Thermo-magnetic effects in quark matter: Nambu--Jona-Lasinio model constrained by lattice QCD

TL;DR

This paper demonstrates that the Nambu--Jona-Lasinio model can reproduce inverse magnetic catalysis in quark matter by allowing its coupling to decrease with magnetic field and temperature, fitting lattice QCD data.

Contribution

The authors introduce a magnetic and thermal dependent coupling in the NJL model, aligning it with lattice QCD results and improving modeling of magnetized quark matter.

Findings

G(B,T) predicts a more dramatic chiral transition at high magnetic fields.

Pressure and magnetization increase with magnetic field at fixed temperature.

The model's ansatz is simple, accurate, and easy to implement in quark matter studies.

Abstract

The phenomenon of inverse magnetic catalysis of chiral symmetry in QCD predicted by lattice simulations can be reproduced within the Nambu--Jona-Lasinio model if the coupling~$G$ of the model decreases with the strength $B$ of the magnetic field and temperature~$T$. The thermo-magnetic dependence of $G(B,T)$ is obtained by fitting recent lattice QCD predictions for the chiral transition order parameter. Different thermodynamic quantities of magnetized quark matter evaluated with $G(B, T)$ are compared with the ones obtained at constant coupling, $G$. The model with $G(B,T)$ predicts a more dramatic chiral transition as the field intensity increases. In addition, the pressure and magnetization always increase with $B$ for a given temperature. Being parametrized by four magnetic field dependent coefficients and having a rather simple exponential thermal dependence our accurate ansatz for the coupling constant can be easily implemented to improve typical model applications to magnetized quark matter.