Inverse Magnetic Catalysis in the three-flavor NJL model with axial-vector interaction

TL;DR

This study uses a three-flavor NJL model with axial-vector interactions to explain inverse magnetic catalysis in QCD, revealing a new phase transition involving local CP violation and chirality imbalance influenced by magnetic fields.

Contribution

It introduces a novel phase transition mechanism in the NJL model with axial-vector interactions, explaining inverse magnetic catalysis and its flavor dependence.

Findings

Inverse magnetic catalysis explained by a new phase transition.

Chiral chemical potentials induce local CP violation.

Flavor-dependent effects align with lattice QCD results.

Abstract

In this paper we explore the chiral phase transition in QCD within the three-flavor Nambu-Jona-Lasinio (NJL) model with a negative coupling constant in the isoscalar axial-vector channel, which is associated with a polarized instanton--anti-instanton molecule background. The QCD phase diagram described in this scenario shows a new first order phase transition around the transition temperature $T_c$ toward a phase without chiral condensates, but with nontrivial dynamic chiral chemical potentials for the light quarks, spontaneously giving rise to local $\mathcal {CP}$ violation and local chirality imbalance. The corresponding critical temperature $T_{5c}$ for this phase transition decreases with the magnetic field and it gives a natural explanation to the inverse magnetic catalysis effect for light quarks when incorporating a reasonable value of the coupling constant in the isoscalar axial-vector channel. Furthermore, when the isoscalar axial-vector interaction is dominant in light quark sector and suppressed in strange quark sector, it is found that there is no inverse magnetic catalysis for strange quark condensate, which agrees with lattice results.