Probabilities in the landscape: The decay of nearly flat space

TL;DR

This paper examines the stability of low-energy de Sitter vacua in the string landscape, showing that their decay rates vary continuously and challenging assumptions of their effective stability in eternal inflation models.

Contribution

It provides analytic and numerical evidence that decay rates of vacua change smoothly across zero energy, disputing claims of their effective stability in the landscape.

Findings

Decay rate varies continuously across zero vacuum energy.

Low-energy de Sitter vacua are not anomalously stable.

Negative and zero cosmological constant regions are significant.

Abstract

We discuss aspects of the problem of assigning probabilities in eternal inflation. In particular, we investigate a recent suggestion that the lowest energy de Sitter vacuum in the landscape is effectively stable. The associated proposal for probabilities would relegate lower energy vacua to unlikely excursions of a high entropy system. We note that it would also imply that the string theory landscape is experimentally ruled out. However, we extensively analyze the structure of the space of Coleman-De Luccia solutions, and we present analytic arguments, as well as numerical evidence, that the decay rate varies continuously as the false vacuum energy goes through zero. Hence, low-energy de Sitter vacua do not become anomalously stable; negative and zero cosmological constant regions cannot be neglected.