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2005年11月15日

【期刊论文】A CHARACTERIZATION OF BILATERAL OPERATOR WEIGHTED SHIFTS BEING COWEN-DOUGLAS OPERATORS

纪友清

，-0001，（）：

-1年11月30日

摘要

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2005年11月15日

【期刊论文】QUASITRIANGULAR + SMALL COMPACT=STRONGLY IRREDUCIBLE

纪友清， YOU QING JI

TRANSACTIONS OF THE AMERICAN MATHEMATICAI, SOCIETY Volume 351, Nomber 11, Pages 4657-4673，-0001，（）：

-1年11月30日

摘要

Let T be a bounded linear operator acting on a separable infinite dimensional Hilbert space. Let E be a positive number. In this article, we prove that the perturbation of T by a compact operator K with ‖K‖<E can be strongly irreducible if T is a quasitriangular operator with the spectrum σ(T) connected. The Main Theorem of this article nearly answers the question below posed by D. A. Herrero. Suppose that T is a bounded linear operator acting on a separable infinite dimensional Hilbert space with σ(T) connected. Let ε>0 be given. Is there a compact operator K with ‖K‖<ε such that T+K is strongly irreducible?

Weyl spectrum,， index,， strongly irreducible,， quasituiangular.，

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2005年11月15日

【期刊论文】STRONGLY APPROX1MAT1VE SIMILARITY OF OPERATORS

纪友清， You Qing Ji， and Juc Xian Li

TAIWANI SE JOUKNAL OF MATJE,ATOCS Vol.5, No.4, pp. 739-753, December 2001，-0001，（）：

-1年11月30日

摘要

For the bounded linear operators acting on a complex separable Hilbert space H, we introduce a binary relation ～sas called strongly approxi-mative similarity It lies between the similarity and the essential similarity. For a class of biquasitriangular operators and a class of quasitriangular operators, this relation is characterized respectively. As a result, the relation ～sas is an equivalent relation in this two cases.

Compact operator,， spectral picture,， quasitriangular operator.，

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2005年11月15日

【期刊论文】A CHARACTERIZATION OF BILATERAL OPERATOR WEIGHTED SHIFTS BEING COWEN-DOUGLAS OPERATORS

纪友清， YOU QING JI， JUEXIAN LI， AND YIHUA YANG

PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 129, Number 11, Pages 3205-3210，-0001，（）：

-1年11月30日

摘要

It is characterized when a bilateral operator weighted shift is a Cowen-Douglas operator.

Bilateral operator weighted shift,， Cowen-Douglas operator.，

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2005年11月15日

【期刊论文】The Closure of the Unitary Orbit of the Strongly Irreducible Operators in Continuous Nest Algebra

纪友清， Ji Youqing， Jiang Chunlan， Wang Zongyao

Acta Mathemaica Smica, New Series 1998. Dec., Vol. 14, Supplement, pp.605-612，-0001，（）：

-1年11月30日

摘要

In this paper. N always denotes continuous nest, and T(N)={TεL(H), TM с M; M ε N}. We describe the spectral picture of some strongly irreducible operators in T(N), and characterize the closure of the unitary orbit of the strongly irreducible operaiors in T(N). Continuous nest, Nest algebra, Strongly irreducible, Spectral picture

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