A study of neutron star property based on parity-doublet-models

In this contribution to the proceedings, we briefly summarize the works in Refs. [1,2,3,4,5,6,7], in which we studied neutron star property based on parity doublet models (PDMs). In the low-density region, we construct the equation of state (EoS) using hadronic models based on the parity doublet structure with the chiral invariant mass of nucleons. In the high density region, the EoS is obtained in an Nambu–Jona-Lasinio (NJL)-type quark model. By connecting two EoSs with assuming the quark-hadron crossover or first order phase transition, we construct unified EoSs for dense matter. We then derive the mass-radius relation of neutron stars from the unified EoSs and compare the result with the observational constraints to obtain an allowed range for the chiral invariant mass.