Spinning Black Holes May Grow Hair

Dolan, Sam R.

doi:10.1103/physics.10.83

Cited by 2 publications

(3 citation statements)

References 29 publications

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“…These BHs circumvent no-Proca hair theorems [21] by virtue of a harmonic time dependence of the bosonic field [19]. The model is free of known pathologies, and the hairy BHs could emerge dynamically via the superradiant instability of Kerr [22], triggered by the bosonic field [23][24][25]. This family of hairy BHs interpolates between the bald Kerr solution and horizonless self-gravitating solitons known as Proca stars (PSs) [26].…”

Section: Introductionmentioning

confidence: 99%

Kerr black holes with synchronised Proca hair: lensing, shadows and EHT constraints

Sengo

Cunha

Herdeiro

et al. 2023

J. Cosmol. Astropart. Phys.

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We investigate the gravitational lensing by spinning Proca stars and the shadows and lensing by Kerr black holes (BHs) with synchronised Proca hair, discussing both theoretical aspects and observational constraints from the Event Horizon Telescope (EHT) M87* and Sgr A* data. On the theoretical side, this family of BHs interpolates between Kerr-like solutions — exhibiting a similar optical appearance to that of Kerr BHs — to very non-Kerr like solutions, exhibiting exotic features such as cuspy shadows, egg-like shadows and ghost shadows. We interpret these features in terms of the structure of the fundamental photon orbits, for which different branches exist, containing both stable and unstable orbits, with some of the latter not being shadow related. On the observational side, we show that current EHT constraints are compatible with all such BHs that could form from the growth of the superradiant instability of Kerr BHs. Unexpectedly, given the (roughly) 10% error bars in the EHT data — and in contrast to their scalar cousin model —, some of the BHs with up to 40% of their energy in their Proca hair are compatible with the current data. We estimate the necessary resolution of future observations to better constrain this model.

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Section: Introductionmentioning

confidence: 99%

Kerr black holes with synchronised Proca hair: lensing, shadows and EHT constraints

Sengo

Cunha

Herdeiro

et al. 2023

J. Cosmol. Astropart. Phys.

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“…This process is, likely, non-conservative, ejecting some energy and, especially, angular momentum towards infinity; but for particular solutions with a given m, if a neighbouring solution (in terms of global quantities) exists for m + 1, the process could be approximately conservative. In fact, this approximate conservativeness has been observed in the transition from the Kerr BH (which corresponds to m = 0) to the m = 1 hairy solution in [45][46][47]. For this approximately conservative migration to be possible, the higher m neighbouring solution would have to be entropically favoured.…”

mentioning

confidence: 84%

“…These hairy BH solutions have a relation with the physical phenomenon of superradiance [67], from which they can form dynamically from the Kerr solution [45][46][47] -see also [54,57] for a discussion on the metastability of these solutions against superradiance. They also reduce to Kerr BHs and boson stars [68,69], in appropriate limits.…”

Section: Introductionmentioning

confidence: 99%

Kerr black holes with synchronised scalar hair and higher azimuthal harmonic index

2019

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Kerr black holes with synchronised scalar hair and azimuthal harmonic index m > 1 are constructed and studied. The corresponding domain of existence has a broader frequency range than the fundamental m = 1 family; moreover, larger ADM masses, M and angular momenta J are allowed. Amongst other salient features, non-uniqueness of solutions for fixed global quantities is observed: solutions with the same M and J co-exist, for consecutive values of m, and the ones with larger m are always entropically favoured. Our analysis demonstrates, moreover, the qualitative universality of various features observed for m = 1 solutions, such as the shape of the domain of existence, the typology of ergo-regions, and the horizon geometry, which is studied through its isometric embedding in Euclidean 3-space. IntroductionKerr black holes (BHs) with synchronised scalar hair [1] are a counterexample to the no-hair conjecture [2]see [3-5] for reviews -occurring in a simple and physically sound model: Einstein-(complex and massive-)Klein-Gordon theory. Many related solutions, relying on a similar synchronisation mechanism, have been found in the last few years, in different setups and approximations. An incomplete list of references, including also various studies of physical properties, is .These hairy BH solutions have a relation with the physical phenomenon of superradiance [67], from which they can form dynamically from the Kerr solution [45-47] -see also [54,57] for a discussion on the metastability of these solutions against superradiance. They also reduce to Kerr BHs and boson stars [68,69], in appropriate limits. Boson stars are a sort of gravitating soliton interpreted as a Bose-Einstein condensate of an ultra-light scalar field, that could be a dark matter candidate [70,71]. Moreover, the existence of the hairy BH solutions does not rely on particular choices of scalar field potentials that violate energy conditions, unlike other examples of asymptotically flat BHs with scalar hair, see e.g. [72,73]. Thus, besides the issue of the no-hair conjecture in BH physics, these hairy BHs contain different angles of interest.Kerr BHs with synchronised hair comprise a family that, besides the continuous parameters mass, angular momentum and Noether charge, is labelled by two discrete numbers: the azimuthal harmonic index of the scalar field m ∈ Z + and its node number n. Most of the studies of the solutions have focused on the fundamental solutions, n = 0, with the smallest value of m = 1. Recently, excited solutions (n = 0) have also been constructed [63]. Solutions with m > 1, on the other hand, have only been considered in the solitonic (boson star) limit [14,74], with the exception of the non-minimal model studied in [16]. The purpose of this work is to construct solutions with m > 1 in the minimal, simplest model, and to study some of the basic physical properties of these new solutions.

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Spinning Black Holes May Grow Hair

Cited by 2 publications

References 29 publications

Kerr black holes with synchronised Proca hair: lensing, shadows and EHT constraints

Kerr black holes with synchronised Proca hair: lensing, shadows and EHT constraints

Kerr black holes with synchronised scalar hair and higher azimuthal harmonic index

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