Upper triangular operator matrices and limit points of the essential spectrum

• Karmouni, Mohammed ^[1] ; Tajmouati, A. ^[2] ; A. El Bakkali, A. ^[3]
  1. [1] Cadi Ayyad University

     Cadi Ayyad University

     Marrakech-Medina, Marruecos

     
  2. [2] Sidi Mohamed Ben Abdellah University

     Sidi Mohamed Ben Abdellah University

     Fes-Medina, Marruecos

     
  3. [3] Université Chouaib Doukkali

     Université Chouaib Doukkali

     Marruecos

     

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• Localización: Proyecciones: Journal of Mathematics, ISSN 0716-0917, ISSN-e 0717-6279, Vol. 38, Nº. 3, 2019, págs. 401-409
• Idioma: inglés
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  • In this paper, we investigate the limit points set of essential spectrum of upper triangular operator matrices 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.