@article{Karmouni_Tajmouati_A. El Bakkali_2019, title={Upper triangular operator matrices and limit points of the essential spectrum}, volume={38}, url={https://www.revistaproyecciones.cl/index.php/proyecciones/article/view/3691}, DOI={10.22199/issn.0717-6279-2019-03-0026}, abstractNote={In this paper, we investigate the limit points set of essential spectrum of upper triangular operator matrices <p><img src="/public/site/images/rvidal/art25proy.png"></p> We prove that accσe(MC) ∪ W = accσe(A) ∪ accσe(B) where W is the union of certain holes in accσe(MC), which happen to be subsets of accσe(B) ∩ accσe(A). Also, several sufficient conditions for accσe(MC) = accσe(A) ∪ accσe(B) holds are given.}, number={3}, journal={Proyecciones (Antofagasta, On line)}, author={Karmouni, Mohammed and Tajmouati, A. and A. El Bakkali, A.}, year={2019}, month={Aug.}, pages={401-409} }