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arXiv · 2404.11371

The boundary of bordified Outer space

Karen Vogtmann
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Abstract

We study the boundary of the "Jewel space" $\mathcal J_n$ constructed in arXiv:1709.01296. This is an equivariant deformation retract of Outer space $CV_n$ on which $Out(F_n)$ acts properly and cocompactly, and is homeomorphic to the Bestvina-Feighn bordification of $CV_n$. In the current paper we analyze the structure of the boundary of $\mathcal J_n$. We then use the desctiption of the simplicial closure $CV_n^*$ as the sphere complex of a connected sum of $n$ copies of $S^1\times S^2$ to prove that this boundary is homotopy equivalent to the subcomplex of $CV_n^*$ spanned by vertices at infinity.

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Karen Vogtmann. 2024-04-17. The boundary of bordified Outer space. https://arxiv.org/abs/2404.11371

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