Chiral crystallization in an external magnetic background - Chiral spiral versus Real kink crystal -

TL;DR

This paper investigates how external magnetic fields influence the phase structure of QCD, revealing that even weak fields induce a transition from real kink crystal to chiral spiral, significantly altering the inhomogeneous chiral condensate phases.

Contribution

It introduces a universal coupling in a Ginzburg-Landau framework showing magnetic fields induce a chiral spiral, replacing the real kink crystal in QCD's phase diagram.

Findings

Magnetic fields eliminate the Lifshitz point and induce chiral spirals.

Current quark mass protects the critical point against magnetic effects.

Critical magnetic field strength is approximately 50 MeV for phase transition.

Abstract

We study how an external magnetic field modifies the chiral phase structure of QCD, in particular the phases characterized by inhomogeneous chiral condensates. The magnetic field can be systematically incorporated into a generalized Ginzburg-Landau framework, and it turns out to induce a model independent universal coupling between the magnetic field and the axial isospin current. The resulting effect is found to be drastic especially in the chiral limit; no matter how small the magnetic intensity is, the tricritical Lifshitz point is totally washed out, and the real kink crystal is replaced by a magnetically induced chiral spiral. The current quark mass, on the other hand, has an opposite effect, protecting the chiral critical point from the magnetically induced chiral spiral. But once the magnetic intensity exceeds a critical value, the critical point no longer exists. We draw a semiquantitative conclusion that the critical point disappears for $\sqrt{eB}\geq 50$ MeV.