AR_final file_2018-19

Misra. Ritabrata Biswas Evolution of universe as a homogeneous system: Changes of scale factors with different dark energy EoSs We analyze the universe as a thermodynamic sys- tem, homogeneously filled up by exotic matters popularly named as dark energies. Different dark energy models are chosen. We start with the equa- tion of continuity and derive the time and scale factor relations for different EoSs of different dark energy models. To do the time-scale factor rela- tion analysis, nature of dependences on different dark energy modelling parameters have been stud- ied. For this, the help of different plots are used. In general, different dark energies show different properties while occurrences of future singularities are considered. Those properties can be supported by the graphical analysis of their cosmic time-scale factor studies. This work has been done in collab- oration with Promila Biswas. Geometrothermodynamic analysis and PV critical- ity of higher dimensional charged Gauss-Bonnet black holes with first order entropy correction We consider a charged Gauss-Bonnet black hole in d-dimensional spacetime and examine the effect of thermal fluctuations on the thermodynamics of the black hole. At first, we take the first order log- arithmic correction term in entropy and compute the thermodynamic potentials like Helmholtz free energy F, enthalpy H and Gibbs free energy G in the spherical, Ricci flat and hyperbolic topology of the black hole horizon, respectively. We also inves- tigate the P - V criticality and calculate the critical volume V c , critical pressure P c and critical temper- ature T c using different equations when P - V crit- icality appears and show that there is no critical point without thermal fluctuations for this type of black hole. We find that the presence of loga- rithmic correction in it is necessary to have critical points and stable phases. Moreover, we study the stability of the black holes by employing the spe- cific heat. Finally, we study the geometrothermo- dynamics and analyse the Ricci scalar of the Rup- peiner metric graphically for the same. Subenoy Chakraborty Is Cold/Warm in ationary scenario a consequence of particle creation process ? The present work describes a model of inflationary scenario with particle creation mechanism, in the frame work of non-equilibrium thermodynamics. In the background of homogeneous and isotropic spa- tially flat FLRW model of the Universe, the cosmic substratum is chosen as dissipative fluid. Here dis- sipation in the form of bulk viscous pressure is as- sumed to be due to particle creation formalism. For constant and slow–roll phases of (cold) inflationary scenario, the particle creation rate has been derived and an analogous inflaton field has been calculated. Finally, an equivalence of the warm inflation with the present particle creation mechanism has been shown. This work has been done in collaboration with Dipanjana Das, and Sourav Dutta. Cosmological consequences in the framework of generalized Rastall theory of gravity The work deals with generalized Rastall theory of gravity and its cosmological consequences in the background of homogeneous and isotropic flat FLRW model with perfect fluid as the matter con- text. The model shows a non singular era (emer- gent scenario) at the early phase of expansion for a particular choice of the Rastall parameter. Also the model finds to be equivalent to the particle creation mechanism in Einstein gravity in the framework of non-equilibrium thermodynamics. Universal ther- modynamics is briefly presented, and it is found that the entropy function in Rastall theory is the usual Bekenstein entropy and there is no correction to it. Finally, a complete cosmic history starting from inflation to late time acceleration is presented for suitable choices of the Rastall parameter. This work has been done in collaboration with Dipan- jana Das, and Sourav Dutta. Nand Kumar Chakradhari Broad-line type Ic supernova SN 2014ad Optical and ultraviolet photometric, and spectro- scopic results of a broad-line type Ic supernova SN 2014ad in the galaxy PGC 37625 (Mrk 1309) are presented. Observations cover the evolution of su- pernova during − 5 to +87 d with respect to the date of maximum in B -band. Study of a late phase spectrum obtained at +340 d is also presented. ( 177 )