In this study,the gravitational deflection angle of photons 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 th...In this study,the gravitational deflection angle of photons 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 influences of the BH charge Q,quintessence parameterγ,and string cloud parameter a on the weak deflection angle are studied using the Gauss-Bonnet theorem.in addition to studying the influences on the radius of photon spheres and size of the BH shadow in the spacetime geometry of the chargedKiselev BH in string clouds.Moreover,we study the effects of plasma(uniform and non-uniform)on the weak deflection angle and shadow cast by the charged-Kiselev BH surrounded by the clouds of strings.In the presence of a uniform/nonuniform plasma medium,an increase in the string cloud parameter a increases the deflection angleα.In contrast,a decrease in the BH charge Q decreases the deflection angle.Further,we observe that an increase in the BH charge Q causes a decrease in the size of the shadow of the BH.We notice that,with an increase in the values of the parametersγand a,the size of the BH shadow 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 the string cloud background is 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 parametersγand a.展开更多
In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the p...In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the photon sphere of the Ellis-Bronnikov wormhole and the size of the wormhole shadow become larger under the influence of the parameter a.The upper limit of the parameter a in the Ellis-Bronnikov wormhole spacetime was obtained.Second,we investigated the weak gravitational lensing for the Ellis-Bronnikov wormhole and calculated the deflection angle for uniform and non uniform plasma cases.The value of the deflection angle for uniform plasma increased with the increase in plasma parameter value,and vice versa for non uniform plasma.We found that,under the influence of the parameter a,the values of the deflection angles for two cases decreased.Finally,we investigated the magnification of image brightness using the deflection angle of the light rays around the wormhole in the EllisBronnikov theory.展开更多
基金Partly supported by the Uzbekistan Ministry for Innovative Development(FZ-20200929344 and F-FA-2021-510)supported by Postdoctoral Fellowship of Zhejiang Normal University(ZC304022919)。
文摘In this study,the gravitational deflection angle of photons 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 influences of the BH charge Q,quintessence parameterγ,and string cloud parameter a on the weak deflection angle are studied using the Gauss-Bonnet theorem.in addition to studying the influences on the radius of photon spheres and size of the BH shadow in the spacetime geometry of the chargedKiselev BH in string clouds.Moreover,we study the effects of plasma(uniform and non-uniform)on the weak deflection angle and shadow cast by the charged-Kiselev BH surrounded by the clouds of strings.In the presence of a uniform/nonuniform plasma medium,an increase in the string cloud parameter a increases the deflection angleα.In contrast,a decrease in the BH charge Q decreases the deflection angle.Further,we observe that an increase in the BH charge Q causes a decrease in the size of the shadow of the BH.We notice that,with an increase in the values of the parametersγand a,the size of the BH shadow 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 the string cloud background is 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 parametersγand a.
基金partly Supported by Grants F-FA-2021-432,F-FA-2021-510,and MRB-2021-527 of the Ministry of Higher Education,Science and Innovations of the Republic of Uzbekistan。
文摘In this study,we investigated the gravitational weak lensing and shadow of the Ellis-Bronnikov wormhole.First,we studied the photon motion in a plasma medium and a wormhole shadow.It was shown that the radius of the photon sphere of the Ellis-Bronnikov wormhole and the size of the wormhole shadow become larger under the influence of the parameter a.The upper limit of the parameter a in the Ellis-Bronnikov wormhole spacetime was obtained.Second,we investigated the weak gravitational lensing for the Ellis-Bronnikov wormhole and calculated the deflection angle for uniform and non uniform plasma cases.The value of the deflection angle for uniform plasma increased with the increase in plasma parameter value,and vice versa for non uniform plasma.We found that,under the influence of the parameter a,the values of the deflection angles for two cases decreased.Finally,we investigated the magnification of image brightness using the deflection angle of the light rays around the wormhole in the EllisBronnikov theory.