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arXiv · 2306.14193

Hairy Black Holes: Non-existence of Short Hairs and Bound on Light Ring Size

Rajes Ghosh·Selim Sk·Sudipta Sarkar
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Abstract

Several hairy black hole solutions are known to violate the original version of the celebrated no-hair conjecture. This prompted the development of a new theorem that establishes a universal lower bound on the extension of hairs outside any $4$-dimensional black hole solutions of general relativity. Our work presents a novel generalization of this ``no-short hair'' theorem, which notably does not use gravitational field equations and is valid for arbitrary spacetime dimensions ($D \geq 4$). Consequently, irrespective of the underlying theory of gravity, the ``hairosphere'' must extend to the innermost light ring of the black hole spacetime. Various possible observational implications of this intriguing theorem are discussed, and other useful consequences are explored.

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Rajes Ghosh, Selim Sk, Sudipta Sarkar. 2023-06-25. Hairy Black Holes: Non-existence of Short Hairs and Bound on Light Ring Size. https://doi.org/10.1103/physrevd.108.l041501

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