Prof. Dr. Bobomurat Ahmedov
Ulugh Beg Astronomical Institute
'%3e%3cpath%20d='M22.1642%2019.0924C21.7317%2018.068%2021.1041%2017.1375%2020.3163%2016.3527C19.5309%2015.5656%2018.6006%2014.9381%2017.5766%2014.5048C17.5674%2014.5002%2017.5582%2014.4979%2017.5491%2014.4933C18.9774%2013.4616%2019.9059%2011.7811%2019.9059%209.88504C19.9059%206.74408%2017.3611%204.19922%2014.2201%204.19922C11.0792%204.19922%208.53429%206.74408%208.53429%209.88504C8.53429%2011.7811%209.46282%2013.4616%2010.8912%2014.4956C10.882%2014.5002%2010.8728%2014.5025%2010.8636%2014.5071C9.83652%2014.9404%208.91487%2015.5617%208.1239%2016.355C7.33685%2017.1404%206.70933%2018.0707%206.276%2019.0947C5.85031%2020.0972%205.62072%2021.172%205.59967%2022.2609C5.59905%2022.2853%205.60335%2022.3097%205.61229%2022.3325C5.62123%2022.3553%205.63465%2022.376%205.65174%2022.3935C5.66883%2022.4111%205.68926%2022.425%205.71182%2022.4345C5.73437%2022.444%205.7586%2022.4489%205.78308%2022.4489H7.15868C7.25956%2022.4489%207.3398%2022.3686%207.3421%2022.2701C7.38795%2020.5001%208.09868%2018.8425%209.35506%2017.5861C10.655%2016.2862%2012.3814%2015.5709%2014.2201%2015.5709C16.0588%2015.5709%2017.7852%2016.2862%2019.0852%2017.5861C20.3415%2018.8425%2021.0523%2020.5001%2021.0981%2022.2701C21.1004%2022.3709%2021.1807%2022.4489%2021.2815%2022.4489H22.6571C22.6816%2022.4489%2022.7058%2022.444%2022.7284%2022.4345C22.751%2022.425%2022.7714%2022.4111%2022.7885%2022.3935C22.8056%2022.376%2022.819%2022.3553%2022.8279%2022.3325C22.8369%2022.3097%2022.8412%2022.2853%2022.8406%2022.2609C22.8176%2021.165%2022.5907%2020.0989%2022.1642%2019.0924ZM14.2201%2013.8284C13.1678%2013.8284%2012.1773%2013.418%2011.4322%2012.6729C10.6871%2011.9278%2010.2767%2010.9374%2010.2767%209.88504C10.2767%208.83271%2010.6871%207.84227%2011.4322%207.09715C12.1773%206.35204%2013.1678%205.94165%2014.2201%205.94165C15.2724%205.94165%2016.2629%206.35204%2017.008%207.09715C17.7531%207.84227%2018.1635%208.83271%2018.1635%209.88504C18.1635%2010.9374%2017.7531%2011.9278%2017.008%2012.6729C16.2629%2013.418%2015.2724%2013.8284%2014.2201%2013.8284Z'%20fill='%238590A2'/%3e%3c/g%3e%3c/svg%3e)
Co-authors
Following
Followers
Research Focus & Metrics
Explore full metrics on Scilit
Academic Career Length
33Years (1994-Present)
(Calculated once Scilit publication data is synced: current year − year of first publication + 1)
Representative Publications
View All Publications3 May 2016 in Physical Review D
Journal Article
Ahmadjon AbdujabbarovMAMuhammed Amir
Muhammed AmirBobomurat Ahmedov
Sushant G GhoshWe study the shadows cast by the different types of rotating regular black holes viz. Ayón-Beato-García (ABG), Hayward, and Bardeen. These black holes have in addition to the total mass () and rotation parameter (), different parameters as electric charge (), deviation parameter (), and magnetic charge (). Interestingly, the size of the shadow is affected by these parameters in addition to the rotation parameter. We found that the radius of the shadow in each case decreases monotonically, and the distortion parameter increases when the values of these parameters increase. A comparison with the standard Kerr case is also investigated. We have also studied the influence of the plasma environment around regular black holes to discuss its shadow. The presence of the plasma affects the apparent size of the regular black hole’s shadow to be increased due to two effects: (i) gravitational redshift of the photons and (ii) radial dependence of plasma density.
3 September 2013 in Physical Review D
Journal Article
Farruh AtamurotovAhmadjon AbdujabbarovBobomurat AhmedovThe shadow of a rotating non-Kerr black hole has been studied, and it was shown that in addition to the specific angular momentum , the deformation parameter of non-Kerr spacetime essentially deforms the shape of the black hole shadow. For a given value of the black hole spin parameter , the presence of a deformation parameter reduces the shadow and enlarges its deformation with respect to the one in the Kerr spacetime. Optical features of the rotating non-Kerr black hole in terms of rotation of the polarization vector along null congruences have been studied. A comparison of the obtained theoretical results on the polarization angle with the observational data on Faraday rotation measurements provides the upper limit for the dimensionless deformation parameter as .
30 July 2014 in Physical Review D
Journal Article
UPUma Papnoi
Uma PapnoiFarruh AtamurotovSushant G GhoshBobomurat AhmedovA black hole casts a shadow as an optical appearance because of its strong gravitational field. We study the shadow cast by the five-dimensional Myers-Perry black hole with equal rotation parameters. We demonstrate that the null geodesic equation can be integrated, which provides us an opportunity to investigate the shadow cast by a black hole. The shadow of a black hole is found to be a dark zone covered by a deformed circle. Interestingly, the shapes of the black hole shadow are more distorted and the size decreases for larger black hole spins. Interestingly, it turns out that, for fixed values of the rotation parameter, the shadow is slightly smaller and less deformed than for its four-dimensional Kerr black hole counterpart. Further, the shadow of the five-dimensional Kerr black hole is concentric deformed circles. The effect of the rotation parameter on the shape and size of a naked singularity shadow is also analyzed.
9 May 2014 in Physical Review D
Journal Article
BTBobir Toshmatov
Bobir ToshmatovBobomurat AhmedovAhmadjon Abdujabbarov
Zdeněk StuchlíkBased on the Newman-Janis algorithm, the Ay\'on-Beato-Garc\'\ia spacetime metric [Phys. Rev. Lett. 80, 5056 (1998)
13 October 2015 in Monthly Notices of the Royal Astronomical Society
Journal Article
Ahmadjon AbdujabbarovLRL. Rezzolla
L. Rezzolla
Bobomurat AhmedovA large international effort is under way to assess the presence of a shadow in the radio emission from the compact source at the centre of our Galaxy, Sagittarius A* (Sgr A*). If detected, this shadow would provide the first direct evidence of the existence of black holes and that Sgr A* is a supermassive black hole. In addition, the shape of the shadow could be used to learn about extreme gravity near the event horizon and to determine which theory of gravity better describes the observations. The mathematical description of the shadow has so far used a number of simplifying assumptions that are unlikely to be met by the real observational data. We here provide a general formalism to describe the shadow as an arbitrary polar curve expressed in terms of a Legendre expansion. Our formalism does not presume any knowledge of the properties of the shadow, e.g. the location of its centre, and offers a number of routes to characterize the distortions of the curve with respect to reference circles. These distortions can be implemented in a coordinate-independent manner by different teams analysing the same data. We show that the new formalism provides an accurate and robust description of noisy observational data, with smaller error variances when compared to previous approaches for the measurement of the distortion.
2 October 2015 in Physical Review D
Journal Article
Farruh AtamurotovBobomurat AhmedovAhmadjon AbdujabbarovWe have studied photon motion around axially symmetric rotating Kerr black holes in the presence of a plasma with radial power-law density. It is shown that in the presence of a plasma, the observed shape and size of the shadow changes depending on the (i) plasma parameters, (ii) black hole spin, and (iii) inclination angle between the observer plane and the axis of rotation of the black hole. In order to extract the pure effect of the plasma influence on the black hole image, the particular case of the Schwarzschild black hole has also been investigated and it has been shown that the photon sphere around the spherically symmetric black hole is left unchanged under the plasma influence; however, the Schwarzschild black hole shadow size in the plasma is reduced due to the refraction of the electromagnetic radiation in the plasma environment of the black hole. The study of the energy emission from the black hole in plasma environment shows that in the presence of the plasma the maximal energy emission rate from the black hole decreases.
About Me
Bobomurat Ahmedov (PhD, 1993, Inst. Nuclear Physics, Tashkent; D.Sc., 2001, Natl Univ. Uzbekistan - NUUz, Tashkent; Fellow, 2018, The World Academy of Sciences (TWAS); Fellow, 2020, The Islamic World Academy of Sciences (IAS)) is head of the Theoretical Astrophysics department at Ulugh Beg Astronomical Institute and a professor at NUUz. He was awarded the Researcher of the Year in 2018 in Uzbekistan by the Scopus Science Leader Web of Science award (2017) as a highly cited author in Uzbekistan. He has also been awarded the following: Uzbekistan State Order Glory of Labor, 2012; Award of TWAS for Young Scientists in Physics in Uzbekistan, 2001; Award of Uzbekistan Acad. Sci. for Young Scientists in Physics,1996; International Science Foundation Award, 1994; CNR-NATO Grant, 2004; NATO Reintegration Grant, 2004–2007; Abdus Salam International Centre for Theoretical Physics (ICTP) Regular Associate, Italy, 2005-2010; Volkswagen Stiftung Grant, Germany, 2013–2016; German Academic Exchange Service - DAAD, Germany, grants 2017, 2012, 2009, 2006; UNESCO-TWAS Regular Associate at Tata Institute of Fundamental Research, Mumbai, India, 2012–2014, at Inter-University Centre for Astronomy and Astrophysics (Pune, India), 2010–2012, 2002–2004; Fudan Fellowship, China, 2017, 2019; Coordinator of ICTP Affiliated Center, Network and Project (AC-83, NT-01, PRJ-29). Ahmedov is Editor-in-Chief of the Uzbek Journal of Physics and Editor of the Arabian Journal of Mathematics by Springer.