scholarly journals Thin Structures With Imposed Metric

2018 ◽  
Vol 62 ◽  
pp. 79-90 ◽  
Author(s):  
Marta Lewicka ◽  
Annie Raoult
Keyword(s):  
Curvature Tensor ◽  
Three Dimensional ◽  
Riemannian Curvature ◽  
Algebraic Proof ◽  
Isometric Immersions ◽  
Bending Energy ◽  
Thin Structures ◽  
Riemannian Curvature Tensor ◽  
Membrane Energy ◽  
Limit Models

We consider thin structures with a non necessarily realizable imposed metric, that only depends on the surface variable. We give a unified presentation of the three main limit models. We establish the generalized membrane model and we show, by means of an algebraic proof, that the internal membrane energy vanishes on short maps of the metric restricted to the plane. We recall that a generalized bending model can occur only when this reduced metric admits sufficiently regular isometric immersions. When the entries R12.. of the Riemannian curvature tensor are null, this bending energy can vanish; then the next model is necessarily a generalized von Kármán model whose minimum is zero if and only if the three-dimensional metric is flat.

scholarly journals ON THE $\mathcal{M}$--PROJECTIVE CURVATURE TENSOR OF A $(k, \mu)$-CONTACT METRIC MANIFOLD

2017 ◽  
pp. 117
Author(s):  
D. G. Prakasha ◽  
Kakasab Mirji
Keyword(s):  
Curvature Tensor ◽  
Ricci Tensor ◽  
Sasakian Manifold ◽  
Riemannian Curvature ◽  
Contact Metric Manifold ◽  
Contact Metric Manifolds ◽  
Riemannian Curvature Tensor ◽  
Projective Curvature ◽  
Projective Curvature Tensor

The paper deals with the study of $\mathcal{M}$-projective curvature tensor on $(k, \mu)$-contact metric manifolds. We classify non-Sasakian $(k, \mu)$-contact metric manifold satisfying the conditions $R(\xi, X)\cdot \mathcal{M} = 0$ and $\mathcal{M}(\xi, X)\cdot S =0$, where $R$ and $S$ are the Riemannian curvature tensor and the Ricci tensor, respectively. Finally, we prove that a $(k, \mu)$-contact metric manifold with vanishing extended $\mathcal{M}$-projective curvature tensor $\mathcal{M}^{e}$ is a Sasakian manifold.

scholarly journals A CLASSIFICATION OF SPHERICAL SYMMETRIC CR MANIFOLDS

2009 ◽  
Vol 80 (2) ◽  
pp. 251-274 ◽  
Author(s):  
G. DILEO ◽  
A. LOTTA
Keyword(s):  
Curvature Tensor ◽  
Riemannian Curvature ◽  
Cr Manifolds ◽  
Hermitian Manifolds ◽  
Riemannian Curvature Tensor ◽  
Webster Metric ◽  
Simply Connected

AbstractIn this paper we get different characterizations of the spherical strictly pseudoconvex CR manifolds admitting a CR-symmetric Webster metric by means of the Tanaka–Webster connection and of the Riemannian curvature tensor. As a consequence we obtain the classification of the simply connected, spherical symmetric pseudo-Hermitian manifolds.

Convergence of Riemannian 4-manifolds with L 2 L^{2} -curvature bounds

2019 ◽  
Vol 0 (0) ◽  
Author(s):  
Norman Zergänge
Keyword(s):  
Curvature Tensor ◽  
Curvature Flow ◽  
Riemannian Curvature ◽  
Hausdorff Topology ◽  
Curvature Bounds ◽  
Prove Theorem ◽  
Riemannian Curvature Tensor ◽  
Convergence Results ◽  
Uniform Diameter ◽  
Gromov Hausdorff Topology

Abstract In this work we prove convergence results of sequences of Riemannian 4-manifolds with almost vanishing {L^{2}} -norm of a curvature tensor and a non-collapsing bound on the volume of small balls. In Theorem 1.1 we consider a sequence of closed Riemannian 4-manifolds, whose {L^{2}} -norm of the Riemannian curvature tensor tends to zero. Under the assumption of a uniform non-collapsing bound and a uniform diameter bound, we prove that there exists a subsequence that converges with respect to the Gromov–Hausdorff topology to a flat manifold. In Theorem 1.2 we consider a sequence of closed Riemannian 4-manifolds, whose {L^{2}} -norm of the Riemannian curvature tensor is uniformly bounded from above, and whose {L^{2}} -norm of the traceless Ricci-tensor tends to zero. Here, under the assumption of a uniform non-collapsing bound, which is very close to the Euclidean situation, and a uniform diameter bound, we show that there exists a subsequence which converges in the Gromov–Hausdorff sense to an Einstein manifold. In order to prove Theorem 1.1 and Theorem 1.2, we use a smoothing technique, which is called {L^{2}} -curvature flow. This method was introduced by Jeffrey Streets. In particular, we use his “tubular averaging technique” in order to prove distance estimates of the {L^{2}} -curvature flow, which only depend on significant geometric bounds. This is the content of Theorem 1.3.

scholarly journals On the $k$-th nullity space of the Riemannian curvature tensor

1975 ◽  
Vol 27 (1) ◽  
pp. 25-30
Author(s):  
Shun-ichi Tachibana ◽  
Masami Sekizawa
Keyword(s):  
Curvature Tensor ◽  
Riemannian Curvature ◽  
Riemannian Curvature Tensor

scholarly journals QUASI-CONFORMAL CURVATURE TENSOR OF GENERALIZED SASAKIAN-SPACE-FORMS

2020 ◽  
Vol 35 (1) ◽  
pp. 089
Author(s):  
Braj B. Chaturvedi ◽  
Brijesh K. Gupta
Keyword(s):  
Curvature Tensor ◽  
Ricci Tensor ◽  
Space Form ◽  
Riemannian Curvature ◽  
Space Forms ◽  
Conformal Curvature ◽  
Conformal Curvature Tensor ◽  
Sasakian Space Forms ◽  
Riemannian Curvature Tensor

The present paper deals the study of generalised Sasakian-space-forms with the conditions Cq(ξ,X).S = 0, Cq(ξ,X).R = 0 and Cq(ξ,X).Cq = 0, where R, S and Cq denote Riemannian curvature tensor, Ricci tensor and quasi-conformal curvature tensor of the space-form, respectively and at last, we have given some examples to improve our results.

On Strongly Convex Indicatrices in Minkowski Geometry

2002 ◽  
Vol 45 (2) ◽  
pp. 232-246 ◽  
Author(s):  
Min Ji ◽  
Zhongmin Shen
Keyword(s):  
Vector Space ◽  
Curvature Tensor ◽  
Riemannian Metric ◽  
Minkowski Geometry ◽  
Riemannian Curvature ◽  
Strongly Convex ◽  
Riemannian Curvature Tensor ◽  
Cartan Torsion ◽  
The Mean ◽  
The Relationship

AbstractThe geometry of indicatrices is the foundation of Minkowski geometry. A strongly convex indicatrix in a vector space is a strongly convex hypersurface. It admits a Riemannian metric and has a distinguished invariant—(Cartan) torsion. We prove the existence of non-trivial strongly convex indicatrices with vanishing mean torsion and discuss the relationship between the mean torsion and the Riemannian curvature tensor for indicatrices of Randers type.

scholarly journals Curvature Estimates in Asymptotically Flat Lorentzian Manifolds

2005 ◽  
Vol 57 (4) ◽  
pp. 708-723 ◽  
Author(s):  
Felix Finster ◽  
Margarita Kraus
Keyword(s):  
Fundamental Form ◽  
Curvature Tensor ◽  
Lorentzian Manifold ◽  
Second Fundamental Form ◽  
Riemannian Curvature ◽  
Lorentzian Manifolds ◽  
Asymptotically Flat ◽  
Riemannian Curvature Tensor ◽  
Curvature Estimates

AbstractWe consider an asymptotically flat Lorentzian manifold of dimension (1, 3). An inequality is derived which bounds the Riemannian curvature tensor in terms of the ADM energy in the general case with second fundamental form. The inequality quantifies in which sense the Lorentzianmanifold becomes flat in the limit when the ADM energy tends to zero.

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