Elementary embeddings into ultrapower $\mathrm{II}_1$ factors without a UCP lift

Fuente: arXiv
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Autori principali: Gao, David, Jekel, David
Natura: Preprint
Pubblicazione: 2025
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author Gao, David
Jekel, David
author_facet Gao, David
Jekel, David
contents We show that there are $\mathrm{II}_1$ factors $M$ and elementary embeddings $M \to M^{\mathcal{U}}$ which do not lift to sequences of UCP maps, and in fact $M$ can be chosen from any given elementary equivalence class. Furthermore, under continuum hypothesis, we show that in the sense of cardinality "most" automorphisms of a ultrapower $M^{\mathcal{U}}$ of a separable $\mathrm{II}_1$ factor do not lift to a sequence of UCP maps $φ_n: M \to M$.
format Preprint
id arxiv_https___arxiv_org_abs_2512_10129
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Elementary embeddings into ultrapower $\mathrm{II}_1$ factors without a UCP lift
Gao, David
Jekel, David
Operator Algebras
Logic
46L10, 03C66, 03C20
We show that there are $\mathrm{II}_1$ factors $M$ and elementary embeddings $M \to M^{\mathcal{U}}$ which do not lift to sequences of UCP maps, and in fact $M$ can be chosen from any given elementary equivalence class. Furthermore, under continuum hypothesis, we show that in the sense of cardinality "most" automorphisms of a ultrapower $M^{\mathcal{U}}$ of a separable $\mathrm{II}_1$ factor do not lift to a sequence of UCP maps $φ_n: M \to M$.
title Elementary embeddings into ultrapower $\mathrm{II}_1$ factors without a UCP lift
topic Operator Algebras
Logic
46L10, 03C66, 03C20
url https://arxiv.org/abs/2512.10129