In this paper, we give a criterion of the absolutely Cesàro bounded weighted backward shift in spirit of the comparison method. Our approach is to construct the proper product of weight functions <img src=&quo...In this paper, we give a criterion of the absolutely Cesàro bounded weighted backward shift in spirit of the comparison method. Our approach is to construct the proper product of weight functions <img src="Edit_7232e0dc-07ab-41c5-8657-a49f0463b47c.bmp" alt="" />by the fraction of two monomials of the indexes, then we apply proper scaling to give Cesàro boundedness. In particular, we present a new example of non Cesàro bounded weighted backward shift on <img src="Edit_799dadb7-40ab-48f9-bae3-191378f96164.bmp" alt="" />.展开更多
Let {an}∞n=0be a weight sequence and let W denote the associated unilateral weighted shift on H. In this paper, we consider the connection between the M-hyponormal and hyponormalizable weighted shift operator. Main r...Let {an}∞n=0be a weight sequence and let W denote the associated unilateral weighted shift on H. In this paper, we consider the connection between the M-hyponormal and hyponormalizable weighted shift operator. Main results are Theorems 4.1 and Theorems4.2. Theorem 4.1 gives the sufficient condition that a weighted shifts M-hyponormal operator is hyponormalizable. Theorem 4.2 gives the sufficient condition that a hyponormalizable weighted shift operator is M-hyponormal. Finally, invariant subspaces of such operators are discussed.展开更多
Extending previous results of Grosse-Erdmann and Peris we obtain a characterization of chaotic unilateral weighted backward shifts on sequentially complete topological sequence spaces in which the canonical unit vecto...Extending previous results of Grosse-Erdmann and Peris we obtain a characterization of chaotic unilateral weighted backward shifts on sequentially complete topological sequence spaces in which the canonical unit vectors(e_(n))_(n=1)^(∞) form an unconditional basis.展开更多
Abstract In this paper, it is characterized when a multiple unilateral weighted shift belongs to the classes An （1 ≤ n ≤ x0）. As a result, we perfect and generalize the previous conclusions given by H. Bercovici, ...Abstract In this paper, it is characterized when a multiple unilateral weighted shift belongs to the classes An （1 ≤ n ≤ x0）. As a result, we perfect and generalize the previous conclusions given by H. Bercovici, C. Foias, and C. Pearcy. Moreover, we remark that Question 21 posed by Shields has been negatively answered.展开更多
It is shown in[6]and[7]that a necessary and sufficient condition for a hyponormal weightedunilateral shift to be unitarily equivalent to a Toeplitz operator is that its weights satisfy(1-|an|2)=(1-|a0|2)(1-|an-1|2)n≥...It is shown in[6]and[7]that a necessary and sufficient condition for a hyponormal weightedunilateral shift to be unitarily equivalent to a Toeplitz operator is that its weights satisfy(1-|an|2)=(1-|a0|2)(1-|an-1|2)n≥1,where ansatisfiesan=1.In[8],the author obtainedsimilar result for the hyponormal weighted unilateral shift of multiplicity 2.The aim of this展开更多
A unilateral weighted shift A is said to be simple if its weight sequence {α_n} satisfies ▽~3(α_n^2)≠0for all n≥2.We prove that if A and B are two simple unilateral weighted shifts,then AI+IB is reducible if and ...A unilateral weighted shift A is said to be simple if its weight sequence {α_n} satisfies ▽~3(α_n^2)≠0for all n≥2.We prove that if A and B are two simple unilateral weighted shifts,then AI+IB is reducible if and only if A and B are unitarily equivalent.We also study the reducing subspaces of A^kI+IB^l and give some examples.As an application,we study the reducing subspaces of multiplication operators Mzk+αωl on function spaces.展开更多
文摘In this paper, we give a criterion of the absolutely Cesàro bounded weighted backward shift in spirit of the comparison method. Our approach is to construct the proper product of weight functions <img src="Edit_7232e0dc-07ab-41c5-8657-a49f0463b47c.bmp" alt="" />by the fraction of two monomials of the indexes, then we apply proper scaling to give Cesàro boundedness. In particular, we present a new example of non Cesàro bounded weighted backward shift on <img src="Edit_799dadb7-40ab-48f9-bae3-191378f96164.bmp" alt="" />.
基金Supported by the NNSF of China(11126286,11201095)Supported by the Research Fund of Heilongjiang Provincial Education Department(12541618)
文摘Let {an}∞n=0be a weight sequence and let W denote the associated unilateral weighted shift on H. In this paper, we consider the connection between the M-hyponormal and hyponormalizable weighted shift operator. Main results are Theorems 4.1 and Theorems4.2. Theorem 4.1 gives the sufficient condition that a weighted shifts M-hyponormal operator is hyponormalizable. Theorem 4.2 gives the sufficient condition that a hyponormalizable weighted shift operator is M-hyponormal. Finally, invariant subspaces of such operators are discussed.
基金Supported by Research Program of Science at Universities of Inner Mongolia Autonomous Region(Grant No.NJZY22328)。
文摘Extending previous results of Grosse-Erdmann and Peris we obtain a characterization of chaotic unilateral weighted backward shifts on sequentially complete topological sequence spaces in which the canonical unit vectors(e_(n))_(n=1)^(∞) form an unconditional basis.
文摘Abstract In this paper, it is characterized when a multiple unilateral weighted shift belongs to the classes An （1 ≤ n ≤ x0）. As a result, we perfect and generalize the previous conclusions given by H. Bercovici, C. Foias, and C. Pearcy. Moreover, we remark that Question 21 posed by Shields has been negatively answered.
基金This research was supported in part by a Foundation from Academy of Sciences of China.
文摘It is shown in[6]and[7]that a necessary and sufficient condition for a hyponormal weightedunilateral shift to be unitarily equivalent to a Toeplitz operator is that its weights satisfy(1-|an|2)=(1-|a0|2)(1-|an-1|2)n≥1,where ansatisfiesan=1.In[8],the author obtainedsimilar result for the hyponormal weighted unilateral shift of multiplicity 2.The aim of this
基金supported by National Natural Science Foundation of China(Grant Nos.11371096 and 11471113)
文摘A unilateral weighted shift A is said to be simple if its weight sequence {α_n} satisfies ▽~3(α_n^2)≠0for all n≥2.We prove that if A and B are two simple unilateral weighted shifts,then AI+IB is reducible if and only if A and B are unitarily equivalent.We also study the reducing subspaces of A^kI+IB^l and give some examples.As an application,we study the reducing subspaces of multiplication operators Mzk+αωl on function spaces.
