Hilbert空间上交换自伴算子组的C_p－类扰动

本文证明，如果Ｈｉｌｂｅｒｔ空间上交换自伴算子组Ｔ＝（Ｔ１，…，Ｔｎ）的Ｔａｙｌｏｒ谱之Ｈａｕｓｄｏｒｆｆ直维数等于α，α≥１，则对任意的ｐ＞α，存在Ｃｐ－范数充分小的Ｃｐ－类算子组Ｋ，使得Ｔ－Ｋ是交换对角算子组。     

加权Dirichlet空间上的复合算子

本文研究复平面中单位圆盘的加权Ｄｉｒｉｃｈｌｅｔ空间上的复合算子Ｃψ。利用Ｃａｒｌｅｓｏｎ测度的概念，给出了Ｃｐ为有界算子，紧算子的充要条件。同时，对复合算子Ｃｐ为Ｓｃｈａｔｔｅｎ Ｐ－类算子时，函数ψ应满足的条件作了讨论，给出了积分形式的刻划。     

Banach空间中有限秩算子的逼近问题

利用Banach空间几何方法证得: Banach空间中有界线性算子成为紧线性算子的充分必要条件是这个算子可以被有限秩的有界齐性算子一致逼近. 由此可揭示Enflo反例的本质所在.     

拟相似算子的右本质谱的连通分支

设算子S和T拟相似,通过引进RT类算子、R类算子和RR类算子的概念,给出右本质谱σre(S)的连通分支与σre(T)相交的充分条件和必要条件以及σre(S)的连通分支与本质谱盯σe(T)的某些子集的相交关系,并给出算子是属于RT类算子和RR类算子的充分条件和必要条件.     

一类自伴微分算子谱的离散性

本文研究了２ｎ阶实系数Ｅｕｌｅｒ微分算式生成的对称微分算子,得到了自伴Ｅｕｌｅｒ微分算子的谱是离散的充分必要条件．     

2n阶微分算子乘积自伴的充分必要条件

给定Hilbert空间L2[a,∞)上两个由2n阶对称微分算式生成的微分算子Li(i=1,2),该文给出了乘积算子L2L1是自伴算子的一个充分必要条件．     

度量图上两个微分算子乘积的自伴性

本文研究了度量图上二阶及四阶局部微分算子积的自伴顶点条件.在研究闭区间[a,b]上积算子自伴性的基础上,运用度量图上高阶局部微分算子的自伴顶点条件得到了积算子自伴的充分必要条件.此外,给出了积算子自伴与原算子自伴之间的关系.     

两类四阶微分算子积的自伴性研究

利用算子理论及矩阵运算方法,讨论了由两类不同的对称微分算式D~((4))+D~((2))+q_1(t)和D~((4))+q_2(t)(D=d/dt,t∈I=[a,b])生成的微分算子的积算子的自伴性,获得了积算子是自伴算子的充分必要条件.     

一类二阶与四阶微分算子积的自伴性

利用矩阵运算及算子的基本理论,讨论了由微分算式L_1=D~((2))+q_1(t)和L_2=D~((4))+q_2(t)其中(D=d/dx,t∈I=[a,b])生成的两个微分算子L_i(i=1,2)积L_1L_2的自伴性问题,并在常型情形下,获得了积算子自伴的充分必要条件.     

二项自伴向量微分算子的本质谱

首先利用算子比较的方法,研究了二项自伴向量微分算子的本质谱,得到了这类微分算子的本质谱分布范围;然后利用算子分解定理,得到了这类算子谱的离散性的一个充分条件;最后得到了Sturm-Liouville算子和Schr?dinger算子的本质谱范围,以及这两类算子谱的离散性的一个充分条件.     

Singular Values of Compact Pseudodifferential Operators

This paper investigates the asymptotic decay of the singular values of compact operators arising from the Weyl correspondence. The motivating problem is to find sufficient conditions on a symbol which ensure that the corresponding operator has singular values with a prescribed rate of decay. The problem is approached by using a Gabor frame expansion of the symbol to construct an approximating finite rank operator. This establishes a variety of sufficient conditions for the associated operator to be in a particular Schatten class. In particular, an improvement of a sufficient condition of Daubechies for an operator to be trace-class is obtained. In addition, a new development and improvement of the Calderón–Vaillancourt theorem in the context of the Weyl correspondence is given. Additional results of this type are then obtained by interpolation.     

Congruence of selfadjoint operators

Given a bounded selfadjoint operator a in a Hilbert space , the aim of this paper is to study the orbit of a, i.e., the set of operators which are congruent to a. We establish some necessary and sufficient conditions for an operator to be in the orbit of a. Also, the orbit of a selfadjoint operator with closed range is provided with a structure of differential manifold.      

About the Limit Spectra of Some Unbounded Selfadjoint Integral Operators

Siberian Mathematical Journal - We establish sufficient conditions for the zero to belong to the limit spectra of some unbounded selfadjoint integral operator.     

亚超循环算子与可逆算子的亚超循环性

设X为无限维可分的Banach空间,T是X上的有界线性算子.利用轨道C·Orb(x,T)的d稠密性给出了T是亚超循环算子的充分条件.此外,还考虑可逆的亚超循环算子T并从循环向量的角度刻画了T和T~(-1)的亚超循环性.     

多圆盘Bergman空间上Toeplitz算子的乘积和交换性

该文给出了多圆盘Bergman空间上两个带有某种符号的Toeplitz算子的乘积等于另一个Toeplitz算子的充分必要条件,并且给出了乘积算子所带符号的公式.接下来,相应的研究了它的交换性.这些研究结果都是根据符号函数的Mellin变换.     

A Blaschke-type condition for analytic functions on finitely connected domains. Applications to complex perturbations of a finite-band selfadjoint operator

This is a sequel of the article by Borichev, Golinskii and Kupin (2009) [1], where the authors obtain Blaschke-type conditions for special classes of analytic functions in the unit disk, which satisfy certain growth hypotheses. These results were applied to get Lieb–Thirring inequalities for complex compact perturbations of a selfadjoint operator with a simply connected resolvent set. The first result of the present paper is an appropriate local version of the Blaschke-type condition from Borichev et al. (2009) [1]. We apply it to obtain a similar condition for an analytic function in a finitely connected domain of a special type. Such condition is by and large the same as a Lieb–Thirring type inequality for complex compact perturbations of a selfadjoint operator with a finite-band spectrum. A particular case of this result is the Lieb–Thirring inequality for a selfadjoint perturbation of the Schatten class of a periodic (or finite-band) Jacobi matrix.     

B~α空间和Q_K空间之间的加权Cesro算子

讨论了B~α空间和Q_K空间之间的加权Cesro算子T_g的有界性,给出了B~α空间到Q_K空间的加权Cesro算子T_g有界的充要条件.另外也给出了Q_K空间到B~α空间的加权Cesro算子T_g有界的充要条件.     

On the Similarity of Perturbed Multiplication Operators

Let S be the multiplication operator by an independent variable x in L ₂(0,1), and let V be an integral operator of Volterra type. In this note, we find sufficient conditions for the similarity of the operators T := S + V and S and discuss some generalizations to an abstract setting of the results obtained.     

BMOA空间与Bloch型空间之间的加权Ces\''{a}ro算子

本文研究单位圆盘上的BMOA空间和$\a$-Bloch型空间之间的加权 Ces\'{a}ro 算子,给出了$\tg$是BMOA空间到$\ba$空间的有界算子或紧算子的充分必要条件.     

Positive Schatten(-Herz) Class Toeplitz Operators on the Half-space

On the harmonic Bergman space of the half-space, we give characterizations for an arbitrary positive Toeplitz operator to be a Schatten (or Schatten-Herz) class operator in terms of averaging functions and Berezin transforms. Examples are provided to show that various results are sharp. This research was supported by KOSEF(R01-2003-000-10243-0).