PJC: Pier Giuseppe Catinari "Instanton NDA and Applications to Axion Models"

Thursday 7 Mar 2024, 13:00 → 14:00 Europe/Rome

Sala direzione INFN

 

Abstract: We present a simple set of power counting rules which allows us to easily estimate

calculable instanton effects up to O(1) factors. We apply the resulting Instanton NDA to

examine the effects of small instantons on various axion models. We confirm 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. For generic models, new sources of CP violation in the UV must be absent in

order to raise the axion mass above the QCD prediction. However, we find that ZN and

composite axions are UV-safe against these misalignment effects. Axion GUT models are

also insensitive to UV contributions at the GUT scale, unless a very large number of extra

states are introduced below this scale.