Sadeeb Ottenburger
Abstract
Let T(γ) be the total space of the canonical line bundle γover CP¹ and r an integer which is greater than one and coprime to six. We prove that L_r³× T(γ) admits an infinite sequence of metrics of nonnegative sectional curvature with pairwise non-homeomorphic souls, where L_r³ is the standard 3-dimensional lens space with fundamental group isomorphic to Z/r. We classify the total spaces of S¹-fibre bundles over S²× S² with fundamental group isomorphic to Z/r up to diffeomorphism and use these results to give examples of manifolds N which admit two complete metrics of nonnegative sectional curvature with souls S and S' of codimension two such that S and S' are diffeomorphic whereas the pairs (N,S) and (N,S') are not diffeomorphic. This solves a problem posed by I. Belegradek, S. Kwasik and R. Schultz.