Compositions of operator ideals and their regular hulls
F. Oertel (1995)
Acta Universitatis Carolinae. Mathematica et Physica
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F. Oertel (1995)
Acta Universitatis Carolinae. Mathematica et Physica
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Ehrhard Behrends, Peter Harmand (1985)
Studia Mathematica
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Raphaël Carroy, Yann Pequignot (2014)
Fundamenta Mathematicae
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On the one hand, the ideals of a well quasi-order (wqo) naturally form a compact topological space into which the wqo embeds. On the other hand, Nash-Williams' barriers are given a uniform structure by embedding them into the Cantor space. We prove that every map from a barrier into a wqo restricts on a barrier to a uniformly continuous map, and therefore extends to a continuous map from a countable closed subset of the Cantor space into the space of ideals of the...
F. Oertel (1998)
Czechoslovak Mathematical Journal
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In addition to Pisier’s counterexample of a non-accessible maximal Banach ideal, we will give a large class of maximal Banach ideals which are accessible. The first step is implied by the observation that a “good behaviour” of trace duality, which is canonically induced by conjugate operator ideals can be extended to adjoint Banach ideals, if and only if these adjoint ideals satisfy an accessibility condition (theorem 3.1). This observation leads in a natural way to a characterization...
F. Oertel (1996)
Acta Universitatis Carolinae. Mathematica et Physica
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Víctor M. Sánchez (2017)
Open Mathematics
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There are just a few general criteria on spaceability. This survey paper is the history of one of the first ones. Let I1 and I2 be arbitrary operator ideals and E and F be Banach spaces. The spaceability of the set of operators I1(E, F) I2(E, F) is studied. Before stating the criterium, the paper summarizes the main results about lineability and spaceability of differences between particular operator ideals obtained in recent years. They are the seed of the ideas contained in the general...
L. Waelbroeck (1983)
Studia Mathematica
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