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arXiv 1801.04750math.GTmath.GR
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双曲自由循环群的可视边界

The visual boundary of hyperbolic free-by-cyclic groups

Yael Algom-Kfir, Arnaud Hilion, Emily Stark

摘要:

设$ϕ$是自由群$F_n$的超环面外自同构.研究了双曲群$G_ϕ = F_n \rtimes_ϕ \mathbb{Z}$的Gromov边界.我们明确地描述了一个家庭的完全二部图$K_{3,3}$到$\partial G_ϕ$的嵌入。为此,我们定义了方向Whitehead图,并证明了一个不可分解的$F_n$ -树是Levitt型的当且仅当它的一个方向Whitehead图包含一个以上的边缘。作为应用,我们得到了Kapovich-Kleiner定理的一个直接证明:如果自同构是环向的且完全不可约,则$\partial G_ϕ$同胚于Menger曲线.

英文摘要:

Let $ϕ$ be an atoroidal outer automorphism of the free group $F_n$. We study the Gromov boundary of the hyperbolic group $G_ϕ = F_n \rtimes_ϕ \mathbb{Z}$. We explicitly describe a family of embeddings of the complete bipartite graph $K_{3,3}$ into $\partial G_ϕ$. To do so, we define the directional Whitehead graph and prove that an indecomposable $F_n$-tree is Levitt type if and only if one of its directional Whitehead graphs contains more than one edge. As an application, we obtain a direct proof of Kapovich-Kleiner's theorem that $\partial G_ϕ$ is homeomorphic to the Menger curve if the automorphism is atoroidal and fully irreducible.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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