Non-oscillatory gravitational quasinormal modes of Reissner-Nordstr\"om-de Sitter spacetime

TL;DR

This paper investigates the non-oscillatory gravitational quasinormal modes of Reissner-Nordström-de Sitter black holes, providing accurate numerical data and linking these modes to exponential decay tails in the spacetime.

Contribution

It presents the first detailed numerical analysis of the purely imaginary modes of these black holes, filling a gap in the existing literature.

Findings

Identified the non-oscillatory mode branch for the first time.

Provided accurate numerical values for these modes.

Linked these modes to exponential tail behavior in perturbations.

Abstract

Proper oscillation frequencies of black holes (quasinormal modes) of asymptotically de Sitter black holes were extensively studied, yet the non-oscillatory (purely imaginary) branch of modes of gravitational perturbations of the four-dimensional Reissner-Nordstr\"om-de Sitter solution was omitted in the literature. This branch of modes appears as deformations of the modes of empty de Sitter space. Here we find accurate numerical values of this branch of quasinormal modes and show that they are responsible for the exponential asymptotic tails.