English

Tracing projective modules over noncommutative orbifolds

Operator Algebras 2021-06-17 v2 K-Theory and Homology

Abstract

For an action of a finite cyclic group FF on an nn-dimensional noncommutative torus Aθ,A_\theta, we give sufficient conditions when the fundamental projective modules over AθA_\theta, which determine the range of the canonical trace on Aθ,A_\theta, extend to projective modules over the crossed product C*-algebra AθF.A_\theta \rtimes F. Our results allow us to understand the range of the canonical trace on AθFA_\theta \rtimes F, and determine it completely for several examples including the crossed products of 2-dimensional noncommutative tori with finite cyclic groups and the flip action of Z2\mathbb{Z}_2 on any nn-dimensional noncommutative torus. As an application, for the flip action of Z2\mathbb{Z}_2 on a simple nn-dimensional torus AθA_\theta, we determine the Morita equivalence class of AθZ2,A_\theta \rtimes \mathbb{Z}_2, in terms of the Morita equivalence class of Aθ.A_\theta.

Keywords

Cite

@article{arxiv.2102.07691,
  title  = {Tracing projective modules over noncommutative orbifolds},
  author = {Sayan Chakraborty},
  journal= {arXiv preprint arXiv:2102.07691},
  year   = {2021}
}

Comments

19 pages, minor corrections. To appear in the Journal of Noncommutative Geometry

R2 v1 2026-06-23T23:10:49.059Z