Pseudo-redundant vacuum energy

TL;DR

This paper proposes models where dark energy arises from breaking a redundancy in the cosmological constant, with mechanisms compatible with solar system tests and possibly favored in string theory landscapes.

Contribution

It introduces a framework for constructing models where vacuum energy is a redundant coupling that is broken to produce dark energy, including R + 1/R and Gauss-Bonnet gravity models.

Findings

Models satisfy solar system constraints

Gauss-Bonnet model explains dark energy naturally

Large cosmological constant leads to diverse curvature solutions

Abstract

We discuss models that can account for today's dark energy. The underlying cosmological constant may be Planck scale but starts as a redundant coupling which can be eliminated by a field redefinition. The observed vacuum energy arises when the redundancy is explicitly broken, say by a non-minimal coupling to curvature. We give a recipe for constructing models, including R + 1/R type models, that realize this mechanism and satisfy all solar system constraints on gravity. A similar model, based on Gauss-Bonnet gravity, provides a technically natural explanation for dark energy and exhibits an interesting see-saw behavior: a large underlying cosmological constant gives rise to both low and high curvature solutions. Such models could be statistically favored in the string landscape.