On embeddings of the Kerr geometry

1981 ◽  
Vol 59 (5) ◽  
pp. 688-692 ◽  
Author(s):  
Nigel A. Sharp
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Equatorial Plane ◽  
Kerr Metric ◽  
Intrinsic Structure ◽  
Kerr Geometry ◽  
Rotating Black Hole ◽  
Isometric Embeddings

The use of isometric embeddings of curved geometries reveals their intrinsic structure in a way that is readily appreciated. This is done for 3 two-surfaces sliced from the Kerr metric which describes a rotating black hole: the equatorial plane, the event horizon, and the ergosurface.

Shadow from a rotating black hole in an extended gravity

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040060
Author(s):  
Vjacheslav Prokopov ◽  
Stanislav Alexeyev
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Rotating Black Hole ◽  
Extended Gravity ◽  
Extended Theories Of Gravity ◽  
Theories Of Gravity ◽  
Extended Theories

We focus on the consequences of that the Event Horizon Telescope obtained images of the black hole shadow in the center of the M87 galaxy. We show that to test extended theories of gravity the improving of the resolution by 3 orders is necessary. In addition it is demonstrated that the rotation distorts the shape of the shadow and corrections from the extended gravity may affect on this distortion.

scholarly journals Quantum-Gravitational Trans-Planckian Energy of a Time-Dependent Black Hole

Symmetry ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1303
Author(s):  
A. J. Nurmagambetov ◽  
I. Y. Park
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Black Hole Solution ◽  
Energy Analysis ◽  
Scaling Behavior ◽  
Time Dependent ◽  
Higgs Potential ◽  
Rotating Black Hole ◽  
Basic Features

We continue our recent endeavor in which a time-dependent black hole solution of a one-loop quantum-corrected Einstein-scalar system was obtained and its near-horizon behavior was analyzed. The energy analysis led to a trans-Planckian scaling behavior near the event horizon. In the present work, the analysis is extended to a rotating black hole solution of an Einstein–Maxwell-scalar system with a Higgs potential. Although the analysis becomes much more complex compared to that of the previous, we observe the same basic features, including the quantum-gravitational trans-Planckian energy near the horizon.

scholarly journals Estimate of the superradiance spectrum in dispersive media

2020 ◽  
Vol 378 (2177) ◽  
pp. 20190236 ◽  
Author(s):  
Theo Torres
Keyword(s):  
Black Hole ◽  
Reflection Coefficient ◽  
Event Horizon ◽  
Vortex Flow ◽  
Theoretical Description ◽  
Dispersive Media ◽  
Next Generation ◽  
Rotating Black Hole ◽  
Analogue Gravity ◽  
The Many

In 2016, the Nottingham group detected the rotational superradiance effect. While this experiment demonstrated the robustness of the superradiance process, it still lacks a complete theoretical description due to the many effects at stage in the experiment. In this paper, we shine new light on this experiment by deriving an estimate of the reflection coefficient in the dispersive regime by means of a Wentzel–Kramers–Brillouin analysis. This estimate is used to evaluate the reflection coefficient spectrum of counter-rotating modes in the Nottingham experiment. Our finding suggests that the vortex flow in the superradiance experiment was not purely absorbing, contrary to the event horizon of a rotating black hole. While this result increases the gap between this experimental vortex flow and a rotating black hole, it is argued that it is in fact this gap that is the source of novel ideas. This article is part of a discussion meeting issue ‘The next generation of analogue gravity experiments’.

Extremal Kerr Black Holes, Naked Singularity & Wormholes

2020 ◽  
Author(s):  
Deep Bhattacharjee
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Angular Momentum ◽  
Event Horizon ◽  
Kerr Black Hole ◽  
Naked Singularity ◽  
Kerr Metric ◽  
Spin Angular Momentum ◽  
The Way

This paper is totally based on the mathematical physics of the Black holes. In Einstein’s theory of “General Relativity”, Schwarzschild solution is the vacuum solutions of the Einstein Field Equations that describes the gravity potential from outside the body of a spherically symmetric object having zero charge, zero mass and zero cosmological constant[1]. It was discovered by Karl Schwarzschild in 1916, a little more than a month after the publication of the famous GR and the singularity is a point singularity which can be best described as a coordinate singularity rather than a real singularity, however, the drawback of this theory is that it fails to take into account the real life scenario of black holes with charge and spin angular momentum. The black hole is based on event horizon and Schwarzschild radius. However, Physicists were trying to develop a metric for the real life scenario of a black hole with a spin angular momen-tum and ultimately the exact solution of a charged rotating black hole had been discovered by Roy Kerr in 1965 as the Kerr-Newman metric[2][3]. The Kerr metric is one of the toughest metric in physics and is the extensional generalization to a rotating body of the Schwarzschild metric. The metric describes the vacuum geometry of space-time around a rotating axially-symmetric black hole with a quasipotential event horizon. In Kerr metric there are two event hori-zons (inner and outer), two ergospheres and an ergosurface. The most important effect of the Kerr metric is the frame dragging (also known as Lense-Thirring Precession) is a distinctive prediction of General relativity. The first direct observation of the collision of two Kerr Black Holes has been discovered by LIGO in 2016 hence setting up a milestone of General Relativity in the history of Physics. Here, the Kerr metric has been introduced in the Boyer-Lindquist forms and it is derived from the Schwarzschild metric using the Spin-Coefficient formalism. According to the “Cosmic Censorship Hypothesis”, a naked singularity cannot exist in nature as nature always hides the singularity via an event horizon. However, in this paper I will prove the existence of the “Naked Singularity" 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. I will not go in detail about the contradiction of ‘Chronology Protection Conjecture” [4]whether the Stress-Energy-Momentum Tensor can violate the ANEC (Average Null Energy Conditions) or not with the values of less than zero or greater than, equal to zero, instead I will focus definitely on the creation of the mathematical formulation of a wormhole from a Naked Ring Kerr Singularity of a Kerr Black Hole without any event horizon or ergosphere. Another important thing to mention in this paper is that I have taken the time to be imaginary[5] as because, a singularity being an eternal point of time can only be smoothen out if the time is imaginary rather than real which will allow the particle or null rays inside a wormhole to cross the singularity and making entrance to the other universe. The final conclusion would be to determine the mass-energy equivalence principle as spin angular momentum increases with a decrease in BH mass due to the vanishing event horizon and ergosphere thereby maintaining the equivalence via apparent and absolute masses in relation to spin J along the orthogonal Z axis. A ‘NAKED SINGULARITY’ alters every parameters of a BH and to include this parameters along with affine spin coefficient, it has been proved that without any spin angular momentum the generation of wormhole and vanishing of event horizon and singularity is not possible.

WIGGLY STRING SOLUTIONS IN KERR–NEWMAN BLACK HOLE

2011 ◽  
Vol 26 (16) ◽  
pp. 1221-1230 ◽  
Author(s):  
HIROMI SUZUKI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equatorial Plane ◽  
Circular Orbit ◽  
Axially Symmetric ◽  
Rotating Black Hole ◽  
Open Strings ◽  
Newman Black Hole ◽  
Kerr Black Holes

Previously we investigated the cosmic wiggly strings in (3+1)-dimensional Schwarzschild, Reissner–Nordström and Kerr black holes. As an extension, the solutions in (3+1)-dimensional axially symmetric charged rotating black hole are investigated. The solution for the wiggly string exhibits open strings lying along the circular orbit in the equatorial plane outside horizon.

scholarly journals Quantum-Gravitational Trans-Planckian Energy of a Time-Dependent Black Hole

2019 ◽  
Author(s):  
A. J. Nurmagambetov ◽  
I. Y. Park
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Black Hole Solution ◽  
Energy Analysis ◽  
Scaling Behavior ◽  
Time Dependent ◽  
Higgs Potential ◽  
Rotating Black Hole ◽  
Basic Features

We continue our recent endeavor in which a time-dependent black hole solution of a one-loop quantum-corrected Einstein-scalar system was obtained and its near-horizon behavior was analyzed. The energy analysis led to a trans-Planckian scaling behavior near the event horizon. In the present work the analysis is extended to a rotating black hole solution of an Einstein-Maxwell-scalar system with a Higgs potential. Although the analysis becomes much more complex compared to that of the previous, we observe the same basic features, including the quantum-gravitational trans-Planckian energy near the horizon.

scholarly journals TESTING THE KERR BLACK HOLE HYPOTHESIS

2011 ◽  
Vol 26 (33) ◽  
pp. 2453-2468 ◽  
Author(s):  
COSIMO BAMBI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Gravitational Collapse ◽  
State Of The Art ◽  
Kerr Black Hole ◽  
The State ◽  
Kerr Geometry

It is thought that the final product of the gravitational collapse is a Kerr black hole and astronomers have discovered several good astrophysical candidates. While there are some indirect evidences suggesting that the latter have an event horizon, and therefore that they are black holes, a proof that the spacetime around these objects is described by the Kerr geometry is still lacking. Recently, there has been an increasing interest in the possibility of testing the Kerr black hole hypothesis with present and future experiments. In this paper, I briefly review the state-of-the-art of the field, focusing on some recent results and works in progress.

scholarly journals Testing Kerr black hole mimickers with quasi-periodic oscillations from GRO J1655-40

2021 ◽  
Vol 81 (11) ◽  
Author(s):  
Xin Jiang ◽  
Peng Wang ◽  
Haitang Yang ◽  
Houwen Wu
Keyword(s):  
Black Hole ◽  
Kerr Black Hole ◽  
Compact Object ◽  
Kerr Metric ◽  
Observation Data ◽  
Periodic Oscillations ◽  
Regular Black Hole ◽  
Rotating Black Hole ◽  
Traversable Wormholes ◽  
Limiting Case

AbstractThe measurements of quasi-periodic oscillations (QPOs) provide a quite powerful tool to test the nature of astrophysical black hole candidates in the strong gravitational field regime. In this paper, we use QPOs within the relativistic precession model to test a recently proposed family of rotating black hole mimickers, which reduce to the Kerr metric in a limiting case, and can represent traversable wormholes or regular black holes with one or two horizons, depending on the values of the parameters. In particular, assuming that the compact object of GRO J1655-40 is described by a rotating black hole mimicker, we perform a $$\chi $$ χ -square analysis to fit the parameters of the mimicker with two sets of observed QPO frequencies from GRO J1655-40. Our results indicate that although the metric around the compact object of GRO J1655-40 is consistent with the Kerr metric, a regular black hole with one horizon is favored by the observation data of GRO J1655-40.

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