English

A simple C*-algebra with a finite and an infinite projection

Operator Algebras 2010-11-24 v2

Abstract

An example is given of a simple, unital C*-algebra which contains an infinite and a non-zero finite projection. This C*-algebra is also an example of an infinite simple C*-algebra which is not purely infinite. A corner of this C*-algebra is a finite, simple, unital C*-algebra which is not stably finite. Our example shows that the type decomposition for von Neumann factors does not carry over to simple C*-algebras. Added March 2002: We also give an example of a simple, separable, nuclear C*-algebra in the UCT class which contains an infinite and a non-zero finite projection. This nuclear C*-algebra arises as a crossed product of an inductive limit of type I C*-algebras by an action of the integers.

Keywords

Cite

@article{arxiv.math/0204339,
  title  = {A simple C*-algebra with a finite and an infinite projection},
  author = {Mikael Rordam},
  journal= {arXiv preprint arXiv:math/0204339},
  year   = {2010}
}

Comments

Revised version (contains a nuclear example), revised again August 2002

R2 v1 2026-07-22T16:44:56.389Z