Differentiable structures on punctured 4-manifolds (Q690273)

By a result of Quinn, any closed simply-connected 4-manifold becomes smoothable after removing a point. In this paper, the authors give sufficient conditions for such punctured 4-manifolds to have uncountably many differentiable structures. For example, they prove this result if the closed 4-manifold (not necessarily simply-connected) was smooth to begin with or if one introduces two punctures instead of one. This generalizes the famous construction of uncountably many differentiable structures on Euclidean 4-space (which is the punctured 4-sphere).