Acta mathematica scientia,Series B ›› 2024, Vol. 44 ›› Issue (6): 2225-2248.doi: 10.1007/s10473-024-0610-4

Previous Articles     Next Articles

MULTIPLICATION OPERATORS ON WEIGHTED DIRICHLET SPACES

Kaikai HAN1,†, Yucheng LI2, Maofa WANG3   

  1. 1. School of Statistics and Mathematics, Hebei University of Economics and Business, Shijiazhuang 050061, China;
    2. School of Mathematical Sciences, Hebei Normal University, Shijiazhuang 050024, China;
    3. School of Mathematics and Statistics, Wuhan University, Wuhan 430072, China
  • Received:2023-08-15 Published:2024-12-06
  • Contact: † Kaikai HAN, E-mail: kkhan.math@whu.edu.cn
  • About author:Yucheng LI, E-mail: liyucheng@hebtu.edu.cn; Maofa WANG, E-mail: mfwang.math@whu.edu.cn
  • Supported by:
    National Natural Science Foundation of China (12101179, 12171138, 12171373) and the Natural Science Foundation of Hebei Province of China (A2022207001).

Abstract: In this paper, we study multiplication operators on weighted Dirichlet spaces $\mathcal{D}_{\beta}$ $(\beta\in \mathbb{R})$. Let $n$ be a positive integer and $\beta\in \mathbb{R}$, we show that the multiplication operator $M_{z^{n}}$ on $\mathcal{D}_{\beta}$ is similar to the operator $\oplus_{1}^{n}M_{z}$ on the space $\oplus_{1}^{n}\mathcal{D}_{\beta}$. Moreover, we prove that $M_{z^{n}}$ $(n\geq 2)$ on $\mathcal{D}_{\beta}$ is unitarily equivalent to $\oplus_{1}^{n}M_{z}$ on $\oplus_{1}^{n}\mathcal{D}_{\beta}$ if and only if $\beta=0$. In addition, we completely characterize the unitary equivalence of the restrictions of $M_{z^{n}}$ to different invariant subspaces $z^{k}\mathcal{D}_{\beta}$ $(k\geq 1)$, and the unitary equivalence of the restrictions of $M_{z^{n}}$ to different invariant subspaces $S_{j}$ $(0\leq j<n)$.
Abkar, Cao and Zhu [Complex Anal Oper Theory, 2020, 14: Art 58] pointed out that it is an important, natural, and difficult question in operator theory to identify the commutant of a bounded linear operator. They characterized the commutant $\mathcal{A}'(M_{z^{n}})$ of $M_{z^{n}}$ on a family of analytic function spaces $A_{\alpha}^{2}$ $(\alpha\in \mathbb{R})$ on $\mathbb{D}$ (in fact, the family of spaces $A_{\alpha}^{2}$ $(\alpha\in \mathbb{R})$ is the same with the family of spaces $\mathcal{D}_{\beta}$ $(\beta\in \mathbb{R})$) in terms of the multiplier algebra of the underlying function spaces. In this paper, we give a new characterization of the commutant $\mathcal{A}'(M_{z^{n}})$ of $M_{z^{n}}$ on $\mathcal{D}_{\beta}$, and characterize the self-adjoint operators and unitary operators in $\mathcal{A}'(M_{z^{n}})$. We find that the class of self-adjoint operators (unitary operators) in $\mathcal{A}'(M_{z^{n}})$ when $\beta \neq 0$ is different from the class of self-adjoint operators (unitary operators) in $\mathcal{A}'(M_{z^{n}})$ when $\beta =0$.

Key words: multiplication operator, weighted Dirichlet space, similarity, unitary equivalence, commutant

CLC Number: 

  • 47B35
Trendmd