Irreducible operators in von Neumann algebras

Fuente: arXiv
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Main Authors: Adappa, Sukitha, Ma, Minghui, Shen, Junhao, Shi, Rui, Yang, Shanshan
Format: Preprint
Published: 2025
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author Adappa, Sukitha
Ma, Minghui
Shen, Junhao
Shi, Rui
Yang, Shanshan
author_facet Adappa, Sukitha
Ma, Minghui
Shen, Junhao
Shi, Rui
Yang, Shanshan
contents Let $\mathcal{M}$ be a separable von Neumann algebra with center $\mathcal{Z}(\mathcal{M})$. An operator $T$ in $\mathcal{M}$ is called irreducible if the von Neumann algebra $W^*(T)$ generated by $T$ has trivial relative commutant, i.e., $W^*(T)'\cap\mathcal{M}=\mathcal{Z}(\mathcal{M})$. In this paper, we show that irreducible operators in $\mathcal{M}$ form a norm-dense $G_δ$ set, which is a generalization of Halmos' theorem. Moreover, we prove that every operator in $\mathcal{M}$ is the sum of two irreducible operators, which is an analogue of Radjavi's theorem.
format Preprint
id arxiv_https___arxiv_org_abs_2512_03448
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Irreducible operators in von Neumann algebras
Adappa, Sukitha
Ma, Minghui
Shen, Junhao
Shi, Rui
Yang, Shanshan
Operator Algebras
Let $\mathcal{M}$ be a separable von Neumann algebra with center $\mathcal{Z}(\mathcal{M})$. An operator $T$ in $\mathcal{M}$ is called irreducible if the von Neumann algebra $W^*(T)$ generated by $T$ has trivial relative commutant, i.e., $W^*(T)'\cap\mathcal{M}=\mathcal{Z}(\mathcal{M})$. In this paper, we show that irreducible operators in $\mathcal{M}$ form a norm-dense $G_δ$ set, which is a generalization of Halmos' theorem. Moreover, we prove that every operator in $\mathcal{M}$ is the sum of two irreducible operators, which is an analogue of Radjavi's theorem.
title Irreducible operators in von Neumann algebras
topic Operator Algebras
url https://arxiv.org/abs/2512.03448