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arXiv · 2508.20155

Fermionic Love of Black Holes in General Relativity

Sumanta Chakraborty·Pierre Heidmann·Paolo Pani
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Abstract

Black holes in General Relativity exhibit a remarkable feature: their response to static scalar, electromagnetic, and gravitational perturbations -- as quantified by the so-called tidal Love numbers -- vanishes identically. We present the first exception to this rule: the Love numbers of a black hole perturbed by a fermionic field are nonzero. We derive a closed-form expression of these fermionic Love numbers for generic spin in the background of a Kerr black hole with arbitrary angular momentum. In contrast, we show that the fermionic dissipation numbers vanish for static perturbations, reflecting the absence of superradiance for fermions. These results highlight a fundamental distinction between bosonic and fermionic perturbations, which can be interpreted as a breaking of the hidden symmetries that underlie the vanishing of Love numbers in the bosonic sector.

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Sumanta Chakraborty, Pierre Heidmann, Paolo Pani. 2025-08-27. Fermionic Love of Black Holes in General Relativity. https://doi.org/10.1103/2yr1-9ymw

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