Discrete gauge anomalies and instantons

Abstract We revisit anomalous phases related to large gauge transformations, such as the Witten anomaly. The latter, known to plague d = 4 Sp(k) theories, is well-understood in terms of π 4(Sp(k)) = ℤ2, but it also has an oblique relation to the instantons, labeled by π 3(G) = ℤ, via the fermion zer...

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Main Authors: Qiang Jia, Piljin Yi
Format: Article
Language:English
Published: SpringerOpen 2024-08-01
Series:Journal of High Energy Physics
Subjects:
Online Access:https://doi.org/10.1007/JHEP08(2024)018
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author Qiang Jia
Piljin Yi
author_facet Qiang Jia
Piljin Yi
author_sort Qiang Jia
collection DOAJ
description Abstract We revisit anomalous phases related to large gauge transformations, such as the Witten anomaly. The latter, known to plague d = 4 Sp(k) theories, is well-understood in terms of π 4(Sp(k)) = ℤ2, but it also has an oblique relation to the instantons, labeled by π 3(G) = ℤ, via the fermion zero mode counting. We revisit this relation and point out how SU(N) theories escape an anomalous sign of the latter type, only thanks to the perturbative anomaly cancelation condition that restricts the chiral fermion spectrum. This leads to the question of what happens if the latter, more mundane anomaly is canceled by an inflow instead. After raising an open question about fractional D3 probe theories, we explore the simplest bottom-up model of such a kind, due to Witten and Yonekura, from which we find the relevant chiral theories to be free of such a disease despite the unrestricted chiral spectra. We close with a simple but often-overlooked observation about how fermionic zero modes enter physics differently between Euclidean and Lorentzian descriptions and point out a related issue in d = 3.
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spelling doaj-art-c8cc8163356f457e8a21b8c4757eb27d2024-11-24T12:05:09ZengSpringerOpenJournal of High Energy Physics1029-84792024-08-012024812910.1007/JHEP08(2024)018Discrete gauge anomalies and instantonsQiang Jia0Piljin Yi1School of Physics, Korea Institute for Advanced StudySchool of Physics, Korea Institute for Advanced StudyAbstract We revisit anomalous phases related to large gauge transformations, such as the Witten anomaly. The latter, known to plague d = 4 Sp(k) theories, is well-understood in terms of π 4(Sp(k)) = ℤ2, but it also has an oblique relation to the instantons, labeled by π 3(G) = ℤ, via the fermion zero mode counting. We revisit this relation and point out how SU(N) theories escape an anomalous sign of the latter type, only thanks to the perturbative anomaly cancelation condition that restricts the chiral fermion spectrum. This leads to the question of what happens if the latter, more mundane anomaly is canceled by an inflow instead. After raising an open question about fractional D3 probe theories, we explore the simplest bottom-up model of such a kind, due to Witten and Yonekura, from which we find the relevant chiral theories to be free of such a disease despite the unrestricted chiral spectra. We close with a simple but often-overlooked observation about how fermionic zero modes enter physics differently between Euclidean and Lorentzian descriptions and point out a related issue in d = 3.https://doi.org/10.1007/JHEP08(2024)018Anomalies in Field and String TheoriesSolitons Monopoles and Instantons
spellingShingle Qiang Jia
Piljin Yi
Discrete gauge anomalies and instantons
Journal of High Energy Physics
Anomalies in Field and String Theories
Solitons Monopoles and Instantons
title Discrete gauge anomalies and instantons
title_full Discrete gauge anomalies and instantons
title_fullStr Discrete gauge anomalies and instantons
title_full_unstemmed Discrete gauge anomalies and instantons
title_short Discrete gauge anomalies and instantons
title_sort discrete gauge anomalies and instantons
topic Anomalies in Field and String Theories
Solitons Monopoles and Instantons
url https://doi.org/10.1007/JHEP08(2024)018
work_keys_str_mv AT qiangjia discretegaugeanomaliesandinstantons
AT piljinyi discretegaugeanomaliesandinstantons