34th Annual Report (2021-22)

171 Gurukula Kangri (Deemed to be University), Haridwar April 1, 2021-March 31, 2022 Coordinator: Dr. Hemwati Nandan Areas of research ¬ ¬ ¬ ¬ ¬ Researchworkdone GR and Alternative Theory of Gravity Black Hole Physics Dark Energy and Dark Matter Gravitational Lensing and Shadow Non-Linear Dynamics and Chaos The members associated with ICARD, Haridwar have worked on different issues related to the areas as mentioned in the areas of research during the assessment period. We have worked on the optical properties (shadow and gravitational lensing) and thermodynamic properties of some interesting spacetimes in general relativity (GR) and in alternative theories of gravity. In particular, we have studied the motion of photons in ADS geometry to observe the effect of different charges on the path of the light along with the shadows and the relation for distance of closest approach with the magnetic charges, the gauge coupling constant and NUT charge. We have also investigated the shadow and deflection angle of charged rotating black hole surrounded by perfect fluid darkmatter and Rotating charged black hole in 4D Einstein–Gauss–Bonnet gravity. The horizon, energy emission from a given black hole spacetime has been investigated. The study of bending angle of light in a solution representing a fluid with a constant equation of state which can for example describe an effectivewarmdarkmatter fluid around a black hole was performed. We had analyzed the deflection angle produced by the black hole in view of various black hole parameters. An exact solution for bending angle was also determined for a particular value of the equation of state parameter. The study of gravitational lensing and black hole shadows around a dual-charged stringy black hole spacetime derived in dilaton-Maxwell gravity. The variation of deflection angle with the impact parameter for different values of black hole parameters was studied. The shadow of this black hole spacetime was investigated also the radius of the shadow was studied in detail. We had also contributed to the study of gravitational lensing around a rotating Bañados–Teitelboim–Zanelli (BTZ) black hole in (2 + 1)-dimensional gravity inwhich a detailed discussion for orbits for massless test particles around this black hole spacetime to understand the nature of cosmological constant in lower dimensions was presented. The effect of the cosmological constant on the photon orbit in view of other critical black hole parameters had studied. The bending angle of light was also investigated for different values of cosmological constant for direct and retrograde motion of test particles. In another paper entitled “Optical and thermodynamic properties of a rotating dyonic black hole spacetime in gauged supergravity” a detailed study of gravitational shadows and thermodynamics was performed. The null geodesics and the distance of the closest approach for the photon were also studied. Further, the investigation of various 2 N=2, U (1) thermodynamic properties for BH with dyonic charges is also studied. We have ob t a i ned v a r i ous t he rmodynami c parameters at the horizon. More recently, we have also performed the stability analysis of circular geodesics along with quasinormal modes for scalar field perturbation in the vicinity of a dual stringy black hole and non-commutative geometry inspired Schwarzschild black hole. Stability analysis of circular orbits around a charged BTZ black hole spacetime in a nonlinear electrodynamics model is studied. Also, stability analysis of circular orbits around Kerr black hole and traversable wormhole with massless conformally coupled scalar field are investigated via Lyapunov stability criteria. n-butyl, S-2-nitro-1-(p-tolyl) ethyl dithiocarbamate - a bio-relevant sulfur molecule; T. Yadav, G. Brahmachari, I. Karmakar, P. Yadav, A. K. Prasad, A. Pathak , A. Agarwal, R. Kumar, V. Mukherjee, G. N. Pandey, R. R. F. Bento, N. P. Yadav; Journal of Molecular Structure, 1238, 130450, 2021. 7. Accretion disc sizes from continuum reverberation mapping of AGN selected from the ZTF survey; V. K. Jha, R. Joshi, H. Chand, X. Wu, L. C. Ho, S. Rastogi , Q. Ma; MNRAS, 511(2), 3005 – 16, 2022. 8. A comparative study of the physical properties for a representative sample of Narrow and Broad-line Seyfert galaxies; V. K. Jha, H. Chand, V. Ojha, A. Omar, S. Rastogi ; MNRAS, 510(3), 4379 – 93, 2022. Outreachprogrammes 1. Shantanu Rastogi delivered online lecture on Measuring the Universe on 10-Dec-2021 organized by the Astronomy and Astrophysics Club (VINN), Central Univ. of T.N. 2. Science day film show on Cosmic Collisions was organized at DDUGU for M.Sc. students on 28-Feb-2022.