Quantum fields as Cosmic Censors in (2 + 1)-dimensions

2018 ◽  
Vol 27 (11) ◽  
pp. 1843011 ◽  
Author(s):  
Marc Casals ◽  
Alessandro Fabbri ◽  
Cristián Martínez ◽  
Jorge Zanelli
Keyword(s):  
Black Hole ◽  
Naked Singularity ◽  
Quantum Effects ◽  
Conical Singularity ◽  
Cauchy Horizon ◽  
Quantum Fields ◽  
Rotating Black Hole ◽  
Scalar Quantum ◽  
Do So ◽  
Classical Background

We discuss the effect of quantum fields on classical background spacetimes which contain timelike singularities. We do so for the case that the background is a [Formula: see text]-dimensional BTZ spacetime, whether corresponding to a rotating black hole ([Formula: see text]) or to a naked conical singularity ([Formula: see text]). In the black hole case, scalar quantum fields render its Cauchy horizon unstable, while for the conical geometry, they produce a horizon around the naked singularity. Thus, quantum effects improve the predictability of the spacetime acting as effective Cosmic Censors.

Observing the contour profile of a Kerr–Sen black hole

2018 ◽  
Vol 33 (17) ◽  
pp. 1850099 ◽  
Author(s):  
X. G. Lan ◽  
J. Pu
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Naked Singularity ◽  
Extremal Case ◽  
Distortion Parameter ◽  
Rotating Black Hole ◽  
Dark Zone ◽  
Spin Parameter ◽  
The Mean ◽  
In The Beginning

In this paper, the shadow and the corresponding naked singularity cast by a Kerr–Sen black hole are studied. It is found that the shadow of a rotating black hole would be a dark zone surrounded by a deformed circle, and the shadow is distorted more away from a circle when the black hole approaches the extremal case. Besides, it is shown that the mean radius of the shadow decreases and distortion parameter increases with the increasing of charge, respectively. However, the mean radius and the distortion parameter vary complicatedly with the change of spin parameter. In the beginning, both observables decrease rapidly with the increasing of specific angular momentum, nevertheless, they increase slightly in the latter part. These results show that there would be a significant effect of the spin on the shadows, which would be of great importance for probing the nature of the black hole.

scholarly journals INSTABILITIES IN KERR SPACETIMES

2011 ◽  
Vol 20 (supp01) ◽  
pp. 27-31 ◽  
Author(s):  
GUSTAVO DOTTI ◽  
REINALDO J. GLEISER ◽  
IGNACIO F. RANEA-SANDOVAL
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Infinite Family ◽  
Dirac Field ◽  
Cauchy Horizon ◽  
Kerr Spacetime ◽  
Gravitational Perturbations ◽  
Black Hole Interior ◽  
The Stability ◽  
Do So

We present a generalization of previous results regarding the stability under gravitational perturbations of nakedly singular super extreme Kerr spacetime and Kerr black hole interior beyond the Cauchy horizon. To do so we study solutions to the radial and angular Teukolsky's equations with different spin weights, particulary s = ±1 representing electromagnetic perturbations, s = ±1/2 representing a perturbation by a Dirac field and s = 0 representing perturbations by a scalar field. By analizing the properties of radial and angular eigenvalues we prove the existence of an infinite family of unstable modes.

scholarly journals Solutions of Kerr Black Holes subject to Naked Singularity and Wormholes

2020 ◽  
Author(s):  
Deep Bhattacharjee
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Kerr Black Hole ◽  
Naked Singularity ◽  
The Other ◽  
Cauchy Horizon ◽  
White Hole ◽  
Kerr Black Holes ◽  
The Way

The existence of the “Naked Singularity" has been shown taking the advantage of the Ring Singularity of the Kerr Black Hole and thereby making the way to manipulate the mathematics by taking the larger root of Δ as zero and thereby vanishing the ergosphere and event horizon making the way for the naked ring singularity which can be easily connected via a cylindrical wormhole and as ‘a wormhole is a black hole without an event horizon’ therefore, this cylindrical connection paved the way for the Einstein-Rosen Bridge allowing particles or null rays to travel from one universe to another ending up in a future directed Cauchy horizon while changing constantly from spatial to temporal and again spatial paving the entrance to another Kerr Black hole (which would act as a white hole) in the other universes.

scholarly journals Dynamics of the nonrotating and rotating black hole scalarization

2021 ◽  
Vol 103 (6) ◽  
Author(s):  
Daniela D. Doneva ◽  
Stoytcho S. Yazadjiev
Keyword(s):  
Black Hole ◽  
Rotating Black Hole

scholarly journals Black hole S-matrix for a scalar field

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Panos Betzios ◽  
Nava Gaddam ◽  
Olga Papadoulaki
Keyword(s):  
Black Hole ◽  
Normal Modes ◽  
Massless Scalar ◽  
Scattering Process ◽  
Schwarzschild Black Hole ◽  
Asymptotically Flat ◽  
Scalar Particles ◽  
Black Hole Background ◽  
S Matrix ◽  
Do So

Abstract We describe a unitary scattering process, as observed from spatial infinity, of massless scalar particles on an asymptotically flat Schwarzschild black hole background. In order to do so, we split the problem in two different regimes governing the dynamics of the scattering process. The first describes the evolution of the modes in the region away from the horizon and can be analysed in terms of the effective Regge-Wheeler potential. In the near horizon region, where the Regge-Wheeler potential becomes insignificant, the WKB geometric optics approximation of Hawking’s is replaced by the near-horizon gravitational scattering matrix that captures non-perturbative soft graviton exchanges near the horizon. We perform an appropriate matching for the scattering solutions of these two dynamical problems and compute the resulting Bogoliubov relations, that combines both dynamics. This allows us to formulate an S-matrix for the scattering process that is manifestly unitary. We discuss the analogue of the (quasi)-normal modes in this setup and the emergence of gravitational echoes that follow an original burst of radiation as the excited black hole relaxes to equilibrium.

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