scholarly journals Bumblebee gravity with a Kerr–Sen like solution and its Shadow

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Sohan Kumar Jha ◽  
Anisur Rahaman
Keyword(s):  
Black Hole ◽  
Emission Rate ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Field Vector ◽  
Axially Symmetric ◽  
System A ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole ◽  
Careful Investigation

AbstractWe have considered the bumblebee gravity model where lorentz-violating (LV) scenario gets involved through a bumblebee field vector field $$B_\mu $$ B μ . A spontaneous symmetry breaking allows the field to acquires a vacuum expectation value that generates LV into the system. A Kerr–Sen-like solution has been found out starting from the generalized form of a radiating stationery axially symmetric black hole metric. We compute the effective potential offered by the null geodesics in the bumblebee rotating black hole spacetime. The shadow has been sketched for different variations of the parameters involved in the system. A careful investigation has been carried out to study how the shadow gets affected when Lorentz violation enters into the picture. The emission rate of radiation has also been studied and how it varies with the LV parameter $$\ell $$ ℓ is studied scrupulously.

scholarly journals Blandford-Znajek mechanism in the general stationary axially-symmetric black-hole spacetime

2021 ◽  
Vol 2021 (12) ◽  
pp. 002
Author(s):  
R.A. Konoplya ◽  
J. Kunz ◽  
A. Zhidenko
Keyword(s):  
Black Hole ◽  
Deformation Parameter ◽  
Rotation Parameter ◽  
Energy Extraction ◽  
Axially Symmetric ◽  
Asymptotically Flat ◽  
Kerr Spacetime ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole ◽  
The Magnetic Field

Abstract We consider the Blandford-Znajek process of electromagnetic extraction of energy from a general axially symmetric asymptotically flat slowly rotating black hole. Using the general parametrization of the black-hole spacetime we construct formulas for the flux of the magnetic field and the rate of energy extraction, which are valid not only for the Kerr spacetime, but also for its arbitrary axially symmetric deformations. We show that in the dominant order these quantities depend only on a single deformation parameter, which relates the spin frequency of a black hole with its rotation parameter.

scholarly journals High-energy collision of particles in the magnetic field far from black holes

2014 ◽  
Vol 29 (29) ◽  
pp. 1450151
Author(s):  
O. B. Zaslavskii
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Center Of Mass ◽  
High Energy ◽  
Axially Symmetric ◽  
High Energy Collision ◽  
Mass Frame ◽  
Symmetric Black Hole ◽  
Rotating Star ◽  
The Magnetic Field

We consider collision of two particles in the axially symmetric black hole metric in the magnetic field. If the value of the angular momentum |L| of one particles grows unbound (but its Killing energy remains fixed) one can achieve unbound energy in the center-of-mass frame E c.m. In the absence of the magnetic field, collision of this kind is known to happen in the ergoregion. However, if the magnetic field strength B is also large, with the ratio |L|/B being finite, large E c.m. can be achieved even far from a black hole, in the almost flat region. Such an effect also occurs in the metric of a rotating star.

scholarly journals Connection between Sinc Approximation for High-Energy Absorption Cross Section and Shadow of Black Holes

2021 ◽  
Author(s):  
Ali Övgün
Keyword(s):  
Black Hole ◽  
Energy Absorption ◽  
Cross Section ◽  
Absorption Cross Section ◽  
High Energy ◽  
Absorption Cross ◽  
Sinc Approximation ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole ◽  
High Energy Absorption

This letter aims to show the connection between the sinc approximation for high-energy absorption cross section and the shadow radius of the spherically symmetric black hole. This connection can give a physical interpretation of the absorption cross section in the eikonal limit parameters. Moreover, the use of this alternative way, one can extract its shadow radius from the absorption cross section in high energy limits to gain more information about the black hole spacetime. Our results indicate that the increasing the value of the shadow radius of the black hole, exponentially increase the the absorption cross section of the black hole in high-energy limits which can be captured by the Event Horizon Telescope (EHT) collaboration.

scholarly journals Two mass conjectures on axially symmetric black hole-disk systems

2019 ◽  
Vol 99 (2) ◽  
Author(s):  
Wojciech Kulczycki ◽  
Patryk Mach ◽  
Edward Malec
Keyword(s):  
Black Hole ◽  
Axially Symmetric ◽  
Symmetric Black Hole

scholarly journals Quasi-normal modes of near-extremal black holes in generalized spherically symmetric spacetime and strong cosmic censorship conjecture

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
Piyabut Burikham ◽  
Supakchai Ponglertsakul ◽  
Taum Wuthicharn
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Normal Modes ◽  
Cosmic Censorship ◽  
Analytic Formula ◽  
Spherically Symmetric ◽  
Black Hole Background ◽  
Strong Cosmic Censorship ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole

AbstractA number of near-extremal conditions are utilized to simplify the equation of motion of the neutral scalar perturbations in generalized spherically symmetric black hole background into a differential equation with the Pöschl–Teller potential. An analytic formula for quasinormal frequencies is obtained. The analytic formula is then used to investigate strong cosmic censorship conjectures (SCC) of the generalized black hole spacetime for the smooth initial data. The Christodoulou version of the SCC is found to be violated for certain regions of the black hole parameter space including the black holes in general relativity while the $$C^{1}$$ C 1 version of the SCC is always valid.

scholarly journals Embedding into flat spacetime and black hole thermodynamics

2019 ◽  
Vol 35 (05) ◽  
pp. 2050013 ◽  
Author(s):  
T. R. Govindarajan ◽  
Sumanta Chakraborty
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Thermodynamic Description ◽  
Scaling Law ◽  
Black Hole Entropy ◽  
Flat Spacetime ◽  
Higher Dimensional ◽  
Black Hole Spacetime ◽  
Symmetric Black Hole ◽  
Black Hole Temperature

It is known that static and spherically symmetric black hole solutions of general relativity in different spacetimes can be embedded into higher-dimensional flat spacetime. Given this result, we have explored the thermodynamic nature of black holes á la its embedding into flat spacetime. In particular, we have explicitly demonstrated that black hole temperature can indeed be determined starting from the embedding and hence mapping of the static observers in black hole spacetime to Rindler observers in flat spacetime. Furthermore, by considering the dynamics of a scalar field in the flat spacetime, it is indeed possible to arrive at the area scaling law for black hole entropy. Thus, by using the flat spacetime field theory, one can indeed provide a thermodynamic description of black holes. Implications are also discussed.

scholarly journals Charged fermions tunneling from stationary axially symmetric black holes with generalized uncertainty principle

2019 ◽  
Vol 34 (23) ◽  
pp. 1950184 ◽  
Author(s):  
Muhammad Rizwan ◽  
Muhammad Zubair Ali ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Uncertainty Principle ◽  
Emission Rate ◽  
Generalized Uncertainty Principle ◽  
Axially Symmetric ◽  
Black String ◽  
Fermions Tunneling ◽  
Newman Black Hole ◽  
Kaluza Klein

In this paper, we study the tunneling of charged fermions from the stationary axially symmetric black holes using the generalized uncertainty principle (GUP) via Wentzel, Kramers, and Brillouin (WKB) method. The emission rate of the charged fermions and corresponding modified Hawking temperature of Kerr–Newman black hole, Einstein–Maxwell-dilaton-axion (EMDA) black hole, Kaluza–Klein dilaton black hole, and then, charged rotating black string are obtained and we show that the corrected thermal spectrum is not purely thermal because of the minimal scale length which cause the black hole’s remnant.

scholarly journals Can shadows reflect phase structures of black holes?

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Ming Zhang ◽  
Minyong Guo
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Phase Structure ◽  
Black Hole Thermodynamics ◽  
Spherically Symmetric ◽  
Axially Symmetric ◽  
Phase Structures ◽  
Correct Information ◽  
Symmetric Black Hole

Abstract The relation between the black hole shadow and the black hole thermodynamics is investigated. We find that the phase structure can be reflected by the shadow radius for the spherically symmetric black hole. We also find that the shadow size gives correct information but the distortion of the shadow gives wrong information of the phase structure for the axially symmetric black hole.

Global symmetries and Noether’s theorem

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Global Symmetries ◽  
Symmetry Transformation ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
Quantum Field ◽  
Expectation Value ◽  
Minkowski Space Time ◽  
Integral Measure ◽  
Colour Charge ◽  
Internal Symmetries

Noethers theorem shows that continuous global symmetries lead classically to conservation laws. Such symmetries can be divided into spacetime and internal symmetries. The invariance of Minkowski space-time under global Poincaré transformations leads to the conservation of the four-momentum and the total angular momentum. Examples for conserved charges due to internal symmetries are electric and colour charge. The vacuum expectation value of a Noether current is shown to beconserved in a quantum field theory if the symmetry transformation keeps the path-integral measure invariant.

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