| Abstract: |
In this talk, I will revisit anomalous phases related to large gauge transformations, such asthe 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. 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. |
