The QCD equation of state from Heavy ion collisions and neutron star mergersHYBRID

The properties of dense and hot nuclear matter are currently investigated in disparate physical environments. Neutron stars, their mergers, and core-collapse supernovae explore matter at densities several times that of nuclear saturation, characterized by a high asymmetry in isospin and zero to low temperatures. At the same time in laboratories, the equation of state of almost isospin symmetric matter can be studied with the collisions of heavy nuclei at low to ultra-relativistic energies. 

While these macroscopic astrophysical objects and microscopic collision systems at wildly different beam energies, seem to be disjoint, in fact they all can be seen as part of the major remaining challenge in the study of the strong interaction, i.e. to map out the phase diagram of QCD in terms of temperature and net baryon density.

In this seminar I will present the current status of our knowledge on the equation of state of dense QCD matter in neutron stars as well as from heavy ion reactions. This also includes some of our recent results on using statistical inference to constrain the high-density part of the equation of state with the best currently available flow data in heavy ion reactions. From these results the current shortcomings in experimental data and microscopic modelling will become apparent. 

The latter part of the seminar I will discuss how the finite temperature regions of the QCD phase diagram can be studied simultaneously with heavy ion reactions in the sub-1 GeV beam energy range, available at GSI/FAIR and other accelerator facilities and binary neutron star mergers as well as core-collapse supernovae. Here, it is important to discuss similarities but also differences, for example in the iso-spin composition of the system and how these differences can be overcome to arrive at a firm conclusion on the nature of dense nuclear matter.

Finally, the seminar will address open problems and propose potential solutions for incorporating microscopic simulations of heavy ion reactions into future statistical analyses of the dense QCD equation of state.