Periodic ends and knot concordance

AbstractSome topological applications are given for Taubes' theorem on nonexistence of certain definite 4-manifolds with periodic ends. In particular, it is shown that the group of topologically slice knots up to smooth concordance is larger than Z, even modulo torsion. A corollary of the proof is that there are uncountably many diffeomorphism types of Casson handles. A specific collection of doubled knots is exhibited, no two members of which are smoothly concordant