Year: 2017
Type: dissertation
Abstract: We model the dynamics of a spherically symmetric radiating dynamical star, emitting \noutgoing null radiation, with three spacetime regions. The local internal atmosphere \nis a two-component system consisting of standard pressure-free, null radiation and an \nadditional string \nfluid with energy density and nonzero pressure obeying all physically \nrealistic energy conditions. The middle region is purely radiative which matches to \na third region which is the Schwarzschild exterior. A large family of solutions to the \nfield equations are presented for various realistic equations of state. A comparison of \nour solutions with earlier well known results is undertaken and we show that all these \nsolutions, including those of Husain, are contained in our family. We then generalise \nour class of solutions to higher dimensions and consider the effects of diffusive transport \nWe also study the gravitational collapse in the context of the cosmic censorship \nconjecture. We outline the general mathematical framework to study the conditions on \nthe mass function so that future directed nonspacelike geodesics can terminate at the \nsingularity in the past. Mass functions for several equations of state are analysed using \nthis framework and it is shown that the collapse in each case terminates at a locally \nnaked central singularity. These singularities are strong curvature singularities which \nimplies that no extension of spacetime through them is possible. These results are then \nextended to modified gravity. We establish the result that the standard Boulware-Deser \nspacetime can radiate. This allows us to model the dynamics of a spherically symmetric \nradiating dynamical star in ve-dimensional Einstein-Gauss-Bonnet gravity with \nthree spacetime regions. Finally, the junction conditions are derived entirely in five dimensional \nEinstein-Gauss-Bonnet gravity via the matching of two spacetime region \nleading to a model for a radiating star in higher order gravity.
Author: Byron P. Brassel
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2902622767