Nonnegatively curved fixed point homogeneous 5-manifolds. [Preprint]

Let G be a compact Lie group acting effectively by isometries on a compact Riemannian manifold M with nonempty fixed point set Fix(M,G). We say that the action is \emph{fixed point homogeneous} if G acts transitively on a normal sphere to some component of Fix(M,G), equivalently, if Fix(M,G) has codimension one in the orbit space of the action. We classify up to diffeomorphism closed, simply connected 5-manifolds with nonnegative sectional curvature and an effective fixed point homogeneous isometric action of a compact Lie group.