Some lightlike submanifolds of almost complex manifolds with Norden metric

In this paper we study submanifolds of an almost complex manifold with Norden metric which are non-degenerate with respect to the one Norden metric and lightlike with respect to the other Norden metric on the manifold. Relations between the induced geometric objects of some of these submanifolds are given. Examples of the considered submanifolds are constructed.     

On semi-parallel lightlike hypersurfaces of indefinite Kenmotsu manifolds

We study semi-parallel lightlike hypersurfaces of an indefinite Kenmotsu manifold, tangent to the structure vector field. Some Theorems on parallel and semi-parallel vector field, geodesibility of lightlike hypersurfaces are obtained. The geometrical configuration of such lightlike hypersurfaces is established. We prove that, in totally contact umbilical lightlike hypersurfaces of an indefinite Kenmotsu manifold which has constant ${\overline{\phi}}$ -holomorphic sectional curvature c, tangent to the structure vector field and such that its distribution is parallel, the parallelism and semi-parallelism notions are equivalent.     

Semi-Riemannian hypersurfaces in manifolds with metric mixed 3-structures

The mixed 3-structures are the counterpart of paraquaternionic structures in odd dimension. A compatible metric with a mixed 3-structure is necessarily semi-Riemann and mixed 3-Sasakian manifolds are Einstein. We investigate the differential geometry of the semi-Riemannian hypersurfaces of co-index both 0 and 1 in a manifold endowed with a mixed 3-structure and a compatible metric.     

A classification of almost contact metric manifolds

Summary It is obtained a complete classification for almost contact metric manifolds through the study of the covariant derivative of the fundamental 2- form on those manifolds.This work was supported by the « Consejería de Educación del Gobierno de Canarias ».     

Harmonicity on some almost contact metric manifolds

In this paper we shall study some classes of harmonic maps on Trans-Sasakian manifolds.     

Riemannian submersions from almost contact metric manifolds

In this paper we obtain the structure equation of a contact-complex Riemannian submersion and give some applications of this equation in the study of almost cosymplectic manifolds with Kähler fibres.     

On the classification of almost contact metric manifolds

On connected manifolds of dimension higher than three, the non-existence of 132 Chinea and González-Dávila types of almost contact metric structures is proved. This is a consequence of some interrelations among components of the intrinsic torsion of an almost contact metric structure. Such interrelations allow to describe the exterior derivatives of some relevant forms in the context of almost contact metric geometry.     

Harmonicity on maps between almost contact metric manifolds

We study (φ,φ′)-holomorphic maps between almost contact metric manifolds, in particular horizontally conformal (φ,φ′)-holomorphic submersions, and obtain some criteria for the harmonicity of such maps.     

Chern numbers of almost complex manifolds

It is shown that any system of numbers that can be realised as the system of Chern numbers of an almost complex manifold of dimension , , can also be realised in this way by a connected almost complex manifold. This answers an old question posed by Hirzebruch.

     

Lelong functional on almost complex manifolds

We establish plurisubharmonicity of the envelope of Lelong functional on almost complex manifolds of real dimension four, thereby we generalize the corresponding result for complex manifolds.     

Extension formulae on almost complex manifolds

We give the extension formulae on almost complex manifolds and give decompositions of the extension formulae.As applications,we study(n,0)-forms,the(n,0)-Dolbeault cohomology group and(n,q)-forms on almost complex manifolds.