English

Circle actions on UHF-absorbing $C^*$-algebras

Operator Algebras 2020-04-06 v2 Functional Analysis

Abstract

We study circle actions with the Rokhlin property, in relation to their restrictions to finite subgroups. We construct examples showing the following: the restriction of a circle action with the Rokhlin property (even on a real rank zero CC^*-algebra), need not have the Rokhlin property; and even if every restriction of a given circle action has the Rokhlin property, the circle action itself need not have it. As a positive result, we show that the restriction of a circle action with the Rokhlin property to the subgroup Zn\mathbb{Z}_n has the Rokhlin property if the underlying algebra absorbs MnM_{n^\infty}. The condition on the algebra is also necessary in most cases of interest. Despite the fact that there are no circle actions with the Rokhlin property on UHF-algebras, we construct many such actions on certain UHF-absorbing simple AT-algebras. Additionally, we show that circle actions with the Rokhlin property on O2\mathcal{O}_2-absorbing CC^*-algebras are generic, in a suitable sense.

Keywords

Cite

@article{arxiv.1406.4198,
  title  = {Circle actions on UHF-absorbing $C^*$-algebras},
  author = {Eusebio Gardella},
  journal= {arXiv preprint arXiv:1406.4198},
  year   = {2020}
}

Comments

24 pages

R2 v1 2026-06-22T04:39:48.661Z