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

TL;DR

This study investigates chiral symmetry restoring phase transitions in two-flavor quark matter under electrical neutrality using the NJL model, revealing how the order of phase transitions depends on model parameters and neutrality constraints.

Contribution

It provides a comprehensive phase diagram and shows how electrical neutrality influences the nature and extent of phase transitions in the model.

Findings

Second order phase transition region is wider with electrical neutrality.

Phase transition is first order for parameters from QCD phenomenology.

Complete phase diagram of u quark chemical potential versus model parameters.

Abstract

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 two-flavor normal quark matter. Depending on that $m_0/\Lambda$, 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 second or first order. A complete phase diagram of $u$ quark chemical potential versus $m_0$ is given. With the electrical neutrality constraint, the region where second order phase transition happens will be wider than the one without electrical neutrality limitation. The results also show that, for the value of $m_0/\Lambda$ from QCD phenomenology, the phase transition must be first order.