Ringing Regularity: Gravitational Perturbations and Quasinormal Modes of Einasto-Supported Black Holes

TL;DR

This paper studies how Einasto-supported matter distributions around black holes affect their gravitational perturbations and quasinormal modes, revealing significant deviations from classical black hole spectra.

Contribution

It introduces the analysis of axial gravitational perturbations and quasinormal modes for regular black holes with Einasto matter, highlighting environmental effects on the spectrum.

Findings

Quasinormal frequencies are shifted by halo matter.

Damping rates can be significantly suppressed in near-extremal cases.

Regularity and environmental effects exceed numerical uncertainties.

Abstract

We investigate axial gravitational perturbations and quasinormal modes of regular black holes supported by an Einasto distribution of matter. Halo matter not only removes the central singularity but also modifies the quasinormal spectrum. We show that the resulting quasinormal spectrum deviates systematically from the Schwarzschild case, with shifts in both oscillation frequencies and damping rates that grow with the halo scale parameter and the Einasto index. In near-extremal configurations, the damping rate can be significantly suppressed, leading to long-lived modes. The effects of regularity and environmental factors on the spectrum are found to be substantially larger than the estimated numerical uncertainty, as confirmed independently by high-order WKB calculations with Pad\'e resummation and time-domain integration.