Discrete gauge anomalies in string theory
Joshua P. Gray · CERN Document Server (European Organization for Nuclear Research) · 2001
We search for non-perturbative consistency conditions in string theory. Focussing on possible anomalies in discrete symmetries, we develop several types of string theory orbifolds as a natural setting to study this question. Since it is generally believed that discrete symmetries in string theories are gauge symmetries, discrete anomalies would provide evidence for inconsistencies non-perturbatively. Some arguments are given that support the locality of these symmetries and we explain the connection of the anomalies with the non- perturbative physics of instantons. We then search for anomalies in discrete symmetries in a variety of models, both with and without supersymmetry. We explain the construction of these orbifold models in some detail. All of the examples we consider are consistent (modular invariant) in perturbation theory. In symmetric orbifold models we extend previous searches, and show in a variety of examples that all anomalies can be cancelled by a discrete Green-Schwarz mechanism. We find, however, asymmetric orbifolds generically have discrete anomalies.