Essentially subnormal operators

An operator is essentially subnormal if its image in the Calkin algebra is subnormal. We shall characterize the essentially subnormal operators as those operators with an essentially normal extension. In fact, it is shown that an essentially subnormal operator has an extension of the form ``normal plus compact'.

The essential normal spectrum is defined and is used to characterize the essential isometries. It is shown that every essentially subnormal operator may be decomposed as the direct sum of a subnormal operator and some irreducible essentially subnormal operators. An essential version of Putnam's Inequality is proven for these operators. Also, it is shown that essential normality is a similarity invariant within the class of essentially subnormal operators. The class of essentially hyponormal operators is also briefly discussed and several examples of essentially subnormal operators are given.

     

每个算子都是两个强不可约算子的和

本文证明了可分无穷维 Hilbert空间上每个有界线性算子均可写成两个强不可约算子之和 .这回答了文献 [9]中提出一个公开问题     

本质正规算子的模小紧相似

本文证明了一类本质正规算子Ａ＇（Ω＇;１）（Ｔ∈Ａ＇（Ω＇;１）,如果Ｔ满足（１）Ｔ,Ｔ｜Ｈ（Ｔ）分别是本质正规算子;（２）σ（Ｔ）＝Ω,ρＦ（Ｔ）∩σ（Ｔ）＝Ω;（３）ｉｎｄ（Ｔ－λ）＝－１,ｎｕｌ（Ｔ－λ）＝０,λ∈Ω＇;（４）σ（Ｔ｜Ｈ（Ｔ））是一完全集,这里Ω＇是一连通的解析Ｃａｕｃｈｙ域, Ｈｌ（Ｔ）＝ Ｖ｛ｋｅｒ（Ｔ－λ）＊：λ∈ρｒｓ－Ｆ（Ｔ）｝是模小紧相似的．     

Strongly Irreducible Submodules of Modules

Strongly irreducible submodules of modules are defined as follows： A submodule N of an Rmodule M is said to be strongly irreducible if for submodules L and K of M, the inclusion L ∩ K ∈ N implies that either L ∈ N or K ∈ N. The relationship among the families of irreducible, strongly irreducible, prime and primary submodules of an R-module M is considered, and a characterization of Noetherian modules which contain a non-prime strongly irreducible submodule is given.     

严格循环与强不可约分解

Let W be an injective unilateral weighted shift, and let W(n) be the orthogonal direct sum of n copies of W. In this paper, we prove that, if the commutant of W is strictly cyclic, then W(n) has a unique (SI) decomposition with respect to similarity for every natural number n.     

强不可约算子理论及其应用(英文)

在有限维空间的矩阵理论中,著名的约当标准型定理充分揭示了矩阵的内在结构.在这篇综述中,我们给出复可分的无穷维希尔伯特空间上类似的约当标准型定理.同时也展示了该理论在其它数学分支中的应用。     

ESSENTIALLY NORMAL ＋ SMALL COMPACT = STRONGLY IRREDUCIBLE

Given an essentially normal operator T with connected spectrum and ind(λ -- T) > 0 for λ in pF(T) ∩ σ(T), and a positive number ε, the authors show that there exists a compact K with ‖K‖< ε such that T + K is strongly irreducible.     

Strongly irreducible operators and Cowen-Douglas operators on c 0, l p (1 ? p < ��)

This paper gives some sufficient conditions for the strongly irreducibility of operators which have the forms of upper triangular operator matrices on Banach spaces. Based on these results, strongly irreducible Cowen-Douglas operators of index n are constructed on c₀, l_p (1≤p<∞) for all 1≤n≤∞.     

β_∞(Ω)中算子的小紧扰动(英文)

We consider an approximation problem related to strongly irreducible operators, that is, does the direct sum of a strongly irreducible operator in в∞(Ω) and certain operator have a small compact perturbation which is a strongly irreducible operator in в∞(Ω)? In this paper, we prove that the direct sum of any strongly irreducible operator in в∞(Ω) and certain biquasitriangular operator have small compact perturbations which are strongly irreducible operators in в∞(Ω).     

THE （u＋К）-ORBIT OF ESSENTIALLY NORMAL OPERATORS AND COMPACT PERTURBATIONS OF STRONGLY IRREDUCIBLE OPERATORS

Let Н be a complex,separable,infinite dimensional Hilbert space,T∈L(Н),(U+κ)(T) denotes the (U+κ)-orbit of T,i.e.,(U+κ)(T)={R^-1 TR:R is invertible and of the form unitary plus compact}.Let Ω be an analytic and simply connected Cauchy domain in C and n∈N,A（Ω,n）denotes the class of operators,each of which satisfies (i) T is essentially normal;(ii)σ(T)=Ω^-,ρF（T）∩σ（T）=Ω;（iii）ind(λ-T)=-n,nul(λ-T)=0,(λ∈Ω）。it is proved that given T1,T2∈A(Ω,n）and c&gt;0,there exists a compact operator K with ||K||&lt;ε such that T1+K∈(u+κ)(T2),this result generalizes a result of P.S.Guinand and L.Marcoux[6,15],Furthermore,the authors give a character of the norm closure of (u+κ)(T),and prove that for each T∈А(Ω,n）,there exists a compact (SI) perturbation of T whose norm can be arbitrarily small.     

ESSENTIALLY NORMAL SMALL COMPAC=STRONGLY IRREDUCIBLE

ＥＳＳＥＮＴＩＡＬＬＹＮＯＲＭＡＬ＋ＳＭＡＬＬＣＯＭＰＡＣ＝ＳＴＲＯＮＧＬＹＩＲＲＥＤＵＣＩＢＬＥＪＩＪＯＵＱＩＮＧ＊ＪＡＮＧＣＨＵＮＬＡＮ＊ＷＡＮＧＺＯＮＧＹＡＯ＊＊ＡｂｓｔｒａｃｔＧｉｖｅｎａｎｅｓｓｅｎｔｉａｌｙｎｏｒｍａｌｏｐｅｒａｔｏｒＴｗ...     

算子强不可约的充要条件

本文证明了Cowen-Douglas 算子是强不可约的充要条件,是它的换位代数模去其Jacobson 根同构于$H^{\infty}(D)$中的一个闭子代数,这里$D$表示开单位圆盘, $H^{\infty}(D)$表示$D$上的有界解析函数的全体.     

强伪压缩算子带误差的Ishikawa迭代的强稳定性

设X是任意实Banach空间，T：X→X是一Lipschitz强伪压缩算子，本给出T带误差的Ishikawa迭代过程的强稳定性，并给出一个涉及Lipschitz强增生算子T的非线性方程Tx=f迭代解的强稳定性。     

Small Compact Perturbation of Operators in B∞（Ω）

Abstract： We consider an approximation problem related to strongly irreducible operators, that is, does the direct sum of a strongly irreducible operator in B∞（Ω） and certain operator have a small compact perturbation which is a strongly irreducible operator in B∞（Ω）？ In this paper, we prove that the direct sum of any strongly irreducible operator in B∞（Ω） and certain biquasitriangular operator have small compact perturbations which are strongly irreducible operators in B∞（Ω）.     

拟正规算子的Jord标准形

An operator on a Hilbert space is said to have (SI) decomposition if it is similar to the orthogonal direct sum of some (SI) operators. In this paper, we prove that every operator, which is similar to a quasinormal operator, has (SI)decomposition if and only if it is similar to D ( 0≤j相似文献   

A Completely Irreducible Compact Perturbation of a Class of Essentially Normal Operators

Ａ　Ｃｏｍｐｌｅｔｅｌｙ　Ｉｒｒｅｄｕｃｉｂｌｅ　Ｃｏｍｐａｃｔ　Ｐｅｒｔｕｒｂａｔｉｏｎ　ｏｆ　ａ　Ｃｌａｓｓ　ｏｆ　Ｅｓｓｅｎｔｉａｌｌｙ　Ｎｏｒｍａｌ　ＯｐｅｒａｔｏｒｓＪｉａｎｇＣｈｕｎｌａｎ（蒋春澜）ＣａｏＧｕａｎｇｆｕ（曹广福）ＳｕｎＳｈ...     

算子权移位的换位代数的交换性

令T是以{Wk}∞k=1B(Cn)为权序列的内射算子权移位.设T是强不可约的,而且sup1k<∞‖W-1k‖< ∞.用A′(T)表示T的换位代数,radA′(T)表示A′(T)的Jacobson根.本文刻划了radA′(T)并且证明了商代数A′(T)/radA′(T)是交换的.     

Strongly Singular Calderon-Zygmund Operator and Commutator on Morrey Type Spaces

In this paper, the author considers the boundedness of strongly singular Calderdn Zygmund operator and commutator generated by this operator and Lipschitz function on the classical Morrey space and generalized Morrey space. Moreover, the boundedness of strongly singular Calderón- Zygmund operator on the predual of Morrey space is discussed.     

Quasitriangular + small compact = strongly irreducible

Let be a bounded linear operator acting on a separable infinite dimensional Hilbert space. Let be a positive number. In this article, we prove that the perturbation of by a compact operator with can be strongly irreducible if is a quasitriangular operator with the spectrum connected. The Main Theorem of this article nearly answers the question below posed by D. A. Herrero.

Suppose that is a bounded linear operator acting on a separable infinite dimensional Hilbert space with connected. Let be given. Is there a compact operator with such that is strongly irreducible?

     

Three-step Iterations with Errors for Nonlinear Strongly Accretive Operator Equations

In this paper, we suggest and analyse a three-step iterative scheme with errors for solving nonlinear strongly accretive operator equation Tx = f without the Lipshitz condition. The results presented in this paper improve and extend current results in the more general setting.