The free splitting complex of a free group I: Hyperbolicity
arXiv:1111.1994 · doi:10.2140/gt.2013.17.1581
Abstract
We prove that the free splitting complex of a finite rank free group, also known as Hatcher's sphere complex, is hyperbolic.
85 pages, including index and glossary. Many figures in the free splitting complex, in the guise of commutative diagrams of maps between free splittings. Changes from Version 1 to Version 2: Corrected an error in the proof of Proposition 6.5, Step 2. Revamped the theory of free splitting units in Section 5