Local spectral theory of endomorphisms of the disk algebra

Abstract

Let A(𝔻) denote the disk algebra. Every endomorphism of A(𝔻) is induced by some ϕ ∈ A(𝔻) with ‖ϕ‖ ≤ 1. In this paper, it is shown that if ϕ is not an automorphism of 𝔻 and ϕ has a fixed point in the open unit disk then the endomorphism induced by ϕ is decomposable if and only if the fixed set of ϕ is singleton. Further, we determine the local spectra of the endomorphism induced by ϕ in the cases when the fixed set of ϕ either includes unit circle or is a singleton.

Keywords

• composition operator
• decomposability and super-decomposability
• endomorphism
• local spectrum
• Single Valued Extension Property
• 47A10
• 47B33
• 47B40