Constraints on the strength of first-order phase transition and its relation to nucleon mass

Abstract

We investigate the constraints on the strength of first-order phase transitions in neutron star matter and its relation to the origin of nucleon mass. By combining the parity doublet model for the hadronic phase, the Nambu-Jona-Lasinio model for quark matter, and the integral constraint framework for intermediate densities, we construct equation of states spanning the full density range relevant to neutron stars. Our approach systematically explores how the chiral invariant mass $m_0$ affects the allowable properties of first-order quark-hadron phase transitions. Through comparison with recent neutron star observations, we establish a inverse correlation between the allowed phase transition strength and the chiral invariant mass. Our results demonstrate a direct connection between fundamental questions about the microscopic origin of nucleon mass and macroscopic neutron star observables, providing a novel astrophysical probe of chiral dynamics and QCD physics under extreme conditions.