AUTHOR=Boyanov Valentin 

TITLE=On destabilising quasi-normal modes with a radially concentrated perturbation

JOURNAL=Frontiers in Physics

VOLUME=Volume 12 - 2024

YEAR=2025

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2024.1511757

DOI=10.3389/fphy.2024.1511757

ISSN=2296-424X

ABSTRACT=In this work we explore some aspects of the spectral instability of back hole quasi-normal modes, using a specific model as an example. The model is that of a small bump perturbation to the effective potential of linear axial gravitational waves on a Schwarzschild background, and our focus is on three different aspects of the instability: identifying and distinguishing between the two different types of instabilities studied previously in the literature, quantifying the size of the perturbations applied to the system and testing the validity of the pseudospectral numerical method in providing a convergent result for this measure, and finally, relating the size and other features of the perturbation to the degree of destabilisation of the spectrum.