Reducing Subspaces for a Class of Multiplication Operators

Let D be the open unit disk in the complex plane C. The Bergmanspace is the Hilbert space of analytic functions f in D such that where dA is the normalized area measure on D. If are two functions in , then the inner product of f and g is given by We study multiplication operators on induced by analytic functions. Thus for H (D), the space ofbounded analytic functions in D, we define by It is easy to check that M is a bounded linear operator on with ||M||=||||=sup{|(z)|:zD}.     

Dirichlet空间上一类乘法算子的酉等价类

本文研究了Dirichlet空间D上由二阶Blaschke积φ定义的乘法算子M_φ的酉等价类.主要结果表明对于D的一个乘子ψ,乘法算子M_ψ酉等价于M_φ当且仅当存在常数θ,|θ|θ=1,使得ψ(z)=φ(θz).这一结果是完全不同于Hardy空间与Bergman空间上的相应结果.     

双圆盘加权Dirichlet空间上Toeplitz算子的约化子空间

刻画了双圆盘加权Dirichlet空间D_α(D~2)上Toeplitz算子T_Z_1N(或T_z_2N)和T_z_1N_z_2N的约化子空间.结果表明Toeplitz算子T_z_1N(或T_z_2N)的约化子空间结构与权系数α无关,而Toeplitz算子T_2_1N_z_2N的约化子空间结构与权系数α有关.     

Joint Reducing Subspaces of Multiplication Operators and Weight of Multi-variable Bergman Spaces

This paper mainly concerns a tuple of multiplication operators defined on the weighted and unweighted multi-variable Bergman spaces, their joint reducing subspaces and the von Neumann algebra generated by the orthogonal projections onto these subspaces. It is found that the weights play an important role in the structures of lattices of joint reducing subspaces and of associated von Neumann algebras. Also, a class of special weights is taken into account. Under a mild condition it is proved that if those multiplication operators are defined by the same symbols, then the corresponding von Neumann algebras are $*$-isomorphic to the one defined on the unweighted Bergman space.     

Multiplication Operators on Invariant Subspaces of Function Spaces

Let M_φ be the operator of multiplication by φ on a Hilbert space of functions analytic on the open unit disk. For an invariant subspace F for the multiplication operator M_z, we derive some spectral properties of the multiplication operator M_φ : F → F. We characterize norm, spectrum, essential norm and essential spectrum of such operators when F has the codimension n property with n ∈ {1, 2, …, + ∞}.     

Fock空间上的乘法算子

Fock空间是由整函数组成的具有再生核的Hilbert空间.Fock空间上的乘法算子的定义域不是整个Fock空间,它在Fock空间上是稠定的.研究了Fock空间上的乘法算子的性质,对其值域进行了刻画,并得出了乘法算子作用在Fock空间的拟不变子空间上值域余一维的充要条件.     

Toeplitz Operators on the Dirichlet Space

In this paper a decomposition of Sobolev space is obtained. Then we prove that a Toeplitz operator on the Dirichlet space is compact only when it is the zero operator. For two Toeplitz operators on the Dirichlet space, we obtain the conditions for that they commute, their product is a Toeplitz operator, and their commutator or semi-commutator has finite rank, respectively.     

Dirichlet空间上的紧算子

若S是Dirichlet空间上有限个Toeplitz算子乘积的有限和, S为紧算子的充要条件是: 当z→∂D时, S的Berezin型变换收敛到0; 若S是Dirichlet空间上Hankel算子, S为紧算子的充要条件是: 当z→ D时, S作用在类再生核上按范数收敛到0.     

一类解析Toeplitz算子的约化子空间

考虑了由对称测度定义的解析函数Hilbert空间上解析Toeplitz算子的约化子空间.特别地,对任一正整数n,解析Toeplitz算子T_z~n的约化子空间得到了完全刻画.     

Hardy空间上某些解析Toeplitz算子的换位及约化子空间

讨论了Hardy空间上以非退化有界单叶解析函数的幂为符号的解析Toeplitz算子的换位.并且刻划了符号为三个Blaschke因子积的解析Toeplitz算子的约化子空间.     

调和Dirichlet空间上的Toeplitz算子

刻画了调和Dirichlet空间上Toeplitz算子的有界性、紧性,讨论了Toeplitz算子的代数性质,得到了Toeplitz代数与Hankel代数的短正合列.还计算了Toeplitz代数与Hankel代数中Fredholm算子的Fredholm指标,得到了Toeplitz代数与Hankel代数的K_0与K_1群.     

Dirichlet空间上的循环复合算子

该文主要证明了在Dirichlet空间上由复合算子{C\-φ:φ∈Aut(D)}生成的代数为循环算子代数;同时对任意的解析映射φ:D→D,C\-φ都不可能为超循环算子给出了证明.     

Orlicz空间上的乘法算子

函数空间上的乘法算子是包含许多重要算子的算子类,该文主要研究Orlicz空间上乘法算子的一系列重要性质,包括有界性、紧性、Fredholm性质以及谱的计算等     

Semigroups of Composition Operators on the Dirichlet Space

We show that semigroups of composition operators are strongly continuous on the Dirichlet space. The infinitesimal generator is identified and we give some spectral properties.     

Toeplitz算子在Dirichlet空间上的亚正规性

In this paper,we prove that the necessary and sufficient condition for a Toeplitz operator Tu on the Dirichlet space to be hyponormal is that the symbol u is constant for the case that the projection of u in the Dirichlet space is a polynomial and for the case that u is a class of special symbols,respectively.We also prove that a Toeplitz operator with harmonic polynomial symbol on the harmonic Dirichlet space is hyponormal if and only if its symbol is constant.     

Dirichlet空间上Toeplitz算子的亚正规性

讨论单位圆盘中Dirichlet空间上Toeplitz算子的性质,给出了Dirichiet空间上以一类连续函数为符号的Toeplitz算子满足亚正规性的充分必要条件．     

圆环上的Dirichlet空间及其算子

本文主要讨论了圆环上Dirichlet空间中Toeplitz算子的Fredholm性质,计算了符号在C~1和H_1~∞+C~1中的Toeplitz算子的本性谱.     

Dirichlet空间上的Bergman型Toeplitz算子

证明了在Dirichlet空间上以有界调和函数φ为符号的Bergman-型Toeplitz算子T_φ是紧算子的充分必要条件是其符号φ为0;如果φ是单位圆盘D上的连续函数,那么T_φ是紧算子的充分必要条件是φ在D的边界上为0.我们还讨论了此类Toeplitz算子的半换位子.     

Multiplication Operators on the Lipschitz Space of a Tree

In this paper, we study the multiplication operators on the space of complex-valued functions f on the set of vertices of a rooted infinite tree T which are Lipschitz when regarded as maps between metric spaces. The metric structure on T is induced by the distance function that counts the number of edges of the unique path connecting pairs of vertices, while the metric on ℂ is Euclidean. After observing that the space L{\mathcal{L}} of such functions can be endowed with a Banach space structure, we characterize the multiplication operators on L{\mathcal{L}} that are bounded, bounded below, and compact. In addition, we establish estimates on the operator norm and on the essential norm, and determine the spectrum. We then prove that the only isometric multiplication operators on L{\mathcal{L}} are the operators whose symbol is a constant of modulus one. We also study the multiplication operators on a separable subspace of L{\mathcal{L}} we call the little Lipschitz space.