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 Ergosphere, Photon Region Structure, and the Shadow of a Rotating Charged Weyl Black Hole

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 43
Author(s):  
Mohsen Fathi ◽  
Marco Olivares ◽  
José R. Villanueva
Keyword(s):  
Black Hole ◽  
Electric Charge ◽  
Angular Diameter ◽  
Static Limit ◽  
Rotating Black Hole ◽  
Spin Parameter

In this paper, we explore the photon region and the shadow of the rotating counterpart of a static charged Weyl black hole, which has been previously discussed according to null and time-like geodesics. The rotating black hole shows strong sensitivity to the electric charge and the spin parameter, and its shadow changes from being oblate to being sharp by increasing in the spin parameter. Comparing the calculated vertical angular diameter of the shadow with that of M87*, we found that the latter may possess about 1036 protons as its source of electric charge, if it is a rotating charged Weyl black hole. A complete derivation of the ergosphere and the static limit is also presented.

Bound orbits around modified Hayward black holes

2021 ◽  
Author(s):  
Bo Gao ◽  
Xue-Mei Deng
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Gravitational Field ◽  
Periodic Orbits ◽  
Kerr Black Hole ◽  
Periodic Oscillations ◽  
Test Particles ◽  
Spin Parameter ◽  
Bound Orbits

The neutral time-like particle’s bound orbits around modified Hayward black holes have been investigated. We find that both in the marginally bound orbits (MBO) and the innermost stable circular orbits (ISCO), the test particle’s radius and its angular momentum are all more sensitive to one of the parameters [Formula: see text]. Especially, modified Hayward black holes with [Formula: see text] could mimic the same ISCO radius around the Kerr black hole with the spin parameter up to [Formula: see text]. Small [Formula: see text] could mimic the ISCO of small-spinning test particles around Schwarzschild black holes. Meanwhile, rational (periodic) orbits around modified Hayward black holes have also been studied. The epicyclic frequencies of the quasi-circular motion around modified Hayward black holes are calculated and discussed with respect to the observed Quasi-periodic oscillations (QPOs) frequencies. Our results show that rational orbits around modified Hayward black holes have different values of the energy from the ones of Schwarzschild black holes. The epicyclic frequencies in modified Hayward black holes have different frequencies from Schwarzschild and Kerr ones. These might provide hints for distinguishing modified Hayward black holes from Schwarzschild and Kerr ones by using the dynamics of time-like particles around the strong gravitational field.

scholarly journals Deflection of light by a rotating black hole surrounded by “quintessence”

2020 ◽  
Vol 35 (26) ◽  
pp. 2050155 ◽  
Author(s):  
Prateek Sharma ◽  
Hemwati Nandan ◽  
Radouane Gannouji ◽  
Rashmi Uniyal ◽  
Amare Abebe
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Deflection Angle ◽  
Energy Condition ◽  
Additional Parameter ◽  
Deviation Angle ◽  
Extremal Case ◽  
Rotating Black Hole ◽  
State Formula ◽  
Kerr Space

We present a detailed analysis of a rotating black hole surrounded by “quintessence.” This solution represents a fluid with a constant equation of state, [Formula: see text], which can for example describe an effective warm dark matter fluid around a black hole. We clarify the conditions for the existence of such a solution and study its structure by analyzing the existence of horizons as well as the extremal case. We show that the deflection angle produced by the black hole depends on the parameters [Formula: see text] which need to obey the condition [Formula: see text] because of the weak energy condition, where [Formula: see text] is an additional parameter describing the hair of the black hole. In this context, we found that for [Formula: see text] (consistent with warm dark matter) and [Formula: see text], the deviation angle is larger than that in the Kerr space–time for direct and retrograde orbits. We also derive an exact solution in the case of [Formula: see text].

Cosmic Censorship!: Thermal Transport in a ‘Naked’ Black Hole

2011 ◽  
Vol 312-315 ◽  
pp. 27-32
Author(s):  
R. Leticia Corral Bustamante ◽  
Aarón Raúl Rodríguez-Corral ◽  
T.J Amador-Parra ◽  
E.A. Vázquez-Tapia
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Event Horizon ◽  
Naked Singularity ◽  
Major Axis ◽  
Cosmic Censorship ◽  
Einstein Equations ◽  
Semi Major Axis ◽  
High Entropy ◽  
Apparent Horizons

Cosmic censorship!: black hole wrapped up by its entropy and hidden by its event horizon. In this paper, we postulate a metric to solve the Einstein equations of general relativity, which predicts the thermodynamic behavior of a gigantic mass that collapses to a black hole; taking into account the third law of thermodynamics that states that neither physical process can produce a naked singularity. However, under certain conditions, the model allows to evident violation to the cosmic censorship, exposing the hole nakedness. During the collapse of the hole, quantum effects appear: the area decrease and radiation produced has a high entropy, so that increases total entropy and expose the presence of the hole, while the appearance of the event horizon hide the singularity of the exterior gazes. It is verified that in certain circumstances, the model predicts that the hole mass is bigger than its angular momentum; and in all circumstances, this predicts an hole with enormous superficial graveness that satisfy a relationship of the three parameters that describe the hole (mass, charge and angular momentum); factors all indicative that the singularity is not naked. Then, there are no apparent horizons in accord with cosmic censorship conjecture. Even though the surface gravity of the hole prevents destroying its horizon wrapping singularity, there exists evidence of this singularity by the results of the spin-mass relationship and the escape velocity obtained. The lost information and the slow rate of rotation of the semi-major axis of the mass (dragging space and time around itself as it rotates), agree with Einstein's prediction, show the transport of energy through heat and mass transfer, which were measured by entropy of the hole by means of coordinated semi-spherical that include the different types of intrinsic energy to the process of radiation of the hole event horizon.

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.

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.

scholarly journals Shadow of a Kerr-like black hole

2014 ◽  
Vol 10 (S312) ◽  
pp. 135-136
Author(s):  
Farruh Atamurotov
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Deformation Parameter ◽  
Space Time ◽  
Black Hole Spin ◽  
Spin Parameter ◽  
Kerr Space ◽  
The One

AbstractThe shadow of a Kerr-like black hole has been considered and it was shown that in addition to the specific angular momentum a, deformation parameter of Kerr-like space-time essentially deforms the shape of the black hole shadow. For a given value of the black hole spin parameter a, the presence of a deformation parameter ε reduces the shadow and enlarges its deformation with respect to the one in the Kerr space-time.

Two Mechanisms for Extracting Energy and Angular Momentum from a Rotating Black Hole

2002 ◽  
Vol 34 (5) ◽  
pp. 619-632 ◽  
Author(s):  
Ding-Xiong Wang ◽  
Kan Xiao ◽  
Wei-Hua Lei
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Rotating Black Hole
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