M.Phil / MS
Permanent URI for this collectionhttps://repository.cuilahore.edu.pk/handle/123456789/52
This collection archives the complete set of theses produced by students of the COMSATS University Islamabad, Lahore Campus.
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Item Cosmic Inflation Evading Swampland Conjectures(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Kashaf Embreen; CIIT/FA19-RMT-022/LHR; Dr. Abdul Jawad; LHR TP 7440In this thesis, we study the inflationary scenario in the realm of k-essence model and swampland conjecture. Taking into account three models of Chaplygin gas, that is, generalized, modified and generalized cosmic Chap- lygin gas models, we discuss the slow roll parameters (²(φ), η(φ)), curvature perturbation (Ps), tensor to scaler ratio (r) and scaler spectral index (ns). In reference to k-essence model, the coupling function as a function of scaler field L(φ) is used. We investigate the swampland conjecture and then find the value of ζ(φ) i.e bound of second conjecture for the above three models by unifying swampland conjecture and k-essence. We plot the inflationary parameters and bound of swampland conjecture r −ns, ζ(φ) − φ, and check their values according to Planck data 2018.Item Inflationary Dynamics and Thermodynamics of Chaplygin Gas Models(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2018) Muhammad Adeel Sultan; CIIT/SP17-RMT-006/LHR; Dr. Abdul Jawad; LHR TP 5441In this thesis, we study the reconstruction of warm inflation model with the help of tensor to scalar ratio (r) and scalar spectral index (ns) in terms of number of e-folds (N). In this regards, we take flat FRW metric and discuss the general forms of dissipative coefficient Γ(φ, T ) as well as effec- tive potential V (φ, T ) for two dissipative regimes i.e., the weak and strong. We use inflationary parameters like slow roll parameters, power spectrum of the curvature perturbation, tensor spectrum, spectral index, scalar to tensor ratio and Hubble parameter to find the generalized form of dissi- pative coefficient and effective potential. Further, we discuss generalized cosmic Chaplygin gas in the scenario of particle creation. We examine energy density (ρ), Hubble parameter (H), declaration parameter (q), tem- perature (T ) and particle number density (n) under three different models of particle creation rate. We also analyze the production of entropy and Bekenstein entropy in the scenario of first law of thermodynamics. We dis- cuss the validity of generalized second law of thermodynamics and thermal equilibrium under three models of Γ and discuss the graphical behavior of above mentioned terms.Item Modified Entropy Inspired Scalar Field Cosmic Inflation with Well-known Potentials(Library Information Services COMSATS University Lahore Campus, 2024-03-17) Hafiza Iqra Nadeem; FA22-RMT-022; Dr. Abdul Jawad; LHR TP 9377This thesis is dedicated to discuss the inflationary setup with the help of modified Barrow entropy with f(R) gravity framework. We derive the Friedmann equations by using the first law of thermodynamics. With the help of these equations, we reconstruct f(R) gravity model to establish the relationships governing scalar and tensor perturbation power spectra and interestingly this model mimics thermodynamically under the slow-roll approximation. Two different types of potentials like the β potential and the exponential potential are used to explore the insights of inflationary parameters in the underlying scenario. Thus, the inflation-related quantities like scalar spectral index and tensor-to-scalar ratio are discussed graphically in our scenario by developing contour plots. It is worthwhile mention here that our results are consistent with Planck 2018 data.