Superradiant instability of Kerr-de Sitter black holes in scalar-tensor theory

Zhang, Cheng-Yong; Zhang, Shaojun; Wang, Bin

doi:10.1007/jhep08(2014)011

Cited by 39 publications

(17 citation statements)

References 67 publications

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“…One is suggested to refer to the comprehensive review [7] to overlook the whole picture. Therein, superradiance from black holes in alternative theories of gravity has been studied only in a few cases [10][11][12][13][14][15]. Whether superradiance can be stronger in modified theories of gravity still remains a open question [7].…”

Section: Jhep08(2020)105mentioning

confidence: 99%

Superradiance and stability of the regularized 4D charged Einstein-Gauss-Bonnet black hole

Zhang

et al. 2020

J. High Energ. Phys.

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We investigated the superradiance and stability of the regularized 4D charged Einstein-Gauss-Bonnet black hole which is recently inspired by Glavan and Lin [Phys. Rev. Lett. 124, 081301 (2020)]. We found that the positive Gauss-Bonnet coupling constant α enhances the superradiance, while the negative α suppresses it. The condition for superradiant instability is proved. We also worked out the quasinormal modes (QNMs) of the charged Einstein-Gauss-Bonnet black hole and found that the real part of all the QNMs does not satisfy the superradiance condition and the imaginary parts are all negative. Therefore this black hole is stable. When α makes the black hole extremal, there are normal modes.

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Section: Jhep08(2020)105mentioning

confidence: 99%

Superradiance and stability of the regularized 4D charged Einstein-Gauss-Bonnet black hole

Zhang

et al. 2020

J. High Energ. Phys.

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“…Several new things could be investigated as follow up works. For example, a systematic analysis of the superradiance for various spin fields (see [24,25,26,27,28] for scalar) in KdS and evaluating their profile in various extremal limits would be highly interesting. Also, it seems very important to establish a topological version of the generalized area theorem for de Sitter black holes, analogous to that of the asymptotic flat spacetimes e.g.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, superradiance has been studied for the anti-de Sitter black hole spacetimes [20,21,22,23], including nonlinear backreaction effects [22]. For de Sitter black holes on the other hand, which is our focus, we refer our reader to [24,25,26,27,28]. The condition for energy extraction for such black holes is given by (ω − λΩ C ) > 0 where Ω C is the angular speed on the cosmological event horizon, along with the usual (ω −λΩ H ) < 0.…”

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confidence: 99%

Kerr-de Sitter spacetime, Penrose process, and the generalized area theorem

Bhattacharya

2018

Phys. Rev. D

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We investigate various aspects of energy extraction via the Penrose process in the Kerr-de Sitter spacetime. We show that the increase in the value of a positive cosmological constant, Λ, always reduces the efficiency of this process. The Kerr-de Sitter spacetime has two ergospheres -associated with the black hole and the cosmological event horizons. We prove by analysing turning points of the trajectory that the Penrose process in the cosmological ergoregion is never possible. We next show that in this process both black hole and cosmological event horizons' areas increase, the later becomes possible when the particle coming from the black hole ergoregion escapes through the cosmological event horizon. We identify a new, local mass function instead of the mass parameter, to prove this generalized area theorem. This mass function takes care of the local spacetime energy due to the cosmological constant as well, including that arises due to the frame dragging effect due to spacetime rotation. While the current observed value of Λ is much tiny, its effect in this process could be considerable in the early universe scenario endowed with a rather high value of it, where the two horizons could have comparable sizes. In particular, the various results we obtain here are also evaluated in a triply degenerate limit of the Kerr-de Sitter spacetime we find, in which radial values of the inner, the black hole and the cosmological event horizons are nearly coincident.The existence of such negative energy particles gives rise to a classical mechanism for energy extraction from a black hole, namely the Penrose process, as follows [1,2,3], also references therein. Let a particle carrying positive energy enters the ergoregion of a Kerr black hole. We imagine that it breaks into two pieces there -one carrying negative energy and the other, positive. The negative energy particle enters the BEH and the positive energy particle, after reaching a turning point, comes out of the ergosphere and finally gets intercepted by an outside observer. With respect to such an observer the usual (positive) energy conservation must be valid. Thus it is clear that the ejecta will carry more energy than the initial incoming particle, effectively extracting energy from the black hole. It turns out that the energy thus extracted is largely rotational and the process can only continue until the black hole settles down into the Schwarzschild spacetime, where no ergosphere is present.Since the Penrose process reduces more the rotation of a black hole than its mass, a Kerr black hole can never become a naked curvature singularity under this process, see [4] for a formal proof of this. In [5], it was proved that the black hole horizon area must increase under this process, thereby providing evidence in favour of the second law of black hole mechanics. We further refer our reader to [6,7] for various inequalities (respectively, the Wald and the Bardeen-Press-Teukolsky inequality) regarding the local speed of the fragments within the ergoregion. In order tha...

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“…In fact, the non-smoothness is not occasional for gravitational systems. For example, let us consider a spherically symmetric black hole endowed with a spherical thin-shell located at some radius [26,27]. Then a junction condition must be imposed, in which the physical quantities such as the mass function is continuous but not analytical at the critical radius.…”

Section: Rn-ds Black Holementioning

confidence: 99%

The fate of instability of de Sitter black holes at large D

Li¹,

Zhang²,

Chen³

2019

J. High Energ. Phys.

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We study non-linearly the gravitational instabilities of the Reissner-Nordstrom-de Sitter and the Gauss-Bonnet-de Sitter black holes by using the large D expansion method. In both cases, the thresholds of the instability are found to be consistent with the linear analysis, and on the thresholds the evolutions of the black holes under the perturbations settle down to stationary lumpy solutions. However, the solutions in the unstable region are highly time-dependent, and resemble the fully localized black spots and black ring with S D−2 and S 1 × S D−3 topologies, respectively. Our study indicates the possible transition between the lumpy black holes and the localized black holes in higher dimensions. * One important aspect of a black hole is its stability under gravitational perturbations. In contrast to the D = 4 case, the black holes in higher dimensions can have various topologies and could be unstable under gravitational perturbations. This was first illustrated by Gregory and Laflamme (GL) for the black strings (branes) [1]. Since then, a lot of black objects with distinct topologies in higher dimensions have been discovered, and similar instabilities have been demonstrated [2-4]. Compared with the linear dynamics, determining the final state of the unstable black objects is more intriguing, as which may lead to violation of the Weak Cosmic Censorship and topology-changing transitions of black hole horizons. A well-known example is the non-linear evolution of the GL instability of the five dimensional black string [5]. Recently, a new type of dynamical instability was discovered for the higher dimensional Reissner-Nordstrom-de Sitter (RN-dS) and Gauss-Bonnet-de Sitter (GB-dS) black holes [6-8]. The RN-dS black hole becomes gravitationally unstable for large values of the electric charge and cosmological constant. The GB-dS black hole is unstable as well when the cosmological constant is sufficiently large. In both cases the instability is triggered by a positive cosmological constant.Such instability is called "Λ instability". One interesting feature of the "Λ instability" is that such instability only happens with an electromagnetic field or a GB term. Moreover, it was noticed that at the threshold point of the instability the shape of the RN-dS black hole is slightly deformed.This fact suggests that the unstable RN-dS black hole could either split into two black holes or transform into a black ring. However, due to the limitation of the linear analysis, the final stage of the evolution of the unstable black holes has not been settled yet, though some non-linear efforts have been made from the viewpoint of gravitational collapse [9].The goal of this work is to better understand the "Λ instability" of the two kinds of black holes by using the large D expansion method [10]. Taking the large dimension limit, the non-trivial dynamics of black holes is localized at the near region of the horizon, such that a full non-linear effective theory can be formulated [11][12][13][14][15][16][17][18][19][20]. The large D s...

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Superradiant instability of Kerr-de Sitter black holes in scalar-tensor theory

Cited by 39 publications

References 67 publications

Superradiance and stability of the regularized 4D charged Einstein-Gauss-Bonnet black hole

Superradiance and stability of the regularized 4D charged Einstein-Gauss-Bonnet black hole

Kerr-de Sitter spacetime, Penrose process, and the generalized area theorem

The fate of instability of de Sitter black holes at large D

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