Magnetic Phase Diagram of Dense Holographic Multiquarks in the Quark-gluon Plasma

TL;DR

This paper investigates the phase diagram of dense holographic quark matter under magnetic fields, revealing that multiquark phases are thermodynamically favored over quark-gluon plasma at high density and magnetic field, with temperature-dependent properties.

Contribution

It introduces a detailed holographic analysis of multiquark phases in magnetic fields, highlighting their thermodynamic preference and temperature dependence in the Sakai-Sugimoto model.

Findings

Multiquark-pion gradient phase is favored at high density and magnetic field.

Pion gradient response is linear for small and moderate magnetic fields.

Temperature effects on chemical potential and free energy follow a specific analytic form.

Abstract

We study phase diagram of the dense holographic gauge matter in the Sakai-Sugimoto model in the presence of the magnetic field above the deconfinement temperature. Even above the deconfinement, quarks could form colour bound states through the remaining strong interaction if the density is large. We demonstrate that in the presence of the magnetic field for a sufficiently large baryon density, the multiquark-pion gradient (MQ-$\mathcal{5}\phi$) phase is more thermodynamically preferred than the chiral-symmetric quark-gluon plasma. The phase diagrams between the holographic multiquark and the chiral-symmetric quark-gluon plasma phase are obtained at finite temperature and magnetic field. In the mixed MQ-$\mathcal{5}\phi$ phase, the pion gradient induced by the external magnetic field is found to be a linear response for small and moderate field strengths. Its population ratio decreases as the density is raised and thus the multiquarks dominate the phase. Temperature dependence of the baryon chemical potential, the free energy and the linear pion gradient response of the multiquark phase are well approximated by a simple analytic function $\sqrt{1-\frac{T^{6}}{T^{6}_{0}}}$ inherited from the metric of the holographic background.