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Cyclic Group Actions on Contractible 4-Manifolds (1412.5877v2)
Published 18 Dec 2014 in math.GT and math.AT
Abstract: There are known infinite families of Brieskorn homology 3-spheres which can be realized as boundaries of smooth contractible 4-manifolds. In this paper we show that free periodic actions on these Brieskorn spheres do not extend smoothly over a contractible 4-manifold. We give a new infinite family of examples in which the actions extend locally linearly but not smoothly.