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.
Browse
4 results
Search Results
Item Cosmic Acceleration in Modified Horava- Lifshitz Gravity(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Sameen Ashraf; CIIT/FA19-RMT-094/LHR; Dr. Abdul Jawad; LHR TP 7395We discuss the cosmological implications of the interacting Barrow holo- graphic dark energy model in the context of flat deformed Hoˇrava-Lifshitz gravity by assuming the interaction (Γ) between dark energy and pressure- less dark matter. To understand the mechanism of recent accelerated ex- pansion of the universe, we consider Hubble and event horizons as infrared cutoff. We investigate the evolutionary history of cosmological parame- ters especially the equation of state, Hubble, deceleration, squared speed of sound and find results that favor observational data of Planck 2018. It is found that the Hubble parameter lies in the range 72+2 −2 (for event horizon) and 74.004+0.004 −0.004 (for Hubble horizon). The equation of state parameter pro- vides the phantom phase of the universe, while the deceleration parameter illustrates the accelerated phase of the universe. On the other hand, we plot the squared speed of sound and find the positive behavior which ensures the stability of underlying model. Moreover, we examine the generalized second law of thermodynamics of this cosmological system with barrow entropy as horizon entropy and observe that this law holds for both horizons.Item Geometric Thermodynamics of Well-Known Black Holes(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Syeda Rabab Fatima; CIIT/FA19-RMT-111/LHR; Dr. Abdul Jawad; LHR TP 7532We study the phase transition and thermodynamic geometries of a charged AdS black hole with a global monopole. For this purpose, we develop the thermodynamic quantities such as Hawking temperature, spe- cific heat and pressure on horizon radius in the presence of Barrow entropy. The stability of this black hole is being observed through specific heat. Also, we investigate the thermodynamic curvatures behavior of black hole by applying Weinhold and Ruppiner formulations. It is found that ther- modynamic curvatures exhibit the attractive and repulsive nature of black hole for specific constants. We also study the thermodynamic curvature of charged BTZ black hole by fixing phase space of entropy, pressure and volume on curvature, i.e., entropy-pressure corrected curvature (RSP ) and entropy-volume corrected curvature (RSV ). It is found that there present a repulsive force by the charged BTZ black hole for its molecules, qual- itatively or phenomenologically. However, RSV shows negative behavior initially which exhibits the attractive nature of charged BTZ black hole.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 Swampland Criteria of Inflationary Cosmology with Well-Known Potentials(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Aneesa Majeed; CIIT/FA19-RMT-115/LHR; Dr. Abdul Jawad; LHR TP 7383We explore the swampland conjectures of quintessence and tachyon scalar field models in f(T ) and Einstein gravities, respectively. In f(T ) gravity, we consider cold and warm (by assuming generalized dissipative coefficient) inflationary scenario and develop constraints on de-Sitter con- jectures through Bekenstein entropy relation. In usual inflation, the de- Sitter conjecture constraint becomes constant (in terms of models constant parameters) which can be easily analyzed for its validity (i.e., |V 0| V ≤ O(1)). However, in warm inflation, we analyze the de-Sitter conjecture constraint through T 0V TV 0 , i.e., if T 0V TV 0 < 1 then |V 0| V ≤ O(1) and hence we can obtain required result. For evaluating this condition, we choose three well-known potentials such as monomial chaotic, hilltop and generalized exponential. It is observed that the condition T 0V TV 0 < 1 satisfied for all three potentials in both regimes of dissipative coefficient for specific choice of constants. Sim- ilarly, we also obtain satisfactory results of de-Sitter conjecture for tachyon and polytropic (with quintessence scalar field) in general relativity.