arXiv subjects
Publications and source records attributed to Eungil Ko.
This paper focuses on the binormality of block Toeplitz operators with matrix valued circulant symbols. We also study some {\Gamma}-dilations of Toeplitz operators. Moreover, we also analyze the invariant subspace of Toeplitz operators with matrix-valued symbols.
In this paper, we study complex symmetry of Toeplitz operators and block Toeplitz operators. In particular, we give a characterization of complex symmetric block Toeplitz operators with the special conjugation on the vector-valued Hardy space $H_{{\mathbb C}^2}^2$. As some applications, we provide examples of such operators.
This paper is a sequel to [6]. In that paper we transferred the discussions in [1] and [13] concerning almost invariant half-spaces for operators on complex Banach spaces to the context of operators on Hilbert space, and we gave easier proofs of the main results in [1] and [13]. In the present paper we discuss consequences of the above-mentioned results for the matricial structure of operators on Hilbert space.
We completely characterize the spectrum of a weighted composition operator $W_{ψ, φ}$ on $H^{2}(\mathbb{D})$ when $φ$ has Denjoy-Wolff point $a$ with $0<|φ'(a)|< 1$, the iterates, $φ_{n}$, converge uniformly to $a$, and $ψ$ is in $H^{\infty}(\mathbb{D})$ and continuous at $a$. We also give bounds and some computations when $|a|=1$ and $φ'(a)=1$ and, in addition, show that these symbols include all linear fractional $φ$ that are hyperbolic and parabolic non-automorphisms. Finally, we use these results to eliminate possible weights $ψ$ so that $W_{ψ, φ}$ is seminormal.