English

Building highly conditional quasi-greedy bases in classical Banach spaces

Functional Analysis 2017-12-13 v1

Abstract

It is known that for a conditional quasi-greedy basis B\mathcal{B} in a Banach space X\mathbb{X}, the associated sequence (km[B])m=1(k_{m}[\mathcal{B}])_{m=1}^{\infty} of its conditionality constants verifies the estimate km[B]=O(logm)k_{m}[\mathcal{B}]=\mathcal{O}(\log m) and that if the reverse inequality logm=O(km[B])\log m =\mathcal{O}(k_m[\mathcal{B}]) holds then X\mathbb{X} is non-superreflexive. However, in the existing literature one finds very few instances of non-superreflexive spaces possessing quasi-greedy basis with conditionality constants as large as possible. Our goal in this article is to fill this gap. To that end we enhance and exploit a combination of techniques developed independently, on the one hand by Garrig\'os and Wojtaszczyk in [Conditional quasi-greedy bases in Hilbert and Banach spaces, Indiana Univ. Math. J. 63 (2014), no. 4, 1017-1036] and, on the other hand, by Dilworth et al. in [On the existence of almost greedy bases in Banach spaces, Studia Math. 159 (2003), no. 1, 67-101], and craft a wealth of new examples of non-superreflexive classical Banach spaces having quasi-greedy bases B\mathcal{B} with km[B]=O(logm)k_{m}[\mathcal{B}]=\mathcal{O}(\log m).

Keywords

Cite

@article{arxiv.1712.04004,
  title  = {Building highly conditional quasi-greedy bases in classical Banach spaces},
  author = {Fernando Albiac and José L. Ansorena},
  journal= {arXiv preprint arXiv:1712.04004},
  year   = {2017}
}