arXiv 1108.06532011-08-02hep-ph

软墙AdS/QCD的动力学和热力学

The Dynamics and Thermodynamics of Soft-Wall AdS/QCD

Thomas M. Kelley

备注：: PhD Thesis

摘要：

规范/引力对偶性打开了强耦合规范理论的非微扰领域，使之可以进行解析处理。反德西特空间/共形场理论是将引力对偶模型与规范理论联系起来的一种方法，它是AdS 5 \times S 5中的10维IIB超弦理论与N = 4的超杨米尔斯理论的对应。然而，为了描述实验上可接受的系统，形式对应被修改为五维引力模型和强耦合类QCD规范理论之间的唯象对偶。这种对偶性被称为AdS/QCD。这项工作探讨了软壁AdS/QCD模型的各个方面。“软壁”一词指的是打破共形对称性并在对偶的规范侧引入质量标度的方法。我们将高阶项添加到软壁拉格朗日量中，并计算对物理观测量的影响。介子质谱获得了更复杂的结构，表现出更好的匹配与实验值比以前的模型。Gell-Mann-Oakes-Renner关系自然地从模型中出现。我们计算了形状因子Fπ和耦合gρππ，作为对我们的软壁模型极限的非平凡测试。在引力对偶度规中引入黑膜使我们能够导出规范理论中的热力学量。正如所预期的那样，在高温下，熵与温度的立方成比例，而声速达到其共形极限的三分之一。热凝聚贡献领导阶项，修改的温度，熵，和自由能的行为。我们发现，在临界温度，系统经历了从强子物质到强耦合夸克-胶子等离子体的相变。

英文摘要：

Gauge/Gravity dualities open the non-perturbative realms of strongly-coupled gauge theories to analytic treatment. Anti-de Sitter Space/Conformal Field The- ory, one way of connecting gravity dual models to gauge theories, is a correspon- dence between a ten-dimensional Type IIB superstring theory in AdS5 \times S 5 and a N = 4 super Yang Mills theory. To describe systems that are experimentally ac- cessible, however, the formal correspondence is modified into a phenomenological duality between a five-dimensional gravity model and a strongly coupled QCD-like gauge theory. This duality is referred to as AdS/QCD. This work explores aspects of the soft-wall AdS/QCD model. The phrase 'soft wall' refers to the means of breaking the conformal symmetry and introducing a mass scale to the gauge side of the duality. We add higher-order terms to the soft-wall Lagrangian and calculate the effect on physical observables. Meson mass spectra gain a more complex structure, exhibiting a better match with the experimental values than previous models. The Gell-Mann-Oakes-Renner rela- tion naturally emerges from the model. We calculate the form factor Fπ and the coupling gρππ as a non-trivial test on the limits of our soft-wall model. Introducing a black brane into the gravity dual metric allows us to derive thermodynamic quantities in the gauge theory. As expected at high temperatures, the entropy scales as the cube of the temperature, and the speed of sound reaches its conformal limit of one-third. Thermal condensates contribute leading-order terms, modifying the temperature, entropy, and free energy behavior. We find that the system undergoes a phase transition from hadronic matter to a strongly coupled quark-gluon plasma at a critical temperature.

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