Relaxion measure problem

Gupta, Rick S.

Abstract

We examine the necessity of requiring that relaxion dynamics is dominated by classical slow roll and not quantum fluctuations. It has been recently proposed by Nelson and Prescod-Weinstein [Phys. Rev. D 96, 113007 (2017)] that abandoning this requirement can lead to a unified solution of the hierarchy and strong C P problems in QCD relaxion models. In more general models this results in a higher value of the allowed cutoff. In this work we find, however, that relaxing this condition can result in the Universe being dominated in physical volume by regions arising from large quantum fluctuations of the relaxion. These regions turn out to be problematic for the relaxion mechanism because either the relaxion does not stabilize at all or it stabilizes at vacua which cannot reproduce the observed properties of our Universe. The size of these undesirable regions is moreover ambiguous because of the measure problem. For instance, we show that if one chooses to use the scale-factor cutoff measure such dangerous regions occupy a negligible volume and these issues do not arise.

Citation

Gupta, R. S. (2018). Relaxion measure problem. Physical Review D, 98(5), Article 055023. https://doi.org/10.1103/physrevd.98.055023

• Journal Article Type: Article
• Online Publication Date: Sep 19, 2018
• Publication Date: Sep 19, 2018
• Deposit Date: Oct 4, 2018
• Publicly Available Date: Oct 4, 2018
• Journal: Physical Review D
• Print ISSN: 2470-0010
• Electronic ISSN: 2470-0029
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 98
• Issue: 5
• Article Number: 055023
• DOI: https://doi.org/10.1103/physrevd.98.055023
• Public URL: https://durham-repository.worktribe.com/output/1312682