Adiabatic evolution of the self-interacting axion field around rotating black holes
Adiabatic evolution of the self-interacting axion field around rotating black holes
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旋转黑洞周围自相互作用轴子场的绝热演化
DOI：
10.1093/ptep/ptac058
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发表时间：
2022
影响因子：
3.5
通讯作者：
Tanaka Takahiro
中科院分区：
文献类型：
--
作者：
Omiya Hidetoshi;Takahashi Takuya;Tanaka Takahiro
受弦理论启发的超轻轴子场通过超辐射不稳定性在旋转黑洞周围形成大凝聚体（轴子云）。由于轴子云的一些影响，如黑洞的自旋和单色引力波的发射，打开了一个新的窗口，通过天体物理观测寻找轴子。当考虑轴子的自相互作用时，云的演化会发生显著的改变，并可能发生一种称为玻色超新星的爆炸现象。因此，有必要了解自相互作用云的精确演化，以便通过天体物理观测来检测轴子。在本文中，我们提出了一种新的方法来跟踪整个过程的自相互作用轴子云的增长采用绝热近似。我们强调，我们的方法既不依赖于非相对论近似，也不依赖于微扰处理的自相互作用，这是经常在文献中使用。我们的主要发现是，在强自相互作用制度的云的演化取决于轴子和黑洞之间的引力耦合的强度。对于一个大的耦合，云演变成一个准稳态，超辐射能量增益与能量耗散到无穷大的自相互作用平衡。另一方面，当耦合的大小减小时，云在某些能量下变得不稳定，这将被解释为玻色新星的开始。
Ultra-light axion fields, motivated by string theory, form a large condensate (axion cloud) around rotating black holes through superradiant instability. Several effects due to the axion cloud, such as the spin-down of black holes and the emission of monochromatic gravitational waves, open a new window to search for axions by astrophysical observations. When the axion self-interaction is considered, the evolution of clouds is altered significantly, and an explosive phenomenon called a bosenova can happen. Thus, it is necessary to understand the precise evolution of self-interacting clouds for the detection of axions by astrophysical observations. In this paper, we propose a new method to track the whole process of the growth of self-interacting axion clouds employing the adiabatic approximation. We emphasize that our method relies neither on the non-relativistic approximation nor on perturbative treatment of the self-interaction, which is often used in the literature. Our main finding is that the evolution of clouds in the strongly self-interacting regime depends on the strength of the gravitational coupling between the axion and the black hole. For a large coupling, the cloud evolves into a quasi-stationary state where the superradiant energy gain is balanced with the energy dissipation to infinity by the self-interaction. On the other hand, when one decreases the size of the coupling, clouds become unstable at some energy, which would be interpreted as the onset of a bosenova.