scholarly journals Gravitational deflection of massive particles in Schwarzschild-de Sitter spacetime

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Guansheng He ◽  
Xia Zhou ◽  
Zhongwen Feng ◽  
Xueling Mu ◽  
Hui Wang ◽  
...  
Keyword(s):  
Neutral Particle ◽  
Deflection Angle ◽  
Weak Field ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Field Limit ◽  
Weak Field Limit ◽  
Sitter Spacetime ◽  
Massive Particles ◽  
Gravitational Deflection

AbstractIn this paper, the gravitational deflection of a relativistic massive neutral particle in the Schwarzschild-de Sitter spacetime is studied via the Rindler–Ishak method in the weak-field limit. When the initial velocity $$v_0$$ v 0 of the particle tends to the speed of light, the result is consistent with that obtained in the previous work for the light-bending case. Our result is reduced to the Schwarzschild deflection angle of massive particles up to the second order, if the contributions from the cosmological constant $$\varLambda $$ Λ are dropped. The observable correctional effects due to the deviation of $$v_0$$ v 0 from light speed on the $$\varLambda $$ Λ -induced contributions to the deflection angle of light are also analyzed.

scholarly journals Effect of the Magnetic Charge on Weak Deflection Angle and Greybody Bound of the Black Hole in Einstein-Gauss-Bonnet Gravity

2021 ◽  
Author(s):  
Wajiha Javed ◽  
Muhammad Aqib ◽  
Ali Övgün
Keyword(s):  
Deflection Angle ◽  
Magnetic Charge ◽  
Weak Field ◽  
Einstein Gravity ◽  
Plasma Medium ◽  
Field Limit ◽  
Bonnet Gravity ◽  
Weak Field Limit ◽  
Rigorous Bounds ◽  
Bonnet Theorem

The objective of this paper is to analyze the weak deflection angle of Einstein-Gauss-Bonnet gravity in the presence of plasma medium. To attain our results, we implement the Gibbons and Werner approach and use the Gauss-Bonnet theorem to Einstein gravity to acquire the resulting deflection angle of photon's ray in the weak field limit. Moreover, we illustrate the behavior of plasma medium and non-plasma mediums on the deflection of photon's ray in the framework of Einstein-Gauss-Bonnet gravity. Similarly, we observe the graphical influences of deflection angle on Einstein-Gauss-Bonnet gravity with the consideration of both plasma and non-plasma mediums. Later, we observe the rigorous bounds phenomenon of the greybody factor in contact with Einstein-Gauss-Bonnet gravity and calculate the outcomes, analyze graphically for specific values of parameters.

Gravitational lensing by multi-polytropic wormholes

2020 ◽  
Vol 98 (11) ◽  
pp. 1046-1054
Author(s):  
S.N. Sajadi ◽  
N. Riazi
Keyword(s):  
Gravitational Lensing ◽  
Deflection Angle ◽  
Weak Field ◽  
Light Curves ◽  
Energy Conditions ◽  
Field Limit ◽  
Asymptotically Flat ◽  
Weak Field Limit ◽  
Polytropic Equation ◽  
The Deflection Angle

We obtain static, asymptotically flat, multi-polytropic wormhole solutions in the framework of general relativity. We examine gravitational lensing in the presence of the wormhole and calculate the deflection angle for both weak and strong fields. We investigate microlensing in the weak field limit and obtain corresponding light curves for both galactic and extragalactic situations. We discuss the astrophysical motivation of considering the multi-polytropic equation of state that supports the wormhole geometry. Finally, we investigate the energy conditions.

scholarly journals Existence of Electrically Charged Structures with Regular Center in Nonlinear Electrodynamics Minimally Coupled to Gravity

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Irina Dymnikova ◽  
Evgeny Galaktionov ◽  
Eduard Tropp
Keyword(s):  
Electric Field ◽  
Energy Condition ◽  
Weak Field ◽  
Nonlinear Electrodynamics ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Field Limit ◽  
Weak Field Limit ◽  
Symmetric Configuration ◽  
Electrically Charged

We address the question of correct description of Lagrange dynamics for regular electrically charged structures in nonlinear electrodynamics coupled to gravity. Regular spherically symmetric configuration satisfying the weak energy condition has obligatory de Sitter center in which the electric field vanishes while the energy density of electromagnetic vacuum achieves its maximal value. The Maxwell weak field limitLF→Fasr→∞requires vanishing electric field at infinity. A field invariantFevolves between two minus zero in the center and at infinity which makes a LagrangianLFwith nonequal asymptotic limits inevitably branching. We formulate the appropriate nonuniform variational problem including the proper boundary conditions and present the example of the spherically symmetric Lagrangian describing electrically charged structure with the regular center.

scholarly journals Kerr–Schild form of the exact metric for a constantly moving Kerr black hole and null gravitational deflection

2021 ◽  
pp. 2150067
Author(s):  
Weijun Li ◽  
Zhongwen Feng ◽  
Xia Zhou ◽  
Xueling Mu ◽  
Guansheng He
Keyword(s):  
Black Hole ◽  
Constant Velocity ◽  
Arbitrary Constant ◽  
Kerr Black Hole ◽  
Weak Field ◽  
Field Limit ◽  
Bending Angle ◽  
Weak Field Limit ◽  
Gravitational Deflection

The exact metric of a moving Kerr black hole with an arbitrary constant velocity is derived in Kerr–Schild coordinates. We then calculate the null equatorial gravitational deflection caused by a radially moving Kerr source up to the second post-Minkowskian order, acting as an application of the weak-field limit of the metric. The bending angle of light is found to be consistent with the result given in the previous works.

scholarly journals Weak Deflection Angle by Casimir Wormhole Using Gauss-Bonnet Theorem and Its Shadow

2020 ◽  
Author(s):  
Wajiha Javed ◽  
Ali Hamza ◽  
Ali Övgün
Keyword(s):  
Deflection Angle ◽  
Weak Field ◽  
Plasma Medium ◽  
Field Limit ◽  
Spacetime Geometry ◽  
Weak Field Limit ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Limit Approximation ◽  
Optical Metric

In this paper, we calculate the deflection angle of photon by Casimir wormhole in the weak field limit approximation. First we calculate Gaussian optical curvature with the help of optical spacetime geometry and so we use the Gauss-Bonnet theorem on the Gaussian optical metric. Then we find the deflection angle of photon by Casimir wormhole. Moreover, we calculate the photon's deflection angle in the presence of plasma medium and we also see the graphical nature of deflection angle in both cases. Second, we move towards the shadow of Casimir wormhole. After the observations of Event Horizon Telescope, the study of shadow become very important so that we plot the shapes of shadow of Casimir wormhole, and we calculate the photon geodesic around the Casimir wormhole.

scholarly journals A new nonlinear electrodynamics and electrically charged regular black holes

2021 ◽  
pp. 2150079
Author(s):  
Mohammad Bagher Jahani Poshteh ◽  
Nematollah Riazi
Keyword(s):  
Black Hole ◽  
Black Hole Solution ◽  
Weak Field ◽  
Nonlinear Electrodynamics ◽  
Spherically Symmetric ◽  
De Sitter ◽  
Field Limit ◽  
Weak Field Limit ◽  
Spherically Symmetric Solution ◽  
Electrically Charged

A regular static, spherically symmetric electrically charged black hole solution of general relativity coupled to a new theory for nonlinear electrodynamics is presented. This theory has the interesting feature that, at far distances from the black hole, in the weak field limit, the theory reduces to Maxwell Lagrangian with Heisenberg–Euler correction term of quantum electrodynamics. The singular center of the black hole is replaced by flat, de Sitter, or anti de Sitter space, if the spacetime in which the black hole is embedded is asymptotically flat, de Sitter, or anti de Sitter, respectively. Requiring the correspondence to Heisenberg–Euler Lagrangian at large distances, in the weak field limit, we find that (i) a minimum mass is required for the formation of an event horizon for the regular static, spherically symmetric solution of the theory, and, (ii) the mass of the solution must be quantized. We also study the basic thermodynamic properties of the black hole solution and show that they are qualitatively similar to those of Reissner–Nordström black hole.

scholarly journals Unimodular vs nilpotent superfield approach to pure dS supergravity

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Sukruti Bansal ◽  
Silvia Nagy ◽  
Antonio Padilla ◽  
Ivonne Zavala
Keyword(s):  
String Theory ◽  
General Framework ◽  
Recent Progress ◽  
High Energy ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
New Approach ◽  
Sitter Spacetime ◽  
Novel Approach ◽  
De Sitter Vacua

Abstract Recent progress in understanding de Sitter spacetime in supergravity and string theory has led to the development of a four dimensional supergravity with spontaneously broken supersymmetry allowing for de Sitter vacua, also called de Sitter supergravity. One approach makes use of constrained (nilpotent) superfields, while an alternative one couples supergravity to a locally supersymmetric generalization of the Volkov-Akulov goldstino action. These two approaches have been shown to give rise to the same 4D action. A novel approach to de Sitter vacua in supergravity involves the generalisation of unimodular gravity to supergravity using a super-Stückelberg mechanism. In this paper, we make a connection between this new approach and the previous two which are in the context of nilpotent superfields and the goldstino brane. We show that upon appropriate field redefinitions, the 4D actions match up to the cubic order in the fields. This points at the possible existence of a more general framework to obtain de Sitter spacetimes from high-energy theories.

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