of a entropy conserving expansion starting from a compact source. The properties of this hypothetic source, however, are in conflict with the assumptions used in fireball models. Moreover, this hypothetical source is not formed in the dynamical evolution of the system.