On the transition temperature(s) of magnetized two-flavour holographic QCD

TL;DR

This paper uses gauge-gravity duality to explore how strong magnetic fields affect the chiral phase transition temperatures in two-flavor holographic QCD, revealing flavor-dependent effects and a phase diagram extension.

Contribution

It introduces a flavor-dependent analysis of the QCD phase diagram under magnetic fields using the non-antipodal Sakai-Sugimoto model, including geometric coupling differences.

Findings

Magnetic fields cause a split in the chiral phase transition temperatures by flavor.

The phase diagram is extended to include magnetic field effects and variable brane separation.

Results show similarities to NJL model predictions at small brane separations.

Abstract

During heavy ion collisions, high temperatures and strong magnetic fields are generated. We employ the gauge-gravity duality to study the N_f=2 QCD phase diagram under these extreme conditions in the quenched approximation, in particular we use the non-antipodal Sakai-Sugimoto model (SSM). We take the different coupling of up and down flavours to the magnetic field into account geometrically, resulting in a split of the chiral phase transition according to flavour. We discuss the influence of the magnetic field on the chiral temperatures -in physical GeV units- in terms of the choice of the confinement scale in the model, extending hereby our elsewhere presented discussion of fixing the non-antipodal SSM parameters to the deconfinement phase. The flavour-dependent (T,L,eB) phase diagram, with variable asymptotic brane-antibrane separation L, is also presented, as a direct generalization of the known (T,L) phase diagram of the non-antipodal SSM at zero magnetic field. In particular, for sufficiently small L we are probing a NJL-like boundary field theory in which case we do find results very reminiscent of the predictions in NJL models.