AR-2019-2020

bital decay and apsidal precession ephemeris mod- els to transit time data. The orbital decay study shows decreasing period of TrES-3b with the decay rate equals to 4 . 112 ± 3 . 104 msyr − 1 . By assum- ing this decay rate is real, the estimated remaining lifetime of TrES-3b and the modified tidal quality factor ( Q ∗ ) of the parent star (TrES-3) are found to be ∼ 4 . 9 Myr and ∼ 1 . 11 × 10 5 , respectively. From the apsidal precession study, the precession rate of the orbit of TrES-3 system is found to be 0 . 000472 ± 0 . 000320 radepoch − 1 . Corresponding to this precession rate, the estimated planetary tidal Love number (kp) of 1 . 15 ± 0 . 32 is found to be larger than that of Jupiter. For the selection of op- timal model that shows the best fit to the timing data, we have used the Bayesian Information Cri- terion ( BIC = χ 2 + klogN , where N is the total number of data points and k is the number of free parameters) statistic. Because of the smaller value of BIC obtained in the linear model as compared to the orbital decay and apsidal precession models, we have preferred the linear model as best possi- ble model to represent our considered transit time data. This work has been done in collaboration with Vineet Kumar Mannaday, Ing-Guey Jiang, Devendra Kuamr Sahu, and Yogesh C. Joshi. Sunil Kumar Tripathy Phantom cosmology in an extended theory of grav- ity Some phantom cosmological models without big rip singularity have been constructed in a simple ex- tended theory of gravity. In the geometrical part of the action, a minimally coupled linear function of the Ricci scalar and the trace of the energy mo- mentum tensor have been considered in place of the Ricci scalar. Four Little Rip and Pseudo Rip models have been investigated, where the equation of state parameter evolves asymptotically and suf- ficiently rapidly to − 1. The effect of the coupling constant of the extended gravity theory on the dy- namics has been discussed. Possible wormhole so- lutions for the phantom models are obtained. The possibility of Big trip in wormholes are discussed for the models. This work is done in collaboration with Bivudutta Mishra. Bouncing cosmology in an extended gravity theory We have investigated some bouncing models in the framework of an extended gravity theory, where the usual Ricci scalar in the gravitational action is replaced by the sum of the Ricci scalar and a term proportional to the trace of the energy mo- mentum tensor. The dynamical parameters of the models are derived in a most general manner. We considered two bouncing scenarios described by an exponential and a power law scale factors. The non-singular bouncing models also favour a late time cosmic speed up phenomenon. The dynam- ical behaviour of the equation of state parameter is studied for the models. It is observed that near the bounce, the dynamics is substantially affected by the coupling parameter of the modified grav- ity theory and is least affected by the parameter of the bouncing scale factors. This work is done in collaboration with Rakesh Kumar Khuntia, and Priyabrata Parida. Vinutha Tummala Modified holographic Ricci dark energy model in a scalar tensor Theory of gravitation In this work, we have studied homogeneous and anisotropic Bianchi type-V metric filled with dark mater (DM) and modified holographic Ricci dark energy (MHRDE) in the framework of scalar- tensor theory of gravitation proposed by Saez and Ballester. To find a deterministic solution for Saez- Ballester field equations, we have used the hybrid expansion law (HEL) for the average scale factor a(t), which yields a time dependent deceleration parameter and exhibits a transition of the Uni- verse from early decelerated phase to the recent accelerating phase. We also have taken the scalar expansion to be proportional to the shear scalar. We have investigated the physical and geometrical properties of the model. It is observed that our model is in good agreement with the ΛCDM model at late times. This work is done in collaboration with V.Uma Maheswara Rao, and Molla Mengesha Nigus Bianchi type cosmological models in f(R, T) theory with quadratic functional form The spatially homogeneous and anisotropic Bianchi type III, V and VI 0 cosmological models have been investigated in gravity by choosing the function of the form R + αR 2 + λT . Here, R is the Ricci scalar, T is the trace of the energy momentum tensor and α , λ are constants. Exact solutions to the field equations of three models are obtained with the