Duality in stable planes and related closure and kernel operations

We compare two constructions that dualize a stable plane in some sense, namely the dual plane and the opposite plane. Applying both constructions one after another we obtain a closure or kernel operation, depending on the order of execution.We examine the effect of these constructions on the automorphism group and apply our results in order to compute the automorphism groups of the complex cylinder plane, the complex united cylinder plane, and their duals. Beside the complex projective, affine, and punctured projective plane these planes are in fact the most homogeneous four-dimensional stable planes, as will be shown elsewhere [1].Supported by Studienstiftung des deutschen Volkes.     

A recurrence/transience result for circle packings

It is known that any infinite simplicial complex homeomorphic to the plane and satisfying a couple of other conditions is the nerve of a circle packing of either the plane or the disc (and not of both). We prove that such a complex is the nerve of a packing of the plane or the disc according as the simple random walk on its 1-skeleton is recurrent or transient, and discuss some applications. We also prove a criterion for transience of simple random walk on the 1-skeleton of a triangulation of the plane, in terms of average degrees of suitable sets of vertices.

     

Holomorphic Hermite functions and ellipses

In 1990 van Eijndhoven and Meyers introduced systems of holomorphic Hermite functions and reproducing kernel Hilbert spaces associated with the systems on the complex plane. Moreover they studied the relationship between the family of all their Hilbert spaces and a class of Gelfand–Shilov functions. After that, their systems of holomorphic Hermite functions have been applied to studying quantization on the complex plane, combinatorics, and etc. On the other hand, the author recently introduced systems of holomorphic Hermite functions associated with ellipses on the complex plane. The present paper shows that their systems of holomorphic Hermite functions are determined by some cases of ellipses, and that their reproducing kernel Hilbert spaces are some cases of the Segal–Bargmann spaces determined by the Bargmann-type transforms introduced by Sjöstrand.     

Alexander polynomials and Poincaré series of sets of ideals

Earlier the authors considered and, in some cases, computed Poincaré series for two sorts of multi-index filtrations on the ring of germs of functions on a complex (normal) surface singularity (in particular, on the complex plane). A filtration of the first class was defined by a curve (with several branches) on the surface singularity. A filtration of the second class (called divisorial) was defined by a set of components of the exceptional divisor of a modification of the surface singularity. Here we define and compute in some cases the Poincaré series corresponding to a set of ideals in the ring of germs of functions on a surface singularity. For the complex plane, this notion unites the two classes of filtrations described above.     

On geometric interpretations of split quaternions

Quaternions are an important tool that provides a convenient and effective mathematical method for representing reflections and rotations in three-dimensional space. A unit timelike split quaternion represents a rotation in the Lorentzian space. In this paper, we give some geometric interpretations of split quaternions for lines and planes in the Minkowski 3-space with the help of mutual pseudo orthogonal planes. We classified mutual planes with respect to the casual character of the normals of the plane as follows; if the normal is timelike, then the mutual plane is isomorphic to the complex plane; if the normal is spacelike, then the plane is isomorphic to the hyperbolic number plane (Lorentzian plane); if the normal is lightlike, then the plane is isomorphic to the dual number plane (Galilean plane).     

Projective Compactification of $$\mathbb {R}^{1,1}$$ and Its Möbius Geometry

We examine the semi-Riemannian manifold \(\mathbb {R}^{1,1}\), which is realized as the split complex plane, and its conformal compactification as an analogue of the complex plane and the Riemann sphere. We also consider conformal maps on the compactification and study some of their basic properties.     

平面上解析的无穷级Laplace-Stieltjes变换

应用孙道椿一个无穷级的型函数,研究复平面解析的Laplace-Stieltjes变换的增长性,推广了Dirichlet级数的相关结论.     

On Some Integral Operators Related to the Poisson Equation

In this paper we estimate various norms of some integral operators related to the Poisson equation defined in a bounded domain in the complex plane with vanishing boundary data.     

Analytic continuation by summation-methods

The paper deals with the analytic continuation of the geometric series by a family of linear transformations into some special domains of the complex plane.     

On the Best Approximation in the Mean of Functions of a Complex Variable by Fourier Series in the Bergman Space

Russian Mathematics - In a simply connected domain of the complex plane, we consider the problem of mean-square approximation of analytic functions by Fourier series in orthogonal systems. For some...     

Bergman空间上的加权复合算子及应用(英文)

本文研究了单位圆盘上Bergman空间上的加权复合算子和复平面的单连通域(不是全平面)上Bergman空间上的复合算子的有界性和紧性.利用复分析方法,获得了有界性与紧性的一些充分条件和必要条件,推广了Hardy空间上的若干相关结果.     

半平面中解析函数的积分表示及在逼近中的应用

在该文中, 作者证明了满足一定增长性条件的右半平面上的解析函数可以由它在边界上的积分和其加权Blaschke乘积的和表示, 作为应用, 作者还考虑了指数多项式在实数轴上加权 Banach 空间C_α 中的完备性.     

Injectivity Conditions in the Complex Plane

We give a survey on some recent results concerning injectivity conditions in the complex plane, which are obtained by using certain geometric properties (as starlikeness, spiralikeness, convexity, close-to-convexity). These results extend to continuously differentiable maps some well-known univalence conditions for analytic functions.     

Fractal geometry derived from complex bases

Each complex number can be expressed as a single number in positional notation using certain complex bases, just as the positive real numbers can be expressed as decimal expansions. These representations yield some intriguing geometric patterns in the complex plane, whose boundaries are fractal curves. One of these curves is known from the investigation of dragon curves; the others are new examples of fractals.     

Riemann 映射与单连通区域分类

设G为复平面上一个单连通区域及φ为G的Riemann 映射. 本文通过φ是否属于G上多项式在不同拓扑下的闭包的情况对G进行分类. 特别地, 我们对已知的几类单连通给出了刻画.     

On arithmetical functions having constant values in some domain

This paper shows that any completely additive complex valued function over a principal configuration in the complex plane, having constant values in some discs, is the identically zero function. In other words, there exists no non-trivial completely additive complex valued function over a principal configuration in  $\mathbb{C}$ which assumes constant values in some domain.     

ON THE ZEROS OF A CLASS OF POLYNOMIALS AND RELATED ANALYTIC FUNCTIONS

In this paper we prove some interesting extensions and generalizations of Enestrom- Kakeya Theorem concerning the location of the zeros of a polynomial in a complex plane. We also obtain some zero-free regions for a class of related analytic functions. Our results not only contain some known results as a special case but also a variety of interesting results can be deduced in a unified way by various choices of the parameters.     

Graeffe's, Chebyshev-like, and Cardinal's Processes for Splitting a Polynomial into Factors

Numerical splitting of a real or complex univariate polynomial into factors is the basic step of the divide-and-conquer algorithms for approximating complex polynomial zeros. Such algorithms are optimal (up to polylogarithmic factors) and are quite promising for practical computations. In this paper, we develop some new techniques, which enable us to improve numerical analysis, performance, and computational cost bounds of the known splitting algorithms. In particular, we study a Chebyshev-like modification of Graeffe's lifting iteration (which is a basic block of the splitting algorithms, as well as of several other known algorithms for approximating polynomial zeros), analyze its numerical performance, compare it with Graeffe's, prove some results on numerical stability of both lifting processes (that is, Graeffe's and Chebyshev-like), study their incorporation into polynomial root-finding algorithms, and propose some improvements of Cardinal's recent effective technique for numerical splitting of a polynomial into factors. Our improvement relies, in particular, on a modification of the matrix sign iteration, based on the analysis of some conformal mappings of the complex plane and of techniques of recursive lifting/recursive descending. The latter analysis reveals some otherwise hidden correlations among Graeffe's, Chebyshev-like, and Cardinal's iterative processes, and we exploit these correlations in order to arrive at our improvement of Cardinal's algorithm. Our work may also be of some independent interest for the study of applications of conformal maps of the complex plane to polynomial root-finding and of numerical properties of the fundamental techniques for polynomial root-finding such as Graeffe's and Chebyshev-like iterations.     

Hardy’s theorem and rotations of several complex variables

In this paper, Hardy’s theorem and rotations characterized by complex Gaussians in the complex plane due to Hogan and Lakey are extended to complex spaces of several variables. We point out that conditions under which a function on the n-dimensional real Euclidean space has an analytic extension to the complex space. Moreover, we prove that the function is a rotation of a multiple of real Gaussians through some angle if the extension satisfies certain assumptions.     

Sets of Approximation and Interpolation in ℂ for Manifold-Valued Maps

We give examples of non-smooth sets in the complex plane with the property that every holomorphic map continuous to the boundary from these sets into any complex manifold may be uniformly approximated by maps holomorphic in some neighborhood of the set (Mergelyan-type approximation for manifold-valued maps.) Similar results are proved for sections of complex-valued holomorphic submersions from complex manifolds.