Some topological properties of stable norms.
J. Bastero Eleizalde, J. M. Mira Ros (1987)
Extracta Mathematicae
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Displaying similar documents to “Gap and perturbation of non-semi-Fredholm operators.”
Some topological properties of stable norms.
A generalization of semi-Fredholm operators.
Manuel González, Antonio Martinón (1990)
Extracta Mathematicae
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Quotients and interpolation spaces of stable Banach spaces
J. Bastero, Y. Raynaud (1989)
Studia Mathematica
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Operational quantities derived from the norm and generalized Fredholm theory
Manuel Gonzalez, Antonio Martinón (1991)
Commentationes Mathematicae Universitatis Carolinae
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We introduce and study some operational quantities associated to a space ideal . These quantities are used to define generalized semi-Fredholm operators associated to , and the corresponding perturbation classes which extend the strictly singular and strictly cosingular operators, and we study the generalized Fredholm theory obtained in this way. Finally we present some examples and show that the classes of generalized semi-Fredholm operators are non-trivial for several classical space...
Unconditionally converging operators and Fredholm theory
Manuel González Ruiz, Víctor M. Onieva Aleixandre (1988)
Extracta Mathematicae
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A fixed point theorem for a class of differentiable stable operators in Banach spaces.
Azhmyakov, Vadim (2006)
Fixed Point Theory and Applications [electronic only]
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Selecting basic sequences in φ-stable Banach spaces
Tadeusz Figiel, Ryszard Frankiewicz, Ryszard A. Komorowski, Czesław Ryll-Nardzewski (2003)
Studia Mathematica
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In this paper we make use of a new concept of φ-stability for Banach spaces, where φ is a function. If a Banach space X and the function φ satisfy some natural conditions, then X is saturated with subspaces that are φ-stable (cf. Lemma 2.1 and Corollary 7.8). In a φ-stable Banach space one can easily construct basic sequences which have a property P(φ) defined in terms of φ (cf. Theorem 4.5). This leads us, for appropriate functions φ, to new results on the existence...
Operational quantities derived from the norm and generalized Fredholm theory.
Manuel González, Antonio Martinón (1991)
Extracta Mathematicae
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Several operational quantities, defined in terms of the norm and the class of finite dimensional Banach spaces, have been used to characterize the classes of upper and lower semi-Fredholm operators, strictly singular and strictly cosingular operators, and to derive some perturbation results. In this paper we shall introduce and study some operational quantities derived from the norm and associated to a space ideal. By means of these quantities we construct a generalized...