KEK Theory workshop 2019

2d 't Hooft anomaly, orbifolding, and boundary states

4 Dec 2019, 16:50

15m

Kobayashi Hall, Kenkyu-Honkan bldg. 1F (KEK)

Short talks

Speaker

Dr Ken Kikuchi

Description

We study anomalies for a discrete internal global symmetry $G$ in two-dimensional conformal field theories based on twisted torus partition functions. The 't Hooft anomaly of $G$ can be seen from the noncommutativity of two symmetry lines inserted along the nontrivial circles of two-torus and we propose a criterion to detect the 't Hooft anomaly, which agrees with the truncated modular $S$-matrix approach as well as the cohomology classification. The obstruction for orbifolding has been recently interpreted as a mixed anomaly between $G$ and large diffeomorphisms. We clarify the relations among 't Hooft anomaly-free, orbifolding condition and invariant boundary state condition, focusing on Wess-Zumino-Witten models.