Analytic Quasinormal Spectrum of Effective de Sitter Space in Generalized Proca Theory

Abstract: Quasinormal modes describe the relaxation of perturbed black holes and relate ringdown observables to the background geometry. In this work we study the problem in a de Sitter setting within a generalized Proca branch that generates an effective positive cosmological constant and admits an exact de Sitter vacuum. Using this vacuum, we derive closed expressions for scalar mode frequencies and identify the change in damping behavior between light and heavy fields. The resulting formulas show explicitly how the theory parameters determine the de Sitter-like part of the spectrum.