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On the number of permutatively inequivalent basic sequences in a Banach space
Authors:Valentin Ferenczi
Institution:Equipe d'Analyse Fonctionnelle, Université Pierre et Marie Curie - Paris 6, Boîte 186, 4, Place Jussieu, 75252, Paris cedex 05, France
Abstract:Let X be a Banach space with a Schauder basis (en)nN. The relation E0 is Borel reducible to permutative equivalence between normalized block-sequences of (en)nN or X is c0 or ?p saturated for some 1?p<+∞. If (en)nN is shrinking unconditional then either it is equivalent to the canonical basis of c0 or ?p, 1<p<+∞, or the relation E0 is Borel reducible to permutative equivalence between sequences of normalized disjoint blocks of X or of X. If (en)nN is unconditional, then either X is isomorphic to ?2, or X contains ω2 subspaces or ω2 quotients which are spanned by pairwise permutatively inequivalent normalized unconditional bases.
Keywords:Borel reducibility  Permutative equivalence  Block basis  Homogeneous space  Dichotomy
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