轴子现象学专题：宇宙弦与超辐射的案例
Topics in the phenomenology of axions: the cases of cosmic strings and superradiance
浏览论文内容
中文总结 AI 辅助
本论文研究轴子现象学的两个案例：宇宙弦的轴子发射及黑洞周围的超辐射引力原子，推导相关物理量的解析公式并确定未来引力波探测的有望系统。
中文摘要 AI 辅助
轴子最初被提出作为强CP问题的解决方案，后来被认为是良好的暗物质候选体，已出现在多种超出标准模型的理论中，并具有丰富的现象学后果。在本论文中，我们将研究其中两种后果：宇宙弦的轴子发射以及黑洞物理中的超辐射机制。早期宇宙中整体对称性的自发对称性破缺会产生宇宙弦网络，该网络会发射超轻类轴子粒子，这些粒子可对暗物质密度产生贡献。我们将讨论如何通过将这些粒子视为平面波集合，从头计算其相关密度涨落；随后计算密度功率谱，并将其与成熟的宇宙学可观测量及未来巡天的可观测量进行比较，以推导粒子质量和对称性破缺能标的限制。这些轻类轴子粒子还可通过超辐射过程在旋转黑洞周围形成引力原子。若黑洞属于双星系统，伴星的潮汐势会周期性扰动该引力原子，使其发生两个能级之间的原子跃迁，跃迁期间云团会发射引力波。我们将推导该信号的应变波形和频率谱的解析公式，并确定最有可能在未来天基引力波天文台中探测到该信号的系统。
英文摘要
Originally proposed as a solution to the strong CP problem and later understood to be a good dark matter candidates, axions have appeared in a variety of beyond-the-standard-model theories and are imbued with rich phenomelogical consequences. In this dissertation, we will examine two of these consequences: the emission of axions from cosmic strings and the superradiant mechanism in black hole physics. The spontaneous symmetry breaking of a global symmetry in the early universe can give rise to a network of cosmic strings, which emit ultra light, axion-like particles that can contribute to the dark matter density. We will discuss how the associated density fluctuations of these particles can be computed from first principles by treating them as a collection of plane waves. We will then calculate the density power spectrum and compare it to well-established cosmological observables, as well as to observables from future surveys, to derive constraints on the mass of the particles and the symmetry breaking scale. These light axion-like particles can also form a gravitational atom around a spinning black hole through the superradiance process. Considering the black hole to be part of a binary system, the tidal potential of the companion periodically perturbs the gravitational atom such that an atomic transition occurs between two of its energy states. Gravitational waves are emitted by the cloud during this transition. We will derive the analytical formulae of both the strain waveform and frequency spectrum of the signal and identify the systems that would be the most promising for detecting it in future, space-based gravitational wave observatories.
