Results 21 to 30 of about 1,063 (72)
Isometry Lie algebras of indefinite homogeneous spaces of finite volume
Proceedings of the London Mathematical Society, Volume 119, Issue 4, Page 1115-1148, October 2019., 2019 Abstract Let g be a real finite‐dimensional Lie algebra equipped with a symmetric bilinear form ⟨·,·⟩. We assume that ⟨·,·⟩ is nil‐invariant. This means that every nilpotent operator in the smallest algebraic Lie subalgebra of endomorphisms containing the adjoint representation of g is an infinitesimal isometry for ⟨·,·⟩.
Oliver Baues +2 more
wiley +1 more source
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
core +2 more sources
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
wiley +1 more source
Open Mathematics, 2020 In this paper, we discuss the monotonicity of the first nonzero eigenvalue of the Laplace operator and the p-Laplace operator under a forced mean curvature flow (MCF).
Qi Xuesen, Liu Ximin
doaj +1 more source
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
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
wiley +1 more source
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
wiley +1 more source
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
doaj +1 more source
A Geometric Algorithm to construct new solitons in the O(3) Nonlinear Sigma Model [PDF]
, 2002 The O(3) nonlinear sigma model with boundary, in dimension two, is considered. An algorithm to determine all its soliton solutions that preserve a rotational symmetry in the boundary is exhibited.
Albertsson +22 more
core +3 more sources
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
wiley +1 more source