On Asymptotic Properties of Maximal Tubes and Bands in a Neighborhood of an Isolated Singularity in Minkowski Space

We study the asymptotic behavior of maximal surfaces like bands and tubes in a neighborhood of an isolated singular point. In particular, we prove possibility of expansion of the radius vector of a two-dimensional surface in a power series with real-analytic coefficients in the time coordinate. We show also that the tangent rays at a singular point constitute a light-like surface. We prove an exact estimate for the existence time for multidimensional maximal tubes in terms of their asymptotic behavior at a singular point and describe completely the class of surfaces on which this estimate is attained.     

一类Minkowski复空间的拟距离和奇异性质

双曲虚单位对应一类Minkowski复空间并具有方向异性的特点.四维时空中特殊方向上两时空点间的减法对应类时区与类光区的几何关联,在物理中表示粒子和场的相互作用.通过定义拟(虚)距离使Minkowsk空间的时空映射和间隔不变量进行度量公理化.四维时空中不同方向的距离或度量需要用线度因子和角度因子共同刻画,其中角度因子对应模糊集合,决定了Minkowski度量空间的奇异性质.     

关于Minkowski空间的子流形

利用Ｆｉｎｓｌｅｒ法曲率Ａ、Ｌａｎｄｓｂｅｒｇ曲率Ｌｙ、法切曲率Ｆｙ、Ｂｅｒｗａｌｄ联络Ｄ以及第二基本形式Ⅱ_ｙ，研究Ｍｉｎｋｏｗｓｋｉ空间中的子流形、子流形的旗曲率与李齐曲率．     

On Asymptotic Properties of Solutions to Weakly Nonlinear Systems in the Neighborhood of a Singular Point

In this paper, we consider the class of so-called weakly hyperbolic linear systems, which includes correct and hyperbolic (exponentially-dichotomous) systems. We prove new results generalizing related classical theorems on the conditional stability of solutions. We establish the existence of stable manifolds consisting of points corresponding to the solutions of such systems with negative Lyapunov exponents. We study the behavior of solutions starting outside the stable manifold. The technique used in our paper is similar to that in the theory of hyperbolic systems.     

On Developable Ruled Surfaces in Minkowski Space

The aim of this study is to obtain the distribution parameter of a ruled surface generated by a straight line in Frenet trihedron moving along two different spacelike curves with the same parameter. At this time, the Frenet frames of these curves are not the same. We have moved the director vector of the first curve along the second curve. It is shown that the ruled surface is developable if and only if the base curve is helix. In addition, some results and theorems are presented with special cases.     

On the Number of Unbounded Solution Branches in a Neighborhood of an Asymptotic Bifurcation Point

We suggest a method for studying asymptotically linear vector fields with a parameter. The method permits one to prove theorems on asymptotic bifurcation points (bifurcation points at infinity) for the case of double degeneration of the principal linear part. We single out a class of fields that have more than two unbounded branches of singular points in a neighborhood of a bifurcation point. Some applications of the general theorems to bifurcations of periodic solutions and subharmonics as well as to the two-point boundary value problem are given.     

On Combinatorial Properties of Bands

In this paper we study the D-saturated property of bands defined in terms of their Cayley graphs Cay(S,C), where S is a band and C ? Z(S), the center of S. Also we characterize the Cayley graphs of bands. More generally, for a finite graph Γ =Cay(T, D), where T is a band and D ? Z(T), we give an algorithm for finding all bands S and C ? Z(S) such that Γ =Cay(S, C).     

On Conformal Infinity and Compactifications of the Minkowski Space

Using the standard Cayley transform and elementary tools it is reiterated that the conformal compactification of the Minkowski space involves not only the “cone at infinity” but also the 2-sphere that is at the base of this cone. We represent this 2-sphere by two additionally marked points on the Penrose diagram for the compactified Minkowski space. Lacks and omissions in the existing literature are described, Penrose diagrams are derived for both, simple compactification and its double covering space, which is discussed in some detail using both the U(2) approach and the exterior and Clifford algebra methods. Using the Hodge *{star} operator twistors (i.e. vectors of the pseudo-Hermitian space H _2,2) are realized as spinors (i.e., vectors of a faithful irreducible representation of the even Clifford algebra) for the conformal group SO(4, 2)/Z ₂. Killing vector fields corresponding to the left action of U(2) on itself are explicitly calculated. Isotropic cones and corresponding projective quadrics in H _p,q are also discussed. Applications to flat conformal structures, including the normal Cartan connection and conformal development has been discussed in some detail.     

Rate of Asymptotic Convergence Near an Isolated Singularity of $$\hbox {G}_2$$ Manifold

In this paper, a metric with \(\hbox {G}_2\) holonomy and slow rate of convergence to the cone metric is constructed on a ball inside the cone over the flag manifold.     

On Rotation About Lightlike Axis in Three-Dimensional Minkowski Space

We obtain matrix of the rotation about arbitrary lightlike axis in three-dimensional Minkowski space by deriving the Rodrigues’ rotation formula and using the corresponding Cayley map. We prove that a unit timelike split quaternion q with a lightlike vector part determines rotation R _q about lightlike axis and show that a split quaternion product of two unit timelike split quaternions with null vector parts determines the rotation about a spacelike, a timelike or a lightlike axis. Finally, we give some examples.     

Morgan-Scott型剖分上的样条空间的奇异性

Multivariate spline function is an important research object and tool in Computational Geometry. The singularity of multivariate spline spaces is a difficult problem that is ineritable in the research of the structure of multivariate spline spaces. The aim of this paper is to reveal the geometric significance of the singularity of bivariate spline space over Morgan-Scott type triangulation by using some new concepts proposed by the first author such as characteristic ratio, characteristic mapping of lines （or ponits）, and characteristic number of algebraic curve. With these concepts and the relevant results, a polished necessary and sufficient conditions for the singularity of spline space S u＋1^u （△MS^u） are geometrically given for any smoothness u by recursion. Moreover, the famous Pascal＇s theorem is generalized to algebraic plane curves of degree n≥3.     

Structure of the Space of Diametrically Complete Sets in a Minkowski Space

We study the structure of the space of diametrically complete sets in a finite dimensional normed space. In contrast to the Euclidean case, this space is in general not convex. We show that its starshapedness is equivalent to the completeness of the parallel bodies of complete sets, a property studied in Moreno and Schneider (Isr. J. Math. 2012, doi:10.1007/s11856-012-0003-6), which is generically not satisfied. The space in question is, however, always contractible. Our main result states that in the case of a polyhedral norm, the space of translation classes of diametrically complete sets of given diameter is a finite polytopal complex. The proof makes use of a diagram technique, due to P. McMullen, for the representation of translation classes of polytopes with given normal vectors. The paper concludes with a study of the extreme diametrically complete sets.     

On a Lemma of Minkowski

In this paper we show that a generalization of a lemma of Minkowski can be applied to solve two problems concerning kissing numbers of convex bodies. In the first application we give a short proof showing that the lattice kissing number of tetrahedra is eighteen. Moreover, it turns out that for any tetrahedron T there exist a unique 18-neighbour lattice packing of T and an essentially unique 16-neighbour lattice packing of T. Secondly we show that for every integer d ≥ 3 there exists a d-dimensional convex body K such that the difference between its translative kissing number and lattice kissing number is at least 2^d-1.     

On Asymptotic Properties of a Strongly Nonlinear Differential Equation

The paper describes asymptotic properties of a strongly nonlinear system . The existence of an n/2 parametric family of solutions tending to zero is proved. Conditions posed on the system try to be independent of its linear approximation.     

On the Malmquist Theorem for Solutions of Differential Equations in the Neighborhood of an Isolated Singular Point

The statement of the Malmquist theorem (1913) about the growth of meromorphic solutions of the differential equation , where P(z, f) and Q(z, f) are polynomials in all variables, is proved in the case of solutions with isolated singular point at infinity. __________ Translated from Ukrains'kyi Matematychnyi Zhurnal, Vol. 57, No. 4, pp. 505–513, April, 2005.     

Asymptotic Analysis of a Continuous-Discrete Control System with a Singularity in the Coefficients

The article is concerned with the asymptotic analysis of solutions of a continuous-discrete endpoint control system as the operating interval tends to infinity. The author obtains criteria of stable and unstable behavior of the system in the basic and critical cases.     

代数流形奇点的切空间

利用一种新工具极限方程,从初等微积分的角度研究了代数流形奇点的切空间,给出了一般代数流形奇点的切空间决定于定义代数流形方程组的局部.     

Minkowski空间中定向曲面上的第二类松弛弹性线

在Minkowski空间中,定义了定向曲面上的第二类松弛弹性线,推导了在定向曲面上的第二类松弛弹性线的Euler-Lagrange方程．进一步阐明了,这些曲线是否落在曲率线上,最后给出相关的实例．