General aspects of heterotic string compactifications on stacks and gerbes

Understand

In this paper we work out some basic results concerning heterotic string compactifications on stacks and, in particular, gerbes.

• A heterotic string compactification on a gerbe can be understood as, simultaneously, both a compactification on a space with a restriction on nonperturbative sectors, and also, a gauge theory in which a subgroup of the gauge group acts trivially on the massless matter.
• Gerbes admit more bundles than corresponding spaces, which suggests they are potentially a rich playground for heterotic string compactifications.
• After we give a general characterization of heterotic strings on stacks, we specialize to gerbes, and consider three different classes of `building blocks' of gerbe compactifications.