Quasi-normal modes of black holes and naked singularities: revisiting the WKB method

Description

In this paper we revisit the analysis of the ringdown frequencies in the form of quasi-normal modes for Schwarzschild,Schwarzschild de-Sitter and Reissner-Nordstr\"om space-times. We plot these frequencies, using the third-order WKB semi-analytical method against the mass, charge and cosmological constant for each corresponding space-time for various different spin-fields. We verify the stability of each black hole solution, including the extremal Reissner-Nordstr\"om space-time. Finally, we discover four different traits for the Schwarzschild de-Sitter space-time: i) the frequencies vanish in the extremal case; ii) the frequencies swap behavior before and after the extremal value; iii) indication that the naked singularity is stable for positive mass; iv) for the naked singularity case, there exists a cut-off mass in the scalar-field perturbation which depends only on the multipole number $\ell$.

Additional details