Paper detail

Anomalies on Six Dimensional Orbifolds

We consider localized anomalies in six dimensional Z_n orbifolds. We give a very simple expression for the contribution of a bulk fermion to the fixed point gauge anomaly that is independent of the order n of the orbifold twist. We show it can be split into three terms, two of which are canceled by bulk fermions and Green-Schwarz four forms respectively. The remaining anomaly carries an integer coefficient and hence can be canceled by localized fermions in suitable representations. We present various examples in the context of supersymmetric theories. Also we point out that the six-dimensional gravitational symmetries generally have localized anomalies that require localized four-dimensional fields to transform nontrivially under them.