Joint ICTP/SISSA String Seminars: Modular Bootstrap and 't Hooft Anomaly
Starts 3 Apr 2019 16:00
Ends 3 Apr 2019 17:00
Central European Time
Leonardo Building - Budinich Lecture Hall
Abstract. We study the implications of 't Hooft anomaly (i.e. obstruction to gauging) on quantum field theory in the gapless phase, focusing on the case when the global symmetry is Z_2. Using the modular bootstrap method, universal bounds on (1+1)-dimensional bosonic conformal field theory with an internal Z_2 global symmetry are derived. The bootstrap bounds depend dramatically on the 't Hooft anomaly. In particular, there is a universal upper bound on the lightest Z_2 odd operator if the symmetry is anomalous, but there is no bound if the symmetry is non-anomalous. We also consider theories with a U(1) global symmetry. We comment that there is no bound on the lightest U(1) charged operator if the symmetry is non-anomalous, and discuss its implications on the weak gravity conjecture in AdS3/CFT2.
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