Aspects of Gravitational Collapse and the formation of Spacetime Singularities

TL;DR

This thesis investigates the complex behavior of gravitational collapse through analytical solutions of Einstein's equations, exploring singularities, event horizons, and the cosmic censorship conjecture in general relativity.

Contribution

It provides new insights into exact solutions of Einstein's equations describing collapse, challenging the universality of the cosmic censorship conjecture.

Findings

Existence of models with naked singularities without event horizons

Analytical solutions illustrating diverse collapse outcomes

Evidence questioning the general validity of cosmic censorship

Abstract

Possibilities emerging out of the dynamical evolutions of collapsing systems are addressed in this thesis through analytical investigations of the highly non-linear Einstein Field Equations. Studies of exact solutions and their properties, play a non-trivial role in general relativity, even in the current context. Finding non-trivial solutions to the Einstein field equations requires some reduction of the problem, which usually is done by exploiting symmetries or other properties. Exact solutions of the Einsteins field equations describing an unhindered gravitational collapse are studied which generally predict an ultimate singular end-state. In the vicinity of such a spacetime singularity, the energy densities, spacetime curvatures, and all other physical quantities blow up. Despite exhaustive attempts over decades, the famous conjecture that the formation of a singularity during stellar collapse necessarily accompanies the formation of an event horizon, thereby covering the central singularity, still remains without a proof. Moreover, there are examples of stellar collapse models with reasonable matter contribution in which an event horizon does not form at all, giving rise to a naked singularity from which both matter and radiation can fall in and come out. These examples suggest that the so-called cosmic censorship conjecture may not be a general rule. Therefore one must embark upon analysis of realistic theoretical models of gravitational collapse and gradually generalizing previous efforts.