Obstructions to lifting cocycles on groupoids and the associated $C^*$-algebras
Abstract
Given a short exact sequence of locally compact abelian groups and a continuous -valued -cocycle on a locally compact Hausdorff groupoid we construct a twist of by that is trivial if and only if lifts. The cocycle determines a strongly continuous action of into and we prove that the -algebra of the twist is isomorphic to the induced algebra of this action if is amenable. We apply our results to a groupoid determined by a locally finite cover of a space and a cocycle provided by a \v{C}ech 1-cocycle with coefficients in the sheaf of germs of continuous -valued functions. We prove that the -algebra of the resulting twist is continuous trace and we compute its Dixmier-Douady invariant.
Keywords
Cite
@article{arxiv.1612.07257,
title = {Obstructions to lifting cocycles on groupoids and the associated $C^*$-algebras},
author = {Marius Ionescu and Alex Kumjian},
journal= {arXiv preprint arXiv:1612.07257},
year = {2017}
}
Comments
We made some changes indicated by the referee. The paper is accepted for publication in the M\"unster Journal of Mathematics