论文标题
von Neumann代数的不变子代数由负弯曲组引起
Invariant subalgebras of von Neumann algebras arising from negatively curved groups
论文作者
论文摘要
Using an interplay between geometric methods in group theory and soft von Neuman algebraic techniques we prove that for any icc, acylindrically hyperbolic group $Γ$ its von Neumann algebra $L(Γ)$ satisfies the so-called ISR property: \emph{any von Neumann subalgebra $N\subseteq L(Γ)$ that is normalized by all group elements in $Γ$ is of the form $N= L(Σ)$ for a normal subgroup $Σ\lhd Γ$.} In particular, this applies to all groups $Γ$ in each of the following classes: all icc (relatively) hyperbolic groups, most mapping class groups of surfaces, all outer automorphisms of free groups with at least three generators, most graph product groups arising from simple graphs without visual splitting, etc. This result答案对\ cite {aj22}的阿姆鲁丹和江的一个开放问题。 在本文的第二部分中，我们获得了与接受各种自然表示的非平凡（准）群体相关的因素相似的结果。特别是，我们为所有具有阳性的$ l^2 $ -betti编号并包含无限amenable子组的ICC的ISR属性建立了ISR属性。
Using an interplay between geometric methods in group theory and soft von Neuman algebraic techniques we prove that for any icc, acylindrically hyperbolic group $Γ$ its von Neumann algebra $L(Γ)$ satisfies the so-called ISR property: \emph{any von Neumann subalgebra $N\subseteq L(Γ)$ that is normalized by all group elements in $Γ$ is of the form $N= L(Σ)$ for a normal subgroup $Σ\lhd Γ$.} In particular, this applies to all groups $Γ$ in each of the following classes: all icc (relatively) hyperbolic groups, most mapping class groups of surfaces, all outer automorphisms of free groups with at least three generators, most graph product groups arising from simple graphs without visual splitting, etc. This result answers positively an open question of Amrutam and Jiang from \cite{AJ22}. In the second part of the paper we obtain similar results for factors associated with groups that admit nontrivial (quasi)cohomology valued into various natural representations. In particular, we establish the ISR property for all icc, nonamenable groups that have positive first $L^2$-Betti number and contain an infinite amenable subgroup.
