Strong cosmic censorship in near-extremal Kerr-Sen-de Sitter spacetime

TL;DR

This paper investigates the stability of the Cauchy horizon in near-extremal Kerr-Sen-de Sitter black holes by analyzing scalar field perturbations and finds that the strong cosmic censorship conjecture holds in this context.

Contribution

It provides an analytical calculation of quasi-normal modes in Kerr-Sen-de Sitter spacetime and demonstrates the validity of the strong cosmic censorship conjecture with additional scalar fields.

Findings

Quasi-normal modes are characterized by the surface gravity of the near-extremal black hole.

The imaginary part of the modes indicates stability of the Cauchy horizon.

Strong cosmic censorship is respected in this spacetime with scalar fields.

Abstract

We first calculate equations of motion for particles in the Kerr-Sen-de Sitter black hole spacetime. Then in the eikonal regime, we analytically obtain the quasi-normal resonant modes of massless neutral scalar field perturbation and find its imaginary part to be characterized by the surface gravity of the near-extremal Kerr-Sen-de Sitter black hole with Cauchy horizon approaching the event horizon. We further show that the Penrose strong cosmic censorship conjecture is thus respected in this spacetime with dilaton scalar field and axion pseudoscalar field.