Inverse magnetic catalysis in the (2+1)-flavor Nambu--Jona-Lasinio and Polyakov--Nambu--Jona-Lasinio models

TL;DR

This study investigates the QCD phase diagram under magnetic fields using (2+1)-flavor NJL and PNJL models with a magnetic field-dependent scalar coupling, successfully reproducing lattice QCD results for quark condensates and Polyakov loop behavior.

Contribution

It introduces a magnetic field-dependent scalar coupling in NJL and PNJL models, aligning model predictions with lattice QCD data for the first time.

Findings

Magnetic field enhances quark condensates at low and high temperatures.

Polyakov loop increases with magnetic field strength.

Model reproduces lattice QCD results for chiral transition temperatures.

Abstract

The QCD phase diagram at zero chemical potential and finite temperature subject to an external magnetic field is studied within the three flavor Nambu--Jona-Lasinio (NJL) model and the NJL model with the Polyakov loop (PNJL). A scalar coupling parameter dependent on the magnetic field intensity is considered. The scalar coupling has been fitted so that the lattice QCD pseudocritical chiral transition temperatures are reproduced and in the limit of large magnetic field decreases with the inverse of the magnetic field intensity. This dependence of the coupling allows to reproduce the lattice QCD results with respect to the quark condensates and Polyakov loop: due to the magnetic field the quark condensates are enhanced at low and high temperatures and suppressed for temperatures close to the transition temperatures and the Polyakov loop increases with the magnetic field.