AR_final file_2018-19

positively correlated with sunspot area asymme- try, whereas coronal hole asymmetry is uncorre- lated. This study has been done in collaboration with Prantika Bhowmik. Barun Kumar Pal Mutated hilltop inflation revisited Applying Hamilton-Jacobi formalism, we solve in- flationary dynamics and find that inflation goes on along the W − 1 branch of the Lambert function. Depending on the model parameter, mutated hill- top model renders two types of inflationary solu- tions: one corresponds to small inflaton excursion during observable inflation and the other describes large field inflation. The inflationary observables from curvature perturbation are in tune with the current data for a wide range of the model pa- rameter. The small field branch predicts negligible amount of tensor to scalar ratio r ∼ O (10 − 4 ), while the large field sector is capable of generating high amplitude for tensor perturbations, r ∼ O (10 − 1 ). Also, the spectral index is almost independent of the model parameter along with a very small nega- tive amount of scalar running. Finally, we find that the mutated hilltop inflation closely resembles the α -attractor class of inflationary models in the limit of αφ ≫ 1. Gravitationally influenced particle creation models and late-time cosmic acceleration In this work we focus on the gravitationally influ- enced adiabatic particle creation process, a mecha- nism that does not need any dark energy or mod- ified gravity models to explain the current acceler- ating phase of the universe. Introducing some par- ticle creation models that generalize some previous models in the literature, we constrain the cosmo- logical scenarios using the latest compilation of the yype Ia supernovae data only, the first indicator of the accelerating universe. Aside from the ob- servational constraints on the models, we examine the models using two model independent diagnoses, namely the cosmography and Om . Further, we es- tablish the general conditions to test the thermo- dynamic viabilities of any particle creation model. Our analysis shows that at late-time, the models have close resemblance to that of the ΛCDM cos- mology, and the models always satisfy the general- ized second law of thermodynamics under certain conditions. This study has been done in collabora- tion with Supriyapan, and souvik Pramanik. Biswajit Pandey A new method to probe the mass density and the cosmological constant using configuration entropy We study the evolution of the configuration entropy for different combinations of Ω m 0 and Ω Λ0 in the flat ΛCDM universe, and find that the cosmologi- cal constant plays a decisive role in controlling the dissipation of the configuration entropy, which dis- sipates at a slower rate in the models with higher value of Ω Λ0 . We find that the entropy rate de- cays to reach a minimum and then increases with time. The minimum entropy rate occurs at an ear- lier time for higher value of Ω Λ0 . We identify a prominent peak in the derivative of the entropy rate, whose location closely coincides with the scale factor corresponding to the transition from matter to Λ domination. We find that the peak location is insensitive to the initial conditions and only de- pends on the values of Ω m 0 and Ω Λ0 . We propose that measuring the evolution of the configuration entropy in the universe and identifying the location of the peak in its second derivative would provide a new and robust method to probe the mass den- sity and the cosmological constant. This study has been done in collaboration with Supriyapan, and Biswajit Das. Configuration entropy of the Cosmic Web: Can voids mimic the dark energy? We propose an alternative physical mechanism to explain the observed accelerated expansion of the universe based on the configuration entropy of the cosmic web and its evolution. We show that the sheets, filaments, and clusters in the cosmic web act as sinks, whereas the voids act as the sources of information. The differential entropy of the cosmic velocity field increases with time and also act as a source of entropy. The growth of non-linear struc- tures and the emergence of the cosmic web may lead to a situation, where the overall dissipation rate of information at the sinks are about to dom- inate the generation rate of information from the sources. Consequently, the universe either requires a dispersal of the overdense non-linear structures or an accelerated expansion of the underdense voids to prevent a violation of the second law of thermody- namics. The dispersal of the sheets, filaments, and ( 204 )