Axions as Quintessence in String Theory

TL;DR

This paper develops a string theory-based model of dark energy using axion monodromy, where the axion's potential leads to a slowly evolving equation of state, with potential observable effects in CMB polarization.

Contribution

It introduces a novel quintessence model in string theory employing axion monodromy with warped throats, incorporating moduli stabilization and supersymmetry breaking effects.

Findings

Potentially detectable time variation in dark energy equation of state

Presence of very light particles in warped throats

Possible signals in CMB polarization rotation

Abstract

We construct a model of quintessence in string theory based on the idea of axion monodromy as discussed by McAllister, Silverstein and Westphal arXiv:0808.0706. In the model, the quintessence field is an axion whose shift symmetry is broken by the presence of 5-branes which are placed in highly warped throats. This gives rise to a potential for the axion field which is slowly varying, even after incorporating the effects of moduli stabilization and supersymmetry breaking. We find that the resulting time dependence in the equation of state of Dark Energy is potentially detectable, depending on the initial conditions. The model has many very light extra particles which live in the highly warped throats, but these are hard to detect. A signal in the rotation of the CMB polarization can also possibly arise.