Charged Superradiant Instability of Spherically Symmetric Regular Black Holes in de Sitter Spacetime: Time- and Frequency-Domain Analysis

Abstract

We investigate the superradiant instability of Ayón-Beato-García-de Sitter (ABG-dS) black holes under massless charged scalar perturbations using both time-domain evolutions and frequency-domain computations. We show that the instability occurs only for the spherically symmetric mode with $\ell =0$, whereas asymptotically flat ABG black holes remain stable in the massless limit, which underscores the essential role of the cosmological horizon in providing a confining boundary. We further study the dependence of the growth rate on the cosmological constant $\hat{I}›$, the scalar charge $q$, and the black hole charge $Q$, finding that it reaches a maximum at intermediate values of $\hat{I}›$ and $q$ and increases monotonically with $Q$. Compared with Reissner-Nordström-de Sitter black holes, ABG-dS black holes exhibit distinct instability characteristics due to the modified electrostatic potential induced by nonlinear electrodynamics.

15 pages,7 figures