On the structure and symmetry properties of almost S-manifolds

We prove that any simply connected S-manifold of CR-codimension $s\ge 2$ is noncompact by showing that the complete, simply connected S-manifolds are all the CR products NxR^{s-1} with N Sasakian, endowed with a suitable product metric. N is a Sasakian φ-symmetric space if and only if M is CR-symmetric. The locally CR-symmetric S-manifolds are characterized by $\tilde\nabla\tilde R=0$ where $\tilde\nabla$ is the Tanaka-Webster connection. This characterization is showed to be nonvalid for nonnormal almost S-manifolds.