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Title: Evolution of the Universe in F(T, TG) Gravity
Authors: Nazir, Kanwal
Keywords: Physical Sciences
Issue Date: 2018
Publisher: University of the Punjab , Lahore
Abstract: This thesis is devoted to study evolution of the universe in the context of F(T, TG) gravity (T represents torsion scalar and TG is the teleparallel equivalent of the Gauss Bonnet term). Firstly, we explore the reconstruction scenario of spatially homogenous and anisotropic universe model in this framework. We construct F(T, TG) models by assuming different phases of the universe like dark energy dominated era, non relativistic as well as relativistic matter eras and their combinations. The graphical behavior of these models indicate decreasing pattern for dark energy dominated era and its combination with non-relativistic/relativistic matter eras. We also evaluate equation of state parameter by considering F(T, TG) model and study its evolutionary behavior for particular values of dimensionless coupling parameters. Secondly, we study generalized ghost pilgrim dark energy model and bulk viscosity in this gravity with flat FRW universe. For generalized ghost pilgrim dark energy model, we consider four different choices of scale factors as power-law, intermediate, bouncing and scale factor for unification of two phases. We develop F(T, TG) models for each scale factor by applying reconstruction technique. It is found that all the reconstructed models show decreasing behavior for pilgrim dark energy parameter u = −2. On the other hand, the equation of state parameter indicates transition from dust-like matter to phantom era for all choices of the scale factor except intermediate for which this is less than −1. We conclude that all the results are in agreement with pilgrim dark energy phenomenon. xi xii Thirdly, the effect of bulk viscosity is studied for three well-known F(T, TG) mod els. We assume a bulk viscosity coefficient with a specific expression of Hubble para meter. The behavior of the accelerated expanding universe is explored through the viscous equation of state parameter. This indicates phantom dominated era as well as crosses the phantom divide line for all the three models. The universe shows a transition from quintessence to phantom region in the presence of bulk viscosity. Finally, we study static spherically symmetric wormhole solutions for noncommu tative geometry as well as noncommutative Lorentzian distribution in this gravity. We assume a nonzero redshift function as well as two well-known models of this grav ity and discuss the behavior of null/weak energy conditions. There does not exist any physically acceptable noncommutative wormhole solution for the first model but there is a chance to develop physically acceptable noncommutative wormhole solution in a particular region for the second model. We conclude that physically viable stable Lorentzian distributed noncommutative wormhole solutions exist for both models.
Gov't Doc #: 23960
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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