We present a compared analysis of some properties of indefinite almost S-manifolds and indefinite S-manifolds. We give some characterizations in terms of the Levi-Civita connection and of the characteristic vector fields. We study the sectional and φ-sectional curvature of indefinite almost S-manifolds and state an expression of the curvature tensor field for the indefinite S-space forms. We an...

Motivated by the possible characterization of Sasakian manifolds in terms of twistor forms, we give the complete classification of compact Riemannian manifolds carrying a Killing vector field whose covariant derivative (viewed as a 2–form) is a twistor form. 2000 Mathematics Subject Classification: Primary 53C55, 58J50.

Sasakian manifolds provide rich source of constructing new Einstein manifolds in odd dimensions [2]. They play some important role in the superstring theory in mathematical physics [19, 20]. There is a renewed interest on Sasakian manifolds recently. The present paper is devoted to the regularity analysis of a geodesic equation in the space of Sasakian metrics H (definition in (1.2)) and some o...

We study the Lie algebra of innnitesimal isometries of 7{dimensional simply connected manifolds with Killing spinors. We obtain some splitting theorems for the action of this algebra on the space of Killing spinors, and as a corollary we prove that there are no innnites-imal isometry of constant length on a 7{dimensional 3{Sasakian manifold (not isometric to a space form) except the linear comb...

The object of the present paper is to study the extended generalized φ-recurrent trans-Sasakian manifold and its various geometric properties.

We examine topological properties of the seven-dimensional positively curved Eschenburg biquotients and find many examples which are homeomorphic but not diffeomorphic. A special subfamily of these manifolds also carries a 3-Sasakian metric. Among these we construct a pair of 3-Sasakian spaces which are diffeomorphic to each other, thus giving rise to the first example of a manifold which carri...