Department of Mathematics

Permanent URI for this communityhttps://repository.cuilahore.edu.pk/handle/123456789/21

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Author: search.filters.author.Dr. Abdul JawadSubject: search.filters.subject.department of Mathematics

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    Phase Space Analysis and Cosmic Parameters of Dynamical Dark Energy Model
    (Library Information Services COMSATS University Lahore Campus, 2024-03-18) Ruqia Arif; SP23-RMT-027; Dr. Abdul Jawad; LHR TP 9581
    This thesis explores the stability analysis of Friedmann-like spacetimes using dynamical system methods. For this purpose, we begin by considering a modified cosmological sce nario based on Tsallis entropy corrections. These entropic formulations modify the cosmo logical field equations that govern the universe’s dynamics. We incorporate these modified Friedmann equations and convert them into a first-order autonomous system of differential equations. To identify the system’s equilibrium points, we consider the interaction between cosmological fluids. Various linear and non-linear forms of interaction models are exam ined. For each model, we calculate the critical points and discuss their behavior associated with eigenvalues. We investigate the different stages in the universe’s evolution including dust and radiation dominated era of the universe as well as quintessence, ΛCDM and phan tom regimes. In addition, we develop the phase space portraits of all the interaction models revealing the stable, unstable and saddle behavior of critical points. In most of the cases, the system supports stable critical points.
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    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 9377
    This 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.