Minimal Translation Surfaces in Euclidean Space

A translation surface in Euclidean space is a surface that is the sum of two regular curves \(\alpha \) and \(\beta \). In this paper we characterize all minimal translation surfaces. In the case that \(\alpha \) and \(\beta \) are non-planar curves, we prove that the curvature \(\kappa \) and the torsion \(\tau \) of both curves must satisfy the equation \(\kappa ^2 \tau = C\) where C is constant. We show that, up to a rigid motion and a dilation in the Euclidean space and, up to reparametrizations of the curves generating the surfaces, all minimal translation surfaces are described by two real parameters \(a,b\in \mathbb {R}\) where the surface is of the form \(\phi (s,t)=\beta _{a,b}(s)+\beta _{a,b}(t)\).     

三维欧氏空间的仿射乘积曲面

定义了三维欧氏空间中的仿射乘积曲面,给出了极小仿射乘积曲面以及高斯曲率为零的仿射乘积曲面的分类,同时还给出了平均曲率为非零常数的仿射乘积曲面的分类.     

欧氏空间中具有共形Gauss映照的曲面

本文考虑欧氏空间中具有共形Ｇａｕｓｓ映照的曲面．从Ｇａｕｓｓ映照的观点给出了 ｖｅｒｏｎｅｓｅ曲面的一个新特征．     

n维空间正交张量的典则表示和自由度公式

本文借助于正交张量特征值的特性,采用剖分的方法.利用二维正交张量典则表示,很快就构造出一般n维欧氏空间上的正交张量的典则表示.利用Cayley-Hamilton定理,求得了正交张量各主不变量之间的相关方程,从而使得正交张量特征根的求解只需要在一个阶数不大于空间维数n的一半的代数方程上进行.本文还给出了正交张量的独立参数个数——自由度的计算公式.     

Minimal and Pseudo-Umbilical Rotational Surfaces in Euclidean Space {\mathbb{E}^4}

In this paper we study general rotational surfaces in ${\mathbb{E}^4}$ whose meridian curves lie in two-dimensional planes. We firstly find all minimal general rotational surfaces by solving the differential equation that characterizes minimal general rotational surfaces. Then we determine all pseudo-umbilical general rotational surfaces in ${\mathbb{E}^4}$ .     

A Note on Minimal Surfaces in Euclidean 3-Space

In this note, a construction of minimal surfaces in Euclidean 3-space is given. By using the product of Weierstrass data of two known minimal surfaces, one gets a new Weierstrass data and a corresponding minimal surface from the Weierstrass representation.     

Two Characterizations of Diffeomorphisms of Euclidean Space

Two characterizations for a local diffeomorphism of R^n to be global one are given in terms of associated Wazewski equations.The two characterizations could be useful for the investigation of the Jacobian conjecture.     

Codazzi Tensors and the Topology of Surfaces

We introduce the notion of (0,m)-Codazzi tensors relative to an affine connection which extends the well known concept for m = 2. On compact Riemannian surfaces of genus we determine the dimension of the R-vector space of traceless Codazzi tensors, which depends on m and only, additionally we extend these result for genus zero. We give some exemplary applications to submanifolds in affine and in Riemannian geometry and to Weyl geometries.     

正则条件全竞赛空间与混合策略竞赛空间上的两个极值定理

在正则的全竞赛空间与混合策略竞赛空间推广并证明了两个新的最优决策存在定理．     

On the Quaternionic B 2-Slant Helices in the Euclidean Space E 4

In this paper we give a new definition of harmonic curvature functions in terms of B ₂ and we define a new kind of slant helix which we call quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ by using the new harmonic curvature functions. Also we define a vector field D which we call Darboux quaternion of the real quaternionic B ₂–slant helix in 4–dimensional Euclidean space E ⁴ and we give a new characterization such as: "a: I ì \mathbb R ? E⁴{``\alpha : I \subset {\mathbb R} \rightarrow E^4} is a quaternionic B ₂–slant helix ${\Leftrightarrow H^\prime_2 -KH_{1} = 0"}${\Leftrightarrow H^\prime_2 -KH_{1} = 0"} where H ₂, H ₁ are harmonic curvature functions and K is the principal curvature function of the curve α.     

A Maximum Principle at Infinity for Surfaces with Constant Mean Curvature in Euclidean Space

Maximum principles at infinity generalize Hopf's maximum principle for hypersurfaces with constant mean curvature in R ⁿ . We establish such a maximum principle for parabolic surfaces in R³ with nonzero constant mean curvature and bounded Gaussian curvature.     

欧氏空间中紧致超曲面的欧氏直径的一点注记

本文对欧氏空间中分别具有给定截面曲率和Ｒｉｃｃｉ曲率的紧致超曲面的欧氏直径做了估计     

Surfaces in Euclidean 3-space whose normal bundles are tangentially biharmonic

A submanifold is said to be tangentially biharmonic if the bitension field of the isometric immersion that defines the submanifold has vanishing tangential component. The purpose of this paper is to prove that a surface in Euclidean 3-space has tangentially biharmonic normal bundle if and only if it is either minimal, a part of a round sphere, or a part of a circular cylinder.     

Isometries of the Space of Convex Bodies in Euclidean Space

The isometries of the space of convex bodies of E^d with respectto the Hausdorff-metric are precisely the mappings of the formC i(C) + D where i is a rigid motion of E^d and D a fixed convexbody.     

三维Minkowski空间中的新型平移曲面

In this paper we study translation surfaces of some new types in 3-Minkowski space E13 and give some classifications of such surfaces whose mean curvature and Gauss curvature satisfy certain conditions.     

Surfaces in Sol3 Space Foliated by Circles

In this paper we study surfaces foliated by a uniparametric family of circles in the homogeneous space Sol₃. We prove that there do not exist such surfaces with zero mean curvature or with zero Gaussian curvature. We extend this study considering surfaces foliated by geodesics, equidistant lines or horocycles in totally geodesic planes and we classify all such surfaces under the assumption of minimality or flatness.     

Conformal Metrics on the Unit Ball in Euclidean Space

We study densities on the unit ball in euclidean space whichsatisfy a Harnack type inequality and a volume growth conditionfor the measure associated with . For these densities a geometrictheory can be developed which captures many features of thetheory of quasiconformal mappings. For example, we prove generalizationsof the Gehring-Hayman theorem, the radial limit theorem andfind analogues of compression and expansion phenomena on theboundary. 1991 Mathematics Subject Classification: 30C65.