Oldrich Kowalski

Riemannian manifolds of conullity two

Definition and early development local structure of semi-symmetric spaces explicit treatment of foliated semi-symmetric spaces curvature homogeneous semi-symmetric spaces asymptotic distributions and algebraic rank three-dimensional Riemannian manifolds of conullity two asymptotically foliated semi-symmetric spaces elliptic semi-symmetric spaces complete foliated semi-symmetric spaces application - local rigidity problems for hypersurfaces with type number two in IR4 three-dimensional Riemannian manifolds of relative conullity two appendix - more about curvature homogeneous spaces.

On the Ricci operator of locally homogeneous Lorentzian 3-manifolds

We determine the admissible forms for the Ricci operator of three-dimensional locally homogeneous Lorentzian manifolds.