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arXiv · 2601.18185

Relative bi-exactness and structural results for graph-wreath product von Neumann algebras

Taisuke Hoshino
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Abstract

We study relative bi-exactness of graph product and graph-wreath product group von Neumann algebras. In particular, we obtain the relative bi-exactness for graph product von Neumann algebras $LH_Γ=\ast_{v,Γ} LH_v$ and graph-wreath product von Neumann algebras $L(H_Γ\rtimes G)=(\ast_{v,Γ} LH)\rtimes G$, assuming that the component groups are exact. We adopt the $C^{\ast}$-algebraic method of Ozawa for the proof. As an application, for a certain class of graph-wreath products, we establish the rigidity result for the quotient graph $G\backslashΓ$ under stable isomorphism. Furthermore, we obtain a new family of prime $\mathrm{II}_1$ factors.

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Taisuke Hoshino. 2026-01-26. Relative bi-exactness and structural results for graph-wreath product von Neumann algebras. https://arxiv.org/abs/2601.18185

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