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math.GT2022★ 1 cited
Simple spines of homotopy 2-spheres are unique
Patrick Orson, Mark Powell
A locally flatly embedded -sphere in a compact -manifold is called a spine if the inclusion map is a homotopy equivalence. A spine is called simple if the complement of t…
math.GT2022★ 2 cited
Mapping class groups of simply connected 4-manifolds with boundary
Patrick Orson, Mark Powell
We compute the topological mapping class group of every compact, simply connected, topological 4-manifold. This was previously only known in the closed case. If the 4-manifold is s…