Speaker
Description
In this talk, we aim to address the question of whether the quasi-normal modes, which represent the characteristic frequencies associated with perturbed black hole spacetimes and are central to the stability of these black holes, are themselves stable. We begin by presenting a general method for transforming to a hyperboloidal coordinate system in both asymptotically flat and asymptotically de Sitter spacetimes. We shall discuss how such a coordinate system effectively captures the dissipative boundary conditions, resulting in a non-self-adjoint differential operator. To fully understand the behaviour of a non-self-adjoint operator, we must study both the spectrum and the pseudo-spectrum of such an operator. We shall therefore introduce and explain the relevance of the notion of pseudo-spectrum in black hole physics. We then study the spectrum and the pseudo-spectrum of asymptotically de Sitter black holes numerically using spectral methods. Our analysis demonstrates how external perturbations to the scattering potential cause the quasi-normal modes to deviate from their unperturbed values. Additionally, we also highlight the implications of the instability observed in the fundamental quasi-normal mode on issues like the validity of the strong cosmic censorship conjecture.
| subhodeep.sarkar1@gmail.com | |
| Affiliation | Indian Institute of Information Technology, Allahabad |
