Instanton NDA and applications to axion models

Csaba Csáki, Raffaele Tito D’Agnolo, Eric Kuflik, Maximilian Ruhdorfer

Research output: Contribution to journalArticlepeer-review


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.

Original languageAmerican English
Article number74
JournalJournal of High Energy Physics
Issue number4
StatePublished - Apr 2024


  • Axions and ALPs
  • CP Violation
  • Nonperturbative Effects
  • Solitons Monopoles and Instantons

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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