关于从属的若干注记

关于从属的若干注记杨定恭（苏州大学数学系，２１５００６）设Ｈ表示单位圆盘内解析函数的全体；Ａ＿ｎ是Ｈ中形如的ｆ（Ｚ）组成的类，这里ｎ是正整数。设ｆ（Ｚ）和ｇ（Ｚ）在Ｈ中，（ｆ＊ｇ）（Ｚ）表示ｆ（Ｚ）与ｇ（Ｚ）的Ｈａｄａｍａｒｄ乘积或卷积；表示ｆ（Ｚ）...     

圆环的Bergman空间上的Toeplitz算子

设Ω＝｛Ｚ∈Ｃ：Ｒ＜｜ｚ｜＜１｝（０＜ Ｒ＜ １）是复平面 Ｃ上的圆环，Ｌ２ａ（Ω）是Ω的 Ｂｅｒｇｍａｎ空 间，Ｄ是Ｌ２ａ（Ω）上的所有Ｔｏｅｐｌｉｔｚ算子生成的Ｂ（Ｌ２ａ（Ω））的闭子代数．本文证明了对任何非零整数 ｎ，｛Ｔｚｎ｝’∩Ｄ是所有解析Ｔｏｅｐｌｉｔｚ算子．同时，刻划了圆环上以逐段连续函数为符号的Ｔｏｅｐｌｉｔｚ算 子本质谱．     

Nest代数的Jacobson根的μ-核值保持映射

设算子代数Ａ　Ｂ（Ｈ），μ（Ａ）表示Ａ中的部分等距算子全体，若ｐ是Ａ到Ｂ（Ｈ）的线性映射，且对任意的ＵＥｕ（Ａ），有叫Ｕ）（ｋｅｃＵ）Ｇｒ“ｈＣｒ，则称　是Ａ上的μ－核值保持映射。本文将证明：Ｎｅｓｔ代数的Ｊａｃｏｂｓｏｎ根上的范数拓扑连续的μ－核值保持映射是广义内导子。     

Toeplitz算子空间的W—闭包

本文讨论了Ｔｏｅｐｌｉｔｚ算子空间的Ｗ－闭包，我们证明了Ｂｅｒｇｍａｎ空间Ｌ＾２ａ（Ｄ）上全体Ｔｏｅｐｌｉｔｚ算子的Ｗ闭包等于Ｂ（Ｌ＾２ａ（Ｄ）（定理１），另外，我们给出Ｃ＾ｍ（ｎ＞１）中单位球面Ｓ上的Ｈａｒｄｙ空间Ｈ＾２（Ｓ）上的Ｔｏｅｐｌｉｔｚ算子的一个有趣刻划（命题２）。     

Toeplitz算子空间的ω~＊－闭包

本文讨论Ｔｏｅｐｌｉｔｚ算子空间的ω￣＊－闭包．我们证明Ｂｅｒｇｍａｎ空间上全体Ｔｏｅｐｌｉｔｚ算子的ω￣＊－闭包等于（定理１）．另外，我们给出Ｃ￣ｎ（ｎ＞１）中单位球面Ｓ上的Ｈａｒｄｙ空间Ｈ￣２（Ｓ）上的Ｔｏｅｐｌｉｔｚ算子的一个有趣刻划（命题２）．     

用L-预远域系算子、L-预外部算子或L-预边界算子确定L-预拓扑

给定集合X，设T（X）是X上的L-预拓扑的全体。本文证明了可以在R（X）（X上的L-预远域系算子的全体）、E（X）（X上的L-预外部算子的全体）和B（X）（X上的L-预边界算子的全体）上定义适当的序关系，使它们在一定条件下成为与（T（X），包含）同构的完备格。因此一个给定集合X上的L-预拓扑可以由X上的L-预远域系算子、L-预外部算子或L-预边界算子确定。     

Nest代数的Jacobson根的u—核值保持映射

设算子代数Ａ∩→Ｂ（Ｈ），ｕ（Ａ）表示Ａ中的部分等距离子全体，若ψ是Ａ到Ｂ（Ｈ）的线性映射，且对任意的Ｕ∈ＵＡ，有ψ（Ｕ）（ｋｅｒＵ）∩→ｒａｎＵ，则称ψ是Ａ上的Ｕ－核值保持映射。本文将证明：Ｎｅｓｔ代数的Ｊａｃｏｂｓｏｎ根上的范数拓扑连续的Ｕ－核值保持映射是广义内导子。     

核动力反应中的非线性扩散问题

核动力反应中的非线性扩散问题文如庆（中南工业大学）在有关核动力反应扩散的问题中，需要研究如下的方程其中为一致椭圆算子Ｃ．Ｖ．ＰＡＯ本「ｎ中考虑了当Ｌ。１一ｏ（０（１〕７。）．ｆ（。，Ｚ。Ｉ）一ｈ，（Ｈ（。１》（。Ｏ一小【。（。·。川。时的ｔｆｆＪＳ。...     

关于广义Calderon－Zygmund算子

本文讨论了θ（ｔ）型和（ｌｏｇ，θ）型Ｃａｌｄｅｒｏｎ－Ｚｙｇｍｕｎｄ算子在加权Ｈａｒｄｙ型空间ＨＡ＾Ｐｗ上的有界性，θ（ｔ）型Ｃａｌｄｅｒｏｎ－Ｚｙｇｍｕｎｄ算子在Ｈａｒｄｙ型加权块空间Ｂｐ，ｗ上的有界性，以及广义的ｗ－Ｃａｌｄｅｒｏｎ－Ｚｙｇｍｕｎｄ算子是Ｈ＾ｐ上的有界算子。     

关于Ky Fan的一个猜想

设ｆ（ｚ）为单位圆上的规范化的单叶凸像函数，Ｌ（Ｈ）为复Ｈｉｌｂｅｒｔ空间Ｈ上的Ｂａｎａｃｈ算子代数。本文证明了对于Ｌ（Ｈ）中双重可换的真收缩算子Ｔｔ（ｉ＝１，２），ｆ（Ｔ１）与ｆ（Ｔ２）的凸线性组合一定具有形式ｆ（Ｔ），此处Ｔ为Ｌ（Ｈ）中的真收缩算子，同时我们通过一简单例子说明“Ｔｔ双重可换”的条件是不能去掉的，这便回答了由ＫｙＦａｎ提出的一个问题。     

Bifurcation of Limit Cycles and Pseudo-Isochronicity at Degenerate Singular Point in a Septic System

This paper deals with the problems of bifurcation of limit cycles and pseudo-isochronous center conditions at degenerate singular point in a class of septic polynomial differential system. We solve the problems by an indirect method, i.e., we transform the degenerate singular point into an elementary singular point. Then we construct a septic system which allows the appearance of eight limit cycles in the neighborhood of degenerate singular point. Finally, we investigate the pseudo-isochronous center conditions at degenerate singular point for the system. As far as we know, this is the first time that an example of septic system with eight limit cycles bifurcating from degenerate singular point is given, and it is also the first time the pseudo-isochronous center conditions at degenerate singular point in a septic system are discussed.     

On an example of finite hybrid quasi-Monte Carlo point sets

In this paper, we consider finite hybrid point sets in the unit cube. The components of these stem from two well known types of low discrepancy point sets, namely Hammersley point sets on the one hand, and lattice point sets in the sense of Korobov and Hlawka on the other hand. As a quality measure, we consider the star discrepancy, which gives information about the quality of distribution of finite or infinite sequences. We present existence results for finite hybrid point sets with low discrepancy. Thereby, we make analogous results for infinite sequences more explicit in the sense that, theoretically, it is now possible to find such finite hybrid low discrepancy point sets.     

Multiple solutions for fourth-order boundary value problem

In this paper, we study the existence and multiplicity of nontrivial solutions for the fourth-order two point boundary value problems. Making use of the theory of fixed point index in cone and Leray-Schauder degree, under general conditions on nonlinearity, we prove that there exist at least six different nontrivial solutions for the fourth-order two point boundary value problems. Furthermore, if the nonlinearity is odd, we obtain that there exist at least eight different nontrivial solutions.     

On necessary and sufficient conditions for numerical verification of double turning points

Summary. This paper describes numerical verification of a double turning point of a nonlinear system using an extended system. To verify the existence of a double turning point, we need to prove that one of the solutions of the extended system corresponds to the double turning point. For that, we propose an extended system with an additional condition. As an example, for a finite dimensional problem, we verify the existence and local uniqueness of a double turning point numerically using the extended system and a verification method based on the Banach fixed point theorem.Mathematics Subject Classification (2000): 65J15, 65G20, 65P30     

A Proximal Point-Type Method for Multicriteria Optimization

In this paper, we present a proximal point algorithm for multicriteria optimization, by assuming an iterative process which uses a variable scalarization function. With respect to the convergence analysis, firstly we show that, for any sequence generated from our algorithm, each accumulation point is a Pareto critical point for the multiobjective function. A more significant novelty here is that our paper gets full convergence for quasi-convex functions. In the convex or pseudo-convex cases, we prove convergence to a weak Pareto optimal point. Another contribution is to consider a variant of our algorithm, obtaining the iterative step through an unconstrained subproblem. Then, we show that any sequence generated by this new algorithm attains a Pareto optimal point after a finite number of iterations under the assumption that the weak Pareto optimal set is weak sharp for the multiobjective problem.     

Upward straight-line embeddings of directed graphs into point sets

In this paper we study the problem of computing an upward straight-line embedding of a planar DAG (directed acyclic graph) G into a point set S, i.e. a planar drawing of G such that each vertex is mapped to a point of S, each edge is drawn as a straight-line segment, and all the edges are oriented according to a common direction. In particular, we show that no biconnected DAG admits an upward straight-line embedding into every point set in convex position. We provide a characterization of the family of DAGs that admit an upward straight-line embedding into every convex point set such that the points with the largest and the smallest y-coordinate are consecutive in the convex hull of the point set. We characterize the family of DAGs that contain a Hamiltonian directed path and that admit an upward straight-line embedding into every point set in general position. We also prove that a DAG whose underlying graph is a tree does not always have an upward straight-line embedding into a point set in convex position and we describe how to construct such an embedding for a DAG whose underlying graph is a path. Finally, we give results about the embeddability of some sub-classes of DAGs whose underlying graphs are trees on point set in convex and in general position.     

A globally convergent version of the Polak-Ribière conjugate gradient method

In this paper we propose a new line search algorithm that ensures global convergence of the Polak-Ribière conjugate gradient method for the unconstrained minimization of nonconvex differentiable functions. In particular, we show that with this line search every limit point produced by the Polak-Ribière iteration is a stationary point of the objective function. Moreover, we define adaptive rules for the choice of the parameters in a way that the first stationary point along a search direction can be eventually accepted when the algorithm is converging to a minimum point with positive definite Hessian matrix. Under strong convexity assumptions, the known global convergence results can be reobtained as a special case. From a computational point of view, we may expect that an algorithm incorporating the step-size acceptance rules proposed here will retain the same good features of the Polak-Ribière method, while avoiding pathological situations. This research was supported by Agenzia Spaziale Italiana, Rome, Italy.     

On farthest points of sets

For a convex closed bounded set in a Banach space, we study the existence and uniqueness problem for a point of this set that is the farthest point from a given point in space. In terms of the existence and uniqueness of the farthest point, as well as the Lipschitzian dependence of this point on a point in space, we obtain necessary and su.cient conditions for the strong convexity of a set in several infinite-dimensional spaces, in particular, in a Hilbert space. A set representable as the intersection of closed balls of a fixed radius is called a strongly convex set. We show that the condition “for each point in space that is sufficiently far from a set, there exists a unique farthest point of the set” is a criterion for the strong convexity of a set in a finite-dimensional normed space, where the norm ball is a strongly convex set and a generating set.     

构造非线性映射不动点的迭代法

为了构造非线性映射的不动点,许多作者对Mann迭代法进行了研究.后来Ishikawa推广了Mann迭代法,对Hilbert空间H的紧凸子集D的李卜西兹拟压缩映射T,证明了新的迭代法{x_n}强收敛于T的一不动点,{x_n}被定义为