Heavy Holographic QCD

TL;DR

This paper investigates the phase diagram of a holographic QCD model incorporating nonzero quark mass, revealing how mass influences phase transitions and introduces critical points, thus making the model more realistic for real-world QCD.

Contribution

The study extends the Witten-Sakai-Sugimoto model to include quark mass effects, showing how mass stabilizes certain phases and alters the phase transition structure, aligning better with real QCD behavior.

Findings

Quark mass stabilizes configurations with string sources.

Mass breaks first-order phase transition curves, creating critical points.

Phase structure shows similarities to lattice QCD and other holographic models.

Abstract

We study the phase structure of the Witten-Sakai-Sugimoto model in the plane of temperature and baryon chemical potential, including the effect of a nonzero current quark mass. Our study is performed in the decompactified limit of the model, which, at least regarding the chiral phase transition, appears to be closer to real-world QCD than the original version. Following earlier studies, we account for the quark mass in an effective way based on an open Wilson line operator whose expectation value is identified with the chiral condensate. We find that the quark mass stabilizes a configuration with string sources and point out that this phase plays an important role in the phase diagram. Furthermore, we show that the quark mass breaks up the first-order chiral phase transition curve and introduces critical points to the phase diagram. Similarities of the phase structure to other holographic approaches and to lattice simulations of "heavy QCD" are found and discussed. By making holographic QCD more realistic, our results open the door to a better understanding of real-world strongly coupled hot and dense matter.