Hypersurfaces whose mean curvature function is of finite type

We define finite mean type hypersurfaces to be hypersurfaces with mean curvature function of finite Chen-type. Then, we prove that hyperplanes are the only polynomial translation hypersurfaces of finite mean type in a Euclidean spaceE ⁿ⁺¹. And we show that the only non-conic hyperquadrics of finite mean type in Euclidean spaces are the hyperspheres and the cylinders on spheres. Finally, we state that, among all hypercylinders in a Euclidean spaceE ⁿ⁺¹, the only ones of finite mean type are those on finite mean type planar curves.     

Biharmonic hypersurfaces in Euclidean space E5

In this paper, we study biharmonic hypersurfaces in E⁵. We prove that every biharmonic hypersurface in Euclidean space E⁵ must be minimal.     

Zur Theorie verallgemeinerter torsaler Strahlflächen

In this paper we will investigate (k+1)-dimensional generalized ruled surfaces generated by a one-parameter family ofk-dimensional linear subspaces of then-dimensional Euclidean spaceE _n . Some results which are well-known for developable surfaces are proved for generalized ruled surfaces: Generalized developable surfaces are locally either cyclinders, cones or tangent surfaces. Each regular surface on a generalized ruled surface is locally Euclidean if and only if is developable. Each locally Euclidean hypersurface is a generalized developable hypersurface. Furthermore, the hypersurfaces with vanishing Gaussian curvature and the locally Euclidean hypersurfaces on generalized rule hypersurfaces will be characterized.     

Spherical 2-type hypersurfaces

A hypersurface (not necessarily compact) of a hypersphereS ⁿ⁺¹ of a Euclidean spaceE ⁿ⁺² is of 2-type if and only if it has constant nonzero mean curvature inS ⁿ⁺¹ and constant scalar curvature, unless it is a portion of a small hypersphere inS ⁿ⁺¹. This shows that the 2-type compact hypersurfaces of a hypersphere are mass-symmetric.     

The number of nearest and farthest points to a compactum in Euclidean space

A typical (in the sense of Baire category) compactA inE, whereE is either the Euclidean spaceE ⁸,s≧2, or the separable Hilbert space ℍ, generates a dense subsetC ^n,m(A) of the underlying space, such that everyx∈C ^n,m(A) has exactlyn nearest andm farthest points fromA, whenevern andm are positive integers satisfyingn+m≦ dimE+2. Research of this author is in part supported by Consiglio Nazionale delle Ricerche, G.N.A.F.A., Italy.     

Surfaces with simple geodesics through a point

We study compact connected surfaces inm-dimensional Euclidean spaceE ^m (3 m 5) with a point through which every geodesic is aW-curve regarded as a curve in E^m.     

Weakly Convex Biharmonic Hypersurfaces in Nonpositive Curvature Space Forms are Minimal

A submanifold M ^m of a Euclidean space R ^m+p is said to have harmonic mean curvature vector field if ${\Delta \vec{H}=0}$ , where ${\vec{H}}$ is the mean curvature vector field of ${M\hookrightarrow R^{m+p}}$ and Δ is the rough Laplacian on M. There is a famous conjecture named after Bangyen Chen which states that submanifolds of Euclidean spaces with harmonic mean curvature vector fields are minimal. In this paper we prove that weakly convex hypersurfaces (i.e. hypersurfaces whose principle curvatures are nonnegative) with harmonic mean curvature vector fields in Euclidean spaces are minimal. Furthermore we prove that weakly convex biharmonic hypersurfaces in nonpositively curved space forms are minimal.     

Non-Existence of Stable Currents in Hypersurfaces

Let M^m be a compact hypersurface in the Euclidean space E^m+1. In this paper, we study the non-existence of stable integral currents in M^m and its immersed submanifolds. Some vanishing theorems concerning the homology groups of these manifolds are established.AMS Subject Classification (1991): 49Q15 53C40 53C20     

On submanifolds of Lxf F satisfying Chen's basic equality

It is well known that the warped product Lx_f F of a line L and a Kaehler manifold F is an almost contact Riemannian manifold which is characterized by some tensor equations appeared in (1.7) and (1.8). In this paper we determine submanifolds of Lx_f F which are tangent to the structure vector field and satisfy Chen's basic equality. Also, we investigate tubular hypersurfaces of Lx_f CE ^m which satisfy Chen's basic equality where CE ^m is a complex Euclidean m-space. This revised version was published online in June 2006 with corrections to the Cover Date.     

de Sitter空间S1m+1中具有平行Blaschke张量的正则类空超曲面

本文引入两个以de Sitter空间为模型的非齐性坐标来覆盖共形空间Q₁^m+1.利用球面S^m+1中超曲面的Möbius几何的方法,本文研究了Q₁^m+1中正则类空超曲面的共形几何.作为其结果,本文对所有具有平行Blaschke张量的正则类空超曲面进行了完全分类.     

On the first eigenvalue of the linearized operator of ther-th mean curvature of a hypersurface

We generalize Reilly's inequality for the first eigenvalue of immersed submanifolds ofIR ^m +¹ and the total (squared) mean curvature, to hypersurfaces ofIR ^m +¹ and the first eigenvalue of the higher order curvatures. We apply this to stability problems. We also consider hypersurfaces in hyperbolic space.     

Euclidean minimum spanning trees and bichromatic closest pairs

We present an algorithm to compute a Euclidean minimum spanning tree of a given setS ofN points inE ^d in timeO(F _d (N,N) log ^d N), whereF _d (n,m) is the time required to compute a bichromatic closest pair amongn red andm green points inE ^d . IfF _d (N,N)=Ω(N ^1+ε), for some fixed ɛ>0, then the running time improves toO(F _d (N,N)). Furthermore, we describe a randomized algorithm to compute a bichromatic closest pair in expected timeO((nm logn logm)^2/3+m log² n+n log² m) inE ₃, which yields anO(N ^4/3 log^4/3 N) expected time, algorithm for computing a Euclidean minimum spanning tree ofN points inE ³. Ind≥4 dimensions we obtain expected timeO((nm)^{1−1/([d/2]+1)+ε}+m logn+n logm) for the bichromatic closest pair problem andO(N ^{2−2/([d/2]+1)ε}) for the Euclidean minimum spanning tree problem, for any positive ɛ. The first, second, and fourth authors acknowledge support from the Center for Discrete Mathematics and Theoretical Computer Science (DIMACS), a National Science Foundation Science and Technology Center under NSF Grant STC 88-09648. The second author's work was supported by the National Science Foundation under Grant CCR-8714565. The third author's work was supported by the Deutsche Forschungsgemeinschaft under Grant A1 253/1-3, Schwerpunktprogramm “Datenstrukturen und effiziente Algorithmen”. The last two authors' work was also partially supported by the ESPRIT II Basic Research Action of the EC under Contract No. 3075 (project ALCOM).     

Lokale Kennzeichnungen der Minimalhyperregelflächen

Generalized ruled hypersurfaces are generated by a one-parameter family of (n–2)-dimensional linear subspaces of the n-dimensional Euclidean space E_n. In this paper we give local characterizations of generalized ruled hypersurfaces with an everywhere vanishing mean curvature.     

Relativgeometrische Kennzeichnungen euklidischer Hypersphären

This paper deals with local and global characterizations of Euclidean hyperspheres by using relative normalizations of locally strongly convex hypersurfaces in the Euclidean space ⁿ⁺¹. Especially we get characterizations of Euclidean hyperspheres by using terms of affine differential geometry and terms of differential geometry with respect to the Euclidean second fundamental form.

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HERRN PROFESSOR DR. H. BRAUNER ZUM 60. GEBURTSTAG GEWIDMET     

Minding-Isometrien bei (k+1)-Regelflächen

In this paper we investigate (k+1)-dimensional generalized ruled surfaces generated by a oneparameter family ofk-dimensional linear subspaces of then-dimensional Euclidean spaceE. Minding-isometries of ruled surfaces are special isometries, which let the generating space invariant. Some new results will be given, concerned with Mindingisometries of generalized ruled surfaces of arbitrary codimension. In this investigations quadratic hypersurfaces in the normal spaces are of great importance.     

Hypersurfaces with constant scalar curvature and constant mean curvature

Non-spherical hypersurfaces inE ⁴ with non-zero constant mean curvature and constant scalar curvature are the only hypersurfaces possessing the following property: Its position vector can be written as a sum of two non-constant maps, which are eigenmaps of the Laplacian operator with corresponding eigenvalues the zero and a non-zero constant.     

Cyclic surfaces in E 5 generated by equiform motions

In this paper, we study cyclic surfaces in E⁵ generated by equiform motions of a circle. The properties of this cyclic surfaces up to the first order are discussed. We prove the following new result: A cyclic 2-surfaces in E⁵ in general are contained in canal hypersurfaces. Finally we give an example.     

Isotropic submanifolds with pointwise planar normal sections

Submanifolds of E^m with pointwise planar normal sections were studied in [1] and others. In the present paper, we will prove that an isotropic submanifold in E^m with pointwise planar normal sections is isometric to a symmetric space of rank one or to a Euclidean space. Moreover we will determine such surfaces in E^m with the above assumptions.     

A short proof of the generalized Bonnet theorem

In three‐dimensional Euclidean space E³, the Bonnet theorem says that a curve on a ruled surface in three‐dimensional Euclidean space, having two of the following properties, has also a third one, namely, it can be a geodesic, that it can be the striction line, and that it cuts the generators under constant angle. In this work, in n dimensional Euclidean space Eⁿ, a short proof of the theorem generalized for (k + 1) dimensional ruled surfaces by Hagen in 4 is given. Copyright © 2013 John Wiley & Sons, Ltd.