Strong CP problem and axion dark matter with small instantons

The axion mass receives a large correction from small instantons if the QCD gets strongly coupled at high energies. We discuss the size of the new CP violating phases caused by the fact that the small instantons are sensitive to the UV physics. We also discuss the effects of the mass correction on the axion abundance of the Universe. Taking the small-instanton contributions into account, we propose a natural scenario of axion dark matter where the axion decay constant is as large as 10(15-16) GeV. The scenario works in the high-scale inflation models.

Automated summary

This paper discusses the impact of small instantons on the axion mass at high energies and the size of the new CP-violating phases. It also examines the effects of mass corrections on the axion abundance in the Universe. A natural scenario for axion dark matter is proposed, with the axion decay constant as large as 10^(15-16) GeV, functioning well in high-scale inflation models.