[JC] Heterotic String Theory suggests a QCD Axion near 0.5 neV

by Sang-Hui Im

Thursday 1 Oct 2026, 15:00 → 16:00 Asia/Seoul

CTPU seminar room (IBS)

Perturbative heterotic string theory predicts QCD axion mass bounded from below by 0.5 neV. Furthermore, with extensive search over the moduli space of Kreuzer-Skarke compactifications, it could be argued that the QCD axion mass is also bounded from above by 0.8 neV, requiring the gauge coupling unification.

Interestingly, assuming SUSY GUTs, the predicted value of the QCD theta angle is within the reach of future EDM experiments. Also unlike Type IIB axiverse constructions, the heavy axion population in the heterotic ensemble generically decays before BBN and can naturally accommodate leptogenesis.

Referece: 

1) Benbou, Dainelli, Reig, Safdi https://arxiv.org/abs/2605.04142

2) Leedom, Putti, Westphal https://arxiv.org/abs/2509.03578