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.

中文翻译：

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重全息QCD

我们研究了 Witten-Sakai-Sugimoto 模型在温度和重子化学势平面中的相结构，包括非零电流夸克质量的影响。我们的研究是在模型的解压缩极限中进行的，至少在手性相变方面，它似乎比原始版本更接近真实世界的 QCD。根据早期的研究，我们基于开放的威尔逊线算子以一种有效的方式解释了夸克质量，该算子的期望值与手性凝聚物一致。我们发现夸克质量稳定了弦源的配置，并指出该相在相图中起着重要作用。此外，我们表明夸克质量打破了一阶手性相变曲线，并在相图中引入了临界点。发现并讨论了相结构与其他全息方法和“重 QCD”的晶格模拟的相似性。通过使全息 QCD 更加逼真，我们的结果为更好地理解现实世界中强耦合的热致密物质打开了大门。