Chen Yifan, Shu Jing, Xue Xiao, Yuan Qiang, Zhao Yue
CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Laboratoire de Physique Théorique et Hautes Energies (LPTHE), UMR 7589, Sorbonne Université et CNRS, 4 place Jussieu, 75252 Paris Cedex 05, France.
Phys Rev Lett. 2020 Feb 14;124(6):061102. doi: 10.1103/PhysRevLett.124.061102.
With high spatial resolution, polarimetric imaging of a supermassive black hole, like M87^{⋆} or Sgr A^{⋆}, by the Event Horizon Telescope can be used to probe the existence of ultralight bosonic particles, such as axions. Such particles can accumulate around a rotating black hole through the superradiance mechanism, forming an axion cloud. When linearly polarized photons are emitted from an accretion disk near the horizon, their position angles oscillate due to the birefringent effect when traveling through the axion background. In particular, the observations of supermassive black holes M87^{⋆} (Sgr A^{⋆}) can probe the dimensionless axion-photon coupling c=2πg_{aγ}f_{a} for axions with mass around O(10^{-20}) eV [O(10^{-17}) eV] and decay constant f_{a}<O(10^{16}) GeV, which is complimentary to other axion measurements.
利用事件视界望远镜对超大质量黑洞（如M87⋆或Sgr A⋆）进行具有高空间分辨率的偏振成像，可用于探测超轻玻色子粒子（如轴子）的存在。这类粒子可通过超辐射机制在旋转黑洞周围聚集，形成轴子云。当线偏振光子从视界附近的吸积盘发射时，它们在穿过轴子背景时，由于双折射效应，其偏振角会发生振荡。特别是，对超大质量黑洞M87⋆（Sgr A⋆）的观测可以探测质量约为O(10−20) eV [O(10−17) eV]且衰变常数fa < O(1016) GeV的轴子的无量纲轴子-光子耦合c = 2πgaγfa，这与其他轴子测量结果互为补充。
