Resumen de Groups that act pseudofreely on S²× S²

Michael McCooey

• A pseudofree group action on a space X is one whose set of singular orbits forms a discrete subset of its orbit space. Equivalently ¿ when G is finite and X is compact ¿ the set of singular points in X is finite. In this paper, we classify all of the finite groups which admit pseudofree actions on S2 × S2. The groups are exactly those that admit orthogonal pseudofree actions on S2 ×S2 ? R3 × R3, and they are explicitly listed.

  This paper can be viewed as a companion to a preprint of Edmonds, which uniformly treats the case in which the second Betti number of a four-manifold M is at least three.