Nonsingular instantons for the creation of open universes

TL;DR

This paper proposes a method to create stable, nonsingular instantons for open universe creation using axionic scalar fields, avoiding instabilities associated with singular instantons.

Contribution

It introduces a new approach replacing singular instantons with nonsingular, stable instantons via axionic fields and positive cosmological constant.

Findings

Axionic scalar fields lead to stable, nonsingular instantons.

Replacing singular instantons with axionic wormholes resolves instabilities.

Adding a positive cosmological constant makes the instanton finite and stable.

Abstract

We show that the instability of the singular Vilenkin instanton describing the creation of an open universe can be avoided using, instead of a minimally coupled scalar field, an axionic massless scalar field which gives rise to the Giddings-Strominger instanton. However, if we replace the singularity of the Hawking Turok instanton for an axionic wormhole some interpretational and technical difficulties would appear which can be overcome by introducing a positive cosmological constant in the action. This would make the instanton finite and free constant in the action. This would make the instanton finite and free from any instabilities.