The greybody factor for scalar fields in the Schwarzschild spacetime   with an $f(R)$ global monopole
  The greybody factor of massless scalar fields in the four-dimensional Schwarzschild spacetime involving an $f(R)$ global monopole is derived. We show how the monopole parameter and the deviation from the standard general relativity adjust the greybody factor. We also demonstrate that the effects from the global monopole and $f(R)$ gravity theory are manifest in the energy emission rate and the generalized absorption cross section of the scalar fields. 
Jingyun Man, Hongbo Cheng
hep-th