Black holes with axion hair from cubic Riemann interactions
Abstract
An effective field theory (EFT) of gravity with a cubic Riemann invariant coupled to an axion-like field is investigated and shown to propagate no additional independent low-energy degrees of freedom. This interaction generates a curvature-induced scalar profile around black holes, characterised by a secondary axion charge fixed by regularity of the axion field at the horizon, while the requirement of a regular event horizon constrains the asymptotic axion background. We construct the corresponding black hole solutions and show that the backreaction of the axion field could affect the metric only at subleading order in the EFT expansion. The modified geometry impacts black hole thermodynamics and Hawking evaporation, thus providing a controlled realisation of black holes with higher-curvature contributions and secondary axion hair motivated by ultraviolet physics. The modified Hawking temperature allows for the existence of black hole remnants at the end of the evaporation within the regime of validity of the EFT.
Related
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- Axion corrections to photon superradiant scattering by Kerr black holes
- Stimulated capture of axion dark matter around primordial black holes
- Topological black holes of Einsteinian cubic gravity and Born-Infeld-type electrodynamics
- Black holes with torsion hair in cubic Holst-type Poincaré gauge gravity: from singular to regular geometries
BibTeX
@misc{casadio2026black,
title = {{Black holes with axion hair from cubic Riemann interactions}},
author = {Roberto Casadio and Roldao da Rocha},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.34945},
eprint = {2609.34945},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.34945},
}
RIS
TY - UNPB
TI - Black holes with axion hair from cubic Riemann interactions
AU - Roberto Casadio
AU - Roldao da Rocha
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.34945
UR - https://arxiv.org/abs/2609.34945
AB - An effective field theory (EFT) of gravity with a cubic Riemann invariant coupled to an axion-like field is investigated and shown to propagate no additional independent low-energy degrees of freedom. This interaction generates a curvature-induced scalar profile around black holes, characterised by a secondary axion charge fixed by regularity of the axion field at the horizon, while the requirement of a regular event horizon constrains the asymptotic axion background. We construct the corresponding black hole solutions and show that the backreaction of the axion field could affect the metric only at subleading order in the EFT expansion. The modified geometry impacts black hole thermodynamics and Hawking evaporation, thus providing a controlled realisation of black holes with higher-curvature contributions and secondary axion hair motivated by ultraviolet physics. The modified Hawking temperature allows for the existence of black hole remnants at the end of the evaporation within the regime of validity of the EFT.
ER -