35th Annual Report (2022-2023) - ENGLISH

166 The effective potential for null geodesics consists of only a centrifugal part. Further, we characterize each fixed point according to its Lyapunov stability, and thus classify the circular orbits at the fixed point into stable center and unstable saddle points by depicting the corresponding phase- portraits. © 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 the 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 with vacuum case. Variation of shadow radius and deformation parameter with Yang- Mills and plasma parameter has examined. Furthermore, the deflection angle of the massless test particles in weak field approximation around this black hole spacetime in the presence of homogeneous plasma medium is also investigated. Finally, we have compared the obtained results with Kerr-Newman and Schwarzschild black hole solutions in general relativity (GR). (d) We analyze the stability of circular geodesics for timelike as well as null geodesics of the Kerr BH spacetime with rotation parameter on the equatorial plane by Lyapunov stability analysis. Also, we verify the results of stability by presenting the phase portrait for both timelike and null geodesics. Further, by reviewing the Kosambi-Cartan-Chern (KCC) theory, we analyze the Jacobi stability for Kerr spacetime and present a comparative study of the methods used for stability analysis of geodesics. (a) S. Giri, P. Sheoran, H. Nandan and S. Shaymatov, Chaos motion and Periastron precession of spinning test particles moving in the vicinage of a Schwarzschild black hole surrounded by a quintessence matter field, Eur. Phys. J. Plus, 138:245 (2023). (b) S. Giri, H. Nandan, L. K. Joshi and S. D. Maharaj, Stability analysis of circular orbits around a traversable wormhole with massless conformally coupled scalar field, European Physical Journal C82:298, (2022). (c) S. Kala, H. Nandan , P. Sharma, Shadow and weak gravitational lensing of a rotating regular black hole in a non- minimally coupled Einstein-Yang-Mills theory in the presence of plasma, List of publications by using ICARD facilities: European Physical Journal Plus 137:457, (2022). (d) P. Singh, H. Nandan , L. K. Joshi, N. Handa and S. Giri, Stability of circular geodesics in the equatorial plane of Kerr spacetime, European Physical Journal Plus 137:263, (2022). (a) Sky watch programme in ScienceWeek Festival during 28 Feb-03-Mar, 2023 in different campuses of HNBGU, Srinagar Garhwal. (b) Sky watch programme during 19-21 Dec, 2022 at Chauras campus, HNBGU Srinagar Garhwal. In above sky watch activities, more than 3000 students of our campus and nearby schools have participated in this programme to watch sunspots and night sky objects. Extra-ordinary Professor (Honorary position) at Center for Space Research (CSR), North-West University, South Africa. Any outreach programmes, including public lectures/sky watch arranged by ICARD,etc. Any honours/distinctions/awards, etc. received by persons connected with ICARD Coordinator: Professor Asis Kumar Chattopadhyay ICARD Department of Statistics, University of Calcutta, Kolkata: Activities from 01 April 2022 till 31 March 2023 AreaofResearch: During this period 2022-23 the main focus of the researchworkwas theoretical studies as well as data Analysis related to Astronomical Objects, Star formation Rate, Explosion Triggered Star Formation, Thermal Instability driven Star Formation, Distance Determination of nearby as well as far off stars, Measure of Chaos in the presence of SMBH under different halos, Episodicmodel of Star Formation with small scale dissipation. Some large scale simulation studies have been carried out. Some scholars and faculty members of different colleges and Universities in and around Kolkata are very much involved in the use of Mathematical and Statistical software as well as development of Computer programs for the appropriate analysis of Astronomical data. They are also trying to develop new statistical techniques appropriate for the analysis of Astronomical data.