Axion clockworks from heterotic M-theory: the QCD-axion and its ultra-light companion

Abstract

A previously discussed clockwork mechanism within heterotic M-theory is applied to its axion landscape. We identify a unique candidate for a QCD-axion with a decay constant in the preferred "axion window" around $10^{11}$GeV. It is accompanied by at least one ultra-light axion that couples predominantly to hidden sector gauge groups.

Comments: 1+23 pages; v2: references added, version published in JHEP