Observational Constraints on Axions as Quintessence in String Theory

TL;DR

This paper investigates how string theory axion models as quintessence align with observational data, finding they closely mimic a cosmological constant and can constrain supersymmetry breaking scales.

Contribution

It provides the first observational constraints on string theory axion quintessence models and links cosmological data to supersymmetry breaking scales.

Findings

Axion models show minimal deviation from  = -1 in equation of state.

Cosmological data constrains the SUSY breaking scale.

The universe's evolution is sensitive to initial axion field values.

Abstract

We study the observational constraints for the axion models in string theory which can successfully act as quintessence. The evolution of the universe in this model is sensitive to the initial value of the axion field. This initial value of the axion field controls deviation of the cosmic evolution from the \Lambda CDM behaviour. We use the recent Union2 Supernova Type Ia dataset as well as the data from BAO measurements, the WMAP measurement of the shift parameter and the $H(z)$ measurements. Using these data, the reconstructed equation of state of the axion field has extremely small deviation from the cosmological constant \omega = -1 even at 2\sigma confidence level. One interesting outcome of this analysis is that one can put bound on the SUSY breaking scale using cosmological measurements assuming the values of different string related parameters and vice versa.