Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract In this paper, we study the geometry of a semi-Riemannian manifold ¯ M of quasi-constant curvature. The main result is two characterization theorems for ¯ M admits solenoidal and screen totally umbilical r (> 1)-lightlike subm...

Abstract We give conditions for a conformal vector field to be tangent null hypersurface. particularize two important cases: Killing and closed field. In the first case, we obtain result ensuring that hypersurface is horizon. second one, gives rise foliation of manifold by totally umbilical hypersurfaces with constant mean curvature which can spacelike, timelike or null. prove several results e...

We obtain some properties of a hyperbolic Ricci soliton with certain types potential vector fields, and we point out conditions when it reduces to trivial soliton. also study those submanifolds whose fields are the tangential components concurrent field on ambient manifold, in particular, show that totally umbilical is an Einstein manifold. prove if hypersurface Riemannian manifold constant cur...

In this paper, we study a stability problem of free boundary hypersurfaces, and also capillary ones whose supported on horosphere in hyperbolic space. We prove that umbilical hypersurfaces are only stable immersed horosphere. Using the same method, show totally geodesic hyperplane is type-II hypersurface

In this paper, we study gradient Einstein-type structure immersed into a Riemannian warped product manifold. We obtain some triviality results for the potential function and smooth map u . investigate conditions to be totally umbilical, or geodesic I × f M n Furthermore, rotational hypersurface R has structure.

We study Einstein lightlike hypersurfaces M of a Lorentzian space form M̃(c) admitting a semi-symmetric non-metric connection subject to the conditions; (1) M is screen conformal and (2) the structure vector field ζ of M̃ belongs to the screen distribution S(TM). The main result is a characterization theorem for such a lightlike hypersurface.

In this paper, we study the geometry of lightlike hypersurfaces of an indefinite trans-Sasakian manifold with a quarter-symmetric metric connection. The main result is a characterization theorem for such a lightlike hypersurface of an indefinite generalized Sasakian space form. Mathematics Subject Classification: 53C25, 53C40, 53C50