Open Inflation Without False Vacua

TL;DR

This paper demonstrates that open inflation can naturally arise from the Hartle-Hawking no boundary proposal without special potential conditions, predicting a small but adjustable density parameter Omega.

Contribution

It shows that open inflation is generic under the Hartle-Hawking proposal and derives a typical Omega value in simple models, extending to more complex theories.

Findings

Open inflation is generic under the Hartle-Hawking proposal.

Predicted Omega_0 is approximately 0.01 in simple models.

Omega can be increased with additional fields or dimensions.

Abstract

We show that within the framework of a definite proposal for the initial conditions for the universe, the Hartle-Hawking `no boundary' proposal, open inflation is generic and does not require any special properties of the inflaton potential. In the simplest inflationary models, the semiclassical approximation to the Euclidean path integral and a minimal anthropic condition lead to $\Omega_0\approx 0.01$. This number may be increased in models with more fields or extra dimensions.