Violations of the weak cosmic censorship conjecture in the higher dimensional f(R) black holes with pressure

He, Kun; Li, Guoping; Hu, Xin-Yun

doi:10.1140/epjc/s10052-020-7669-4

Cited by 27 publications

(10 citation statements)

References 67 publications

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“…To explain the accelerated-inflation problem without of dark energy and dark matter, Buchdahl in 1970 proposed a type of modified gravity theory, namely the f (R) gravity theory [90][91][92][93]. Since then, many efforts have devoted to study the f (R) gravity theories [94][95][96][97][98][99][100][101][102][103]. In 2012, one has obtained a global monopole black hole solution in f (R) theory [94].…”

Section: Introductionmentioning

confidence: 99%

Observational appearances of a f(R) global monopole black hole illuminated by various accretions

2021

Eur. Phys. J. C

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In this paper, we explore three simple models of accretions on a global monopole black hole in f(R) theory, and numerically study the corresponding observational appearances as seen by an observer located at the asymptotic infinity and the certain region out of black hole. For the thin-disk accretion, the results here show that the brighter lensing ring and the darker photon ring that around black hole shadow, always make a small contribution and a negligible contribution to total observed intensity respectively. While, the direct emission of disk contributes a dominant part, and the size of shadow always depends on the disk’s location. For the static and infalling spherical accretions, it turns out that the radiuses of the shadows and photon spheres are always same for both accretions, which implies that the boundary of shadow represents the signature of the spacetime geometry in this case. However, we also find that the brightness of shadow in infalling accretion is darker than that in static case since the Doppler effect is taken into account. In addition, the effect of the global monopole parameter $$\eta $$ η and f(R) parameter $$\psi _0$$ ψ 0 on observational appearances of black hole are clearly emphasized throughout of this paper. Finally, we conclude that black hole shadows and the related rings with some different observable features can be used for us to distinguish black holes from different gravity theories and set the upper limits to the f(R) parameter $$\psi _0$$ ψ 0 .

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Section: Introductionmentioning

confidence: 99%

Observational appearances of a f(R) global monopole black hole illuminated by various accretions

2021

Eur. Phys. J. C

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“…These thought experiments involve perturbations of the black holes with both test particles , and fields [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. There were also attempts to incorporate quantum effects [44][45][46][47][48][49][50], and test the validity of cosmic censorship for asymptotically anti-de Sitter cases [51][52][53][54][55][56][57][58]. The state of the cosmic censorship conjecture has been evaluated in a recent review [59].…”

Section: Introductionmentioning

confidence: 99%

Cosmic censorship, massless fermionic test fields, and absorption probabilities

Düztaş

2021

Eur. Phys. J. C

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In the conventional approach, fermionic test fields lead to a generic overspinning of black holes resulting in the formation of naked singularities. The absorption of the fermionic test fields with arbitrarily low frequencies is allowed for which the contribution to the angular momentum parameter of the space-time diverges. Recently we have suggested a more subtle treatment of the problem considering the fact that only the fraction of the test fields that is absorbed by the black hole contributes to the space-time parameters. Here, we re-consider the interaction of massless spin (1/2) fields with Kerr and Kerr–Newman black holes, adapting this new approach. We show that the drastic divergence problem disappears when one incorporates the absorption probabilities. Still, there exists a range of parameters for the test fields that can lead to overspinning. We employ backreaction effects due to the self-energy of the test fields which fixes the overspinning problem for fields with relatively large amplitudes, and renders it non-generic for smaller amplitudes. This non-generic overspinning appears likely to be fixed by alternative semi-classical and quantum effects.

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“…The effect of quantum tunnelling and particle creation has also been incorporated in Wald type problems [39,40,41,42,43,44,45]. In recent years, the possibility to destroy the event horizon in the asymptotically anti-de Sitter cases has also become an active field of research [46,47,48,49,50,51,52]. ( For a recent review see [53])…”

Section: Introductionmentioning

confidence: 99%

The variational method, backreactions, and the absorption probability in Wald type problems

Düztaş

2021

Preprint

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We argue that the variational method in Wald type thought experiments, involves order of magnitude problems when one imposes the fact that δM is inherently a first order quantity itself. One observes that the contribution of the second order perturbations is actually of the fourth order. Therefore backreactions have to be explicitly calculated. Here, we re-consider the overspinning problem for Kerr-Newman black holes interacting with test fields. We calculate the backreaction effects due to the induced increase in the angular velocity of the event horizon, which brings a partial solution to the overspinning problem. To bring an ultimate solution, we argue that the absorption probability should be taken into account in Wald type problems where black holes interact with test fields. This fundamentally alters the course of the analysis of the thought experiments. Due to the fact that a small fraction of the challenging modes is absorbed by the black holes, overspinning is prevented for both nearly extremal and extremal cases. Some extreme cases are easily fixed by backreaction effects. The arguments do not apply to the generic overspinning by fermionic fields for which the absorption probability is positive definite.

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Violations of the weak cosmic censorship conjecture in the higher dimensional f(R) black holes with pressure

Cited by 27 publications

References 67 publications

Observational appearances of a f(R) global monopole black hole illuminated by various accretions

Observational appearances of a f(R) global monopole black hole illuminated by various accretions

Cosmic censorship, massless fermionic test fields, and absorption probabilities

The variational method, backreactions, and the absorption probability in Wald type problems

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