On metric characterizations of tree and fragmentability indices of Banach spaces

Fuente: arXiv
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Autores principales: Basset, Estelle, Lancien, Gilles, Procházka, Antonin
Formato: Preprint
Publicado: 2026
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author Basset, Estelle
Lancien, Gilles
Procházka, Antonin
author_facet Basset, Estelle
Lancien, Gilles
Procházka, Antonin
contents We introduce two ordinal indices that are linear invariants for Banach spaces: the dyadic tree index and the sprawling tree index. We show that they are also bi-Lipschitz invariants. In fact, we characterize their values in terms of sub-Lipschitz embeddability of dyadic or countably branching diamond graphs of ordinal height. We derive applications for separable Banach spaces that are universal for complete countable metric spaces and bi-Lipschitz embeddings. We also discuss the links of these tree indices with classical fragmentability indices of Banach spaces such as the dentabilty, weak fragmentability and Szlenk indices.
format Preprint
id arxiv_https___arxiv_org_abs_2605_28311
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On metric characterizations of tree and fragmentability indices of Banach spaces
Basset, Estelle
Lancien, Gilles
Procházka, Antonin
Functional Analysis
Metric Geometry
46B85, 46B80, 46B20, 46B22, 51F30, 30L05
We introduce two ordinal indices that are linear invariants for Banach spaces: the dyadic tree index and the sprawling tree index. We show that they are also bi-Lipschitz invariants. In fact, we characterize their values in terms of sub-Lipschitz embeddability of dyadic or countably branching diamond graphs of ordinal height. We derive applications for separable Banach spaces that are universal for complete countable metric spaces and bi-Lipschitz embeddings. We also discuss the links of these tree indices with classical fragmentability indices of Banach spaces such as the dentabilty, weak fragmentability and Szlenk indices.
title On metric characterizations of tree and fragmentability indices of Banach spaces
topic Functional Analysis
Metric Geometry
46B85, 46B80, 46B20, 46B22, 51F30, 30L05
url https://arxiv.org/abs/2605.28311