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arXiv · 1810.09380

Homotopy type of the complex of free factors of a free group

Benjamin Brück·Radhika Gupta
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Abstract

We show that the complex of free factors of a free group of rank n > 1 is homotopy equivalent to a wedge of spheres of dimension n-2. We also prove that for n > 1, the complement of (unreduced) Outer space in the free splitting complex is homotopy equivalent to the complex of free factor systems and moreover is (n-2)-connected. In addition, we show that for every non-trivial free factor system of a free group, the corresponding relative free splitting complex is contractible.

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Benjamin Brück, Radhika Gupta. 2018-10-22. Homotopy type of the complex of free factors of a free group. https://doi.org/10.1112/plms.12381

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