共查询到20条相似文献,搜索用时 15 毫秒
1.
In Sung Hwang 《Journal of Mathematical Analysis and Applications》2010,361(1):270-275
In this note we give a connection between subnormal Toeplitz operators and the kernels of their self-commutators. This is closely related to P.R. Halmos's Problem 5: Is every subnormal Toeplitz operator either normal or analytic? Our main theorem is as follows: If φ∈L∞ is such that φ and are of bounded type (that is, they are quotients of two analytic functions on the open unit disk) and if the kernel of the self-commutator of Tφ is invariant for Tφ then Tφ is either normal or analytic. 相似文献
2.
本文给出了双侧加权移位算子的近次正常性的完全刻画.作为主要结果的应用,文章的最后提供了Hilbert空间第160问题的许多新的答案. 相似文献
3.
In Sung Hwang 《Journal of Mathematical Analysis and Applications》2011,382(2):883-891
This paper concerns a gap between hyponormality and subnormality for block Toeplitz operators. We show that there is no gap between 2-hyponormality and subnormality for a certain class of trigonometric block Toeplitz operators (e.g., its co-analytic outer coefficient is invertible). In addition we consider the extremal cases for the hyponormality of trigonometric block Toeplitz operators: in this case, hyponormality and normality coincide. 相似文献
4.
Xuanhao Ding 《Journal of Mathematical Analysis and Applications》2008,337(1):726-738
In this paper we completely characterize when the product of a Hankel operator and a Toeplitz operator on the Hardy space is a finite rank perturbation of a Hankel operator, and when the commutator of a Hankel operator and a Toeplitz operators has finite rank. 相似文献
5.
Takahiko Nakazi 《Proceedings of the American Mathematical Society》2008,136(7):2425-2428
The problem of hyponormality for Toeplitz operators with (trigo- nometric) polynomial symbols is studied. We give a necessary and sufficient condition using the zeros of the analytic polynomial induced by the Fourier coefficients of the symbol.
6.
Bebe Prunaru 《Proceedings of the American Mathematical Society》1997,125(6):1689-1691
We show that if is a bounded operator on a Hilbert space such that for every polynomial , then has a nontrivial invariant subspace.
7.
Let H0 (respectively H∞) denote the class of commuting pairs of subnormal operators on Hilbert space (respectively subnormal pairs), and for an integer k?1 let Hk denote the class of k-hyponormal pairs in H0. We study the hyponormality and subnormality of powers of pairs in Hk. We first show that if (T1,T2)∈H1, the pair may fail to be in H1. Conversely, we find a pair (T1,T2)∈H0 such that but (T1,T2)∉H1. Next, we show that there exists a pair (T1,T2)∈H1 such that is subnormal (for all m,n?1), but (T1,T2) is not in H∞; this further stretches the gap between the classes H1 and H∞. Finally, we prove that there exists a large class of 2-variable weighted shifts (T1,T2) (namely those pairs in H0 whose cores are of tensor form (cf. Definition 3.4)), for which the subnormality of and does imply the subnormality of (T1,T2). 相似文献
8.
Lu Shijie 《数学学报(英文版)》1997,13(3):321-326
For finite rank operators in a commutative subspace lattice algebra algℒ we introduce the concept of correlation matrices,
basing on which we prove that a finite rank operator in algℒ can be written as a finite sum of rank-one operators in algℒ,
if it has only finitely many different correlation matrices. Thus we can recapture the results of J.R. Ringrose, A. Hopenwasser
and R.Moore as corollaries of our theorems.
Research supported by NSF of China 相似文献
9.
We study three different problems in the area of Toeplitz operators on the Segal-Bargmann space in Cn. Extending results obtained previously by the first author and Y.L. Lee, and by the second author, we first determine the commutant of a given Toeplitz operator with a radial symbol belonging to the class Sym>0(Cn) of symbols having certain growth at infinity. We then provide explicit examples of zero-products of non-trivial Toeplitz operators. These examples show the essential difference between Toeplitz operators on the Segal-Bargmann space and on the Bergman space over the unit ball. Finally, we discuss the “finite rank problem”. We show that there are no non-trivial rank one Toeplitz operators Tf for f∈Sym>0(Cn). In all these problems, the growth at infinity of the symbols plays a crucial role. 相似文献
10.
B. C. Gupta 《Proceedings Mathematical Sciences》1986,95(1):41-44
LetS be a pure subnormal operator such thatC*(S), theC*-algebra generated byS, is generated by a unilateral shiftU of multiplicity 1. We obtain conditions under which 5 is unitarily equivalent toα + βU, α andβ being scalars orS hasC*-spectral inclusion property. It is also proved that if in addition,S hasC*-spectral inclusion property, then so does its dualT andC*(T) is generated by a unilateral shift of multiplicity 1. Finally, a characterization of quasinormal operators among pure subnormal
operators is obtained. 相似文献
11.
Dragan S. Djordjevi? 《Journal of Mathematical Analysis and Applications》2007,329(2):1181-1190
In this paper normal and hyponormal operators with closed ranges, as well as EP operators, are characterized in arbitrary Hilbert spaces. All characterizations involve generalized inverses. Thus, recent results of S. Cheng and Y. Tian [S. Cheng, Y. Tian, Two sets of new characterizations for normal and EP matrices, Linear Algebra Appl. 375 (2003) 181-195] are extended to infinite-dimensional settings. 相似文献
12.
C. Foias I. B. Jung E. Ko C. Pearcy 《Transactions of the American Mathematical Society》2007,359(6):2899-2913
In this article we employ a technique originated by Enflo in 1998 and later modified by the authors to study the hyperinvariant subspace problem for subnormal operators. We show that every ``normalized'subnormal operator such that either does not converge in the SOT to the identity operator or does not converge in the SOT to zero has a nontrivial hyperinvariant subspace.
13.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
14.
Bebe Prunaru 《Proceedings of the American Mathematical Society》1996,124(11):3411-3412
Let be a pure hyponormal operator with compact self-commutator. We show that the unit ball of the commutant of is compact in the strong operator topology.
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A result of Aliprantis and Burkinshaw shows that weakly compact operators from an AL-space into a KB-space have a weakly compact modulus. Groenewegen characterised the largest class of range spaces for which this remains true whenever the domain is an AL-space and Schmidt proved a dual result. Both of these authors used vector-valued integration in their proofs. We give elementary proofs of both results and also characterise the largest class of domains for which the conclusion remains true whenever the range space is a KB-space. We conclude by studying the order structure of spaces of weakly compact operators between Banach lattices to prove results analogous to earlier results of one of the authors for spaces of compact operators.
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Iryna Schlackow 《Topology and its Applications》2008,155(11):1227-1236
We study properties of Koszmider spaces and introduce a related notion of weakly Koszmider spaces. We show that if the space K is weakly Koszmider and C(K) is isomorphic to C(L) then L is also weakly Koszmider, but the analogous result does not hold for Koszmider spaces. We also show that a connected Koszmider space is strongly rigid. 相似文献
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