Features and stability analysis of non-Schwarzschild black hole in quadratic gravity

TL;DR

This paper investigates the quasinormal modes of scalar fields around non-Schwarzschild black holes in quadratic gravity, revealing similarities to Schwarzschild decay but with smoother slopes, and discusses potential observational implications.

Contribution

It provides a detailed analysis of quasinormal modes in Einstein-Weyl gravity, highlighting differences from Schwarzschild black holes and exploring their potential for testing gravitational theories.

Findings

Quasinormal mode decay is smoother than Schwarzschild.

Mode frequencies can help characterize new black holes.

Potential gravitational wave signatures from these modes.

Abstract

Black holes are found to exist in gravitational theories with the presence of quadratic curvature terms and behave differently from the Schwarzschild solution. We present an exhaustive analysis for determining the quasinormal modes of a test scalar field propagating in a new class of black hole backgrounds in the case of pure Einstein-Weyl gravity. Our result shows that the field decay of quasinormal modes in such a non-Schwarzschild black hole behaves similarly to the Schwarzschild one, but the decay slope becomes much smoother due to the appearance of the Weyl tensor square in the background theory. We also analyze the frequencies of the quasinormal modes in order to characterize the properties of new back holes, and thus, if these modes can be the source of gravitational waves, the underlying theories may be testable in future gravitational wave experiments. We briefly comment on the issue of quantum (in)stability in this theory at linear order.