Phase structures of neutral dense quark matter and applicationto strange stars * *Supported in part by the National Natural Science Foundation of China (11905107), the National Natural Science Foundation of Jiangsu Province of China (BK20190721), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (19KJB140016), Nanjing University of Posts and Telecommunications Science Foundation (NY129032), Innovation Program of Jiangsu

Abstract

In the contact interaction model, the quark propagator has only one solution, namely, the chiral symmetry breaking solution, at vanishing temperature and density in the case of physical quark mass. We generalize the condensate feedback onto the coupling strength from the 2 flavor case to the 2+1 flavor case, and find the Wigner solution appears in some regions, which enables us to tackle chiral phase transition as two-phase coexistences. At finite chemical potential, we analyze the chiral phase transition in the conditions of electric charge neutrality and equilibrium. The four chemical potentials, , , and , are constrained by three conditions, so that one independent variable remains: we choose the average quark chemical potential as the free variable. All quark masses and number densities suffer discontinuities at the phase transition point. The strange quarks appear after the phase transition since the system needs more energy to produce a -quark than an -quark. Taking the EOS as an input, the TOV equations are solved numerically, and we show that the mass–radius relation is sensitive to the EOS. The maximum mass of strange quark stars is not susceptible to the parameter we introduced.