MULTI-BLACK HOLES SOLUTION WITH COSMIC STRINGS

2004 ◽  
Vol 19 (10) ◽  
pp. 1549-1557 ◽  
Author(s):  
F. ÖZDEMIR ◽  
N. ÖZDEMIR ◽  
B. T. KAYNAK
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Cosmic String ◽  
Circular Orbit ◽  
Cosmic Strings ◽  
De Sitter ◽  
Circular Orbits ◽  
Small Oscillations ◽  
String Models

Some black hole-cosmic string models such as Reissner–Nordström, RN–de Sitter, Kerr–Newman and multi-black holes with cosmic string are given. Energy and angular momentum of a timelike particle in circular orbits in multi-black hole space–time are calculated. The geodesic equations for the timelike particles for the far region of the multi-black hole sources are calculated and small oscillations around the circular orbit obtained. It is seen that the particle's orbit precesses like the Lens–Thirring effect.

scholarly journals Polarimetric signatures of the photon ring of a black hole that is pierced by a cosmic axion string

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Alexander Gußmann
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Formation Mechanism ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Supermassive Black Holes ◽  
Rotating Black Hole ◽  
Aharonov Bohm ◽  
Polarized Photons

Abstract A black hole image contains a bright ring of photons that have closely circled the black hole on their way from the source to the detector. Here, we study the photon ring of a rotating black hole which is pierced by a global hyper-light axion-type cosmic string. We show that the coupling 𝜙F$$ \overset{\sim }{F} $$ F ~ between the axion 𝜙 and the photon can give rise to a unique polarimetric structure of the photon ring. The structure emerges due to an Aharonov-Bohm type effect that leads to a change of the polarization directions of linear polarized photons when they circle the black hole. For several parameter choices, we determine concrete polarization patterns in the ring. Measuring these patterns can provide us with a way of determining the value of the coefficient of the mixed anomaly between electromagnetism and the symmetry that gave rise to the cosmic string. Finally, we briefly review a possible formation mechanism of black holes that are pierced by cosmic strings and discuss under which conditions we can expect such objects to be present as supermassive black holes in the center of galaxies.

scholarly journals Photon Spheres, ISCOs, and OSCOs: Astrophysical Observables for Regular Black Holes with Asymptotically Minkowski Cores

Universe ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 2
Author(s):  
Thomas Berry ◽  
Alex Simpson ◽  
Matt Visser
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Circular Orbit ◽  
Schwarzschild Black Hole ◽  
Circular Orbits ◽  
Regular Black Hole ◽  
Astrophysical Interest ◽  
Regular Black Holes ◽  
Recent Advances ◽  
Classical Black Holes

Classical black holes contain a singularity at their core. This has prompted various researchers to propose a multitude of modified spacetimes that mimic the physically observable characteristics of classical black holes as best as possible, but that crucially do not contain singularities at their cores. Due to recent advances in near-horizon astronomy, the ability to observationally distinguish between a classical black hole and a potential black hole mimicker is becoming increasingly feasible. Herein, we calculate some physically observable quantities for a recently proposed regular black hole with an asymptotically Minkowski core—the radius of the photon sphere and the extremal stable timelike circular orbit (ESCO). The manner in which the photon sphere and ESCO relate to the presence (or absence) of horizons is much more complex than for the Schwarzschild black hole. We find situations in which photon spheres can approach arbitrarily close to (near extremal) horizons, situations in which some photon spheres become stable, and situations in which the locations of both photon spheres and ESCOs become multi-valued, with both ISCOs (innermost stable circular orbits) and OSCOs (outermost stable circular orbits). This provides an extremely rich phenomenology of potential astrophysical interest.

scholarly journals Possible imprints of cosmic strings in the shadows of galactic black holes

2014 ◽  
Vol 23 (07) ◽  
pp. 1450060 ◽  
Author(s):  
Vassil K. Tinchev ◽  
Stoytcho S. Yazadjiev
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Cosmic String ◽  
Cosmic Strings ◽  
Kerr Black Hole ◽  
Black Hole Spin ◽  
Deficit Angle ◽  
Spin Parameter ◽  
Shadow Cast

We examine the shadow cast by a Kerr black hole pierced by a cosmic string. The observable images depend not only on the black hole spin parameter and the angle of inclination, but also on the deficit angle yielded by the cosmic string. The dependence of the observable characteristics of the shadow on the deficit angle is explored. The imprints in the black hole shadow left by the presence of a cosmic string can serve in principle as a method for observational detection of such strings.

scholarly journals Energy and angular momentum in D-dimensional Kerr-Ads black holes — New formulation

2021 ◽  
pp. 2150201
Author(s):  
Emel Altas
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Einstein Metrics ◽  
Riemann Tensor ◽  
De Sitter ◽  
Gauge Invariant ◽  
Angular Momenta ◽  
Ads Black Holes ◽  
New Formulation

Recently, it was shown that the conserved charges of asymptotically anti-de Sitter spacetimes can be written in an explicitly gauge-invariant way in terms of the linearized Riemann tensor and the Killing vectors. Here, we employ this construction to compute the mass and angular momenta of the [Formula: see text]-dimensional Kerr-AdS black holes, which is one of the most remarkable Einstein metrics generalizing the four-dimensional rotating black hole.

scholarly journals Dynamics of charged and rotating NUT black holes in Rastall gravity

2020 ◽  
Vol 29 (03) ◽  
pp. 2050021
Author(s):  
Hadyan L. Prihadi ◽  
Muhammad F. A. R. Sakti ◽  
Getbogi Hikmawan ◽  
Freddy P. Zen
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Thermodynamic Properties ◽  
Circular Orbit ◽  
Black Hole Solution ◽  
Event Horizons ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

In this work, the Kerr–Newman-NUT black hole solution in Rastall gravity is proposed and it turns out that the horizon is [Formula: see text] dependence. Black hole dynamics such as the event horizons, ergosurface, zero angular momentum observer (ZAMO), thermodynamic properties, and the equatorial circular orbit around the black hole such as static radius limit, null equatorial circular orbit, and innermost stable circular orbit are investigated in this work. How the NUT and Rastall parameter affect the dynamic of the black hole is also shown.

OPEN STRING IN (3+1)-DIMENSIONAL REISSNER–NORDSTRÖM BLACK HOLE

2010 ◽  
Vol 25 (15) ◽  
pp. 1233-1238 ◽  
Author(s):  
HIROMI SUZUKI
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Equatorial Plane ◽  
Cosmic String ◽  
Circular Orbit ◽  
Open String ◽  
Spherically Symmetric ◽  
Schwarzschild Black Hole ◽  
Charged Black Holes ◽  
Open Strings

Previously we investigated the Nambu–Goto string and the wiggly cosmic string in (3+1)-dimensional Schwarzschild black hole. As an extension the solutions in (3+1)-dimensional spherically symmetric charged black holes are investigated. The solution for the wiggly string exhibits open strings lying along the circular orbit in the equatorial plane outside horizon, while the Nambu–Goto string has only a point-like solution.

scholarly journals Properties of Black Holes Relevant to their Observation

1974 ◽  
Vol 64 ◽  
pp. 132-144 ◽  
Author(s):  
James M. Bardeen
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Hot Spots ◽  
Binary Systems ◽  
X Rays ◽  
Circular Orbits ◽  
Spacetime Geometry ◽  
Inertial Frames ◽  
Physical Effects

Black holes are very small objects by astronomical standards, so in many circumstances they interact with their surroundings like a Newtonian mass point. However, if black holes are present in X-ray binary systems, the X-rays emitted in the inner part of the accretion disk probe the highly curved spacetime geometry near the horizon, particularly if the black hole is rapidly rotating. Some of the properties of circular orbits near the black hole are quite sensitive to the amount of angular momentum. The relativistic corrections remove a Newtonian degeneracy between several of the characteristic frequencies associated with perturbations of the circular orbits.Hot spots in the inner part of the disk can produce dramatic fluctuations in intensity, since the frequency shifts of photons emitted by a given point on the disk are strongly time-dependent. The bending of the photon trajectories by the strong gravitational field can drastically affect the energy balance of the disk; much of the radiation emitted by the inner part of the disk is reabsorbed. The dragging of inertial frames by the angular momentum of the black hole can have striking consequences for the structure of the disk at quite large radii if the angular momentum of the accreting matter is not in the same direction as the angular momentum of the black hole.Dynamic perturbations of black holes are now being intensively studied to see if there are any surprising physical effects associated with the rotation of the black hole. Unfortunately, though quite interesting methods of extracting energy from the black hole exist in principle most of them are unlikely to be realized to an important extent in the real astrophysical world.

scholarly journals Characteristic Orbits Of Charged Particles Around Charged Black Holes

2021 ◽  
Vol 03 (04) ◽  
pp. 78-83
Author(s):  
Xudoyberdiyeva Malika Karomat Qizi ◽  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Angular Momentum ◽  
Boundary Conditions ◽  
Accretion Disk ◽  
Charged Particles ◽  
Circular Orbits ◽  
Charged Black Holes ◽  
Lower Limits

We have considered Reissner-Nordstr¨om (RN) charged nonrotating black hole (BH).We have studied motion of charged particles around charged RN BH. It was found out that there are two boundary conditions for specific angular momentum of stable circular orbits corresponding to: innermost stable circular orbits (ISCO) and outermost stable circular orbits (OSCO) and accretion disk is originated between these two orbits. It was obtained the upper and lower limits for the value of particle’s charge which may exist in the accretion disk matter around the extreme charged Reissner Nordstr¨om black hole.

scholarly journals Driven black holes: from Kolmogorov scaling to turbulent wakes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Tomas Andrade ◽  
Christiana Pantelidou ◽  
Julian Sonner ◽  
Benjamin Withers
Keyword(s):  
Nonlinear Dynamics ◽  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Strong Field ◽  
De Sitter ◽  
Event Horizons ◽  
Binary Mergers ◽  
Tidal Deformations ◽  
Proof Of Principle

Abstract General relativity governs the nonlinear dynamics of spacetime, including black holes and their event horizons. We demonstrate that forced black hole horizons exhibit statistically steady turbulent spacetime dynamics consistent with Kolmogorov’s theory of 1941. As a proof of principle we focus on black holes in asymptotically anti-de Sitter spacetimes in a large number of dimensions, where greater analytic control is gained. We focus on cases where the effective horizon dynamics is restricted to 2+1 dimensions. We also demonstrate that tidal deformations of the horizon induce turbulent dynamics. When set in motion relative to the horizon a deformation develops a turbulent spacetime wake, indicating that turbulent spacetime dynamics may play a role in binary mergers and other strong-field phenomena.

scholarly journals Uptunneling to de Sitter

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Mehrdad Mirbabayi
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
False Vacuum ◽  
De Sitter ◽  
Dimensional Theory ◽  
Hole Geometry ◽  
Horizon Geometry ◽  
Two Sides ◽  
Extremal Black Holes

Abstract We propose a Euclidean preparation of an asymptotically AdS2 spacetime that contains an inflating dS2 bubble. The setup can be embedded in a four dimensional theory with a Minkowski vacuum and a false vacuum. AdS2 approximates the near horizon geometry of a two-sided near-extremal Reissner-Nordström black hole, and the two sides can connect to the same Minkowski asymptotics to form a topologically nontrivial worm- hole geometry. Likewise, in the false vacuum the near-horizon geometry of near-extremal black holes is approximately dS2 times 2-sphere. We interpret the Euclidean solution as describing the decay of an excitation inside the wormhole to a false vacuum bubble. The result is an inflating region inside a non-traversable asymptotically Minkowski wormhole.

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