Magnitude and diversity of trees

Fuente: arXiv
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Main Author: Bouafia, Philippe
Format: Preprint
Published: 2026
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author Bouafia, Philippe
author_facet Bouafia, Philippe
contents We compute the magnitude (an isometric invariant of metric spaces) of compact $\mathbb{R}$-trees and show that it equals $1 + L/2$, where $L \in [0, \infty]$ denotes the total length. Although length is the only geometric invariant captured by magnitude, we show that diversity-maximizing measures on compact $\mathbb{R}$-trees are more sensitive to the branching structure as they tend to be more concentrated toward the leaves: their support contains no branch points. In the finite case, we further show that maximum diversity on a weighted tree can be computed in polynomial time.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03681
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Magnitude and diversity of trees
Bouafia, Philippe
Metric Geometry
51F99, 30L99, 05C05
We compute the magnitude (an isometric invariant of metric spaces) of compact $\mathbb{R}$-trees and show that it equals $1 + L/2$, where $L \in [0, \infty]$ denotes the total length. Although length is the only geometric invariant captured by magnitude, we show that diversity-maximizing measures on compact $\mathbb{R}$-trees are more sensitive to the branching structure as they tend to be more concentrated toward the leaves: their support contains no branch points. In the finite case, we further show that maximum diversity on a weighted tree can be computed in polynomial time.
title Magnitude and diversity of trees
topic Metric Geometry
51F99, 30L99, 05C05
url https://arxiv.org/abs/2605.03681