多连通域的Bergman空间上的Toeplitz算子

In this paper, we investigate the Toeplitz operators with positive measure symbols on the Bergman spaces of bounded multi-connected domains and show that a Toeplitz operator is bounded or compact if and only if the symbol measure is a Carleson or vanishing Carleson measure respectively.     

一类次线性算子在广义Morrey空间上的加权有界性

本证明了如果次线性算子T在Orlicz空间上有介,则也有Morrey空间上有界,该算子包括极大算子和奇异积分算子等重要算子。     

U-标算子的连续演算

本文给出了U-标算子经连续算子演算后有界的充分条件。另外,对一给定的U-标算子T,证明了当函数μ(t)连续可导时算子μ(T)有界,但存在连续函数使得μ(T)无界。     

广义导算子的范数可达性

若B(H)表示希尔伯特空间H中所有有界线性算子之集.本文研究了定义在B(H)上的初等算子和广义导算子的范数可达性,证明了如果定义在B(H)中的初等算子和广义导算子是范数可达的,那么这些算子在B(H)中酉群上的限制也是范数可达的.     

Local residual-type error estimates for adaptive boundary element methods on closed curves

Considering the Galerkin boundary element methods and mesh families with bounded local mesh ratio we derive local error estimates such that the local error is bounded by a local residual together with some global terms which can be expected to be small. If the order of the boundary operator is non-negative and at most two, these estimates show that the local residual is a local error indicator. For the operators of the negative order we obtain the same conclusion if the mesh is β-regular. Our paper improves recent results of Wendland and Yu in several respects.     

Directional maximal operators with smooth densities

We study directional maximal operators on ?ⁿ with smooth densities. We prove that if the classical directional maximal operator in a given set of directions is weak type (1, 1), then the corresponding smooth‐density maximal operator in that set of directions will be bounded on L^q for q suitably large, depending on the order of the stationary points of the density function. In contrast to the classical case, if q is too small, the smooth density operator need not be bounded on L^q. Improving upon previously known results, we also establish that if the density function has only finitely many extreme points, each of finite order, then any maximal operator in a finite sum of diadic directions is bounded on all L^q for q > 1 (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

多圆盘上的本质可换的Toeplitz算子

本文讨论多圆盘上Ｂｅｒｇｍａｎ空间上的具有多重调和符号的Ｔｏｅｐｌｉｔｚ算子的本质可换性与可换性．我们获得了一个解析或共轭解析Ｔｏｅｐｌｉｔｚ算子与具有多重调和符号的Ｔｏｅｐｌｉｔｚ算子本质可换的充分必要条件是它们是可换的．     

A NOTE ON MAJORIZING AND CONE ABSOLUTELY SUMMING OPERATORS IN BANACH LATTICES

Abstract

Operators T which are both majorizing and cone absolutely summing on a Banach lattice E are investigated. Compactness and nuclearity of such operators are discussed and it is shown that a trace can be defined for operators belonging to a large class of these operators. Special results are derived in the case where E is a Banach function space and T a kernel operator. Finally we derive strongly measurable representations for a certain class of cone absolutely summing operators thereby clarifying work done by Dinculeanu and J.J. Uhl.     

Compact adjoint operators and approximation properties

This paper is concerned with the space of all compact adjoint operators from dual spaces of Banach spaces into dual spaces of Banach spaces and approximation properties. For some topology on the space of all bounded linear operators from separable dual spaces of Banach spaces into dual spaces of Banach spaces, it is shown that if a bounded linear operator is approximated by a net of compact adjoint operators, then the operator can be approximated by a sequence of compact adjoint operators whose operator norms are less than or equal to the operator norm of the operator. Also we obtain applications of the theory and, in particular, apply the theory to approximation properties.     

冯·诺依曼代数的可测算子的性质

本文研究了冯·诺依曼代数的可测算子的基本性质,定义了阶梯算子,证明了任意一个正可测算子可以由阶梯算子在定义域内按照强算子拓扑逼近,从而证明了任意一个可测算子可以由投影在定义域内按照强算子拓扑逼近.此外,还讨论了可测算子与有界算子的复合算子的可测性.     

一类解析算子函数空间上的复合算子

本文用算子函数论的方法，研究了解析算子函数的Banach空间X，X0上的复合算子．给出此复合算子为有界的条件，并刻划了此复合算子在X0上为紧的特征．     

保持算子截断的可加映射

Let H be a complex Hilbert space and B(H)the algebra of all bounded linear operators on H.An operator A is called the truncation of B in B(H)if A=P_ABP_A^*,where PA and P_A^*denote projections onto the closures of R(A)and R(A^*),respectively.In this paper,we determine the structures of all additive surjective maps on B(H)preserving the truncation of operators in both directions.     

单位球上Hardy空间之间的加权复合算子

We consider the weighted composition operators between Hardy spaces on the unit ball, and obtain some sufficient and necessary conditions of bounded or compact weighted composition operators. We also prove that the operator from H1 to H1 is compact if and only if it is weakly compact. Meanwhile, we get the analogue on the Bergman spaces.     

Certain classes of sets in Banach spaces and a topological characterization of operators of type RN

We study properties of bounded sets in Banach spaces, connected with the concept of equimeasurability introduced by A. Grothendieck. We introduce corresponding ideals of operators and find characterizations of them in terms of continuity of operators in certain topologies. The following result (Corollary 9) follows from the basic theorems: Let T be a continuous linear operator from a Banach space X to a Banach space Y. The following assertions are equivalent:

1. T is an operator of type RN;
2. for any Banach space Z, for any number p, p > 0, and any p-absolutely summing operator U:Z → X the operator TU is approximately p-Radonifying;
3. for any Banach space Z and any absolutely summing operator U:Z → X the operator TU is approximately 1-Radonifying.

We note that the implication I)?2), is apparently new even if the operator T is weakly compact.     

不同Bers型空间之间的加权复合算子

该文讨论了单位圆盘上不同Bers型空间之间的加权复合算子的有界性、紧性和弱紧性, 给出了一些充分必要的判别条件, 特别地得到不同Bers型空间上加权复合算子的紧性与弱紧性的等价性. 这些推广了经典的复合算子与乘法算子的相关结论. 该文同时也给出了Bers型空间上复合算子的Fredholm性和闭值域问题的刻画, 完善了文献[6]中结论.     

Stable and stabilizable means involving linear operator arguments

In this paper we extend the stability and stabilizability concepts from the case that the variables are positive real numbers to the case that the variables are positive linear operators. Since the algebra of bounded linear operators is not commutative, such extension does not appear to be obvious. As applications, iterative operator algorithms, converging to some operator means, are discussed.     

Positive set‐operators of low complexity

The powerset operator, ??, is compared with other operators of similar type and logical complexity. Namely we examine positive operators whose defining formula has a canonical form containing at most a string of universal quantifiers. We call them ?‐operators. The question we address in this paper is: How is the class of ?‐operators generated ? It is shown that every positive ?‐operator Γ such that Γ(??) ≠ ??, is finitely generated from ??, the identity operator Id, constant operators and certain trivial ones by composition, ∪ and ∩. This extends results of [3] concerning bounded positive operators.     

解析算子函数空间上的复合算子理论初步

本文将经典Hardy空间上复合算子的理论、方法应用到解析算子函数空间上,给出了解析算子函数空间的几个基本性质及复合算子的有界性条件.     

Power bounded operators and supercyclic vectors II

We show that each power bounded operator with spectral radius equal to one on a reflexive Banach space has a nonzero vector which is not supercyclic. Equivalently, the operator has a nontrivial closed invariant homogeneous subset. Moreover, the operator has a nontrivial closed invariant cone if belongs to its spectrum. This generalizes the corresponding results for Hilbert space operators.

For non-reflexive Banach spaces these results remain true; however, the non-supercyclic vector (invariant cone, respectively) relates to the adjoint of the operator.