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Characterization of totally umbilic hypersurfaces in a space form by circles

Toshiaki Adachi, Sadahiro Maeda (2005)

Czechoslovak Mathematical Journal

In this paper we characterize totally umbilic hypersurfaces in a space form by a property of the extrinsic shape of circles on hypersurfaces. This characterization corresponds to characterizations of isoparametric hypersurfaces in a space form by properties of the extrinsic shape of geodesics due to Kimura-Maeda.

Characterization on Mixed Generalized Quasi-Einstein Manifold

Sampa Pahan, Buddhadev Pal, Arindam BHATTACHARYYA (2016)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

In the present paper we study characterizations of odd and even dimensional mixed generalized quasi-Einstein manifold. Next we prove that a mixed generalized quasi-Einstein manifold is a generalized quasi-Einstein manifold under a certain condition. Then we obtain three and four dimensional examples of mixed generalized quasi-Einstein manifold to ensure the existence of such manifold. Finally we establish the examples of warped product on mixed generalized quasi-Einstein manifold.

Characterizations of complex space forms by means of geodesic spheres and tubes

J. Gillard (1996)

Colloquium Mathematicae

We prove that a connected complex space form ( M n ,g,J) with n ≥ 4 can be characterized by the Ricci-semi-symmetry condition R ˜ X Y · ϱ ˜ = 0 and by the semi-parallel condition R ˜ X Y · σ = 0 , considering special choices of tangent vectors X , Y to small geodesic spheres or geodesic tubes (that is, tubes about geodesics), where R ˜ , ϱ ˜ and σ denote the Riemann curvature tensor, the corresponding Ricci tensor of type (0,2) and the second fundamental form of the spheres or tubes and where R ˜ X Y acts as a derivation.

Charles Ehresmann's concepts in differential geometry

Paulette Libermann (2007)

Banach Center Publications

We outline some of the tools C. Ehresmann introduced in Differential Geometry (fiber bundles, connections, jets, groupoids, pseudogroups). We emphasize two aspects of C. Ehresmann's works: use of Cartan notations for the theory of connections and semi-holonomic jets.

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