Asymptotic lifting for completely positive maps
Let A and B be C⁎-algebras with A separable, let I be an ideal in B, and let ψ:A→B/I be a completely positive contractive linear map. We show that there is a continuous family Θt:A→B, for t∈[1,∞), of lifts of ψ that are asymptotically linear, asymptotically completely positive and asymptotically contractive. If ψ is of order zero, then Θt can be chosen to have this property asymptotically. If A and B carry continuous actions of a second countable locally compact group G such that I is G-invariant and ψ is equivariant, we show that the family Θt can be chosen to be asymptotically equivariant. If a linear completely positive lift for ψ exists, we can arrange that Θt is linear and completely positive for all t∈[1,∞). In the equivariant setting, if A, B and ψ are unital, we show that asymptotically linear unital lifts are only guaranteed to exist if G is amenable. This leads to a new characterization of amenability in terms of the existence of asymptotically equivariant unital sections for quotient maps.
Authors
- Marzieh Forough
- Eusebio Gardella (ORCID: https://orcid.org/0000-0003-1150-4522)
- Klaus Thomsen (ORCID: https://orcid.org/0009-0003-3568-9274)
Institutions
- Aarhus University (DK)
- Czech Academy of Sciences, Institute of Mathematics (CZ)
- Czech Technical University in Prague (CZ)
- Chalmers University of Technology (SE)
- University of Gothenburg (SE)
Publication Details
- Journal
- Journal of Functional Analysis
- Published
- 2024-09-02
- DOI
- https://doi.org/10.1016/j.jfa.2024.110655
- Citations
- 2
- Primary Topic
- Advanced Operator Algebra Research
- Type
- article
- Field-Weighted Citation Impact
- 0.89
Funders
- Vetenskapsrådet