https://doi.org/10.1140/epjc/s10052-018-5604-8
Regular Article - Theoretical Physics
Scalar radiation from a radially infalling source into a Schwarzschild black hole in the framework of quantum field theory
1
Campus Salinopólis, Universidade Federal do Pará, Salinópolis, Pará, 68721-000, Brazil
2
Faculdade de Física, Universidade Federal do Pará, Belém, Pará, 66075-110, Brazil
3
Department of Mathematics, University of York, Heslington, York, YO10 5DD, UK
* e-mail: laoliveira@ufpa.br
Received:
15
August
2017
Accepted:
1
February
2018
Published online:
16
February
2018
We investigate the radiation to infinity of a massless scalar field from a source falling radially towards a Schwarzschild black hole using the framework of the quantum field theory at tree level. When the source falls from infinity, the monopole radiation is dominant for low initial velocities. Higher multipoles become dominant at high initial velocities. It is found that, as in the electromagnetic and gravitational cases, at high initial velocities the energy spectrum for each multipole with 
approximately is constant up to the fundamental quasinormal frequency and then drops to zero. We also investigate the case where the source falls from rest at a finite distance from the black hole. It is found that the monopole and dipole contributions in this case are dominant. This case needs to be carefully distinguished from the unphysical process where the source abruptly appears at rest and starts falling, which would result in radiation of an infinite amount of energy. We also investigate the radiation of a massless scalar field to the horizon of the black hole, finding some features similar to the gravitational case.
© The Author(s), 2018
