空间（Lμ^p）^m的弱Banach-Saks性质

证明了由m个Lμp空间产生的Banach向量空间（Lμp）m的弱Banach-Saks性质,其中m是自然数, 1 p 〈＋∞.当m= 1时,这就是著名的Banach-Saks-Szlenk定理.运用该性质,还给出了定义在向量空间Rm的一个凸集上的非负连续凸函数与取值在空间（Lpμ）m的一个弱紧子集中的向量值函数的复合函数的积分不等式.当这些向量值函数属于由m个Lμ∞空间产生的积空间（Lμ∞）m的一个弱＊紧子集时,类似的积分不等式还是成立的.     

On Absolute Uniform Retracts,Uniform Approximation Property and Super Weakly Compact Sets of Banach Spaces

In this paper,we show that every super weakly compact convex subset of a Banach space is an absolute uniform retract,and that it also admits the uniform compact approximation property.These can be regarded as extensions of Lindenstrauss and Kalton's corresponding results.     

本刊英文版Vol.32(2016),No.6论文摘要（英文）

正On Proximinality of Convex Sets in Superspaces Li Xin CHENG Zheng Hua LUO Wen ZHANG Ben Tuo ZHENG Abstract In this paper,we show that a closed convex subset C of a Banach space is strongly proximinal(proximinal,resp.)in every Banach space isometrically containing it if and only if C is locally(weakly,resp.)compact.As a consequence,it is proved that local compactness of C is also equivalent to that for every Banach space Y isometrically containing it,the metric     

On the weak topology of Banach spaces over non-archimedean fields

It is known that within metric spaces analyticity and K-analyticity are equivalent concepts. It is known also that non-separable weakly compactly generated (shortly WCG) Banach spaces over R or C provide concrete examples of weakly K-analytic spaces which are not weakly analytic. We study the case which totally differs from the above one. A general theorem is provided which shows that a Banach space E over a locally compact non-archimedean non-trivially valued field is weakly Lindelöf iff E is separable iff E is WCG iff E is weakly web-compact (in the sense of Orihuela). This provides a non-archimedean version of a remarkable Amir-Lindenstrauss theorem.     

A weak Grothendieck compactness principle

The Grothendieck compactness principle states that every norm compact subset of a Banach space is contained in the closed convex hull of a norm null sequence. In this article, an analogue of the Grothendieck compactness principle is considered when the norm topology of a Banach space is replaced by its weak topology. It is shown that every weakly compact subset of a Banach space is contained in the closed convex hull of a weakly null sequence if and only if the Banach space has the Schur property.     

Embedding weakly compact sets into Hilbert space

We give an example of a weakly compact set in a Banach space, which does not embed topologically as a weakly compact subset of Hilbert space. We also show that a weakly compact set embeds in a super-reflexive space iff it embeds in Hilbert space. This work was done while the authors were visiting Ohio State University. We wish to thank the Department of mathematics at Ohio State University for their kind hospitality. The work of the first author was partially supported by NSF Grant MPS-74-24249. The work of the second author is a part of his Ph.D. Thesis prepared at the University of California at Berkeley.     

Every weakly compact set can be uniformly embedded into a reflexive Banach space

Based on an application of the Davis-Figiel-Johnson-Pelzyski procedure, this note shows that every weakly compact subset of a Banach space can be uniformly embedded into a reflexive Banach space. As its application, we present the recent renorming theorems for reflexive spaces of Odell- Schlumprecht and Hajek-Johanis can be extended and localized to weakly compact convex subsets of an arbitrary Banach space.     

Examples of sets with given approximation properties in WCG-space

An example of a nontrivial convex bounded Chebyshev set is constructed in an arbitrary weakly compactly generated Banach space (WCG-space). An example of bounded approximately compact but not locally compact set is constructed in an arbitrary infinite-dimensional WCG-space.     

On dual locally uniformly rotund norms

We show that the existence of an equivalent dual LUR norm on a dual Banach space can be characterized by a topological property similar to the fragmentability. The compact spaces homeomorphic to weak* compact subsets of a dual LUR Banach space have the same properties as the class of Radon-Nikodym compact spaces. Research supported by the DGICYT PB 95-1025.     

A fixed point result in strictly convex Banach spaces

We define an alternate convexically nonexpansive map T on a bounded, closed, convex subset C of a Banach space X and prove that if X is a strictly convex Banach space and C is a nonempty weakly compact convex subset of X, then every alternate convexically nonexpansive map T : C → C has a fixed point. As its application, we give an existence result for the solution of an integral equation.     

On uniformly convex functions

Non-convex functions that yet satisfy a condition of uniform convexity for non-close points can arise in discrete constructions. We prove that this sort of discrete uniform convexity is inherited by the convex envelope, which is the key to obtain other remarkable properties such as the coercivity. Our techniques allow to retrieve Enflo's uniformly convex renorming of super-reflexive Banach spaces as the regularization of a raw function built from trees. Among other applications, we provide a sharp estimation of the distance of a given function to the set of differences of Lipschitz convex functions. Finally, we prove the equivalence of several possible ways to quantify the super weakly noncompactness of a convex subset of a Banach space.     

Un résultat d'existence de sélection mesurable et compacité forte de l'intégrale d'une multiapplication dans un Banach non nécessairement séparable

Summary An existence result of strongly measurable selection of a weakly measurable multifunction from a compact space with non empty convex weakly compact values in a Banach space is given. Some compactness results concerning the set of integrable selections of a weakly measurable multifunction with non empty convex weakly compact values in a weakly compact set of a Banach space and the multivalued integral of such multifunction are presented.     

Factoring weakly compact operators

The main result is that every weakly compact operator between Banach spaces factors through a reflexive Banach space. Applications of the result and technique of proof include new results (e.g., separable conjugate spaces embed isomorphically in spaces with boundedly complete bases; convex weakly compact sets are affinely homeomorphic to sets in a reflexive space) and simple proofs of known results (e.g., there is a reflexive space failing the Banach-Saks property; if X is separable, then $\text{X =}\text{Z}{}^7\text{Z}$ for some Z; there is a separable space which does not contain l₁ whose dual is nonseparable).     

Applications sous-linéaires à valeurs dans un espace de fonctions continues

Summary We investigate the possibility of representing a convex mapping f with values in some space C(T) of continuous functions on a compact space T, as a supremum of continuous affine mappings, when the domain D of f is some convex subset of a Banach space X. Various limiting examples are presented.     

On well posedness of best simultaneous approximation problems in Banach spaces

The well posedness of best simultaneous approximation problems is considered. We establish the generic results on the well posedness of the best simultaneous approximation problems for any closed weakly compact nonempty subset in a strictly convex Kadec Banach space. Further, we prove that the set of all points inE(G) such that the best simultaneous approximation problems are not well posed is a u- porous set inE(G) whenX is a uniformly convex Banach space. In addition, we also investigate the generic property of the ambiguous loci of the best simultaneous approximation.     

凸幂Domain的极大点的注记

本文讨论了连续Domain D的极大点Max(D)的紧子集Com(Max(D))与凸幂Domain CD的极大点Max(CD)一一对应的条件以及Max(CD)上拓扑的性质, 证明了当X为局部紧Hausdorff空间时,X的上空间UX的凸幂Domain C(UX)的极大点Max(C(UX))与Com(Max(UX))(即X的紧子集)一一对应.X的上空间UX上的Lawson拓扑与X紧子集上的Vietoris拓扑相同,并且与Max(C(UX))带有C(UX)上的相对Scott拓扑同胚.     

A simple proof of inequalities of integrals of composite functions

In this paper we give a simple proof of inequalities of integrals of functions which are the composition of nonnegative continuous convex functions on a vector space Rm and vector-valued functions in a weakly compact subset of a Banach vector space generated by m-spaces for 1?p<+∞. Also, the same inequalities hold if these vector-valued functions are in a weakly* compact subset of a Banach vector space generated by m-spaces instead.     

Banach空间中极大单调算子零点的迭代逼近定理

令E为实光滑、一致凸Banach空间,E为其对偶空间．令A■ E x E为极大单调算子, A-10≠■．本文将引入新的迭代算法,并利用Lyapunov泛函, Qr算子与广义投影算子等技巧,证明了迭代序列弱收敛于极大单调算子A的零点的结论．     

A characterization of state spaces of orthomodular lattices

It is shown that every rational polytope is affinely equivalent to the set of all states of a finite orthomodular lattice, and that every compact convex subset of a locally convex topological vector space is affinely homeomorphic to the set of all states of an orthomodular lattice.     

Banach空间中两个极大单调算子公共零点的迭代格式

令E为实光滑、一致凸Banach空间,E~*为其对偶空间.令A,B(?)E×E~*为极大单调算子且A~(-1)∩B~(-1)0≠(?).本文将引入新的迭代格式,利用Lyapunov泛函与广义投影算子等技巧,证明迭代序列弱收敛于极大单调算子A和B的公共零点.