Thermodynamics and critical behavior in the Nambu-Jona-Lasinio model of QCD

TL;DR

This paper explores the phase diagram of QCD-like matter using Nambu-Jona-Lasinio models, identifying critical points and analyzing observable behaviors near phase transitions, with implications for chiral symmetry restoration.

Contribution

It systematically studies the existence and properties of critical and tricritical points in SU(2) and SU(3) NJL models, including effects of quark masses and meson behavior.

Findings

Existence of a tricritical point in the chiral limit

Transition to a critical end point with realistic quark masses

Analysis of critical exponents for physical observables

Abstract

We investigate the phase diagram of strongly interacting matter as a function of temperature and baryonic density/chemical potential, within Nambu--Jona-Lasinio type models. We perform a systematic study concerning the existence, location, and properties of a critical end point/tricritical point, both in SU(2) and SU(3) versions of the model. We verify that, for $m_u=m_d=0$ and up to a critical strange quark mass, there is a tricritical point, which becomes a critical end point in a world with realistic values of the current quark masses. The properties of physical observables, such as the baryon number susceptibility and the specific heat, are analyzed in the vicinity of the critical end point, with special focus on their critical exponents. The behavior of mesons in the $T-\mu_B(\rho_B)$ plane is analyzed in connection with possible signatures of partial and effective restoration of chiral symmetry.