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Journal of Operator Theory

Volume 35, Issue 1, Winter 1996  pp. 191-201.

On the stability of semi-Fredholm operators

Authors Mostafa Mbekhta
Author institution: Universite des Sciences et Technologies de Lille, U.R.A. D 751 CNRS “GAT”, U.F.R. de Mathematiques, F-59655 Villeneuve d’Ascq Cedex, FRANCE and Universite de Galatasaray, Ciragan cad no. 102, Ortakoy, 80840 Istanbul, TURQUIE

Summary:  We give some stability results for the “nullity” and “deficiency” of semi-Fredholm operators. We also give characterizations of the operators that are bounded from below (resp. surjective) in terms of the stability of the “nullity” (resp. the “deficiency”), as well as a generalization of the “punctured neighbourhood theorem”.

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