Some aspects of the phase diagram of nuclear matter relevant to compact stars

TL;DR

This paper explores phase transitions in dense nuclear matter relevant to neutron stars and supernovae, focusing on the crust-core transition and hyperonic effects, with implications for the matter's equation of state and astrophysical phenomena.

Contribution

It introduces a quasi-particle model for the crust-core transition and analyzes hyperonic phase transitions using a mean-field approach, highlighting new insights into dense matter behavior.

Findings

Clusterized phase due to Coulomb interactions not accessible in grand-canonical ensemble

Quantitative results for supernova dynamics from the quasi-particle model

Characteristics and order of hyperonic phase transitions analyzed

Abstract

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 the equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of neutron stars. In this paper 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 hyperonic 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, a clusterized phase is expected which is not accessible in the grand-canonical ensemble. A specific quasi-particle model will be introduced and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core also modifies the equation of state. The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.