发表机构
Qingdao University of Technology; China University of Petroleum (East China); Yanshan University（青岛理工大学; 中国石油大学（华东）; 燕山大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文研究轴子对混合星的影响，发现轴子场使夸克物质状态方程略变硬但显著降低相变密度，从而增大夸克核心，对最大质量影响微弱。
AI 中文摘要
我们在麦克斯韦构造框架内研究了轴子对混合星性质及其核心中可能发生的强子-夸克相变的影响。强子相由改进的同位旋和动量依赖相互作用（ImMDI）模型描述，而夸克相则由具有轴子修正的Kobayashi-Maskawa-'t Hooft（KMT）相互作用的三味Nambu--Jona-Lasinio（NJL）模型建模。基于所得的状态方程，我们分析了混合星物质的性质，包括声速和多变指数，以及混合星的结构特征，包括质量-半径关系和夸克核心的性质。我们的研究表明，轴子场$a/f_a$略微使夸克物质的状态方程变硬，但显著将强子-夸克相变移至较低的重子密度。这两种效应在影响混合星物质的状态方程方面相互竞争，甚至可能使其变软，这与矢量耦合相互作用的效果不同。因此，轴子场对混合星的最大质量仅有微弱影响，但显著增加了夸克核心的质量和半径，尤其是在弱矢量耦合情况下。这些结果表明，在当前麦克斯韦构造框架内，轴子的主要作用是促进低密度下更早的强子-夸克转变并扩大夸克核心。
英文摘要
We investigate the effects of axions on the properties of hybrid stars and the possible hadron-quark phase transition in their cores within the Maxwell construction. The hadronic phase is described by the improved isospin- and momentum-dependent interaction (ImMDI) model, while the quark phase is modeled by a three-flavor Nambu--Jona-Lasinio (NJL) model with an axion-modified Kobayashi-Maskawa-'t Hooft (KMT) interaction. Based on the obtained equation of state, we analyze the properties of hybrid-star matter, including the speed of sound and the polytropic index, as well as the structural characteristics of hybrid stars, including the mass-radius relation and the properties of the quark core. Our study shows that the axion field $a/f_a$ slightly stiffens the equation of state of quark matter but significantly shifts the hadron-quark phase transition to lower baryon densities. These two effects compete in influencing the equation of state of hybrid-star matter, and may even soften it, which is different from the effect of the vector coupling interaction. Consequently, the axion field has only a weak influence on the maximum mass of hybrid stars, but significantly increases the mass and radius of the quark core, especially for weak vector coupling. These results indicate that, within the present Maxwell construction, the primary role of the axion is to promote an earlier hadron-quark transition at low densities and to enlarge the quark core.
Comments10 pages, 6 figures
