Slowly decaying resonances of massive scalar fields around Schwarzschild-de Sitter black holes

TL;DR

This paper investigates quasinormal modes of massive scalar fields around Schwarzschild-de Sitter black holes, revealing conditions for wave propagation, relations to photon geodesics, and the emergence of slowly decaying resonances linked to the spacetime's effective potential.

Contribution

It introduces the concept of slowly decaying resonances in massive scalar fields and relates their properties to the effective potential's maximum at the static radius.

Findings

Lower mass limit for wave propagation depends on spacetime parameters

Quasinormal mode frequencies relate to unstable photon geodesics

Discovery of slowly decaying resonances at large scalar mass

Abstract

We study in special limiting cases quasinormal modes of massive scalar fields in the Schwarzschild-de Sitter black hole backgrounds. We determine the lower limit on the mass parameter of the scalar field that allows the waves with quasinormal frequencies to propagate to infinity, showing that it depends on the spacetime parameters only. Then we discuss in the large multipole number limit quasinormal modes, whose frequencies can be directly related to the unstable circular photon geodesics. In the large scalar mass approximation, we demonstrate the new interesting phenomenon of slowly decaying resonances, that are strongly related to the maximum of the effective potential of the massive scalar field, which is located at the static radius of the Schwarzschild-de Sitter spacetimes, where the cosmic repulsion is just balanced by the black hole attraction.