Results 11 to 20 of about 1,087 (98)
On Carleman and observability estimates for wave equations on time‐dependent domains
Proceedings of the London Mathematical Society, Volume 119, Issue 4, Page 998-1064, October 2019., 2019 Abstract We establish new Carleman estimates for the wave equation, which we then apply to derive novel observability inequalities for a general class of linear wave equations. The main features of these inequalities are that (a) they apply to a fully general class of time‐dependent domains, with timelike moving boundaries, (b) they apply to linear ...
Arick Shao
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A geometric flow on null hypersurfaces of Lorentzian manifolds
Topological Algebra and its Applications, 2022 We introduce a geometric flow on a screen integrable null hypersurface in terms of its local second fundamental form. We use it to give an alternative proof to the vorticity free Raychaudhuri’s equation for null hypersurface, as well as establishing ...
Massamba Fortuné, Ssekajja Samuel
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A new approach on helices in pseudo-Riemannian manifolds [PDF]
, 2013 In this paper, we give a definition of harmonic curvature functions in terms of V_{n} and define a new kind of slant helix which is called V_{n}-slant helix in n-dimensional pseudo-Riemannian manifold.
Gök, İsmail +2 more
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Screen conformal half‐lightlike submanifolds
International Journal of Mathematics and Mathematical Sciences, Volume 2004, Issue 68, Page 3737-3753, 2004., 2004 We study some properties of a half‐lightlike submanifold M, of a semi‐Riemannian manifold, whose shape operator is conformal to the shape operator of its screen distribution. We show that any screen distribution S(TM) of M is integrable and the geometry of M has a close relation with the nondegenerate geometry of a leaf of S(TM).
K. L. Duggal, B. Sahin
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Algebraic Properties of Curvature Operators in Lorentzian Manifolds with Large Isometry Groups [PDF]
, 2010 Together with spaces of constant sectional curvature and products of a real line with a manifold of constant curvature, the socalled Egorov spaces and $\varepsilon$-spaces exhaust the class of $n$-dimensional Lorentzian manifolds admitting a group of ...
Calvaruso, Giovanni, Garcia-Rio, Eduardo
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Trajectories under a vectorial potential on stationary manifolds
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 23, Page 1481-1495, 2003., 2003 By using variational methods, we study the existence and multiplicity of trajectories under a vectorial potential on (standard) stationary Lorentzian manifolds possibly with boundary.
Rossella Bartolo
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Ricci-flat and Einstein pseudoriemannian nilmanifolds
Complex Manifolds, 2019 This is partly an expository paper, where the authors’ work on pseudoriemannian Einstein metrics on nilpotent Lie groups is reviewed. A new criterion is given for the existence of a diagonal Einstein metric on a nice nilpotent Lie group.
Conti Diego, Rossi Federico A.
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A condition for a perfect-fluid space-time to be a generalized Robertson-Walker space-time [PDF]
, 2016 A perfect-fluid space-time of dimension n>3 with 1) irrotational velocity vector field, 2) null divergence of the Weyl tensor, is a generalised Robertson-Walker space-time with Einstein fiber. Condition 1) is verified whenever pressure and energy density
De, Uday Chand +2 more
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Biharmonic curves in Minkowski 3‐space
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 21, Page 1365-1368, 2003., 2003 We give a differential geometric interpretation for the classification of biharmonic curves in semi‐Euclidean 3‐space due to Chen and Ishikawa (1991).
Jun-Ichi Inoguchi
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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
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