English

A non-nuclear $C^*$-algebra with the Weak Expectation Property and the Local Lifting Property

Operator Algebras 2023-04-05 v5 Functional Analysis

Abstract

We construct the first example of a CC^*-algebra AA with the properties in the title. This gives a new example of non-nuclear AA for which there is a unique CC^*-norm on AAopA \otimes A^{op}. This example is of particular interest in connection with the Connes-Kirchberg problem, which is equivalent to the question whether C(\bbF2)C^*({\bb F}_2), which is known to have the LLP, also has the WEP. Our CC^*-algebra AA has the same collection of finite dimensional operator subspaces as C(\bbF2)C^*({\bb F}_2) or C(\bbF)C^*({\bb F}_\infty). In addition our example can be made to be quasidiagonal and of similarity degree (or length) 3. In the second part of the paper we reformulate our construction in the more general framework of a CC^*-algebra that can be described as the \emph{limit both inductive and projective} for a sequence of CC^*-algebras (Cn)(C_n) when each CnC_n is a \emph{subquotient} of Cn+1C_{n+1}. We use this to show that for certain local properties of injective (non-surjective) *-homomorphisms, there are CC^*-algebras for which the identity map has the same properties as the *-homomorphisms.

Keywords

Cite

@article{arxiv.1908.02705,
  title  = {A non-nuclear $C^*$-algebra with the Weak Expectation Property and the Local Lifting Property},
  author = {Gilles Pisier},
  journal= {arXiv preprint arXiv:1908.02705},
  year   = {2023}
}

Comments

We recommend the shorter initial version for a first reading. Final version v3 will appear in Inventiones Math. v4 contains a more detailed end of proof of Lemma 7.1. v5 clarifies certain ambiguities (mainly in Lemma 5.3 and Th. 9.2) unfortunately overlooked in the (now published) version v3