Inverse Magnetic Catalysis from improved Holographic QCD in the Veneziano limit

TL;DR

This paper uses an improved holographic QCD model in the Veneziano limit to explore how external magnetic fields influence the chiral condensate, revealing conditions for both magnetic catalysis and inverse magnetic catalysis.

Contribution

It demonstrates that holographic QCD models can reproduce both magnetic catalysis and inverse magnetic catalysis phenomena depending on parameter choices, aligning qualitatively with lattice results.

Findings

Holographic model reproduces magnetic catalysis and inverse magnetic catalysis.

Backreaction of flavors decatalyzes the chiral condensate.

Model agrees qualitatively with lattice QCD findings.

Abstract

We study the dependence of the chiral condensate on external magnetic field in the context of holographic QCD at large number of flavors. We consider a holographic QCD model where the flavor degrees of freedom fully backreact on the color dynamics. Perturbative QCD calculations have shown that $B$ acts constructively on the chiral condensate, a phenomenon called "magnetic catalysis". In contrast, recent lattice calculations show that, depending on the number of flavors and temperature, the magnetic field may also act destructively, which is called "inverse magnetic catalysis". Here we show that the holographic theory is capable of both behaviors depending on the choice of parameters. For reasonable choice of the potentials entering the model we find qualitative agreement with the lattice expectations. Our results provide insight for the physical reasons behind the inverse magnetic catalysis. In particular, we argue that the backreaction of the flavors to the background geometry decatalyzes the condensate.