The paper examines the Infante-Webb spectrum within the framework of nonlinear block operator matrices, focusing on the relationship between the spectra of 3 × 3 matrices and their constituent ...

AbstractLet M C =( A C 0 B )∈B(χ⊕χ) be an upper triangulat Banach space operator. The relationship between the spectra of 𝑀𝐶 and 𝑀₀, and their various distinguished parts, has been studied by a ...