Elementary embeddings into ultrapower $\mathrm{II}_1$ factors without a ucp lift
Abstract
We show that there are $\mathrm{II}_1$ factors $M$ and elementary embeddings $M \to M^{\cU}$ 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 an ultrapower $M^{\mathcal{U}}$ of a separable $\mathrm{II}_1$ factor do not lift to a sequence of UCP maps $\varphi_n: M \to M$.
Fields of Study & Subjects
Advanced Topology and Set Theory
Advanced Operator Algebra Research
Homotopy and Cohomology in Algebraic Topology
Publication details
- Journal / source
- Journal of Logic and Analysis
- Volume
- 18
- Publication date
- 27 May 2026