EOS of star matter and its impact on astrophysics

Francesca Gulminelli

LPC/University of Caen, Caen, France

Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of neutron stars.

In this talk we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at sub-saturation density, and the possible strange transition at super-saturation density in the presence of hyperons degrees of freedom.

Concerning the neutron star crust-core phase transition at zero and finite temperature, it will be shown that, as a consequence of the presence of long range Coulomb interactions, the equivalence of statistical ensembles is violated and a clusterized phase is expected which is not accessible in the grand-canonical ensemble.   A specific analytical Nuclear Statistical Equilibrium model will be presented and some quantitative results relevant for the supernova dynamics will be shown.

The opening of hyperons degrees of freedom at the higher densities corresponding to the neutron stars core modifies the equation of state with important consequences on the total mass and radius of the star.  The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.