The chiral transition in a magnetic background: Finite density effects and the functional renormalization group

TL;DR

This paper investigates how an external magnetic field influences the chiral phase transition in the quark-meson model at finite temperature and density, revealing a complex dependence of the critical temperature and point on magnetic field strength.

Contribution

It provides a detailed phase diagram analysis using the functional renormalization group, highlighting the magnetic field's impact on the critical temperature and critical point movement at finite density.

Findings

Critical temperature increases with magnetic field at zero chemical potential.

At higher chemical potentials, the critical temperature decreases with increasing magnetic field.

The critical point shifts from high to low chemical potential as magnetic field strength grows.

Abstract

We compute the phase diagram of the quark-meson model at finite temperature, finite baryon chemical potential $\mu_B=3\mu$ and constant external magnetic field $B$, using the functional renormalization group. Our results show that the critical temperature increases as a function of $B$ at $\mu=0$, but for values $\mu$ larger than about 210-225 MeV, the opposite behavior is realized. As the magnetic field increases, the critical point $(T^*,\mu^*)$ moves from large $\mu$, small $T$ towards small $\mu$, larger $T$ in the $\mu$--$T$ phase diagram.