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 Warm Inflationary Dynamics of Chaplygin Gas Models with Constant Sound Speed(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2019) FA17-RMT-050; Azmat Rustam; Dr. Abdul Jawad, Assistant Profesor; LHR TP 5671This study investigates the warm inflationary dynamics of Chaplygin gas models under the assumption of a constant sound speed. Warm inflation, characterized by the simultaneous production of radiation during the inflationary phase, provides an alternative to the standard cold inflation scenario by eliminating the need for a separate reheating period. In this work, the Chaplygin gas—known for its unified description of dark energy and dark matter—is incorporated into the inflationary framework to explore its viability in describing the early universe. Assuming a constant sound speed simplifies the dynamical equations and allows for analytical treatment of the system. The evolution of key inflationary parameters, including the Hubble parameter, scalar field dynamics, and radiation energy density, is examined in detail. Slow-roll conditions are derived and analyzed within the context of dissipative effects inherent in warm inflation. Additionally, cosmological perturbations are studied to evaluate the scalar spectral index and tensor-to-scalar ratio, providing a means to compare theoretical predictions with observational data. The results demonstrate that Chaplygin gas models with constant sound speed can successfully support a sustained period of warm inflation while remaining consistent with current cosmological observations. This framework offers a promising avenue for connecting early universe inflation with late-time cosmic acceleration, contributing to a more unified cosmological model.Item Thermodynamics of Dyadosphere of Reissner Nordstrom, f(R) Global Monopole and Janis Newman-Winicour Black Holes(Library Information Services, COMSATS University, Lahore Campus, 2016) Ayesha Sadiq,; FA14-BSM-013; Dr. Abdul Jawad, Assistant Profesor; LHR TP 5258In this thesis, we study the effects of thermal fluctuations on Dyadosphere of Reissner-Nordstr¨om, Janis-Newman-Winicour and the fragmentation of f(R) global monopole black holes. In the presence of these fluctuations, we obtain various thermodynamic quantities like entropy, pressure, specific heat, Gibb’s free energy and Helmholtz free energy. We discuss the stability of these black holes using the γ (the ratio of heat capacities). We also discuss the phase transition, grand canonical ensemble and canonical ensemble. It is demonstrated that in Dyadoshpere of Reissner-Nordstr¨om, Janis-Newman Winicour and fragmentation of f(R) global monopole black holes become locally and globally stable with respect to increasing value of horizon radius.Item Thermal Fluctuations Of A Regular And Einstein(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2016) Hafiza Zarish Arshad; , FA14-BSM-001; Dr. Abdul Jawad, Assistant Profesor; LHR TP 5252In this thesis, we study the effects of thermal fluctuations on regular black hole solutions with cosmological constant and Einstein-aether black hole with coupling constant respectively. We consider the logarithmic corrected entropy in order to analyzing the thermal fluctuations on regular black hole solutions and Einstein-aether black hole. We also obtain various thermo dynamical quantities such as entropy, pressure, specific heats, Gibb’s free energy and Helmholtz free energy. We also investigate the stability of reg ular black hole solution and Einstein-aether black hole in terms of γ, phase transition, grand canonical ensemble and canonical ensemble. We analyze that regular black hole are stable when we increase the value of cosmologi cal constant and Einstein-aether black hole are stable when we increase the value of coupling constant respectively.