共查询到19条相似文献,搜索用时 109 毫秒
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若超曲面的Laguerre形式为零且Laguerre第二基本形式的特征值(称为Laguerre主曲率)为常数,则称超曲面为Laguerre等参超曲面.对R~6中的Laguerre等参超曲面进行了研究,得到了分类定理. 相似文献
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水乃翔 《数学年刊A辑(中文版)》1985,(4)
设M~n是n+1维常由率黎曼流形S~(n+1)中的超曲面,其二个主曲率的重数L_1,L_2(L_1+L_2=n)保持为常数。本文证得:1.若L_1,L_2≥2则局部地至少有一个主曲率为常数。2.若L_1,L_2≥2,且M~n是常平均由率的单连通完备超曲面,则M~n=S~(L_1)×S~(L_2)。3.若L_1=1,L_2=n-1且M~n为常数量曲率和常平均曲率的单连通完备超曲面,则M~n=S~1×S~(n-1)。4.若M~n为单连通完备的S-流形,则 M~n=S~(L_1)×S~(L_2)。 相似文献
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本文证明了一个拼嵌的爱因斯坦流形中的任何超曲面在沿其平均曲率向量演化时,如果初发始曲面满足保持其截曲率为正的某些条件,则在有限时间内超曲而将收缩成一点。 相似文献
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给定H_+~n上适合凸条件的正函数F,对L~(n+1)中具有非退化Gauss映射的类空超曲面引入了Θ_F曲率.对适当的F,本文证得:具有常Θ_F曲率,且F-支撑函数介于两个负常数之间的类空超曲面必是类空Wulff形.在F=1的情况下,对H_i/H_n为常数的类空超曲面也建立了类似的唯一性结果. 相似文献
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本文是关于Riemann流形中超曲面逆曲率流的综述文章.首先介绍Euclid空间超曲面的逆曲率流的收敛性,以及其在证明Alexandrov-Fenchel不等式中的应用.其次,介绍在双曲空间以及球面中类似的结论.接着讨论Kottler空间的逆平均曲率流.Kottler空间是一类扭曲乘积空间,它满足物理中的稳态方程且在无穷远处渐近于局部双曲空间.本文将介绍此类空间中的逆平均曲率流的收敛性并用来对星形平均凸超曲面证明Minkowski型不等式.逆曲率流是近几年比较热门的一个研究领域,然而,由于篇幅有限,本文不能一一全部介绍.因此,本文最后列举一些相关的文献供感兴趣的读者参考. 相似文献
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设M^n是De Sitter空间S1^n+1中具有常数平均曲率且第二基本形式长度的平方为常数的完备类空超曲面,若S≤2(n-1)^1/2,则M^n是等参超曲面。 相似文献
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Yan-nan LIU & Huai-yu JIAN Department of Mathematical Sciences Tsinghua University Beijing China 《中国科学A辑(英文版)》2007,50(2):231-239
In this paper, we study the evolution of hypersurface moving by the mean curvature minus an external force field. It is shown that the flow will blow up in a finite time if the mean curvature of the initial surface is larger than some constant depending on the boundness of derivatives of the external force field. For a linear force, we prove that the convexity of the hypersurface is preserved during the evolution and the flow has a unique smooth solution in any finite time and expands to infinity as the time tends to infinity if the initial curvature is smaller than the slope of the force. 相似文献
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A smooth, compact and strictly convex hypersurface evolving in ℝ
n+1 along its mean curvature vector plus a forcing term in the direction of its position vector is studied in this paper. We
show that the convexity is preserving as the case of mean curvature flow, and the evolving convex hypersurfaces may shrink
to a point in finite time if the forcing term is small, or exist for all time and expand to infinity if it is large enough.
The flow can converge to a round sphere if the forcing term satisfies suitable conditions which will be given in the paper.
Long-time existence and convergence of normalization of the flow are also investigated. 相似文献
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Yannan Liu 《Frontiers of Mathematics in China》2010,5(2):311-317
In this paper, we study the evolution of a noncompact hypersurface moving by mean curvature minus an external force field.
We prove that the flow has a long-time smooth solution for a kind of special external force fields if the initial hypersurface
is a Lipschitz entire graph with linear growth. 相似文献
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Takumi Yokota 《Geometriae Dedicata》2008,133(1):169-179
In this paper, we consider the behavior of the total absolute and the total curvature under the Ricci flow on complete surfaces
with bounded curvature. It is shown that they are monotone non-increasing and constant in time, respectively, if they exist
and are finite at the initial time. As a related result, we prove that the asymptotic volume ratio is constant under the Ricci
flow with non-negative Ricci curvature, at the end of the paper.
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This paper is concerned with the following three types of geometric evolution equations: the volume preserving mean curvature flow, the intermediate surface diffusion flow, and the surface diffusion flow. Important common properties of these flows are the preservation of volume and the decrease of perimeter. It is shown in this paper that the intermediate surface diffusion flow can lose convexity. Hence the volume preserving mean curvature flow is the only flow among the evolution equations under consideration which preserves convexity, cf. [11, 16, 14, 17]. Moreover, several sufficient conditions are presented, which illustrate that each of the above mentioned flows can move smooth initial configurations into singularities in finite time. 相似文献
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刘艳楠 《应用泛函分析学报》2012,(2):132-134
研究由仿射平均曲率支配的严格凸超曲面的发展运动.在假定仿射平均曲率流存在并且曲面保持严格凸的条件下,通过对曲面支撑函数的计算,给出了高斯曲率的发展方程. 相似文献
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We introduce a geometric evolution equation of hyperbolic type, which governs the evolution of a hypersurface moving in the direction of its mean curvature vector. The flow stems from a geometrically natural action containing kinetic and internal energy terms. As the mean curvature of the hypersurface is the main driving factor, we refer to this model as the hyperbolic mean curvature flow (HMCF). The case that the initial velocity field is normal to the hypersurface is of particular interest: this property is preserved during the evolution and gives rise to a comparatively simpler evolution equation. We also consider the case where the manifold can be viewed as a graph over a fixed manifold. Our main results are as follows. First, we derive several balance laws satisfied by the hypersurface during the evolution. Second, we establish that the initial-value problem is locally well-posed in Sobolev spaces; this is achieved by exhibiting a convexity property satisfied by the energy density which is naturally associated with the flow. Third, we provide some criteria ensuring that the flow will blow-up in finite time. Fourth, in the case of graphs, we introduce a concept of weak solutions suitably restricted by an entropy inequality, and we prove that a classical solution is unique in the larger class of entropy solutions. In the special case of one-dimensional graphs, a global-in-time existence result is established. 相似文献
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《Journal de Mathématiques Pures et Appliquées》2009,91(6):591-614
We introduce a geometric evolution equation of hyperbolic type, which governs the evolution of a hypersurface moving in the direction of its mean curvature vector. The flow stems from a geometrically natural action containing kinetic and internal energy terms. As the mean curvature of the hypersurface is the main driving factor, we refer to this model as the hyperbolic mean curvature flow (HMCF). The case that the initial velocity field is normal to the hypersurface is of particular interest: this property is preserved during the evolution and gives rise to a comparatively simpler evolution equation. We also consider the case where the manifold can be viewed as a graph over a fixed manifold. Our main results are as follows. First, we derive several balance laws satisfied by the hypersurface during the evolution. Second, we establish that the initial-value problem is locally well-posed in Sobolev spaces; this is achieved by exhibiting a convexity property satisfied by the energy density which is naturally associated with the flow. Third, we provide some criteria ensuring that the flow will blow-up in finite time. Fourth, in the case of graphs, we introduce a concept of weak solutions suitably restricted by an entropy inequality, and we prove that a classical solution is unique in the larger class of entropy solutions. In the special case of one-dimensional graphs, a global-in-time existence result is established. 相似文献
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Studying the geometric flow plays a powerful role in mathematics and physics. In this paper, we introduce the mean curvature flow on Finsler manifolds and give a number of examples of the mean curvature flow. For Minkowski spaces, a special case of Finsler manifolds, we prove the short time existence and uniqueness for solutions of the mean curvature flow and prove that the flow preserves the convexity and mean convexity. We also derive some comparison principles for the mean curvature flow. 相似文献