On the essential spectrum of $λ$-Toeplitz operators over compact Abelian groups

Abstract: In the paper by Mark C. Ho (2014) the notion of a $\lambda$-Toeplitz operator on the Hardy space $H^2(\mathbb{T})$ over the one-dimensional torus $\mathbb{T}$ was introduced and it was shown (under the supplementary condition) that for $\lambda\in \mathbb{T}$ the essential spectrum of such an operator is invariant with respect to the rotation $z\mapsto \lambda z$; if in addition $\lambda$ is not of finite order the essential spectrum is circular. In this paper, we generalize these results to the case when $\mathbb{T}$ is replaced by an arbitrary compact Abelian group whose dual is totally ordered.