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.

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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

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article

Asymptotic lifting for completely positive maps

Marzieh Forough, Eusebio Gardella, Klaus Thomsen
2 citations
Journal of Functional Analysis
Advanced Operator Algebra Research
0.89
article

Asymptotic lifting for completely positive maps

Marzieh Forough, Eusebio Gardella, Klaus Thomsen
article en
2 citations

Abstract

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.

Journal of Functional AnalysisVol. 287(12)
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)
Vetenskapsrådet
Openalex Percentile: Top 41%
Advanced Operator Algebra Research
0.89
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Asymptotic lifting for completely positive maps — Marzieh Forough, Eusebio Gardella, et al. · Journal of Functional Analysis (2024) | TGRS Research Map | TGRS