Scattering and Absorption of Standard Model Fields by Brane-Localized Schwarzschild--de Sitter Black Holes

Abstract: We investigate the propagation and absorption of Standard Model fields -- scalar, electromagnetic, and Dirac -- on a 3+1-dimensional brane embedded in a higher-dimensional Schwarzschild--de Sitter (SdS) spacetime. Using the effective four-dimensional projection of the Tangherlini metric, we compute grey-body factors (GBFs) and absorption cross-sections for each spin sector by means of the sixth-order WKB method and, independently, via the recently proposed correspondence between quasinormal modes (QNMs) and transmission coefficients. The results demonstrate that the cosmological constant and field mass crucially affect the transmission probabilities: increasing $\Lambda$ lowers the potential barrier and enhances the transparency of the geometry, while a larger field mass $\mu$ suppresses low-frequency emission and shifts the absorption spectrum to higher energies. For all fields, the QNM--GBF correspondence proves reliable to within about one percent for multipoles $\ell \ge 2$, while the correspondence remains less accurate for the lowest multipoles. The total absorption cross-sections exhibit the expected transition from the low-frequency suppression to the geometric-optics regime. Overall, these findings provide quantitative insight into the interplay between dimensionality, cosmological expansion, and black-hole radiation on the brane.