Originally Published In
Concrete Operators. Volume 3, Issue 1, Pages 77–84, ISSN (Online) 2299-3282, DOI: 10.1515/conop-2016-0009, May 2016
Operators on function spaces of form Cɸf = f ∘ ɸ, where ɸ is a fixed map are called composition operators with symbol ɸ. We study such operators acting on the Hilbert Hardy space over the right half-plane and characterize the situations when they are invertible, Fredholm, unitary, and Hermitian. We determine the normal composition operators with inner, respectively with Möbius symbol. In select cases, we calculate their spectra, essential spectra, and numerical ranges.
Richter, Stefan and Wick, Brett D., "A remark on the multipliers on spaces of Weak Products of functions" (2016). Mathematics Faculty Publications. 33.