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Bibliographic Details
Main Authors: Ando, Hiroshi, Goldbring, Isaac
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2605.21873
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Table of Contents:
  • We prove, for any W$^*$-probability space $(M,φ)$ where $M$ is a type $\mathrm{III}_1$ factor, any nontrivial, proper closed $F\subseteq \mathbb{R}$, and any nonprincipal ultrafilter $\mathcal{U}$ on $\mathbb{N}$, that the ultrapower $M(σ^φ,F)^{\mathcal{U}}$ of the spectral subspace $M(σ^φ,F)$ is a proper subset of the spectral subspace $M^{\mathcal{U}}(σ^{φ^{\mathcal{U}}},F)$. We discuss the model-theoretic implications of this result.