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 Expansion Phenomenon in Specific Scalar Field Theory(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Farwa Khurshid; CIIT/FA19-RMT-105/LHR; Dr. Shamaila Rani; LHR TP 7430The interaction of newly proposed holographic dark energy model, Bar- row holographic dark energy model is being used to analyze the cosmic expansion phenomenon. We consider the interaction between dark energy and dark matter in the realm of scalar field theory. For the power law, quadratic and quartic (positive and negative) potentials, we investigate the different cosmological implications. This includes the equation of state pa- rameter ωD which identifies different eras of the expanding universe, cosmic plane ωD − ω0 D (where ω0 D shows the evolution of equation of state para- meter ωD where prime shows derivative with respect to ln a) and squared speed of sound parameter v2 s for the stability analysis of the models.Item Barrow Holographic Dark Energy in Extended Teleparallel Theories of Gravity(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Ghulam Murtaza; CIIT/FA19-RMT-085/LHR; Dr. Shamaila Rani; LHR TP 7424In this thesis, we reconstruct some solutions in the context of telepar- allel based extended theories coupled with trace of energy-momentum ten- sor, boundary term and Gauss-Bonnet term. For this purpose, we ob- tain the effective energy density and pressure for these theories for flat FRW universe model. The reconstruction is made through the compari- son of these effective energy densities with the energy density of Barrow holographic dark energy model. In this regards, we use scale factor in terms of power-law form and find some gravitational Lagrangian functions as f(T ) = T +g(T ), f(T, τ ) = T +γh(τ ), f (T, τ ) = βτ +g(T ), f(T, TG) = TGg(T ), f(T, TG) = −T + TGg(T ), f(T, TG) = TG + g(T ), f(T, TG) = T + j(TG), f(T, B) = T + σy(B) and f(T, B) = B + ξg(T ). In order to discuss the cosmic analysis related to these models, we plot equation of state parameter for each model. We investigate the squared speed of sound parameter for these models to determine the stability of the models. We obtain some favorable results related to specific values of model parameters.Item Thermodynamics Quantities and Heat Engines of Various Black Holes(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2021) Misbah Tasleem; CIIT/FA19-RMT-019/LHR; Dr. Shamaila Rani; LHR TP 7425According to Barrow, the impact of quantum-gravitation changes the standard relation of entropy S = A 4 to S = A1+∆ 2 , where A is actual area and ∆ represents the quantum gravitational deformation effects. Keeping in mind the importance of entropy in the thermodynamics of black hole, we study the impact of Barrow entropy on the thermodynamics of charged AdS black hole with global monopole. We derive and plot many thermo- dynamical quantities of charged AdS black hole like temperature, entropy, pressure, Helmholtz free energy, Gibbs free energy, heat capacity of the system at constant pressure and volume. We study the critical behavior, phase transition and thermal stability and find out that more useful work can be extracted from black hole by using Barrow entropy. We also observe that Barrow entropy rapidly increases the Gibbs free energy of black hole which leads to more stable behavior as compare to standard relation of en- tropy. We also discuss charged black hole as heat engine and find out the efficiency of the black hole. In addition, we explore the thermal properties of torus-like black hole and find useful results regarding stability.