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Main Authors: Agrawal, Shreyansh, Charalambous, Panagiotis, Donnay, Laura, Liberati, Stefano, Neri, Giulio
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2604.15260
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author Agrawal, Shreyansh
Charalambous, Panagiotis
Donnay, Laura
Liberati, Stefano
Neri, Giulio
author_facet Agrawal, Shreyansh
Charalambous, Panagiotis
Donnay, Laura
Liberati, Stefano
Neri, Giulio
contents Stationary black hole geometries with non-degenerate Cauchy horizons are classically unstable due to mass inflation. At extremality, mass inflation is absent, but a different dynamical instability arises: the Aretakis instability. In this work, we investigate the properties of degenerate horizons and their associated Aretakis instabilities. By studying examples with increasingly higher-order horizon degeneracy, we show that the Aretakis instability weakens as the degree of degeneracy grows. Motivated by these results, we propose a new black hole geometry characterized by an infinitely degenerate horizon, which we argue is stable under Aretakis-type perturbations and may therefore provide a concrete realization of a "graveyard" end state for these objects.
format Preprint
id arxiv_https___arxiv_org_abs_2604_15260
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Taming the Aretakis instability: extremal black holes with multi-degenerate horizons
Agrawal, Shreyansh
Charalambous, Panagiotis
Donnay, Laura
Liberati, Stefano
Neri, Giulio
General Relativity and Quantum Cosmology
High Energy Physics - Theory
Stationary black hole geometries with non-degenerate Cauchy horizons are classically unstable due to mass inflation. At extremality, mass inflation is absent, but a different dynamical instability arises: the Aretakis instability. In this work, we investigate the properties of degenerate horizons and their associated Aretakis instabilities. By studying examples with increasingly higher-order horizon degeneracy, we show that the Aretakis instability weakens as the degree of degeneracy grows. Motivated by these results, we propose a new black hole geometry characterized by an infinitely degenerate horizon, which we argue is stable under Aretakis-type perturbations and may therefore provide a concrete realization of a "graveyard" end state for these objects.
title Taming the Aretakis instability: extremal black holes with multi-degenerate horizons
topic General Relativity and Quantum Cosmology
High Energy Physics - Theory
url https://arxiv.org/abs/2604.15260