Axion Periodicity and Coupling Quantization in the Presence of Mixing

Understand

Mixing of axion fields is widely used to generate EFTs with phenomenologically advantageous features, such as hierarchies between axion couplings to different gauge fields and/or large effective field ranges.

• While these features are strongly constrained by periodicity for models with only a single axion, mixing has been used in the literature (sometimes incorrectly) to try to evade some of these constraints.
• In this paper, we ask whether it is possible to use axion mixing to generate an EFT of axions that evades these constraints by flowing to a theory of a non-compact scalar in the IR.
• We conclude that as long as the light axion is exactly massless, it will inherit the periodicity and associated constraints of the UV theory.