An infinite set of exotic $\mathbf{R}^4$'s
An infinite set of exotic $\mathbf{R}^4$'s
IntroductionIn 1982, Michael Freedman startled the topological community by pointing out the existence of an "exotic R 4 ", a smooth manifold homeomorphic to R 4 , but not diffeomorphic to it.This result follows easily from Donaldson's Theorem [2] on the nonexistence of certain smooth 4-manifolds, together with Freedman's powerful …