A GNS construction of three-dimensional abelian Dijkgraaf–Witten theories

Abstract

We give a detailed account of the so-called “universal construction” that aims to extend invariants of closed manifolds, possibly with additional structure, to topological field theories and show that it amounts to a generalization of the GNS construction. We apply this construction to an invariant defined in terms of the groupoid cardinality of groupoids of bundles to recover Dijkgraaf–Witten theories, including the vector spaces obtained as a linearization of spaces of principal bundles.