Chiral symmetry restoration and the $\Delta$ matter formation in neutron stars

TL;DR

This paper investigates how chiral symmetry restoration influences the formation of $$ matter in neutron stars, affecting their equation of state and compatibility with astrophysical observations.

Contribution

It introduces a parity doublet model to analyze the impact of $$ baryons and chiral symmetry on neutron star matter, highlighting the effects on the EoS and star properties.

Findings

Early $$ onset softens the EoS, fitting astrophysical constraints.

High-density matter shows EoS stiffening after initial softening.

Variations in $$ interactions alter neutron star core composition.

Abstract

We analyze the effects of chiral symmetry restoration in hadronic matter, including the lowest-lying baryonic resonance $\Delta$ based on the parity doublet model. We study the role of $\Delta$ and its chiral partner on the equation of state (EoS) of dense matter under neutron star (NS) conditions of $\beta$-equilibrium and charge neutrality. We find that the softening of the EoS driven by the early onset of $\Delta$ matter due to partial restoration of chiral symmetry allows accommodating the modern multi-messenger astrophysical constraints on the mass, radius, and tidal deformability. The softening above the saturation density is accompanied by subsequent stiffening at high densities. We also find that the matter composition in the NS cores may be different upon variations of the repulsive interactions of $\Delta$ baryons in hadronic matter.