Time: 10:30-12:00  (Beijing time), Wednesday, 2026/1/21 (Jan 21)

Location: Room 401, Building 7, UCAS Zhongguancun Campus

Speaker: Jia Qiang, KAIST



Abstract : In this talk, I will revisit anomalous phases related to large gauge transformations, such as the Witten anomaly. The latter, known to plague 4D $Sp(k)$ theories, is well-understood in terms of 4th homotopy group of $Sp(k)$, but it also has an oblique relation to the instantons, labeled by 3rd homotopy group, via the fermion zero mode counting. I will revisit this relation and point out how SU(N) theories escape an anomalous sign of the latter type, 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. We explore two models of such a kind, the Witten and Yonekura setup, and also the fractional D3 probe theories in type IIB theory, and show that they are free from the anomalous sign of the fermion zero mode counting.
Link for Zoom meeting:

https://us06web.zoom.us/j/85715129440?pwd=QlJJRFBWWFRLMkxCVmcxZ1RKdlRxQT09

Meeting ID: 857 1512 9440
Passcode: 501105