Non-evident stability of a Dirac field in Schwarzschild-de Sitter spacetime

Abstract

Perturbations of the Dirac field in the Schwarzschild spacetime are characterized by two wave equations (for two chiralities) with effective potentials which are iso-spectral and one of which is positive definite. Therefore, the stability of a Dirac field in the Schwarzschild background is straightforward. This is not so for the Schwarzschild-de Sitter case, because potentials for both chiralities have negative gaps and the fact that the stability is not automatically guaranteed in the asymptotically de Sitter case was apparently omitted in the literature. Performing the time-domain integration of the wave equations and, thereby, taking into consideration all the quasinormal modes of the spectrum, we demonstrate stability of the Dirac field in the Schwarzschild-de Sitter spacetime. The analysis of stability is extended also to the Reissner-Nordstrom-de Sitter solution.