AR_final file_2018-19

ial ellipsoid, the following values of the geometrical axes ratios of the LMC are obtained: 1 . 000 ± 0 . 003 : 1 . 151 ± 0 . 003 : 1 . 890 ± 0 . 014 with the viewing angle parameters: inclination angle of i = 11 0 · 920 ± 0 0 · 315 with respect to the longest axis from the line of sight and position angle of line of nodes θ lon = 128 0 · 871 ± 0 0 · 569. The position angles are measured east- wards from north. This work has been done in col- laboration with Chow-Choong Ngeow, Shashi M. Kanbur, Harinder P. Singh, Daniel Wysocki, and Subhash Kumar. Ujjal Debnath Anisotropic quintessence strange stars in f(T) grav- ity with modified Chaplygin gas We have studied the existence of strange star in the background of f(T) modified gravity, where T is a scalar torsion. In KB metric space, we have derived the equations of motion using anisotropic property within the spherically strange star with modified Chaplygin gas in the framework of mod- ified f(T) gravity. Then we have obtained many physical quantities to describe the physical sta- tus such as anisotropic behaviour, energy condi- tions and stability. By the matching conditions, we have explored the unknown parameters to eval- uate the numerical values of mass, surface redshift, etc. from our model to make comparison with the observational data. This work has been done in collaboration with Pameli Saha. Bouncing universe in the contexts of generalized cosmic Chaplygin gas and variable modified Chap- lygin gas We have assumed the Friedmann-Robertson- Walker (FRW) model of the universe where bounce occurs and the universe is filled with generalized cosmic Chaplygin gas (GCCG) or variable modified Chaplygin gas (VMCG). We have studied the sta- bility analysis through dynamical system for both models and found the critical points in flat, open and closed universe. In presence of scalar field, the dynamical behaviour of scale factor and Hubble pa- rameter are described in both the models. Also have analyzed the energy conditions for both the models in bouncing universe. This work has been done in collaboration with Tanwi Bandyopadhyay. Shantanu Desai Constraints on differential Shapiro delay between neutrinos and photons from IceCube-170922A On 22nd September 2017, the IceCube Collabora- tion detected a neutrino with energy of about 290 TeV from the direction of the gamma-ray blazar TXS 0506+056, located at a distance of about 1.75 Gpc. During the same time, enhanced gamma-ray flaring was also simultaneously observed from mul- tiple telescopes, giving rise to only the second co- incident astrophysical neutrino/photon observation after SN 1987A. We point out that for this event, both neutrinos and photons encountered a Shapiro delay of about 6,300 days along the way from the source. From this delay and the relative time dif- ference between the neutrino and photon arrival times, one can constrain violations of Einstein’s Weak Equivalence Principle (WEP) for TeV neu- trinos. We constrain such violations of WEP using the Parameterized Post-Newtonian (PPN) param- eter γ , which is given by | γ ν − γ EM | < 5 . 5 × 10 − 2 , after assuming time difference of 175 days between neutrino and photon arrival times. This work has been done in collaboration with Sibel Boran, and Enre O. Kahya. Generalized Lomb-Scargle analysis of 90 Sr / 90 Y decay rate measurements from the Physikalisch- Technische Bundesanstalt We apply the generalized Lomb-Scargle (LS) pe- riodogram to independently confirm the claim by Sturrock, et al. of an oscillation at a frequency of 11/year in the decay rates of 90 Sr / 90 Y from mea- surements at the Physikalisch Technische Bunde- sanstalt (PTB), which, however, has been disputed by Kossert and Nahle. For this analysis, we made two different ansatze for the errors. For each peak in the LS periodogram, we evaluate the statistical significance using non-parametric bootstrap resam- pling. We find using both of these error models evidence for ∼ 11/year periodicity in the 90 Sr / 90 Y data for two of the three samples, but at a lower significance than that claimed by Sturrock, et al. This work has been done in collaboration with P. Tejas. ( 186 )