Anomalies, Extensions and Orbifolds

Understand

We investigate gauge anomalies in the context of orbifold conformal field theories.

• Such anomalies manifest as failures of modular invariance in the constituents of the orbifold partition function.
• We review how this irregularity is classified by cohomology and how extending the orbifold group can remove it.
• Working with such extensions requires an understanding of the consistent ways in which extending groups can act on the twisted states of the original symmetry, which leads us to a discrete-torsion like choice that exists in orbifolds with trivially-acting subgroups.