Hadamard积和酉不变范数不等式

设Ｍｎ，ｍ是ｎ×ｍ复矩阵空间，Ｍｎ≡Ｍｎ，ｎ．对于Ｈｅｒｍｉｔｅ阵Ｇ，Ｈ∈Ｍｎ，ＧＨ表示Ｇ－Ｈ半正定．记Ａ和Ｂ的Ｈａｄａｍａｒｄ积为ＡＢ．本文证明了若Ａ，Ｂ∈Ｍｎ正定，而Ｘ，Ｙ∈Ｍｎ，ｍ任意，则（ＸＡ－１Ｘ）（ＹＢ－１Ｙ）（ＸＹ）（ＡＢ）－１（ＸＹ），ＸＡ－１Ｘ＋ＹＢ－１Ｙ（Ｘ＋Ｙ）（Ａ＋Ｂ）－１（Ｘ＋Ｙ）．这推广和统一了一些现存的结果．设‖·‖为任意酉不变范数，Ｉ是单位矩阵．本文还证明了对于Ｘ∈Ｍｎ，ｍ和Ａ∈Ｍｎ，Ｂ∈Ｍｍ，若ＡＩ，ＢＩ，则函数ｆ（ｐ）＝‖ＡｐＸ＋ＸＢｐ‖在［０，∞）上单调递增．     

赋范空间的λ——性质

本文讨论赋范空间的λ－性质，得到了ｌ１（ｘｎ）和Ｌ∞（Ｘｎ）具有λ－性质的充分必要条件，解决了Ｒ．Ｍ．Ａｒｏｎ和Ｒ．Ｈ．Ｌｏｈｍａｎ在文（１）中提出的两个问题，此外，还研究了Ｂａｎａｃｈ空间，ｌｐ（Ｘｎ）（１〈ｐ〈∞）具有一致λ－性质的充分必要条件。     

关于G-M成果研究的若干新动态Ⅰ——G-M型空间的若干品种

结合自己的工作，对Gowers-Maurey系列成果获Fields奖以来的研究的新动态作一综述。本是上篇，主要讨论含遗传不可分解空间在内的G－M型空间的若干品种。     

Banach空间中Moore-Penrose广义逆与不适定边值问题

设Ｘ，Ｙ为Ｂａｎａｃｈ空间，Ｄ（Ａ）Ｘ，Ａ：Ｄ（Ａ）→Ｙ为具有闭值域的闭稠定线性算子．本文不假设Ａ具有“定义域可分解”条件［１８］，引入Ａ的Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆Ａ＋．与Ｍ．Ｚ．Ｎａｓｈｅｄ引入的不同，Ａ＋一般非线性．本文在空间Ｘ，Ｙ的一定几何框架下，证得Ａ＋的存在唯一性、极小性、连续性，并给出了线性的充要条件，便于将Ａ＋应用于方程、优化、控制等问题．作为应用，本文第二部分利用Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆讨论空间ＬＰ（Ω）（１＜Ｐ）中一类不适定的边值问题．在另文，给出广义逆在控制论中的应用．     

映射Fp：X→‖AXB—C‖p^p的临界点的特征

对于Ｈｉｌｂｅｒｔ空间有界线性算子Ａ、Ｂ、Ｃ,考虑了当Ａ有一个广义逆Ａ＾－使得（ＡＡ＾－）＾＊＝ＡＡ＾－,Ｂ有一个广义逆Ｂ＾－Ｔ使得（Ｂ＾－Ｂ）＾＊＝Ｂ＾－Ｂ时,映射Ｆｐ：Ｘ→‖ＡＸＢ－Ｃ‖ｐ＾ｐ临界点的特征的一般形式（１〈ｐ〈∞）,推广了Ｐ．Ｊ．Ｍａｈｅｒ的关于ｐ＝２时的结果,并指出该定理可推广到多个算子的情形。     

Tame遗传代数导出的 Lie代数

设Ａ是有限域ｋ上的有限维ｔａｍｅ遗传代数,Ｘ,Ｙ, Ｍ是有限生成Ａ模,如果Ｘ,Ｙ不可分解,证明了存在 Ｈａｌｌ多项式ＧＭＸＹ．设 Ｌ（Ａ）是以有限生成不可分解模为基的自由 Ａｂｅｌ群,则 Ｌ（Ａ）是退化 Ｒｉｎｇｅｌ－Ｈａｌｌ代数 Ｈ（Ａ）１的 Ｌｉｅ子代数,设 Ｌ’（Ａ）是 Ｌ（Ａ）的由单模生成的 Ｌｉｅ子代数,ｍ是齐次正则单模的长度,证明了当 Ｍ不可分解且ｍ不整除 Ｍ的长度时,［Ｍ］∈ Ｌ’（Ａ） ｚ Ｑ．     

向量值Musielak-Orlicz空间的两种几何性质(英)

设Ｘ是复Ｂａｎｃｈ空间,Ｍ（ｔ,ｕ）是以ｔ为参数的满足某些通常条件的Φ－函数．我们证明了;（ｉ）Ｍｕｓｉｅｌａｋ－Ｏｒｌｉｃｚ空间Ｌ_Ｍ（Ｘ）具有解析ＵＭＤ性质当且仅当Ｘ具有;（ｉｉ） Ｌ_Ｍ（Ｘ）具有解析ＲＮ性质当且仅当Ｘ具有．     

分裂空间的一个性质

设Ｘ为一个拓扑空间，对于任意的Ａ∈Ｘ。存在可分度量空间Ｍ及连续映射ｆ：Ｘ→Ｍ，使得ｆ（Ｘ）＝Ｍ，Ａ＝ｆ＾－１（ｆ（Ａ）），则Ｘ称为分裂空间。本文证明了分裂空间Ｘ在广义连续统假设下：（１）若ｄ（Ｘ）≥２＾ω，则ｄ（Ｘ）＝｜Ｘ｜。（２）若（Ｘ）≤２＾ω，则对角线集△ｘ为Ｇδ集。并且（１）中的条件不能减弱。     

关于超一致空间的一个注记

最近，张德学引入了拓扑构造的ｃｏ－ｔｏｗｅｒ扩张这一概念，并证明了不分明拓扑学中若干的知的范畴构造可以表示为较为简单的范畴构造的 ｃｏ－ｔｏｗｅｒ扩张．本文证明了由Ｊ．Ｇｕｔｉｅｒｒｅｚ Ｇａｒｃｉａ和 Ｍ．Ａ．ｄｅ　Ｐｒａｄａ。Ｖｉｃｅｎｔｅ［３］一致空间构造ＳＵＳ具体同构与Ｒ．Ｌｏｗｅｎ［９］意义下的不分明一致空间构造 ＦＵＳ的 ｃｏ－ｔｏｗｅｒ扩张的一个满子构造，而已知 ＦＵＳ同构于一致空间构造的 ｃｏ－ｔｏｗｅｒ扩张．     

映射F_p:X→‖AXB-C‖_p~p的临界点的特征

对于Ｈｉｌｂｅｒｔ空间上有界线性算子Ａ、Ｂ、Ｃ,考虑了当Ａ有一个广义逆Ａ~－使得（ＡＡ~－）~＊＝ＡＡ~－,Ｂ有一个广义逆 Ｂ~－使得（Ｂ~－ Ｂ）～＊＝ Ｂ~－ Ｂ时,映射 Ｆ_ｐ： Ｘ→｜｜ＡＸＢ－ Ｃ｜｜_ｐ~ｐ临界点的特征的一般形式（１＜ ｐ＜∞）,推广了Ｐ．Ｊ．Ｍａｈａｒ的关于对ｐ＝ ２时的结果,并指出该定理可推广到多个算子的情形．     

Some Characterizations of Hereditarily Indecomposable Banach Spaces

In this paper we first discuss the relations between some G-M-type spaces, and the previous eight kinds of G-M-type Banach spaces are merged into four different kinds. Then we build a Generalized Operator Extension Theorem, and introduce the concept of complete minimal sequences. Some sufficient and necessary conditions under which a Banach space is a hereditarily indecomposable space are given. Finally, we give some characterizations of hereditarily indecomposable Banach Spaces.     

Even infinite-dimensional real Banach spaces

This article is a continuation of a paper of the first author [V. Ferenczi, Uniqueness of complex structure and real hereditarily indecomposable Banach spaces, Adv. Math. 213 (1) (2007) 462–488] about complex structures on real Banach spaces. We define a notion of even infinite-dimensional real Banach space, and prove that there exist even spaces, including HI or unconditional examples from [V. Ferenczi, Uniqueness of complex structure and real hereditarily indecomposable Banach spaces, Adv. Math. 213 (1) (2007) 462–488] and C(K) examples due to Plebanek [G. Plebanek, A construction of a Banach space C(K) with few operators, Topology Appl. 143 (2004) 217–239]. We extend results of [V. Ferenczi, Uniqueness of complex structure and real hereditarily indecomposable Banach spaces, Adv. Math. 213 (1) (2007) 462–488] relating the set of complex structures up to isomorphism on a real space to a group associated to inessential operators on that space, and give characterizations of even spaces in terms of this group. We also generalize results of [V. Ferenczi, Uniqueness of complex structure and real hereditarily indecomposable Banach spaces, Adv. Math. 213 (1) (2007) 462–488] about totally incomparable complex structures to essentially incomparable complex structures, while showing that the complex version of a space defined by S. Argyros and A. Manoussakis [S. Argyros, A. Manoussakis, An indecomposable and unconditionally saturated Banach space, Studia Math. 159 (1) (2003) 1–32] provides examples of essentially incomparable complex structures which are not totally incomparable.     

On Hereditarily Indecomposable Banach Spaces

This paper shows that every non-separable hereditarily indecomposable Banach space admits an equivalent strictly convex norm, but its bi-dual can never have such a one; consequently, every non-separable hereditarily indecomposable Banach space has no equivalent locally uniformly convex norm.     

Banach spaces of typep have arbitrarily distortable subspaces

It is shown that if a Banach space has bounded distortions then it contains an unconditional basic sequence. It follows that Banach spaces of typep > 1 contain arbitrarily distortable subspaces. Furthermore, hereditarily indecomposable Banach spaces are themselves arbitrarily distortable.     

关于Banach空间最小系的扩充

本文就可分Banach空间中元素的最小序列(也称双直交序列)可以扩充到在全空间中完备这一事实,说明在空间不可分情况下,对于由不可数个元素组成的所谓最小系,这种完备性扩充未必可行.此外,还应用最小序列扩充性质给出可分的遗传不可分解空间的一个特征刻画.     

A uniformly convex hereditarily indecomposable banach space

We construct a uniformly convex hereditarily indecomposable Banach space, using a method similar to the one of Gowers and Maurey in [GM], and the theory of complex interpolation for a family of Banach spaces of Coifman, Cwikel, Rochberg, Sagher, and Weiss ([CCRSW1]).     

A dual method of constructing hereditarily indecomposable Banach spaces

A new method of defining hereditarily indecomposable Banach spaces is presented. This method provides a unified approach for constructing reflexive HI spaces and also HI spaces with no reflexive subspace. All the spaces presented here satisfy the property that the composition of any two strictly singular operators is a compact one. This yields the first known example of a Banach space with no reflexive subspace such that every operator has a non-trivial closed invariant subspace.     

On the Borelness of the intersection operation

We study the intersection operation of closed linear subspaces in a separable Banach space. We show that if the ambient space is quasi-reflexive, then the intersection operation is Borel. On the other hand, if the space contains a closed subspace with a Schauder decomposition into infinitely many non-reflexive spaces, then the intersection operation is not Borel. As a corollary, for a closed subspace of a Banach space with an unconditional basis, the intersection operation of the closed linear subspaces is Borel if and only if the space is reflexive. We also consider the intersection operation of additive subgroups in an infinite-dimensional separable Banach space, and show that if this intersection operation is Borel then the space is hereditarily indecomposable.     

On solutions to the Schroeder-Bernstein problem for Banach spaces

We investigate the geometry of the Banach spaces failing Schroeder-Bernstein Property (SBP). Initially we prove that every complex hereditarily indecomposable Banach space H is isomorphic to a complemented subspace of a Banach space S(H) that fails SBP in such a way that the only complemented hereditarily indecomposable subspaces of S(H) are those which are nearly isomorphic to H. Then we show that every Banach space having Mazur property is isomorphic to some complemented subspace of a Banach space which is not isomorphic to its square but isomorphic to its cube. Finally, we prove that if a Banach space X fails SBP then either it is not primary or the Grothendieck group K₀(L(X)) of the algebra of operators on X is not trivial.     

Uniqueness of complex structure and real hereditarily indecomposable Banach spaces

There exists a real hereditarily indecomposable Banach space X=X(C) (respectively X=X(H)) such that the algebra L(X)/S(X) is isomorphic to C (respectively to the quaternionic division algebra H).Up to isomorphism, X(C) has exactly two complex structures, which are conjugate, totally incomparable, and both hereditarily indecomposable. So there exist two Banach spaces which are isometric as real spaces but totally incomparable as complex spaces. This extends results of J. Bourgain and S. Szarek [J. Bourgain, Real isomorphic complex Banach spaces need not be complex isomorphic, Proc. Amer. Math. Soc. 96 (2) (1986) 221-226; S. Szarek, On the existence and uniqueness of complex structure and spaces with “few” operators, Trans. Amer. Math. Soc. 293 (1) (1986) 339-353; S. Szarek, A superreflexive Banach space which does not admit complex structure, Proc. Amer. Math. Soc. 97 (3) (1986) 437-444], and proves that a theorem of G. Godefroy and N.J. Kalton [G. Godefroy, N.J. Kalton, Lipschitz-free Banach spaces, Studia Math. 159 (1) (2003) 121-141] about isometric embeddings of separable real Banach spaces does not extend to the complex case.The quaternionic example X(H), on the other hand, has unique complex structure up to isomorphism; other examples with a unique complex structure are produced, including a space with an unconditional basis and non-isomorphic to l₂. This answers a question of S. Szarek in [S. Szarek, A superreflexive Banach space which does not admit complex structure, Proc. Amer. Math. Soc. 97 (3) (1986) 437-444].