Spectral Bifurcations in Quasinormal Modes of Regular BTZ Black Holes

Kartheek Hegde; Tajron Jurić; A. Naveena Kumara

doi:10.1007/JHEP07(2026)075

paper

Spectral Bifurcations in Quasinormal Modes of Regular BTZ Black Holes

arXiv:2603.14872 · doi:10.1007/JHEP07(2026)075

Abstract

We study the quasinormal spectrum of massless scalar fields propagating on a family of regular BTZ black holes arising from an infinite tower of dimensionally regularized Lovelock corrections. These geometries are asymptotically AdS, reduce to the standard BTZ solution in the limit $ℓ \to 0$ , and resolve the central singularity by introducing a smooth core controlled by the new length scale $ℓ$ . The scalar quasinormal modes are computed using both Leaver's continued-fraction method and the Horowitz-Hubeny power-series method; the two approaches agree to high accuracy across the parameter space. We find that the regularization preserves linear stability ( $ω_{I} < 0$ ) while qualitatively reshaping the spectrum: as $ℓ$ increases, BTZ-like complex branches collide with the imaginary axis and undergo a hierarchy of bifurcations into multiple purely imaginary branches, leading to mode switching and a nontrivial reordering of overtones as functions of $ℓ$ and the harmonic index $m$ . Our results place regular BTZ black holes within the emerging family of bifurcating quasinormal spectra known from nearly extremal and asymptotically AdS black holes, and highlight these $(2 + 1)$ -dimensional geometries as a controlled arena for exploring geometric mechanisms behind spectral branching and late-time ringdown in regular black hole spacetimes.

arXiv comment18 pages, 5 figures. (Matches the published version)

Spectral Bifurcations in Quasinormal Modes of Regular BTZ Black Holes

Abstract

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