Radiation emitted from a swirling source around a black hole in quantum field theory in curved spacetime

We analyze the radiation emitted from a scalar source swirling around a black hole using quantum field theory in curved spacetime. We show that for relativistic circular orbits the emitted power is about 30% smaller than what would be obtained with quantum field theory in Minkowski spacetime. We also show that most of the emitted energy escapes to infinity. Our formalism can be promptly adapted to investigate other similar processes