49 research outputs found

    Unconditionality in tensor products and ideals of polynomials, multilinear forms and operators

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    We study tensor norms that destroy unconditionality in the following sense: for every Banach space EE with unconditional basis, the nn-fold tensor product of EE (with the corresponding tensor norm) does not have unconditional basis. We establish an easy criterion to check weather a tensor norm destroys unconditionality or not. Using this test we get that all injective and projective tensor norms different from ε\varepsilon and π\pi destroy unconditionality, both in full and symmetric tensor products. We present applications to polynomial ideals: we show that many usual polynomial ideals never enjoy the Gordon-Lewis property. We also consider the unconditionality of the monomial basic sequence. Analogous problems for multilinear and operator ideals are addressed.Comment: 23 page

    Extending polynomials in maximal and minimal ideals

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    Given an homogeneous polynomial on a Banach space EE belonging to some maximal or minimal polynomial ideal, we consider its iterated extension to an ultrapower of EE and prove that this extension remains in the ideal and has the same ideal norm. As a consequence, we show that the Aron-Berner extension is a well defined isometry for any maximal or minimal ideal of homogeneous polynomials. This allow us to obtain symmetric versions of some basic results of the metric theory of tensor products.Comment: 13 page

    The symmetric Radon-Nikodým property for tensor norms

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    We introduce the symmetric-Radon-Nikodým property (sRN pr operty) for finitely generated s-tensor norms β of order n and prove a Lewis type theorem for s-tensor norms with this property. As a consequence, if β is a projective s-tensor norm with the sRN prop- erty, then for every Asplund space E , the canonical map e ⊗ n,s β E ′ → e ⊗ n,s β ′ E ′ is a metric surjection. This can be rephrased as the isometric isomorph ism Q min ( E ) = Q ( E ) for certain polynomial ideal Q . We also relate the sRN property of an s-tensor norm with the A splund or Radon-Nikodým properties of different tensor products. S imilar results for full tensor products are also given. As an application, results concern ing the ideal of n -homogeneous extendible polynomials are obtained, as well as a new proof o f the well known isometric isomorphism between nuclear and integral polynomials on As plund spaces.Fil: Carando, Daniel Germán. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Galicer, Daniel Eric. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; Argentin
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