Black hole superradiance signatures of ultralight vectors

Baryakhtar, Masha; Lasenby, Robert; Teo, Mae

doi:10.1103/physrevd.96.035019

“…We focus on the case of a vector field, as it exhibits faster growth than a scalar field. The linear regime of the instability for Proca fields has been studied before in various limits [11,14,[18][19][20]. Here we find numerical solutions of the full Einstein-Proca field equations.…”

mentioning

confidence: 90%

“…Such particles could form large clouds, spinning down the BH in the process. This is of particular interest now that LIGO has begun observing gravitational waves (GWs) [12], since measurements of BH masses and spins from binary mergers can be used to rule out or provide evidence for such particles, in addition to direct searches for the GW signatures of boson clouds [13,14]. See [15] for a review.…”

mentioning

confidence: 99%

Superradiant Instability and Backreaction of Massive Vector Fields around Kerr Black Holes

East

¹

,

Pretorius

²

2017

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We study the growth and saturation of the superradiant instability of a complex, massive vector (Proca) field as it extracts energy and angular momentum from a spinning black hole, using numerical solutions of the full Einstein-Proca equations. We concentrate on a rapidly spinning black hole (a = 0.99) and the dominant m = 1 azimuthal mode of the Proca field, with real and imaginary components of the field chosen to yield an axisymmetric stress-tensor, hence spacetime. We find that in excess of 9% of the black hole's mass can be transferred into the field. In all cases studied, the superradiant instability smoothly saturates when the black hole's horizon frequency decreases to match the frequency of the Proca cloud that spontaneously forms around the black hole.Introduction.-A remarkable feature of spinning black holes (BHs) is that a portion of their massup to 29% for extremal spin -can in principle be extracted. One way to realize this liberation of rotational energy is through the interaction of the BH with an impinging wave -be it scalar, electromagnetic, or gravitational -with frequency ω < mΩ BH , where Ω BH is the BH horizon frequency, and m is the azimuthal number of the wave. Waves satisfying this criterion exhibit superradiance, and carry away energy and angular momentum from the BH. An analogous phenomenon can occur for charged BHs, where the electromagnetic energy of the BH is superradiantly transferred to an interacting charged matter field interacting with the BH.Going back to [1] there has been speculation of how superradiance could be combined with a confining mechanism to force the wave to continuously interact with the BH and hence undergo exponential growth -a so called "black hole bomb." The first nonlinear studies of this process were recently undertaken for a charged scalar field around a charged BH in spherical symmetry, both in a reflective cavity in asymptotically flat space [2], and in the naturally confining environment of an asymptotically Anti-de Sitter domain [3].However, there is an exciting possibility that a variation of this scenario could in fact be realized around astrophysical spinning BHs. Massive bosonic fields with Compton wavelength comparable to, or larger than, the horizon radius of a BH can form bound states around the BH, and if the latter is spinning the bound states can grow from a seed perturbation through superradiance [4][5][6]. This implies that stellar mass BHs can probe the existence of ultralight bosons with masses 10 −10 eV that are weakly coupled to ordinary matter and thus difficult to detect by other

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“…Apart from its theoretical interest, this instability offers an unexpected opportunity for testing the existence of ultralight bosonic particles suggested by beyond the standard model scenarios, e.g., [11]. BHs effectively become particle detectors [12], creating a remarkable synergy between strong gravity, particle physics, and astrophysics, testable by ongoing or future gravitational waves and electromagnetic observations (see, e.g., [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]). …”

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confidence: 99%

Dynamical Formation of Kerr Black Holes with Synchronized Hair: An Analytic Model

Herdeiro

¹

,

Radu

²

2017

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East and Pretorius have successfully evolved, using fully nonlinear numerical simulations, the superradiant instability of the Kerr black hole (BH) triggered by a massive, complex vector field. Evolutions terminate in stationary states of a vector field condensate synchronized with a rotating BH horizon. We show that these end points are fundamental states of Kerr BHs with synchronized Proca hair. Motivated by the "experimental data" from these simulations, we suggest a universal (i.e., field-spin independent), analytic model for the subset of BHs with synchronized hair that possess a quasi-Kerr horizon, applicable in the weak hair regime. Comparing this model with fully nonlinear numerical solutions of BHs with a synchronized scalar or Proca hair, we show that the model is accurate for hairy BHs that may emerge dynamically from superradiance, whose domain we identify.

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“…We focus on the case of a vector field, as it exhibits faster growth than a scalar field. The linear regime of the instability for Proca fields has been studied before in various limits [11,14,[18][19][20]. Here we find numerical solutions of the full Einstein-Proca field equations.…”

Section: Selected For a Viewpoint In Physics P H Y S I C A L R E V Imentioning

confidence: 83%

“…Such particles could form large clouds, spinning down the BH in the process. This is of particular interest now that LIGO has begun observing gravitational waves (GWs) [12], since measurements of BH masses and spins from binary mergers can be used to rule out or provide evidence for such particles, in addition to direct searches for the GW signatures of boson clouds [13,14]. See [15] for a review.…”

mentioning

confidence: 99%

Spinning Black Holes May Grow Hair

Dolan

¹

2017

Physics

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We study the growth and saturation of the superradiant instability of a complex, massive vector (Proca) field as it extracts energy and angular momentum from a spinning black hole, using numerical solutions of the full Einstein-Proca equations. We concentrate on a rapidly spinning black hole (a ¼ 0.99) and the dominant m ¼ 1 azimuthal mode of the Proca field, with real and imaginary components of the field chosen to yield an axisymmetric stress-energy tensor and, hence, spacetime. We find that in excess of 9% of the black hole's mass can be transferred into the field. In all cases studied, the superradiant instability smoothly saturates when the black hole's horizon frequency decreases to match the frequency of the Proca cloud that spontaneously forms around the black hole.

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Black hole superradiance signatures of ultralight vectors

Cited by 259 publications

References 87 publications

Superradiant Instability and Backreaction of Massive Vector Fields around Kerr Black Holes

Superradiant Instability and Backreaction of Massive Vector Fields around Kerr Black Holes

Dynamical Formation of Kerr Black Holes with Synchronized Hair: An Analytic Model

Spinning Black Holes May Grow Hair

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