@article{article_701108, title={$S$-spectra and $S$-essential pseudospectra of the diagonal block operator matrices}, journal={Hacettepe Journal of Mathematics and Statistics}, volume={50}, pages={433–443}, year={2021}, DOI={10.15672/hujms.701108}, author={Ipek Al, Pembe and İsmailov, Zameddin}, keywords={$ S$-spectrum, $ \epsilon$-$S$-essential pseudospectrum, $ S$-spectral radius, $ \epsilon$-$S$-essential pseudospectral radius}, abstract={In this article, the relationships between the $S$-spectra, the $ S$-spectral radius, the $ \epsilon$-$S$-essential pseudospectra, and the $ \epsilon$-$S$-essential pseudospectral radius of the diagonal block operator matrices in the direct sum of Banach spaces and their block coordinate operators are studied. Then, the results are supported by applications.}, number={2}, publisher={Hacettepe University}