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排序方式: 共有274条查询结果,搜索用时 15 毫秒
31.
本文综述了E^n和S^n中极小曲面的若干经典结果和最新发展,指出了一些尚未解决的问题,在第4节中,对E^3中极小曲面的Fujimoto定理给出了一个更直接的证明。 相似文献
32.
A QMR-based interior-point algorithm for solving linear programs 总被引:5,自引:0,他引:5
A new approach for the implementation of interior-point methods for solving linear programs is proposed. Its main feature
is the iterative solution of the symmetric, but highly indefinite 2×2-block systems of linear equations that arise within
the interior-point algorithm. These linear systems are solved by a symmetric variant of the quasi-minimal residual (QMR) algorithm,
which is an iterative solver for general linear systems. The symmetric QMR algorithm can be combined with indefinite preconditioners,
which is crucial for the efficient solution of highly indefinite linear systems, yet it still fully exploits the symmetry
of the linear systems to be solved. To support the use of the symmetric QMR iteration, a novel stable reduction of the original
unsymmetric 3×3-block systems to symmetric 2×2-block systems is introduced, and a measure for a low relative accuracy for
the solution of these linear systems within the interior-point algorithm is proposed. Some indefinite preconditioners are
discussed. Finally, we report results of a few preliminary numerical experiments to illustrate the features of the new approach. 相似文献
33.
34.
本文首先将常曲率黎曼流形中B.Y.Chen和M.Okumura关于数量曲率和截面曲率关系间的一个著名不等式推广到环绕空间是局部对称共形平坦黎曼流形的情形.作为应用,较简捷地将M.Okumura在[2],[3]中的结果推广到这种环绕空间中法联络是平坦的子流形上去. 相似文献
35.
Paul E. Ehrlich 《Journal of Geometry and Physics》1989,6(4):657-670
Employing techniques recently developed by D. Kalish for Riemannian manifolds, we obtain a focal Morse index theorem for a null geodesic segment initially and terminally perpendicular to spacelike submanifolds of arbitrary codimension in a general space-time. 相似文献
36.
In this paper we use a new equivalent condition of Hamiltonian stationary Lagrangian surfaces in ℂP2 to show that any Hamiltonian stationary Lagrangian torus in ℂP2 can be constructed from a pair of commuting Hamiltonian ODEs on a finite dimensional subspace of a certain loop Lie algebra,
i.e., is of finite type.
Mathematics Subject Classifications (2000): Primary 53C40; Secondary 53C42, 53D12 相似文献
37.
We study biharmonic submanifolds in δ-pinched Riemannian manifolds, and obtain some sufficient conditions for biharmonic submanifolds to be minimal ones. 相似文献
38.
林洁珠 《数学物理学报(B辑英文版)》2010,30(3):873-889
I.A.B. Strachan introduced the notion of a natural Frobenius submanifold of a Frobenius manifold and gave a sufficient but not necessary condition for a submanifold to be a natural Frobenius submanifold. This article will give a necessary and sufficient condition and classify the natural Frobenius hypersurfaces. 相似文献
39.
Mehmet Ateken 《数学物理学报(B辑英文版)》2010,30(1):215-224
In this article, the geometry of the slant submanifolds of a Riemannian product manifold is studied. Some necessary and sufficient conditions on slant, bi-slant and semi-slant submanifolds are given. We research fundamental properties of the distributions which are involved in definitions of semi- and bi-slant submanifolds in a Riemannian product manifold. 相似文献
40.
A surface in a semi-Riemannian manifold is called marginally trapped if its mean curvature vector field is light-like at each point. In this article, we classify marginally trapped Lorentzian flat surfaces in the pseudo-Euclidean space . As an application, we obtain the complete classification of biharmonic Lorentzian surfaces in with light-like mean curvature vector. 相似文献