Chiral condensates for neutron stars in hadron-quark crossover; from a parity doublet nucleon model to an NJL quark model

Abstract

In this contribution, we summarize our recent studies on the chiral invariant mass and the chiral condensates in neutron star matter. We construct a unified equations of state assuming the crossover phase transition from hadronic matter described by a parity doublet model to quark matter by an Nambu--Jona-Lasinio type quark model. We first show that the chiral invariant mass is constrained to be $600\,\mbox{MeV}\, \lesssim\, m_0 \,\lesssim \, 900\,\mbox{MeV}$ from recent observations of neutron stars. We then determine the density dependence of the chiral condensate in the crossover description, and show that the chiral condensates are actually smoothly connected from the hadronic matter where the change is driven by the positive chiral scalar charge in a nucleon, to the quark matter where the change is by the modification of the quark Dirac sea, reflecting the hadron-quark crossover.