Deriving Weak Deflection Angle by Black Holes or Wormholes using Gauss-Bonnet Theorem

doi:10.3906/fiz-2110-16

Cited by 5 publications

(2 citation statements)

References 83 publications

(76 reference statements)

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“…[59]. In another work, the weak deflection angle by black holes and wormholes has been extensively studied with different examples and wormhole structures [60]. Apart from these, there are several studies dealing with deflection angle in the domain of black holes and wormholes [61][62][63][64][65].…”

Section: Introductionmentioning

confidence: 99%

Tideless traversable wormholes surrounded by cloud of strings in f(R) gravity

Gogoi

Goswami

2023

J. Cosmol. Astropart. Phys.

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We study the tideless traversable wormholes in the f(R) gravity metric formalism. First we consider three shape functions of wormholes and study their viabilities and structures. The connection between the f(R) gravity model and wormhole shape function has been studied and the dependency of the f(R) gravity model with the shape function is shown. We also obtain a wormhole solution in the f(R) gravity Starobinsky model surrounded by a cloud of strings. In this case, the wormhole shape function depends on both the Starobinsky model parameter and the cloud of strings parameter. The structure and height of the wormhole is highly affected by the cloud of strings parameter, while it is less sensitive to the Starobinsky model parameter. The energy conditions have been studied and we found the ranges of the null energy condition violation for all wormhole structures. The quasinormal modes from these wormhole structures for the scalar and Dirac perturbations are studied using higher order WKB approximation methods. The quasinormal modes for the toy shape functions depend highly on the model parameters. In case of the Starobinsky model's wormhole the quasinormal frequencies and the damping rate increase with an increase in the Starobinsky model parameter in scalar perturbation. Whereas in Dirac perturbation, with an increase in the Starobinsky model parameter the quasinormal frequencies decrease and the damping rate increases. The cloud of strings parameter also impacts prominently and differently the quasinormal modes from the wormhole in the Starobinsky model.

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Section: Introductionmentioning

confidence: 99%

Tideless traversable wormholes surrounded by cloud of strings in f(R) gravity

Gogoi

Goswami

2023

J. Cosmol. Astropart. Phys.

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“…Furthermore, for asymptotically flat black hole spacetimes, many studies have shown that the integration of geodesic curvature κ g along the circular arc C R in the R → ∞ limit reduces to [83,90] ∂D…”

Section: Jcap12(2023)005mentioning

confidence: 99%

Gravitational lensing of Schwarzschild and charged black holes immersed in perfect fluid dark matter halo

Qiao,

Zhou

2023

J. Cosmol. Astropart. Phys.

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Dark matter and dark energy dominate the behavior of our universe. The dark matter usually forms halo structures in large number of galaxies. Properties of dark matter halo can be revealed and understood from the gravitational lensing observations. In this work, a comprehensive study on the gravitational lensing of black holes immersed in dark matter halos is presented. To effectively model the supermassive black hole in a galaxy center (which is surrounded by dark matter halo) in a simple way, we investigate the Schwarzschild black hole and charged Reissner-Nordström black hole immersed in a perfect fluid dark matter halo. In the present work, several basic quantities in gravitational lensing (the gravitational deflection angle of light, photon sphere, black hole shadow radius, gravitational lens equation and Einstein ring) are calculated and analyzed analytically and numerically. A second order analytical expansion of gravitational deflection angle is obtained in the weak deflection limit, and the full gravitational deflection angle (including all order perturbation contributions applicable to both weak and strong deflection limits) is also calculated numerically as comparisons. It enables us to analyze the perfect fluid dark matter influences on gravitational deflection angle and gravitational lensing beyond the leading order, which were not sufficiently studied in previous works. Assuming M ∼ λDM ∼ Q, our results show that dark matter can greatly influence the gravitational lensing of central black holes.

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Weak deflection angle and shadow cast by the charged-Kiselev black hole with cloud of strings in plasma*

Atamurotov

Hussain²,

Mustafa³

et al. 2023

Chinese Phys. C

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In this work, the gravitational deflection angle of photon in the weak field limit (or the weak deflection angle) and shadow cast by the electrically charged and spherically symmetric static Kiselev black hole (BH) in the string cloud background are investigated. The influence of the BH charge $Q$, the quintessential parameter $\gamma$ and the string cloud parameter $a$ is studied on the weak deflection angle using the Gauss-Bonnet theorem, on the radius of photon spheres and on the size of the BH shadow in the spacetime geometry of the charged-Kiselev BH in string clouds. Moreover, we study the effects of plasma (uniform and non-uniform) on the weak deflection angle and on the shadow cast by the charged-Kiselev BH surrounded by the clouds of strings. In the presence of uniform/nonuniform plasma medium, increase in the cloud of string parameter $a$, increases the deflection angle $\alpha$. On the other hand decrease in the BH charge $Q$, decreases the deflection angle. Further we observe that an increase of the BH charge $Q$ causes a decrease in the size of the shadow of the BH. We notice that with increase in the values of the parameters $\gamma$ and $a$, the size of the BH shadow also increases and therefore the intensity of the gravitational field around the charged-Kiselev BH in string clouds increases. Thus the gravitational field of the charged-Kiselev BH in string cloud background would be stronger than the field produced by the pure Reissner-Nordstrom BH. Moreover, we use the data released by the Event Horizon Telescope (EHT) collaboration, for the supermassive BHs M87* and Sgr A*, to obtain constraints on the values of the parameters $\gamma$ and $a$.

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Deriving Weak Deflection Angle by Black Holes or Wormholes using Gauss-Bonnet Theorem

Cited by 5 publications

References 83 publications

Tideless traversable wormholes surrounded by cloud of strings in f(R) gravity

Tideless traversable wormholes surrounded by cloud of strings in f(R) gravity

Gravitational lensing of Schwarzschild and charged black holes immersed in perfect fluid dark matter halo

Weak deflection angle and shadow cast by the charged-Kiselev black hole with cloud of strings in plasma*

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