Some singular spacetimes and their possible alternatives

TL;DR

This review discusses historical singular solutions in gravitation, explores potential quantum and geometric alternatives to singularities, and aims to present a broad, accessible overview for non-specialists.

Contribution

It provides a concise survey of singularities, discusses alternative models like gravastars, and introduces a simple singularity theorem, focusing on recent quantum and geometric approaches.

Findings

Quantum gravity effects may resolve singularities.

Non-commutative geometry offers alternative spacetime structures.

Gravastars are potential non-singular compact objects.

Abstract

This is a brief review article of a seminar given at the International Conference on Gravitation, Astrophysics and Cosmology 2024 (ICGAC-2024), Mathura, India. We begin with a historical survey of some singular solutions in the theory of gravitation, as well as a very brief discussion of how black holes could physically form. Some possible scenarios which could perhaps eliminate these singularities are then reviewed and discussed. Due to the vastness of the field the coverage is not exhaustive, but instead the concentration is on a small subset of topics such as possible quantum gravity effects, non-commutative geometry, and gravastars. A simple singularity theorem is also presented in the appendix. Although parts of the manuscript assume some familiarity with relativistic gravitation or differential geometry, the aim is for the broad picture to be accessible to non-specialists of other physical sciences and mathematics.