Decoupling Dark Energy from Matter

TL;DR

This paper explores how dark energy can be embedded in supergravity models with a shift symmetry, resulting in a weakly coupled, stable, and early-acting cosmological constant consistent with gravitational constraints.

Contribution

It introduces a framework where dark energy arises from a sector with an approximate shift symmetry, ensuring weak coupling and stability against radiative corrections.

Findings

Dark energy sector must have an approximate shift symmetry due to gravitational constraints.

Exact shift symmetry leads to a runaway potential with a nearly massless dark energy field.

Breaking the shift symmetry introduces a minimum in the potential, causing dark energy to behave like a cosmological constant early in cosmic history.

Abstract

We examine the embedding of dark energy in high energy models based upon supergravity and extend the usual phenomenological setting comprising an observable sector and a hidden supersymmetry breaking sector by including a third sector leading to the acceleration of the expansion of the universe. We find that gravitational constraints on the non-existence of a fifth force naturally imply that the dark energy sector must possess an approximate shift symmetry. When exact, the shift symmetry provides an example of a dark energy sector with a runaway potential and a nearly massless dark energy field whose coupling to matter is very weak, contrary to the usual lore that dark energy fields must couple strongly to matter and lead to gravitational inconsistencies. Moreover, the shape of the potential is stable under one-loop radiative corrections. When the shift symmetry is slightly broken by higher order terms in the Kahler potential, the coupling to matter remains small. However, the cosmological dynamics are largely affected by the shift symmetry breaking operators leading to the appearance of a minimum of the scalar potential such that dark energy behaves like an effective cosmological constant from very early on in the history of the universe.