Quintessential Axions

TL;DR

This paper reviews the concept of quintessential axions as a solution to dark energy, discussing theoretical frameworks from field theory and string theory, and exploring the role of confining forces and nearly massless mesons.

Contribution

It introduces a comprehensive strategy for identifying quintessential axions within string theory and explores their potential to explain dark energy through confining forces and mesons.

Findings

Proposes a method to select quintessential axions among many pseudoscalars.

Connects string theory antisymmetric tensors to dark energy models.

Highlights the role of confining forces and near-massless mesons in dark energy explanation.

Abstract

I review the dark energy solutions by a very light pseudoscalar called "quintessential axion". For the explicit breaking terms, we consider both the global anomaly U(1)$_{\rm global}\times$SU(2)$_W^2$ and the potential $\Delta V$. At the field theory level, we will present a strategy for picking up one such pseudoscalar among plenty of pseudoscalars. At string level, numerous antisymmetric tensor fields are pseudoscalars. Including these, we present a confining force example via a $Z_{12-I}$ orbifold compactification of SO(32) heterotic string. In addition, we also aim to draw attention on almost massless mesons of confining nonabelian gauge group, which can be another motivation for introducing an additional confining force, to explain dark energy as the vacuum energy of these mesons.