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Displaying 141 – 160 of 319

New estimates for the first eigenvalue of the Jacobi operator on closed hypersurfaces in Riemannian space forms

Jiancheng Liu, Rong Mi (2020)

Czechoslovak Mathematical Journal

We study the first eigenvalue of the Jacobi operator on closed hypersurfaces with constant mean curvature in non-flat Riemannian space forms. Under an appropriate constraint on the totally umbilical tensor of the hypersurfaces and following Meléndez's ideas in J. Meléndez (2014) we obtain a new sharp upper bound of the first eigenvalue of the Jacobi operator.

Non-degenerate hypersurfaces of a semi-Riemannian manifold with a semi-symmetric metric connection

Ahmet Yücesan, Nihat Ayyildiz (2008)

Archivum Mathematicum

We derive the equations of Gauss and Weingarten for a non-degenerate hypersurface of a semi-Riemannian manifold admitting a semi-symmetric metric connection, and give some corollaries of these equations. In addition, we obtain the equations of Gauss curvature and Codazzi-Mainardi for this non-degenerate hypersurface and give a relation between the Ricci and the scalar curvatures of a semi-Riemannian manifold and of its a non-degenerate hypersurface with respect to a semi-symmetric metric connection....

Non-existence of real lightlike hypersurfaces of an indefinite complex space form.

Ṣahin, Bayram, Güneṣ, Rifat (2000)

Balkan Journal of Geometry and its Applications (BJGA)

On 3-Dimensional Riemannian ...-Spaces.

Oldrich Kowalski, Masami Sekizawa (1987)

Monatshefte für Mathematik

On $4 n$ -dimensional Lie groups as quasi-Kähler manifolds with Killing Norden metric.

Mekerov, Dimitar, Manev, Mancho (2008)

Novi Sad Journal of Mathematics

On a Class of Generalized quasi-Einstein Manifolds with Applications to Relativity

Sahanous Mallick, Uday Chand De (2016)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

Quasi Einstein manifold is a simple and natural generalization of Einstein manifold. The object of the present paper is to study some properties of generalized quasi Einstein manifolds. We also discuss $G {(Q E)}_{4}$ with space-matter tensor and some properties related to it. Two non-trivial examples have been constructed to prove the existence of generalized quasi Einstein spacetimes.

On a class of Ricci-recurrent manifolds.

Ewert-Krzemieniewski, Stanislaw (2003)

Acta Mathematica Academiae Paedagogicae Nyí regyháziensis. New Series [electronic only]

On a variational theory of light rays on Lorentzian manifolds

Fabio Giannoni, Antonio Masiello (1995)

Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti Lincei. Matematica e Applicazioni

In this Note, by using a generalization of the classical Fermat principle, we prove the existence and multiplicity of lightlike geodesics joining a point with a timelike curve on a class of Lorentzian manifolds, satisfying a suitable compactness assumption, which is weaker than the globally hyperbolicity.

On canonical screen for lightlike submanifolds of codimension two

K. Duggal (2007)

Open Mathematics

In this paper we study two classes of lightlike submanifolds of codimension two of semi-Riemannian manifolds, according as their radical subspaces are 1-dimensional or 2-dimensional. For a large variety of both these classes, we prove the existence of integrable canonical screen distributions subject to some reasonable geometric conditions and support the results through examples.

On certain Einstein space-time

B. Gądek, Krzysztof Heberlein, Antoni Jakubowicz (1984)

Commentationes Mathematicae Universitatis Carolinae

On complete linear Weingarten hypersurfaces in locally symmetric Riemannian manifolds

Cícero P. Aquino, Henrique F. de Lima, Fábio R. dos Santos, Marco Antonio L. Velásquez (2015)

Commentationes Mathematicae Universitatis Carolinae

Our aim is to apply suitable generalized maximum principles in order to obtain characterization results concerning complete linear Weingarten hypersurfaces immersed in a locally symmetric Riemannian manifold, whose sectional curvature is supposed to obey standard constraints. In this setting, we establish sufficient conditions to guarantee that such a hypersurface must be either totally umbilical or an isoparametric hypersurface with two distinct principal curvatures one of which is simple.

On complete spacelike hypersurfaces with $R = a H + b$ in locally symmetric Lorentz spaces

Yingbo Han, Shuxiang Feng, Liju Yu (2011)

Archivum Mathematicum

In this note, we investigate $n$ -dimensional spacelike hypersurfaces $M^{n}$ with $R = a H + b$ in locally symmetric Lorentz space. Two rigidity theorems are obtained for these spacelike hypersurfaces.

On conformally flat Lorentz parabolic manifolds

Yoshinobu Kamishima (2014)

Open Mathematics

We introduce conformally flat Fefferman-Lorentz manifold of parabolic type as a special class of Lorentz parabolic manifolds. It is a smooth (2n+2)-manifold locally modeled on (Û(n+1, 1), S 2n+1,1). As the terminology suggests, when a Fefferman-Lorentz manifold M is conformally flat, M is a Fefferman-Lorentz manifold of parabolic type. We shall discuss which compact manifolds occur as a conformally flat Fefferman-Lorentz manifold of parabolic type.

On Conjugate and Focal Points in Semi-Riemannian Geometry.

Demir N. Kupeli (1988)

Mathematische Zeitschrift

On equivariant harmonic maps defined on a Lorentz manifold

Ma Li (1991)

Annales de l'institut Fourier

In this paper, we prove by using the minimax principle that there exist infinitely many $G$ -equivariant harmonic maps from a specific Lorentz manifold to a compact Riemannian manifold.

Currently displaying 141 – 160 of 319

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