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BEGIN:VEVENT
SUMMARY:Seminar\, Junxuan Xu (TDLI)
DTSTART;VALUE=DATE-TIME:20260723T043000Z
DTEND;VALUE=DATE-TIME:20260723T053000Z
UID:169747849415
DESCRIPTION:Title: Deconstructing the Extra-Dimensional Axion\n\nAbstract:
 \nWe present a four-dimensional deconstruction of the extra-dimensional ax
 ion arising from a $U(1)$ gauge theory in a five-dimensional orbifold\, wh
 ere the axion is identified with the Wilson line of the $U(1)$ gauge field
  and its coupling to QCD is generated by a 5D Chern-Simons (CS) term. We c
 onstruct the corresponding 4D moose (quiver) gauge theory with link scalar
  fields\, in which the axion emerges as a collective pseudo-Nambu-Goldston
 e boson. The axion-gluon coupling is described by a gauged Wess-Zumino-Wit
 ten term\, providing the 4D counterpart of the 5D CS term. We further anal
 yze non-perturbative effects from zero-mode and ``fractional'' instanton c
 onfigurations. 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 f
 or smaller instantons whose inverse size exceeds the 5D cutoff scale\, lea
 ding to a potentially significant effect. We also study axion potentials i
 nduced by bulk matter fields and boundary-localized symmetry-breaking oper
 ators\, reproducing the characteristic nonlocal suppression associated wit
 h propagation in the extra dimension. Our construction provides a renormal
 izable 4D framework with a transparent understanding of the axion shift sy
 mmetry and its quality.
LOCATION:721
END:VEVENT
BEGIN:VEVENT
SUMMARY:Seminar\, Ziwen Yin (TDLI)
DTSTART;VALUE=DATE-TIME:20260730T043000Z
DTEND;VALUE=DATE-TIME:20260730T053000Z
UID:127391149246
DESCRIPTION:Titile :\nProbe exotic energy injection from dark sectors thro
 ugh cosmic reionization\n\nAbstract :\nAxions and primordial black holes (
 PBHs) are well-motivated dark matter candidates that can inject energy int
 o the intergalactic medium (IGM) via decay or evaporation over cosmic hist
 ory\, leaving imprints on the cosmic microwave background (CMB). In recent
  work\, we have derived a model-independent ionization history after recom
 bination from CMB power spectra using a Gaussian process approach\, allowi
 ng new physics to be constrained directly from the high-redshift optical d
 epth. Applying this framework\, we investigate the decay of multi-string a
 xions and place the first constraints on the corresponding geometrical par
 ameter space. We also compute the redshift-dependent energy injection from
  Hawking evaporation using BlackHawk\, we obtain upper limits on the initi
 al PBH abundance that are robust against reionization modeling uncertainti
 es and systematically more conservative than existing bounds. Our results 
 demonstrate the power of reionization observables as a precise probe of PB
 H evaporation and other late-time energy-injection scenarios.
LOCATION:721
END:VEVENT
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