This paper is devoted to studying the weak-field gravitational lensing properties of a 4D ESTGB black hole, which is surrounded by the plasma medium. The effects of the magnetic charges and the three plasma distribution models in the deflection of light around a 4D ESTGB black hole are investigated in detail. We find that the uniform plasma leads to a larger deflection of light rays in comparison with the singular isothermal sphere (SIS), the non-singular isothermal sphere (NSIS) models. Moreover, the deflection angle increases slightly as the absolute value of the magnetic charge decreases. Finally, we analyze the total magnification of image due to weak gravitational lensing around the black hole. The result shows that the presence of a uniform plasma medium remarkably enhances the total magnification whereas the non-uniform plasma reduces the total magnification.
We study the optical properties of the Kehagias-Sfetsos (KS) compact objects, characterized by the "Hořava" parameter $ω_{_{KS}}$, in the presence of plasma, considering its homogeneous or power-law density distribution. The strong effects of both "Hořava" parameter $ω_{_{KS}}$ and plasma on the shadow cast by the KS compact objects are demonstrated. Using the weak field approximation, we investigate the gravitational lensing effect. Strong dependence of the deflection angle of the light on both the "Hořava" and plasma parameter is explicitly shown. The magnification of image source due to the…
We study the gravitational lensing in the weak field approximation assuming the presence of a plasma and of a magnetic field around a compact gravitational source. The external magnetic field causes the split of the image, as the counterpart of the Zeeman effect. The magnetic field affects the magnification of images, creating additional components. We also study the time delay of an electromagnetic signal due to the geometry and the gravitational field around the source. We show that the time delay strongly depends on the plasma parameters. Lastly, we consider the effects of the presence of a…
We study weak gravitational lensing around a compact object with arbitrary quadrupole moment in the presence of plasma. The studied compact objects are considered to be spherically symmetric. The additional parameter $ε$ regulating the quadrupole moment in the metric alters the deflection angle of light rays along with the plasma parameters. In the vacuum, the number of images due to the presence of the parameter $ε$ increases and causes the increase of the magnification of the image source. The effects of uniform and nonuniform plasma on gravitational lensing around the compact object are als…
We investigate the strong gravitational lensing of spherically symmetric black holes in the novel Einstein-Gauss-Bonnet(EGB) gravity surrounded by unmagnetised plasma medium. The deflection angle in the strong deflection limit in EGB spacetime with homogeneous plasma is derived. We find that both the coupling constant $α$ in the novel EGB gravity and the presence of plasma can affect the radius of photon sphere, strong field limit coefficient and other lensing observables significantly. While plasma has little effect on the angular image separation and the relative magnifications as $α/M^2\to …
Gravitational lensing around a Kerr-Sen black hole in plasma background
National Institute of Technology, Agartala（阿加塔拉国家理工学院）；The Institute of Mathematical Sciences（数学科学研究所）；Hemvati Nandan Bahuguna Garhwal Central University（赫马瓦蒂·南丹·巴胡加纳加尔瓦尔中央大学）；Centre for Space Research, North-West University（西北大学空间研究中心）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）
In this paper we have assumed a weak-field regime to explore the gravitational lensed photons in a 4 dimensional Einstein-Gauss-Bonnet gravity, which is very much in the limelight these days. The investigation is conducted in three distinct paradigms: uniform plasma, singular isothermal sphere and a non-singular isothermal sphere. The lensing angle associated with the distribution factor of the medium is individually derived for each case and further utilized to study the magnification of the image source brightness, selectively for the uniform plasma and singular isothermal sphere. The attain…
We obtain the deflection angle for a boosted Kerr black hole in the weak field approximation. We also study the behavior of light in the presence of plasma by considering different distributions: singular isothermal sphere, non-singular isothermal gas sphere, and plasma in a galaxy cluster. We find 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 SIS distributions.
We apply the Gauss-Bonnet theorem to the study of light rays in a plasma medium in a static and spherically symmetric gravitational field and also to the study of timelike geodesics followed for test massive particles in a spacetime with the same symmetries. The possibility of using the theorem follows from a correspondence between timelike curves followed by light rays in a plasma medium and spatial geodesics in an associated Riemannian optical metric. A similar correspondence follows for massive particles. For some examples and applications, we compute the deflection angle in weak gravitatio…
We consider a time-like geodesics in the background of rotating Einstein-Born-Infeld (EBI) black hole to examine the horizon and ergosphere structure. The effective potential that governs the particle's motion in the spacetime and the innermost stable circular orbits (ISCO) is also studied. A qualitative analysis is conducted to find the redshifted ultrahigh centre-of-mass (CM) energy as a result of a two-particle collision specifically near the horizon. The recent Event Horizon Telescope (EHT) triggered a surge of interest in strong gravitational lensing by black holes, which provide a new to…
In this paper, we discuss the weak gravitational lensing in the context of stringy black holes. Initially, we examine the deflection angle of photon by charged stringy black hole. For this desire, we compute the Gaussian optical curvature and implement the Gauss-Bonnet theorem to investigate the deflection angle for spherically balanced spacetime of stringy black hole. We also analyze the influence of plasma medium in the weak gravitational lensing for stringy black hole. Moreover, the graphical impact of impact parameter $b$ , black hole charge $Q$ on deflection angle by charged stringy black…
The null geodesics of the regular and rotating magnetically charged black hole in a non-minimally coupled Einstein-Yang-Mills theory surrounded by a plasma medium is studied. The effect of magnetic charge and Yang-Mills parameter on the effective potential and radius of photon orbits has investigated. We then study the shadow of a regular and rotating magnetically charged black hole along with the observables in presence of the plasma medium. The presence of plasma medium affects the apparent size of the shadow of a regular rotating black hole in comparison to vacuum case. Variation of shadow …
We develop a model of gravitational lensing in a non-uniform plasma. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and of a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. We take into account both effects, and derive the expression for the lensing angle in the case of a strongly nonuniform plasma in …
In this article, we present an overview of the new developments in problems of the plasma influence on the effects of gravitational lensing, complemented by pieces of new material and relevant discussions. Deflection of light in the presence of gravity and plasma is determined by a complex combination of various physical phenomena: gravity, dispersion, refraction. In particular, the gravitational deflection itself, in a homogeneous plasma without refraction, differs from the vacuum one and depends on the frequency of the photon. In an inhomogeneous plasma, chromatic refraction also takes place…
Effect of gravitational lensing around black hole in dark matter halo in the presence of plasma
Harbin Institute of Technology（哈尔滨工业大学）；University of Tashkent for Applied Sciences（塔什干应用科学大学）；New Uzbekistan University（新乌兹别克斯坦大学）；Tashkent State Technical University（塔什干国立技术大学）；Institute of Theoretical Physics, National University of Uzbekistan（乌兹别克斯坦国立大学理论物理研究所）；Institute for Advanced Studies, New Uzbekistan University（新乌兹别克斯坦大学高级研究院）
Plasma impact on black hole shadow and gravitational weak lensing for Schwarzschild-like black hole
Harbin Institute of Technology（哈尔滨工业大学）；University of Tashkent for Applied Sciences（塔什干应用科学大学）；New Uzbekistan University（新乌兹别克斯坦大学）；National University of Uzbekistan（乌兹别克斯坦国立大学）
We investigate the influence of plasma presence on relativistic images formed by Schwarzschild black hole lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on a frequency of the electromagnetic wave due to refraction properties, and the dispersion properties of the light propagation in gravitational field in plasma. The last effect leads to difference, even in uniform plasma, of gravitational deflection angle in plasma from vacuum case. This angle depends on the photon frequency, what resembles the properties of the refractive prism spectrometer. Here we con…
Considering a Kerr black hole surrounded by the homogenous unmagnetised plasma medium, we study the strong gravitational lensing on the equatorial plane of the Kerr black hole. We find that the presence of the uniform plasma increases the photon-sphere radius $r_{ps}$, the coefficient $\bar{a},\bar{b}$, the angular position of the relativistic images $θ_{\infty}$, the deflection angle $α(θ)$ and the angular separation $s$. However the relative magnitudes $r_m$ decrease in presence of the uniform plasma medium. It is also shown that the impact of the uniform plasma on the effect of strong gravi…
In this article, we analyze the weak gravitational lensing in the context of Einstein-non-linear Maxwell-Yukawa black hole. To this desire, we derive the deflection angle of light by Einstein-non-linear Maxwell-Yukawa black hole using the Gibbons and Werner method. For this purpose, we obtain the Gaussian curvature and apply the Gauss-Bonnet theorem to find the deflection angle of Einstein-non-linear Maxwell-Yukawa black hole in weak field limits. Moreover, we derive the deflection angle of light in the influence of plasma medium. We also analyze the graphical behavior of deflection angle by E…
In this paper, we study the influence of the axion-plasmon, as proposed in (Phys. Rev. Lett. 120, 181803 (2018)) on the optical properties of the Schwarzschild black hole. Our aim is to provide a test to detect the effects of a fixed axion background using black holes. To accomplish our goal, we explore the effect of the axion-plasmon coupling on the motion of photons around the Schwarzschild black hole and check the possibility of observing those effects upon the black hole shadow, the gravitational deflection angle, Einstein rings and shadow images obtained by radially infalling gas on a bla…
In this paper, we study the deflection angle for wormhole-like static aether solution by using Gibbons and Werner technique in non-plasma, plasma, and dark matter mediums. For this purpose, we use optical spacetime geometry to calculate the Gaussian optical curvature, then implement the Gauss-Bonnet theorem in weak field limits. Moreover, we compute the deflection angle by using a technique known as Keeton and Petters technique. Furthermore, we analyze the graphical behavior of the bending angle $ψ$ with respect to the impact parameter $b$, mass $m$ as an integration constant, and parameter $q…
In this paper, we first analyze the horizon structure of the Van der Waals(VdW) black hole and then investigate its shadow in the absence of a plasma medium as well as the presence of a homogeneous plasma medium. We find that both the Van der Waals parameters $a$ and $b$ have a significant effect on the shadow of the black hole. We also observe that the radius of the shadow in a homogeneous plasma medium decreases while parameter $σ=\frac{ω_p}{ω_{\infty}}$ ( the ratio of plasma frequency and photon frequency) increases and the radius of the shadow inhomogeneous plasma medium is larger than the…
In this article, we demonstrate the weak gravitational lensing in the context of Bocharova-Bronnikov-Melnikov-Bekenstein (BBMB) black hole. To this desire, we derive the deflection angle of light in a plasma medium by BBMB black hole using the Gibbons and Werner method. First, we obtain the Gaussian optical curvature and implement the Gauss-Bonnet theorem to investigate the deflection angle for spherically symmetric spacetime of BBMB black hole. Moreover, we also analyze the graphical behavior of deflection angle by BBMB black hole in the presence of plasma medium.
The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions $N \propto 1/r^h$ with $h \geq 0$ in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens …
In this work we extend the approach used in [Emanuel Gallo and Osvaldo M. Moreschi, Phys. Rev. D 83, 12 083007 (2011)] to the study of weak gravitational lensing in a plasma medium. First, we present expressions for the deflection angle and optical scalars in terms of the components of the energy-momentum tensor for spherically symmetric lenses surrounded by a cold non-magnetized plasma. Second, we show that the same expressions can be deduced using the Gauss-Bonnet theorem. Finally, we establish a correspondence between the spatial orbits of photons in a non-homogeneous plasma and the non-geo…
Frequency-dependent gravitational lens effects are found for trajectories of electromagnetic rays passing through a distribution of plasma near a massive object. Ray propagation through plasma adds extra terms to the equations of motion that depend on the plasma refractive index. For low-frequency rays these refractive effects can dominate, turning the gravitational lens into a mirror. While light rays behave like particles with an effective mass given by the plasma frequency in a medium with constant density, an inhomogeneous plasma introduces more complicated behavior even for the sphericall…
The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhom…
We study the motion of charged and spinning particles and photons in the $4D$ charged Einstein-Gauss-Bonnet (EGB) black hole vicinity. We determine the radius of the innermost stable circular orbit (ISCO) for test particles. We show that the combined effect of the Gauss-Bonnet (GB) coupling parameter and black hole charge decreases the ISCO and the radius of the photon sphere. Further, we study the gravitational deflection angle and show that the impact of GB term and black hole charge on it is quite noticeable. We also consider the effect of plasma and find the analytical form of the deflecti…
In this paper, we mainly aim at highlighting the importance of (hyper-)elliptic integrals in the study of gravitational effects caused by strongly gravitating systems. For this, we study the application of elliptic integrals in calculating the light deflection as it passes a plasmic medium, surrounding a charged Weyl black hole. To proceed with this, we consider two specific algebraic ansatzes for the plasmic refractive index, and we characterize the photon sphere for each of the cases. This will be used further to calculate the angular diameter of the corresponding black hole shadow. We show …
Testing Charged Black Holes Embedded in Anisotropic Matter and Surrounded by Plasma through Gravitational Lensing: Bounds from the Sloan Lens ACS Survey
Centre for Space Research, North-West University（西北大学空间研究中心）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）；Department of Physics, Hemvati Nandan Bahuguna Garhwal Central University（赫姆瓦蒂·南丹·巴胡加纳加尔瓦尔中央大学物理系）；Centre for Theoretical Physics, The British University in Egypt（埃及英国大学理论物理中心）
Optical Signatures of a Black Hole in Effective Quantum Gravity
National Research University TIIAME（国立研究大学TIIAME）；University of Tashkent for Applied Sciences（塔什干应用科学大学）；Harbin Institute of Technology（哈尔滨工业大学）；New Uzbekistan University（新乌兹别克斯坦大学）；Tashkent State Technical University（塔什干国立技术大学）；National University of Uzbekistan（乌兹别克斯坦国立大学）
In this paper, we investigate light bending in the spacetime of regular black holes with cosmic strings in weak field limits. To do so, we apply the Gauss-Bonnet theorem to the optical geometry of the black hole; and, using the Gibbons-Werner method, we obtain the deflection angle of light in the weak field limits which shows that the bending of light is a global and topological effect. Afterwards, we demonstrate the effect of a plasma medium on the deflection of light by RBCS. We discuss that increasing cosmic string parameter $μ$ and mass $M_0$ will increase the bending angle.
In this paper, we study light rays in a Kazakov-Solodukhin black hole. To this end, we use the optical geometry of the Kazakov-Solodukhin black hole within the Gauss-bonnet theorem. We first show the effect of the deformation parameter $a$ on the Gaussian optical curvature, and then we use the modern method popularized by Gibbons and Werner to calculate the weak deflection angle of light. Our calculations of deflection angle show how gravitational lensing is affected by the deformation parameter $a$. Moreover, we demonstrate the effect of a plasma medium on weak gravitational lensing by the Ka…
Electromagnetic rays travel on curved paths under the influence of gravity. When a dispersive optical medium is included, these trajectories are frequency-dependent. In this work we consider the behaviour of rays when a spherically symmetric, luminous compact object described by the Schwarzschild metric is surrounded by an optically thin shell of plasma supported by radiation pressure. Such levitating atmospheres occupy a position of stable radial equilibrium, where radiative flux and gravitational effects are balanced. Using general relativity and an inhomogeneous plasma we find the existence…
Wave effects in lensing form a rich phenomenon at the intersection of classical caustic singularities and quantum interference, yet are notoriously difficult to model. A large number of recently observed pulsars and fast radio bursts in radio astronomy and the prospected increase in sensitivity of gravitational wave detectors suggest that wave effects will likely be observed in the near future. The interference fringes are sensitive to physical parameters which cannot be inferred from geometric optics. In particular, for multi-plane lensing, the pattern depends on the redshifts of the lens pla…
We consider the gravitational lensing of rays emitted by a compact object (CO) within a distribution of plasma with power-law density $\propto r^{-h}$. For the simplest case of a cloud of spherically symmetric cold non-magnetized plasma, the diverging effect of the plasma and the converging effect of gravitational lensing compete with one another. When $h<2$, the plasma effect dominates over the vacuum Schwarzschild curvature, potentially shifting the radius of the unstable circular photon orbit outside the surface of the CO. When this occurs, we define two relatively narrow radio-frequency ba…
Optical Signatures of a Schwarzschild Black Hole in a Dehnen-Type Dark Matter Halo
Institute of Fundamental and Applied Research, National Research University TIIAME（基础与应用研究所，国立研究大学TIIAME）；National Pedagogical University of Uzbekistan named after Nizami（以尼扎米命名的乌兹别克斯坦国立师范大学）；School of Advanced Sciences, Vellore Institute of Technology（韦洛尔技术学院高等科学学院）；University of Tashkent for Applied Sciences（塔什干应用科学大学）；Tashkent State Technical University（塔什干国立技术大学）；School of Physics, Harbin Institute of Technology（哈尔滨工业大学物理学院）；Institute for Advanced Studies, New Uzbekistan University（新乌兹别克斯坦大学高级研究院）；Institute of Theoretical Physics, National University of Uzbekistan（乌兹别克斯坦国立大学理论物理研究所）
Light Deflection and Greybody Bound Around a BTZ-ModMax Black Hole in Plasma Medium
North-West University（西北大学）；The Institute of Mathematical Sciences（数学科学研究所）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）；Hemvati Nandan Bahuguna Garhwal Central University（赫姆瓦蒂·南丹·巴胡加纳加尔瓦尔中央大学）；The British University in Egypt（埃及英国大学）
The principal objective of this project is to investigate the gravitational lensing by asymptotically flat black holes in the framework of Horndeski theory in weak field limits. To achieve this objective, we utilize the Gauss-Bonnet theorem to the optical geometry of asymptotically flat black holes and apply the Gibbons-Werner technique to achieve the deflection angle of photons in weak field limits. Subsequently, we manifest the influence of plasma medium on deflection of photons by asymptotically flat black holes in the context of Horndeski theory. We also examine the graphical impact of def…
In this paper, we study the weak deflection angle of black hole in effective loop quantum gravity using the geometrical technique used by Gibbons and Werner. We first derive the optical metric, calculate the Gaussian optical curvature, and then apply the Gauss-Bonnet theorem. We then also investigate the effect of plasma and dark matter mediums on the weak deflection angle. We show that increasing the impact of these two mediums grows the deflection angle. We also calculate the Hawking temperature via Gauss-Bonnet theorem. In addition, we determine the fermionic greybody bounds. Moreover, we d…
