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The axion mass from 5D small instantons

Gherghetta, Tony; Khoze, Valentin V.; Pomarol, Alex; Shirman, Yuri

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Tony Gherghetta

Alex Pomarol

Yuri Shirman


We calculate a new contribution to the axion mass that arises from gluons propagating in a 5th dimension at high energies. By uplifting the 4D instanton solution to five dimensions, the positive frequency modes of the Kaluza-Klein states generate a power-law term in the effective action that inversely grows with the instanton size. This causes 5D small instantons to enhance the axion mass in a way that does not spoil the axion solution to the strong CP problem. Moreover this enhancement can be much larger than the usual QCD contribution from large instantons, although it requires the 5D gauge theory to be near the non-perturbative limit. Thus our result suggests that the mass range of axions (or axion-like particles), which is important for ongoing experimental searches, can depend sensitively on the UV modification of QCD.


Gherghetta, T., Khoze, V. V., Pomarol, A., & Shirman, Y. (2020). The axion mass from 5D small instantons. Journal of High Energy Physics, 2020(3), Article 063.

Journal Article Type Article
Acceptance Date Feb 22, 2020
Online Publication Date Mar 11, 2020
Publication Date Mar 31, 2020
Deposit Date Mar 22, 2020
Publicly Available Date Mar 22, 2020
Journal Journal of High Energy Physics
Print ISSN 1126-6708
Publisher Scuola Internazionale Superiore di Studi Avanzati (SISSA)
Peer Reviewed Peer Reviewed
Volume 2020
Issue 3
Article Number 063


Published Journal Article (724 Kb)

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Copyright Statement
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

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