Phase diagram of QCD in a magnetic background

TL;DR

This study uses lattice QCD simulations to show that a strong magnetic field can turn the smooth crossover of QCD into a first-order phase transition, identifying the critical endpoint and analyzing confining properties.

Contribution

It provides the first numerical evidence of a magnetic field-induced change in the QCD phase transition nature and locates the critical endpoint using lattice simulations at physical quark masses.

Findings

QCD crossover becomes first order at high magnetic fields

Critical endpoint between eB=4 and 9 GeV^2

Confining properties may change drastically across the transition

Abstract

We provide numerical evidence that the thermal QCD crossover turns into a first order transition in the presence of large enough magnetic background fields. The critical endpoint is found to be located between $eB = 4$ GeV$^2$ (where the pseudocritical temperature is $T_c = (98 \pm 3)$ MeV) and $eB = 9$ GeV$^2$ (where the critical temperature is $T_c = (63 \pm 5)$ MeV). Results are based on the analysis of quark condensates and number susceptibilities, determined by lattice simulations of $N_f = 2+1$ QCD at the physical point, discretized with three different lattice spacings, $a = 0.114, 0.086$ and $0.057$ fm, via rooted stout staggered fermions and a Symanzik tree level improved pure gauge action. We also present preliminary results regarding the confining properties of the thermal theory, suggesting that they could change drastically going across the phase transition