Inverse magnetic catalysis in dense holographic matter

TL;DR

This paper investigates how magnetic fields influence the chiral phase transition in dense holographic matter, revealing inverse magnetic catalysis where magnetic fields lower the critical chemical potential for chiral symmetry restoration, contrary to traditional expectations.

Contribution

It demonstrates the occurrence of inverse magnetic catalysis in a holographic QCD model, linking it to a magnetic phase transition within the symmetric phase, a novel insight in the field.

Findings

Magnetic field decreases critical chemical potential at low temperatures.

Inverse magnetic catalysis occurs contrary to magnetic catalysis at zero chemical potential.

IMC persists up to 10^{19} G at low temperatures.

Abstract

We study the chiral phase transition in a magnetic field at finite temperature and chemical potential within the Sakai-Sugimoto model, a holographic top-down approach to (large-N_c) QCD. We consider the limit of a small separation of the flavor D8-branes, which corresponds to a dual field theory comparable to a Nambu-Jona Lasinio (NJL) model. Mapping out the surface of the chiral phase transition in the parameter space of magnetic field strength, quark chemical potential, and temperature, we find that for small temperatures the addition of a magnetic field decreases the critical chemical potential for chiral symmetry restoration - in contrast to the case of vanishing chemical potential where, in accordance with the familiar phenomenon of magnetic catalysis, the magnetic field favors the chirally broken phase. This "inverse magnetic catalysis" (IMC) appears to be associated with a previously found magnetic phase transition within the chirally symmetric phase that shows an intriguing similarity to a transition into the lowest Landau level. We estimate IMC to persist up to 10^{19} G at low temperatures.