Hyponormality of Toeplitz Operators on the Dirichlet Space

Abstract:

      In this paper, we prove that the necessary and sufficient condition for a Toeplitz operator $T_u$ 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.