Quark-hadron crossover equations of state for neutron stars: constraining the chiral invariant mass in a parity doublet model

Understand

We construct an equation of state (EOS) for neutron stars by interpolating hadronic EOS at low density and quark EOS at high density.

• A hadronic model based on the parity doublet structure is used for hadronic matter and a quark model of Nambu--Jona-Lasinio type is for quark matter.
• We assume crossover between hadronic matter and quark matter in the the color-flavor locked phase.
• The nucleon mass of the parity doublet model has a mass associated with the chiral symmetry breaking, and a chiral invariant mass $m_0$ which is insensitive to the chiral condensate.