We obtain a theory of stratified Sternberg spaces thereby extending
the theory of cotangent bundle reduction for free actions to the singular
case where the action on the base manifold consists of only one orbit
type. We find that the symplectic reduced spaces are stratified topological
fiber bundles over the cotangent bundle of the orbit space. We
also obtain a Poisson stratification of the Sternberg space. To construct
the singular Poisson Sternberg space we develop an appropriate theory
of singular connections for proper group actions on a single orbit type
manifold including a theory of holonomy extending the usual Ambrose–
Singer theorem for principal bundles.