scholarly journals Particle Motion and Plasma Effects on Gravitational Weak Lensing in Lorentzian Wormhole Spacetime

Galaxies ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 54
Author(s):  
Farruh Atamurotov ◽  
Sanjar Shaymatov ◽  
Bobomurat Ahmedov
Keyword(s):  
Particle Motion ◽  
Deflection Angle ◽  
Weak Lensing ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Plasma Effects ◽  
Innermost Stable Circular Orbit ◽  
The Deflection Angle ◽  
Gravitational Weak Lensing ◽  
Uniform Plasma

Here we study particle motion in the specific Lorentzian wormhole spacetime characterized, in addition to the total mass M, with the dimensionless parameter λ. In particular we calculate the radius of the innermost stable circular orbit (ISCO) for test particles and the photonsphere for massless particles. We show that the effect of the dimensionless wormhole parameter decreases the ISCO radius and the radius of the photon orbit. Then, we study plasma effects on gravitational weak lensing in wormhole spacetime and obtain the deflection angle of the light. We show that the effect of λ decreases the deflection angle. We study the effects of uniform and non-uniform plasma on the light deflection angle separately, and show that the uniform plasma causes the deflection angle to be smaller in contrast to the non-uniform plasma.

scholarly journals Weak gravitational lensing Schwarzschild-MOG black hole in plasma

2021 ◽  
Vol 81 (2) ◽  
Author(s):  
Farruh Atamurotov ◽  
Ahmadjon Abdujabbarov ◽  
Javlon Rayimbaev
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Plasma Frequency ◽  
Plasma Medium ◽  
Weak Gravitational Lensing ◽  
Plasma Effects ◽  
Total Magnification ◽  
The Deflection Angle ◽  
Uniform Plasma

AbstractThis paper is devoted to study weak gravitational lensing properties around black hole surrounded plasma medium in modified gravity (MOG). We have investigated the effects of the MOG-parametr and plasma medium on the deflection angle and total magnification of the images. we have presented the comparisons of the effects of the uniform plasma, singular isothermal sphere and non-singular isothermal sphere. We have also shown that the uniform plasma effects significantly stronger than the other models of plasma medium.Through the studies of the total magnifications of images of a remote source we have shown that the effects of the MOG parameter and plasma medium are similar and the increase of the MOG parameter and plasma frequency cause to increase the total magnification. Moreover, we have explored and analyzed how the MOG effects can reflect the plasma medium providing the same values of the total magnification of images.

scholarly journals Particle motion around generic black holes coupled to non-linear electrodynamics

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
Jaroslav Vrba ◽  
Ahmadjon Abdujabbarov ◽  
Arman Tursunov ◽  
Bobomurat Ahmedov ◽  
Zdeněk Stuchlík
Keyword(s):  
Black Hole ◽  
Energy Conditions ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Spin Parameter ◽  
Non Linear ◽  
Innermost Stable Circular Orbit ◽  
Charge Parameter ◽  
Upper Estimate ◽  
Black Hole Solutions

Abstract We study spherically symmetric magnetically charged generic black hole solutions of general relativity coupled to non-linear electrodynamics (NED). For characteristic values of the generic spacetime parameters we give the position of horizons in dependence on the charge parameter, demonstrating separation of the black hole and no-horizon solutions, and possibility of existence of solutions containing three horizons. We show that null, weak and strong energy conditions are violated when the outer horizon is approaching the center. We study effective potentials for photons and massive test particles and location of circular photon orbits (CPO) and innermost stable circular orbit (ISCO). We show that the unstable photon orbit can become stable, leading to the possibility of photon capture which affects on silhouette of the central object. The position of ISCO approaches the horizon with increasing charge parameter q and the energy at ISCO decreases with increasing charge parameter. We investigate this phenomenon and summarize for a variety of the generic spacetime parameters the upper estimate on the spin parameter of the Kerr black which can be mimicked by the generic charged black hole solutions.

scholarly journals Geodesic motion near self-gravitating scalar field configurations

2019 ◽  
Vol 27 (3) ◽  
pp. 231-241
Author(s):  
Ivan M. Potashov ◽  
Julia V. Tchemarina ◽  
Alexander N. Tsirulev
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Circular Orbit ◽  
Naked Singularity ◽  
Schwarzschild Black Hole ◽  
Null Geodesics ◽  
Naked Singularities ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

We study the geodesics motion of neutral test particles in the static spherically symmetric spacetimes of black holes and naked singularities supported by a selfgravitating real scalar field. The scalar field is supposed to model dark matter surrounding some strongly gravitating object such as the centre of our Galaxy. The behaviour of timelike and null geodesics very close to the centre of such a configuration crucially depends on the type of spacetime. It turns out that a scalar field black hole, analogously to a Schwarzschild black hole, has the innermost stable circular orbit and the (unstable) photon sphere, but their radii are always less than the corresponding ones for the Schwarzschild black hole of the same mass; moreover, these radii can be arbitrarily small. In contrast, a scalar field naked singularity has neither the innermost stable circular orbit nor the photon sphere. Instead, such a configuration has a spherical shell of test particles surrounding its origin and remaining in quasistatic equilibrium all the time. We also show that the characteristic properties of null geodesics near the centres of a scalar field naked singularity and a scalar field black hole of the same mass are qualitatively different.

scholarly journals Boosted Kerr Black Hole in the Presence of Plasma

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 6
Author(s):  
Carlos A. Benavides-Gallego ◽  
Ahmadjon-Abdujabbarov Abdujabbarov
Keyword(s):  
Black Hole ◽  
Deflection Angle ◽  
Kerr Black Hole ◽  
Galaxy Cluster ◽  
Field Approximation ◽  
Weak Field ◽  
Weak Field Approximation ◽  
The Deflection Angle ◽  
Isothermal Gas ◽  
Uniform Plasma

In this work, we obtain the deflection angle for a boosted Kerr black hole in the weak field approximation using the optics in a curved spacetime developed by J. L. Synge in 1960. We study the behavior of light in the presence of plasma by considering different distributions: uniform plasma, singular isothermal sphere, non-singular isothermal gas sphere, and plasma in a galaxy cluster. We found that the dragging of the inertial system along with the boosted parameter Λ affect the value of the deflection angle. As an application, we studied the magnification for both uniform and singular isothermal distributions.

scholarly journals Orbital motion of test particles in regular Hayward black hole space–time

2019 ◽  
Vol 97 (1) ◽  
pp. 58-62 ◽  
Author(s):  
Jian-Ping Hu ◽  
Yu Zhang
Keyword(s):  
Black Hole ◽  
Phase Plane ◽  
Orbital Motion ◽  
Space Time ◽  
Plane Method ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit ◽  
Central Energy ◽  
Phase Plane Method

In this paper, all possible orbits of test particles are investigated by using the phase plane method in regular Hayward black hole space–time. Our results show that the time-like orbits are divided into four types: unstable circular orbits, separates stable orbits, stable hyperbolic orbits, and elliptical orbits in regular Hayward black hole space–time. We find that the orbital properties vary with the change of ℓ (a convenient encoding of the central energy density 3/8πℓ2). If ℓ = 1/3 and b < 3.453 21, the test particles moving toward the black hole will definitely plunge into the black hole. In addition, it is obtained that the innermost stable circular orbit happens at rmin = 5.930 55 for b = 3.453 21.

scholarly journals Gravitational bending angle with finite distances by Casimir wormholes

2021 ◽  
Author(s):  
Í. D. D. Carvalho ◽  
G. Alencar ◽  
C. R. Muniz
Keyword(s):  
Uncertainty Principle ◽  
Deflection Angle ◽  
Generalized Uncertainty Principle ◽  
Casimir Energy ◽  
Type Ii ◽  
Bending Angle ◽  
Test Particles ◽  
Self Consistent ◽  
The Deflection Angle ◽  
Jacobi Metric

In this paper, we investigate the gravitational bending angle due to the Casimir wormholes, which consider the Casimir energy as the source. Furthermore, some of these Casimir wormholes regard Generalized Uncertainty Principle (GUP) corrections of Casimir energy. We use the Ishihara method for the Jacobi metric, which allows us to study the bending angle of light and massive test particles for finite distances. Beyond the uncorrected Casimir source, we consider many GUP corrections, namely, the Kempf, Mangano and Mann (KMM) model, the Detournay, Gabriel and Spindel (DGS) model, and the so-called type II model for the GUP principle. We also find the deflection angle of light and massive particles in the case of the receiver and the source are far away from the lens. In this case, we also compute the optical scalars: convergence and shear for these Casimir wormholes as a gravitational weak lens. Our self-consistent iterative calculations indicate corrections to the bending angle by Casimir wormholes in the previous paper.

Geodesic motion near self-gravitating scalar field configurations

2019 ◽  
Vol 27 (3) ◽  
pp. 231-241
Author(s):  
Ivan M. Potashov ◽  
Julia V. Tchemarina ◽  
Alexander N. Tsirulev
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Circular Orbit ◽  
Naked Singularity ◽  
Schwarzschild Black Hole ◽  
Null Geodesics ◽  
Naked Singularities ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

We study the geodesics motion of neutral test particles in the static spherically symmetric spacetimes of black holes and naked singularities supported by a selfgravitating real scalar field. The scalar field is supposed to model dark matter surrounding some strongly gravitating object such as the centre of our Galaxy. The behaviour of timelike and null geodesics very close to the centre of such a configuration crucially depends on the type of spacetime. It turns out that a scalar field black hole, analogously to a Schwarzschild black hole, has the innermost stable circular orbit and the (unstable) photon sphere, but their radii are always less than the corresponding ones for the Schwarzschild black hole of the same mass; moreover, these radii can be arbitrarily small. In contrast, a scalar field naked singularity has neither the innermost stable circular orbit nor the photon sphere. Instead, such a configuration has a spherical shell of test particles surrounding its origin and remaining in quasistatic equilibrium all the time. We also show that the characteristic properties of null geodesics near the centres of a scalar field naked singularity and a scalar field black hole of the same mass are qualitatively different.

scholarly journals Geodesic motion near self-gravitating scalar field configurations

2019 ◽  
Vol 27 (3) ◽  
pp. 231-241
Author(s):  
Ivan M. Potashov ◽  
Julia V. Tchemarina ◽  
Alexander N. Tsirulev
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Circular Orbit ◽  
Naked Singularity ◽  
Schwarzschild Black Hole ◽  
Null Geodesics ◽  
Naked Singularities ◽  
Test Particles ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit

We study the geodesics motion of neutral test particles in the static spherically symmetric spacetimes of black holes and naked singularities supported by a selfgravitating real scalar field. The scalar field is supposed to model dark matter surrounding some strongly gravitating object such as the centre of our Galaxy. The behaviour of timelike and null geodesics very close to the centre of such a configuration crucially depends on the type of spacetime. It turns out that a scalar field black hole, analogously to a Schwarzschild black hole, has the innermost stable circular orbit and the (unstable) photon sphere, but their radii are always less than the corresponding ones for the Schwarzschild black hole of the same mass; moreover, these radii can be arbitrarily small. In contrast, a scalar field naked singularity has neither the innermost stable circular orbit nor the photon sphere. Instead, such a configuration has a spherical shell of test particles surrounding its origin and remaining in quasistatic equilibrium all the time. We also show that the characteristic properties of null geodesics near the centres of a scalar field naked singularity and a scalar field black hole of the same mass are qualitatively different.

scholarly journals A full relativistic thin disc - the physics of the plunging region and the value of the stress at the ISCO

2021 ◽  
Author(s):  
William J Potter
Keyword(s):  
Black Hole ◽  
Surface Temperature ◽  
Accretion Rate ◽  
Speed Of Light ◽  
Thin Disc ◽  
Stable Circular Orbit ◽  
Stress Surface ◽  
Innermost Stable Circular Orbit ◽  
Turbulent Heating ◽  
Local Surface Temperature

Abstract The widely used Novikov-Thorne relativistic thin disc equations are only valid down to the radius of the innermost-stable circular orbit (ISCO). This leads to an undetermined boundary condition at the ISCO, known as the inner stress of the disc, which sets the luminosity of the disc at the ISCO and introduces considerable ambiguity in accurately determining the mass, spin and accretion rate of black holes from observed spectra. We resolve this ambiguity by self-consistently extending the relativistic disc solution through the ISCO to the black hole horizon by calculating the inspiral of an average disc particle subject to turbulent disc forces, using a new particle-in-disc technique. Traditionally it has been assumed that the stress at the ISCO is zero, with material plunging approximately radially into the black hole at close to the speed of light. We demonstrate that in fact the inspiral is less severe, with several (∼4 − 17) orbits completed before the horizon. This leads to a small non-zero stress and luminosity at and inside the ISCO, with a local surface temperature at the ISCO between ∼0.15 − 0.3 times the maximum surface temperature of the disc, in the case where no dynamically important net magnetic field is present. For a range of disc parameters we calculate the value of the inner stress/surface temperature, which is required when fitting relativistic thin disc models to observations. We resolve a problem in relativistic slim disc models in which turbulent heating becomes inaccurate and falls to zero inside the plunging region.

scholarly journals Quantitative evaluation indexes of the spatial steering effect of directional perforation hydraulic fractures

2021 ◽  
pp. 014459872110102
Author(s):  
Lu Weiyong ◽  
He Changchun
Keyword(s):  
Quantitative Evaluation ◽  
Hydraulic Fracture ◽  
Deflection Angle ◽  
Hydraulic Fractures ◽  
Principal Stress Direction ◽  
Perforation Hole ◽  
Evaluation Indexes ◽  
Initiation Pressure ◽  
The Deflection Angle ◽  
Bending Fracture

To better evaluate the spatial steering effect of directional perforation hydraulic fractures, evaluation indexes for the spatial steering effect are first proposed in this paper. Then, these indexes are used to quantitatively evaluate existing physical experimental results. Finally, with the help of RFPA2D-Flow software, the influence of perforation length and azimuth on the spatial steering process of hydraulic fracture are quantitatively analysed using four evaluation indexes. It is shown by the results that the spatial deflection trajectory, deflection distance, deflection angle and initiation pressure of hydraulic fractures can be used as quantitative evaluation indexes for the spatial steering effect of hydraulic fractures. The deflection paths of directional perforation hydraulic fractures are basically the same. They all gradually deflect to the maximum horizontal principal stress direction from the perforation hole and finally represent a double-wing bending fracture. The deflection distance, deflection angle and initiation pressure of hydraulic fractures increase gradually with increasing perforation azimuth, and the sensitivity of the deflection angle to the perforation azimuth of hydraulic fractures also increases. With increasing perforation length, the deflection distance of hydraulic fractures increases gradually. However, the deflection angle and initiation pressure decrease gradually, as does the sensitivity.

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