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On commuting approximation properties of Banach spaces

Published online by Cambridge University Press:  26 May 2009

Eve Oja
Affiliation:
Faculty of Mathematics and Computer Science, Tartu University, J. Liivi 2, 50409 Tartu, Estonia ([email protected]; [email protected])
Indrek Zolk
Affiliation:
Faculty of Mathematics and Computer Science, Tartu University, J. Liivi 2, 50409 Tartu, Estonia ([email protected]; [email protected])

Abstract

Let a, c ≥ 0 and let B be a compact set of scalars. We show that if X is a Banach space such that the canonical projection π from X*** onto X* satisfies the inequality

and 1 ≤ λ < max |B| + c, then every λ-commuting bounded compact approximation of the identity of X is shrinking. This generalizes a theorem by Godefroy and Saphar from 1988. As an application, we show that under the conditions described above both X and X* have the metric compact approximation property (MCAP). Relying on the Willis construction, we show that the commuting MCAP does not imply the approximation property.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 2009

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