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SUMMARY:Deconstructing the Extra-Dimensional Axion
DTSTART;VALUE=DATE-TIME:20260812T024000Z
DTEND;VALUE=DATE-TIME:20260812T030000Z
DTSTAMP;VALUE=DATE-TIME:20260824T154809Z
UID:indico-contribution-2681@indico.itp.ac.cn
DESCRIPTION:Speakers: Junxuan Xu (TDLI)\nWe present a four-dimensional dec
 onstruction of the extra-dimensional axion arising from a $U(1)$ gauge the
 ory in a five-dimensional orbifold\, where the axion is identified with th
 e Wilson line of the $U(1)$ gauge field and its coupling to QCD is generat
 ed by a 5D Chern-Simons (CS) term. We construct the corresponding 4D moose
  (quiver) gauge theory with link scalar fields\, in which the axion emerge
 s as a collective pseudo-Nambu-Goldstone boson. The axion-gluon coupling i
 s described by a gauged Wess-Zumino-Witten term\, providing the 4D counter
 part of the 5D CS term. We further analyze non-perturbative effects from z
 ero-mode and ``fractional'' instanton configurations. While the latter is 
 exponentially suppressed in the regime corresponding to the 5D description
 \, ensuring consistency with the higher-dimensional picture\, we point out
  that this suppression can break down for smaller instantons whose inverse
  size exceeds the 5D cutoff scale\, leading to a potentially significant e
 ffect. We also study axion potentials induced by bulk matter fields and bo
 undary-localized symmetry-breaking operators\, reproducing the characteris
 tic nonlocal suppression associated with propagation in the extra dimensio
 n. Our construction provides a renormalizable 4D framework with a transpar
 ent understanding of the axion shift symmetry and its quality.\n\nhttps://
 indico.itp.ac.cn/event/416/contributions/2681/
LOCATION:Conference Center (2F) Back Area
URL:https://indico.itp.ac.cn/event/416/contributions/2681/
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