Chiral symmetry restoration and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="normal">Δ</mml:mi></mml:math> matter formation in neutron stars
Michał Marczenko, K. Redlich, Chihiro Sasaki
Abstract
We analyze the effects of chiral symmetry restoration in hadronic matter, including the lowest-lying baryonic resonance $\mathrm{\ensuremath{\Delta}}$ based on the parity doublet model. We study the role of $\mathrm{\ensuremath{\Delta}}$ and its chiral partner on the equation of state of dense matter under neutron star conditions of $\ensuremath{\beta}$ equilibrium and charge neutrality. We find that the softening of the equation of state driven by the early onset of $\mathrm{\ensuremath{\Delta}}$ matter due to partial restoration of chiral symmetry allows accommodating the modern multimessenger 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 neutron star cores may be different upon variations of the repulsive interactions of $\mathrm{\ensuremath{\Delta}}$ baryons in hadronic matter.