关于赋范空间上连续自映射的回归点

在赋范空间中讨论回归点的性质,主要得到了结果：（1）如果,是序列紧赋范空间X上的连续双射,x是f的任一回归点,则对于任意整数N〉0都存在f的回归点x0∈X使得f^n（x0）=x;（2）序列紧赋范空间上连续自映射的回归点集是f的强不变子集;（3）如果f是局部连通赋范空间X上的连续自映射,则f的每一个回归点或是类周期点或是类周期点的聚点．作为推论,在实直线段上得到了类似的结论．     

对偶ω^＊-可分的Banach空间上存在具有球覆盖性质的1＋ε-等价范数

我们称赋范空间具有球覆盖性质,如果它的单位球球面能被不含原点的一列开球所覆盖．本文证明了每个对偶ω^＊-可分的Banach空间都可赋1＋ε-等价范数,使该空间对于这个新范数具有球覆盖性质．     

空间L_ρ上可达范数算子问题,0

相广平 《数学研究与评论》1987,(1)

对偶ω*-可分的Banach空间上存在具有球覆盖性质的1+ε-等价范数

我们称赋范空间具有球覆盖性质,如果它的单位球球面能被不含原点的一列开球所覆盖.本文证明了每个对偶ω~*-可分的Banach空间都可赋1+ε-等价范数,使该空间对于这个新范数具有球覆盖性质.     

关于赋范线性空间的λ-性质

本文研究赋范线性空间的λ-性质,并得到以下的主要结果。 1.闭单位球的λ-点。 设X为赋范线性空间,B_X={x;‖x‖≤1}和ext(B_X)为B_X的全体端点的集合。     

概率赋范空间的线性拓扑性质

本文首先扩充了概率赋范空间(probabilistic normed space,简记为PNS)的定义,然后着重研究了它们的线性拓扑性质,所得到的结果不仅包含[3]和[4]中的结果为特例,而且较为彻底地阐明了PNS与赋准范空间、赋B_0型准范空间、以及赋范空间的关系。     

Banach空间中的渐近赋范性质

本文讨论了Banach空间中的一些渐近赋范性质K，给出了Banach空间中一些特殊空间及其它们之间的关系，并特别讨论了1-ANP-K关于KP，KKP，GP性质．     

关于Fuzzy赋范空间的若干问题（Ⅱ）

在1984年,吴从炘、方锦暄和A.K.Katsaras分别提出了两种Fuzzy赋范空间的定义。这些概念既是赋范空间概念的自然推广,又是特殊的Fuzzy拓扑线性空间。在文[3～5]中,不仅考察了这两种定义之间的关系,还讨论了Fuzzy赋范空间的性质以及其上广义Fuzzy线性算子的连续性等。在本文中,我们将继文[4]给出Fuzzy赋范空间中子集有界性、稠密性的刻划条件并利用这些条件给出Fuzzy范数是诱出的充要条件。此外,作为诱出Fuzzy范数的推广,我们给出了两类Fuzzy范数的特征刻划。     

bp(2)空间中的等距映射

度量与线性性质是赋范空间的重要性质,因此,研究线性算子与等距算子的关系成为了泛函分析领域重要的研究课题.本文首先研究一类特殊的赋准范空间,即bp(2)空间的重要性质.然后给出bp(2)空间单位球面间满等距映射的表示定理及延拓性质.     

概率度量空间的基本理论及应用(Ⅰ)*

本文系统地研究概率度量空间的基本理论和应用,讨论了概率度量空间的拓扑结构和性质;给出了概率度量空间,Menger概率度量空间以及概率线性赋范空间可度量化的条件及其度量函数的形式:得出了概率度量空间集合的各种概率有界性的表征等.作为这些结果的应用,我们讨论了概率线性赋范空间中线性算子的理论及概率度量空间中不动点的存在性问题.     

The unit ball is an attractor of the intersection body operator

The intersection body of a ball is again a ball. So, the unit ball Bd⊂Rd is a fixed point of the intersection body operator acting on the space of all star-shaped origin symmetric bodies endowed with the Banach–Mazur distance. E. Lutwak asked if there is any other star-shaped body that satisfies this property. We show that this fixed point is a local attractor, i.e., that the iterations of the intersection body operator applied to any star-shaped origin symmetric body sufficiently close to Bd in Banach–Mazur distance converge to Bd in Banach–Mazur distance. In particular, it follows that the intersection body operator has no other fixed or periodic points in a small neighborhood of Bd. We will also discuss a harmonic analysis version of this question, which studies the Radon transforms of powers of a given function.     

Generic Banach spaces and generic simplexes

We give a systematic study of certain class of generic Banach spaces. We show that they distinguish between an array of different properties related to smoothness of equivalent norms such as for example the Mazur intersection property or the existence of convex sets supported by all of their points. We also examine the dual constructions of generic Choquet simplexes with extra requirements such as for example those of Poulsen and Bauer asking that the set of extremal points is dense or closed, respectively.     

Mazur intersection property for Asplund spaces

The main result of the present note states that it is consistent with the ZFC axioms of set theory (relying on Martin's Maximum MM axiom), that every Asplund space of density character ω₁ has a renorming with the Mazur intersection property. Combined with the previous result of Jiménez and Moreno (based upon the work of Kunen under the continuum hypothesis) we obtain that the MIP renormability of Asplund spaces of density ω₁ is undecidable in ZFC.     

Convex sets which are intersections of closed balls

In this paper we aim to investigate different questions concerning the stability of the set of all intersections of closed balls in a normed space. We are mainly concerned with: (i) the stability of under the closure of the vector sums; (ii) the stability under the addition of balls. We prove that (i) and (ii) are different properties which have strong connections with the geometry of the space. They have interest both in finite and infinite dimension. In the former case, there is a link with linear programming theory. We also study two more stability properties related to the well-known binary intersection property. Mazur sets and Mazur spaces are introduced, as a natural family satisfying (i). We prove that every two-dimensional normed space is a Mazur space, a result which distinguishes dimension d?2 from dimension d?3. We also discuss the connections between Mazur spaces and porosity.     

Property T＊＊ for C＊-algebras

Extending the notion of property T of finite von Neumann algebras to general von Neumann algebras, we define and study in this paper property T** for (possibly non-unital) C* -algebras. We obtain several results of property T** parallel to those of property T for unital C* -algebras. Moreover, we show that a discrete group Γ has property T if and only if the group C* -algebra Cr* (Γ) (or equivalently, the reduced group C* -algebra Cr* (Γ)) has property T**. We also show that the compact operators K(l2 ) has property T** but c0 does not have property T**.     

Mazur Intersection Properties and Differentiability of Convex Functions in Banach Spaces

It is proved that the dual of a Banach space with the Mazurintersection property is almost weak* Asplund. Analogously,the predual of a dual space with the weak* Mazur intersectionproperty is almost Asplund. Through the use of these arguments,it is found that, in particular, almost all (in the Baire sense)equivalent norms on l₁() and l() are Fréchet differentiableon a dense G subset. Necessary conditions for Mazur intersectionproperties in terms of convex sets satisfying a Krein–Milmantype condition are also discussed. It is also shown that, ifa Banach space has the Mazur intersection property, then everysubspace of countable codimension can be equivalently renormedto satisfy this property.     

Strongly irreducible operators on Banach spaces

This paper firstly discusses the existence of strongly irreducible operators on Banach spaces. It shows that there exist strongly irreducible operators on Banach spaces with w*-separable dual. It also gives some properties of strongly irreducible operators on Banach spaces. In particular, if T is a strongly irreducible operator on an infinite-dimensional Banach space, then T is not of finite rank and T is not an algebraic operator. On Banach spaces with subsymmetric bases, including infinite-dimensional separable Hilbert spaces, it shows that quasisimilarity does not preserve strong irreducibility. In addition, we show that the strong irreducibility of an operator does not imply the strong irreducibility of its conjugate operator, which is not the same as the property in Hilbert spaces.     

Mazur Sets in Normed Spaces

In this paper we investigate different questions concerning Mazur sets in normed spaces, which point out the close connections between geometric functional analysis and discrete geometry. Motivated by a result of Chen and Lin, we study the relationship between Mazur disks and weak* denting points of the dual unit ball. We prove that the only Mazur sets of the spaces l₁ⁿ are points and closed balls. Finally, a new stability property for the family of all sets which are intersections of closed balls is found.     

具有阿贝尔Sylow 2-子群的有限群的整群环的正规化子性质

Mazur猜想:具有阿贝尔Sylow 2-子群的有限群有正规化子性质.设G是一个有限群,N是G的一个正规子群且Z(G/N)仅有平凡单位,本文建立了由Z(G/N)中单位诱导的G的自同构与N的Coleman自同构之间的联系,在此基础上证明了若G是一个具有阿贝尔Sylow 2-子群的有限群且Z(G/F*(G))仅有平凡单位,则Mazur猜想对G成立.     

两点齐性的 Finsler 流形

该文证明任何一个两点齐性的 Finsler 流形一定是黎曼流形. 证明过程中作者将泛函分析中经典的Mazur 定理推广到不一定是绝对齐次的 Minkowski 空间上.