Extended Symmetries and Anomaly Resolution in Orbifolds
Symmetries in quantum field theories can carry anomalies which obstruct their gauging. I will discuss a method of resolving such anomalies in two-dimensional conformal field theories by extending the symmetry group. This technique relies on the addition of trivially-acting symmetries, the study of which is known as decomposition. We will see in detail how, through decomposition, orbifolds by extended symmetries can end up equivalent to orbifolds by non-anomalous subgroups.