Electrical Neutrality and Symmetry Restoring Phase Transitions at High Densityin a Two-Flavor Nambu–Jona-Lasinio Model

Abstract

A general research on chiral symmetry restoring phase transitionsat zero temperature and finite chemical potentials under electricalneutrality condition has been conducted in a Nambu–Jona-Lasiniomodel to describe two-flavor normal quark matter. Depending on whetherm0/Λ, the ratio of dynamical quark mass in vacuum and the 3Dmomentum cutoff in the loop integrals, is less or greater than 0.413,the phase transition will be of the second or first order.A complete phase diagram of u quark chemical potential versus m0is given. With the electrical neutrality constraint, the region wherethe second order phase transition happens will be wider than the onewithout electrical neutrality limitation. The results also show that,for the value of m0/Λ from QCD phenomenology,the phase transition must be of the first order.