[论文解读] NJL-model analysis of quark matter at large density

Michael Buballa|arXiv (Cornell University)|Feb 23, 2004

Pulsars and Gravitational Waves Research被引用 69

一句话总结

本文使用Nambu-Jona-Lasinio（NJL）模型研究高密度夸克物质，重点探讨手征对称性的恢复与颜色超导性。该研究将NJL框架扩展至包含二夸克凝聚态，特别是自旋-1配对，并表明在电中性约束下，自洽处理奇异夸克质量可稳定2SC-CFL相，支持中子星中存在夸克物质核心。

ABSTRACT

Investigations of deconfined quark matter within NJL-type models are reviewed, focusing on the regime of low temperatures and ``moderate'' densities, which is not accessible by perturbative QCD. Central issue is the interplay between chiral symmetry restoration and the formation of color superconducting phases. In order to lay a solid ground for this analysis, we begin with a rather detailed discussion of two and three-flavor NJL models and their phase structure, neglecting the possibility of diquark pairing in a first step. An important aspect of this part is a comparison with the MIT bag model. The NJL model is also applied to investigate the possibility of absolutely stable strange quark matter. In the next step the formalism is extended to include diquark condensates. We discuss the role and mutual influence of several conventional and less conventional quark-antiquark and diquark condensates. As a particularly interesting example, we analyze a spin-1 diquark condensate as a possible pairing channel for those quarks which are left over from the standard spin-0 condensate. For three-flavor systems, we find that a self-consistent calculation of the strange quark mass, together with the diquark condensates, is crucial for a realistic description of the 2SC-CFL phase transition. We also study the effect of neutrality constraints which are of relevance for compact stars. Both, homogeneous and mixed, neutral phases are constructed. Although neutrality constraints generally tend to disfavor the 2SC phase we find that this phase is again stabilized by the large values of the dynamical strange quark mass which follow from the self-consistent treatment. Finally, we combine our solutions with existing hadronic equations of state to investigate the existence of quark matter cores in neutron stars.

研究动机与目标

• 通过NJL型模型分析密集夸克物质中手征对称性恢复与颜色超导相之间的相互作用。
• 通过对比两味与三味NJL模型与MIT袋模型，为研究致密夸克物质奠定基础。
• 在NJL框架内探讨奇异夸克物质绝对稳定的可能性。
• 将NJL模型扩展以包含二夸克凝聚态，并评估其对相结构的影响，特别是在三味系统中的影响。
• 研究电中性约束对颜色超导相的影响及其在致密星中的相关性。

提出的方法

• 使用两味与三味NJL模型描述低温与中等密度下的夸克物质，初始阶段排除二夸克配对。
• 将NJL模型结果与MIT袋模型进行对比，以验证框架并突出相结构上的差异。
• 将二夸克凝聚态纳入NJL形式体系，包括传统的自旋-0与较不常见的自旋-1配对通道。
• 自洽计算奇异夸克质量与二夸克凝聚态，以准确描述2SC-CFL相变。
• 构建符合致密星相关电中性约束的均匀相与混合中性相。
• 将基于NJL的夸克物质状态方程与现有强子状态方程结合，以模拟中子星内部结构。

实验结果

研究问题

• RQ1 在NJL模型中，手征对称性恢复与颜色超导性在致密夸克物质中如何共存？
• RQ2 二夸克凝聚态，特别是自旋-1配对，在稳定颜色超导相中起什么作用？
• RQ3 对奇异夸克质量进行自洽处理如何影响三味夸克物质中2SC-CFL相变？
• RQ4 电中性约束在多大程度上抑制或稳定致密星环境中的2SC相？
• RQ5 当将基于NJL的夸克物质状态方程与强子状态方程结合时，中子星中是否可能存在夸克物质核心？

主要发现

• 包含二夸克凝聚态，特别是自旋-1配对，为未参与标准自旋-0凝聚态的夸克提供了可行的配对机制。
• 对奇异夸克质量的自洽处理对于准确描述三味系统中2SC-CFL相变至关重要。
• 电中性约束通常不利于2SC相，但这一趋势被大的动力学奇异夸克质量所抵消，从而稳定了该相。
• 由于动力学夸克质量与二夸克配对之间的相互作用，2SC相在电中性约束下仍具有可行性。
• 将基于NJL的夸克物质状态方程与强子状态方程结合，支持中子星中存在夸克物质核心。