Abstract
The equation of state (EOS) of nuclear matter is of fundamental interest and has been the object of intense theoretical efforts since several decades. The interest is boosted by the fact that it is an important ingredient in modelling astrophysical phenomena such as compact stars and core collapse supernovae. A method to approach the nuclear equation of state, practiced since the mid-eighties, is the use of heavy ion collisions over a wide range of incident energies, system sizes and compositions. From FOPI experimental data on elliptic flow of protons, we extract constraints for the equation of state (EOS) of compressed symmetric nuclear matter using the transport code IQMD. The best agreement with the data is obtained with the soft EOS assumption, including a momentum dependent interaction. The code predicts that the densities which have been probed by the specific flow observable – hence, for which this EOS applies – range from one up to 2.5-3 times the saturation density.