Maximilian Ruhdorfer (Cornell)

10:00am Wednesday April 24, 2024

Instanton NDA for Axion Models

In this talk I will present a simple set of power counting rules which make it possible to estimate instanton effects up to O(1) factors. Subsequently I will apply the resulting instanton NDA to examine effects of small instantons on various axion models. Among other things I will demonstrate that mechanisms that increase the axion mass via small instantons generically also lead to an enhancement of misaligned instanton contributions to the axion potential, deepening the axion quality problem. Finally I will point out that for generic models (with a few exceptions that I will discuss), new sources of CP violation in the UV must be absent in order to raise the axion mass above the QCD prediction.