Model-dependent Axion as Quintessence with Almost Massless Hidden Sector Quarks

TL;DR

This paper proposes a model where a model-dependent axion in superstring theories acts as a quintessence field, with its potential suppressed by nearly massless hidden-sector quarks, offering a candidate for dark energy.

Contribution

It introduces a specific superstring-inspired model with a hidden sector that naturally suppresses the axion potential, making it suitable as a quintessence candidate.

Findings

Hidden-sector instanton effects are suppressed by almost massless quarks.

The model links the model-dependent axion to dark energy dynamics.

The QCD axion remains consistent with strong CP problem solutions.

Abstract

A pseudo-Goldstone boson for {\it quintessence} is known to require the decay constant $F_q\sim M_P$ and the height of the potential $(0.003 {\rm eV})^4$, and hence the pseudo-Goldstone boson mass of order $10^{-33}$ eV. The model-dependent axion in some superstring models is suggested as a good candidate for the quintessence. We realize this idea with a hidden-sector gauge group $SU(3)_H\times U(1)_H$. The hidden-sector instanton contribution to the quintessence potential is suppressed by the almost massless hidden-sector quarks. The model-independent axion is the QCD axion required for the strong CP solution.