Results 21 to 30 of about 1,037 (71)
A New Quasi-local Mass and Positivity [PDF]
, 2007 We use an idea of Wang and Yau to give a new definition of quasi-local mass for a topological sphere in an initial date set. The new definition modifies Brown-York's definition by using certain spinor norm as lapse function.
Zhang, Xiao
core +3 more sources
Chern‐Simons forms of pseudo‐Riemannian homogeneity on the oscillator group
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 47, Page 3007-3014, 2003., 2003 We consider forms of Chern‐Simons type associated to homogeneous pseudo‐Riemannian structures. The corresponding secondary classes are a measure of the lack of a homogeneous pseudo‐Riemannian space to be locally symmetric. In the present paper, we compute these forms for the oscillator group and the corresponding secondary classes of the compact ...
P. M. Gadea, J. A. Oubiña
wiley +1 more source
Pseudoinversion of degenerate metrics
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 55, Page 3479-3501, 2003., 2003 Let (M, g) be a smooth manifold M endowed with a metric g. A large class of differential operators in differential geometry is intrinsically defined by means of the dual metric g∗ on the dual bundle TM∗ of 1‐forms on M. If the metric g is (semi)‐Riemannian, the metric g∗ is just the inverse of g. This paper studies the definition of the above‐mentioned
C. Atindogbe, J.-P. Ezin, Joël Tossa
wiley +1 more source
Hypersurfaces in a conformally flat space with curvature collineation
International Journal of Mathematics and Mathematical Sciences, Volume 14, Issue 3, Page 595-604, 1991., 1990 We classify the shape operators of Einstein and pseudo Einstein hypersurfaces in a conformally flat space with a symmetry called curvature collineation. We solve the fundamental problem of finding all possible forms of non‐diagonalizable shape operators.
K. L. Duggal, R. Sharma
wiley +1 more source
Examples of naturally reductive pseudo-Riemannian Lie groups
, 2011 We provide examples of naturally reductive pseudo-Riemannian spaces, in particular an example of a naturally reductive pseudo-Riemannian 2-step nilpotent Lie group $(N, _N)$, such that $_N$ is invariant under a left action and for which the center is ...
Ovando, Gabriela P.
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A note on the existence of standard splittings for conformally stationary spacetimes
, 2012 Let $(M,g)$ be a spacetime which admits a complete timelike conformal Killing vector field $K$. We prove that $(M,g)$ splits globally as a standard conformastationary spacetime with respect to $K$ if and only if $(M,g)$ is distinguishing (and, thus ...
Beem J K +11 more
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Osculating curves in 4-dimensional semi-Euclidean space with index 2
Open Mathematics, 2017 In this paper, we give the necessary and sufficient conditions for non-null curves with non-null normals in 4-dimensional Semi-Euclidian space with indeks 2 to be osculating curves.
İlarslan Kazim +2 more
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Null scrolls with prescribed curvatures in Lorentz-Minkowski 3-space
Analele Stiintifice ale Universitatii Ovidius Constanta: Seria Matematica, 2020 In Lorentz-Minkowski 3-space, null scrolls are ruled surfaces with a null base curve and null rulings. Their mean, as well as their Gaussian curvature, depends only on a parameter of a base curve. In the present paper, we obtain the first-order nonlinear
Šipuš Željka Milin +2 more
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On a Class Almost Contact Manifolds with Norden Metric [PDF]
, 2010 Certain curvature properties and scalar invariants of the manifolds belonging to one of the main classes almost contact manifolds with Norden metric are considered.
Teofilova, Marta
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Ricci‐Bourguignon Solitons With Certain Applications to Relativity
Journal of Mathematics, Volume 2025, Issue 1, 2025.This article concerns with the investigation of Ricci‐Bourguignon solitons and gradient Ricci‐Bourguignon solitons in perfect fluid space‐times and generalised Robertson–Walker space‐times. First, we deduce the criterion for which the Ricci‐Bourguignon soliton in a perfect fluid space‐time is steady, expanding or shrinking. Then, we establish that if a
Krishnendu De +4 more
wiley +1 more source