Phys. Rev. D, 106, L081702 (2022)
Soft theorems in curved spacetime
Peng Cheng1,2 and Pujian Mao1
1 Center for Joint Quantum Studies and Department of Physics, School of Science, Tianjin University, 135 Yaguan Road, Tianjin 300350, China.
2 Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, Lanzhou University, 222 South Tianshui Road, Lanzhou 730000, Gansu, China.
* p.cheng.nl@outlook.com, pjmao@tju.edu.cn
Abstract
In this paper, we derive a soft photon theorem in the near horizon region of the Schwarzschild black hole from the Ward identity of the near horizon large gauge transformation. The flat spacetime soft photon theorem can be recovered as a limiting case of the curved spacetime. The soft photons on the horizon are indeed soft electric hairs. This accomplishes the triangle equivalence on the black hole horizon.
