Radiation spectra and effective temperatures in higher-dimensional charged de Sitter black holes

In this study, a scalar field propagating in a higher-dimensional Reissner-Nordström-de Sitter black hole is investigated. Scalar fields are assumed to have nonminimal coupling to the brane or bulk scalar curvature. Five different definitions of black hole temperatures are discussed: temperature based on surface gravity, Bousso-Hawking temperature, and three effective temperatures. The greybody factors of minimally and nonminimally coupled scalar fields on the brane and in the bulk are examined under the effect of particle and spacetime properties. The energy emission spectra of black holes are determined at various temperatures for both the brane and bulk channels. The energy emission rates at the Bousso-Hawking temperature are found to be dominant over those at other temperatures. The energy emission curves are suppressed by the presence of coupling parameters. Finally, the bulk-over-brane emission ratios are calculated. Notably, bulk dominance becomes possible for a certain definition of the temperatures and regime of the cosmological constant.