Greybody factors for nonminimally coupled scalar fields in Schwarzschild–de Sitter spacetime

We compute the greybody factors for nonminimally coupled scalar fields in four-dimensional Schwarzschild--de Sitter spacetime. In particular, we demonstrate that the zero-angular-momentum greybody factor generically tends to zero in the zero-frequency limit like frequency squared if there is nonvanishing coupling to the scalar curvature. This is in contrast with the minimally coupled case, where this greybody factor is known to tend to a finite constant. We also study the Hawking radiation for nonminimally coupled massless scalar fields in Schwarzschild--de Sitter spacetime, formulate a sensible notion of a generalized absorption cross section and investigate its properties.