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

<正> A general research on chiral symmetry restoring phase transitions at zero temperature and finite chemicalpotentials under electrical neutrality condition has been conducted in a Nambu-Jona-Lasinio model to describe two-flavor normal quark matter.Depending on whether m_0/A,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 firstorder.A complete phase diagram of u quark chemical potential versus m_0 is given.With the electrical neutralityconstraint,the region where the second order phase transition happens will be wider than the one without electricalneutrality limitation.The results also show that,for the value of m_0/A from QCD phenomenology,the phase transitionmust be of the first order.

A general research on chiral symmetry restoring phase transitions at zero temperature and finite chemical potentials under electrical neutrality condition has been conducted in a Nambu-Jona-Lasinio model to describe twoflavor normal quark matter. Depending on whether mo/A, the ratio of dynamical quark mass in vacuum and the 3D momentum 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 mo is given. With the electrical neutrality constraint, the region where the second order phase transition happens will be wider than the one without electrical neutrality limitation. The results also show that, for the value ofmo/A from QCD phenomenology, the phase transition must be of the first order.