Session 36. Topology in Functional Analysis

Unconditional bases in Banach spaces and Tukey ordering

Grzegorz Plebanek,  Uniwersytet Wrocławski, Poland
The talk is based on the joint work with Antonio Avilés and José Rodrígez
Let \(B=(e_n)_n\) be an unconditional basic sequence in a Banach space \(X\) and let \(\mathcal{N}(B)\) be a family of those sets \(A\subseteq{\mathbb N}\) for which \((e_n)_{n\in A}\) is a weakly null subsequence. One can examine properties of \(B=(e_n)_n\) by looking at the cofinal structure of the ideal \(\mathcal{N}(B)\).

We present a certain classification of bases in Banach spaces using Tukey reductions between partially ordered sets of the form \(\mathcal{N}(B)\).

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