Hyperons in neutron stars and supernova cores

TL;DR

This paper explores the role of hyperons and other non-nucleonic particles in dense stellar matter, analyzing phase transitions, thermal effects on the equation of state, and implications for neutron star phenomena.

Contribution

It provides a detailed phase diagram of baryonic matter with strangeness and examines thermal effects on the emergence of hyperons and quark matter in stellar environments.

Findings

Hyperons may appear in dense matter with a rich phase coexistence.

Thermal effects promote the formation of non-nucleonic particles.

Non-nucleonic degrees of freedom significantly influence neutron star mergers and supernovae.

Abstract

The properties of compact stars and their formation processes depend on many physical ingredients. The composition and the thermodynamics of the involved matter is one of them. We will investigate here uniform strongly interacting matter at densities and temperatures, where potentially other components than free nucleons appear such as hyperons, mesons or even quarks. In this paper we will put the emphasis on two aspects of stellar matter with non-nucleonic degrees of freedom. First, we will study the phase diagram of baryonic matter with strangeness, showing that the onset of hyperons, as that of quark matter, could be related to a very rich phase structure with a large density domain covered by phase coexistence. Second, we will investigate thermal effects on the equation of state (EoS), showing that they favor the appearance of non-nucleonic particles. We will finish by reviewing some recent results on the impact of non-nucleonic degrees freedom in compact star mergers and core-collapse events, where thermal effects cannot be neglected.