Color, Flavor, Temperature and Magnetic Field Dependence of QCD Phase Diagram: Magnetic Catalysis and its Inverse

TL;DR

This paper investigates how temperature and magnetic fields influence the QCD phase diagram, revealing phenomena like magnetic catalysis and inverse catalysis, using a symmetry-preserving Schwinger-Dyson equations approach with a contact interaction model.

Contribution

It introduces a unified model that captures the effects of temperature and magnetic fields on chiral symmetry breaking and confinement in QCD, including inverse magnetic catalysis.

Findings

Magnetic catalysis occurs at strong magnetic fields.

Deconfinement and chiral symmetry restoration happen above a critical number of flavors.

Inverse magnetic catalysis can be triggered by decreasing coupling strength with magnetic field.

Abstract

We study dynamical chiral symmetry breaking for quarks in the fundamental representation of $SU(N_c)$ for $N_f$ number of light quark flavors. We also investigate the phase diagram of quantum chromodynamics at finite temperature $T$ and/or in the presence of a constant external magnetic field $eB$. The unified formalism for this analysis is provided by a symmetry-preserving Schwinger-Dyson equations treatment of a vector$\times$vector contact interaction model which encodes several well-established features of quantum chromodynamics to mimic the latter as closely as possible. Deconfinement and chiral symmetry restoration are triggered above a critical value of $N_f$ at $T=0=eB$. On the other hand, increasing temperature itself screens strong interactions, thus ensuring that a smaller value of $N_f$ is sufficient to restore chiral symmetry at higher temperatures. We also observe the well-known phenomenon of magnetic catalysis for a strong enough magnetic field. However, we note that if the effective coupling strength of the model decreases as a function of magnetic field, it can trigger inverse magnetic catalysis in a certain window of this functional dependence. Our model allows for the simultaneous onset of dynamical chiral symmetry breaking and confinement for each case. Qualitative as well as quantitative predictions of our simple but effective model are in reasonably satisfactory agreement with lattice results and other reliable and refined predictions based upon intricate continuum studies of quantum chromodynamics.