Phase diagram of QCD in strong background magnetic field

TL;DR

This paper uses lattice QCD simulations to explore how a strong magnetic field affects the phase transition nature of QCD, revealing a transition from crossover to first order at high magnetic fields.

Contribution

It provides the first numerical evidence that strong magnetic fields induce a first order phase transition in QCD, identifying the critical endpoint and associated temperatures.

Findings

QCD crossover becomes first order at high magnetic fields

Critical endpoint located between eB=4 and 9 GeV^2

Critical temperature decreases with increasing magnetic field

Abstract

We discuss the phase diagram of QCD in the presence of a strong background magnetic field, providing numerical evidence, based on lattice simulations of QCD with $2+1$ flavours and physical quark masses, that the QCD crossover turns into a first order phase transition for large enough magnetic field, with a critical endpoint located between $eB=4$ GeV$^2$ (where we found an analytic crossover at a pseudo-critical temperature $T_c=(98\pm3)$ MeV) and $eB=9$ GeV$^2$ (where the measured critical temperature is $T_c=(63\pm5)$ MeV).