Approximate representability of finite abelian group actions on the Razak-Jacelon algebra

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1. Verfasser: Nawata, Norio
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Veröffentlicht: 2023
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author Nawata, Norio
author_facet Nawata, Norio
contents Let $A$ be a simple separable nuclear monotracial C$^*$-algebra, and let $α$ be an outer action of a finite abelian group $Γ$ on $A$. In this paper, we show that $α\otimes \mathrm{id}_{\mathcal{W}}$ on $A\otimes\mathcal{W}$ is approximately representable if and only if the characteristic invariant of $\tildeα$ is trivial, where $\mathcal{W}$ is the Razak-Jacelon algebra and $\tildeα$ is the induced action on the injective II$_1$ factor $π_{τ_{A}}(A)^{''}$. As an application of this result, we classify such actions up to conjugacy and cocycle conjugacy. In particular, we show the following: Let $A$ and $B$ be simple separable nuclear monotracial C$^*$-algebras, and let $α$ and $β$ be outer actions of a finite abelian group $Γ$ on $A$ and $B$, respectively. Assume that the characteristic invariants of $\tildeα$ and $\tildeβ$ are trivial. Then $α\otimes \mathrm{id}_{\mathcal{W}}$ and $β\otimes \mathrm{id}_{\mathcal{W}}$ are conjugate (resp. cocycle conjugate) if and only if $\tildeα$ on $π_{τ_{A}}(A)^{''}$ and $\tildeβ$ on $π_{τ_{B}}(B)^{''}$ are conjugate (resp. cocycle conjugate). We also construct the model actions.
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id arxiv_https___arxiv_org_abs_2302_10550
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Approximate representability of finite abelian group actions on the Razak-Jacelon algebra
Nawata, Norio
Operator Algebras
Primary 46L55, Secondary 46L35, 46L40
Let $A$ be a simple separable nuclear monotracial C$^*$-algebra, and let $α$ be an outer action of a finite abelian group $Γ$ on $A$. In this paper, we show that $α\otimes \mathrm{id}_{\mathcal{W}}$ on $A\otimes\mathcal{W}$ is approximately representable if and only if the characteristic invariant of $\tildeα$ is trivial, where $\mathcal{W}$ is the Razak-Jacelon algebra and $\tildeα$ is the induced action on the injective II$_1$ factor $π_{τ_{A}}(A)^{''}$. As an application of this result, we classify such actions up to conjugacy and cocycle conjugacy. In particular, we show the following: Let $A$ and $B$ be simple separable nuclear monotracial C$^*$-algebras, and let $α$ and $β$ be outer actions of a finite abelian group $Γ$ on $A$ and $B$, respectively. Assume that the characteristic invariants of $\tildeα$ and $\tildeβ$ are trivial. Then $α\otimes \mathrm{id}_{\mathcal{W}}$ and $β\otimes \mathrm{id}_{\mathcal{W}}$ are conjugate (resp. cocycle conjugate) if and only if $\tildeα$ on $π_{τ_{A}}(A)^{''}$ and $\tildeβ$ on $π_{τ_{B}}(B)^{''}$ are conjugate (resp. cocycle conjugate). We also construct the model actions.
title Approximate representability of finite abelian group actions on the Razak-Jacelon algebra
topic Operator Algebras
Primary 46L55, Secondary 46L35, 46L40
url https://arxiv.org/abs/2302.10550