Spectral properties for polynomial and matrix operators involving demicompactness classes
- Autores: Fatma Ben Brahim
- Localización: Extracta mathematicae, ISSN-e 0213-8743, Vol. 33, Nº 1, 2018, págs. 11-32
- Idioma: inglés
- Enlaces
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Resumen
The first aim of this paper is to show that a polynomially demicompact operator satisfying certain conditions is demicompact. Furthermore, we give a refinement of the Schmo¨eger and the Rakocevi´c essential spectra of a closed linear operator involving the class of demicompact ones. The second aim of this work is devoted to provide some sufficient conditions on the inputs of a closable block operator matrix to ensure the demicompactness of its closure. An example involving the Caputo derivative of fractional of order α is provided.
Moreover, a study of the essential spectra and an investigation of some perturbation results
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