The Value of Singularities

TL;DR

This paper discusses the role of spacetime singularities in gravitational theories, arguing that their absence in modifications of general relativity leads to unstable ground states, impacting both classical and quantum gravity models.

Contribution

It presents a theoretical argument that nonsingular modifications of general relativity cannot possess stable ground states, highlighting the importance of singularities in gravitational physics.

Findings

Nonsingular gravity theories lack stable ground states.

Singularities help eliminate unphysical solutions.

Implications for classical and quantum gravity models.

Abstract

We point out that spacetime singularities play a useful role in gravitational theories by eliminating unphysical solutions. In particular, we argue that any modification of general relativity which is completely nonsingular cannot have a stable ground state. This argument applies both to classical extensions of general relativity, and to candidate quantum theories of gravity.