Erdős's diameter conjecture for separated distances fails in high dimensions

Fuente: arXiv
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Main Author: Ho, Boon Suan
Format: Preprint
Published: 2026
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author Ho, Boon Suan
author_facet Ho, Boon Suan
contents Erdős asked whether every $n$-point set in Euclidean space whose $\binom{n}{2}$ pairwise distances are mutually at least $1$ apart must have diameter at least $(1+o(1))n^2$. We disprove this statement by constructing for every prime power $q$ a set $\mathcal X_q\subset \mathbb R^{q^2+q}$ of $n=q+1$ points such that all pairwise distances in $\mathcal X_q$ are mutually at least $1$ apart, while $$\operatorname{diam}(\mathcal X_q)\le\Bigl(1-\frac{1}{π^2}+o(1)\Bigr)n^2.$$ The proof is fully formalized in Lean 4.
format Preprint
id arxiv_https___arxiv_org_abs_2604_15305
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Erdős's diameter conjecture for separated distances fails in high dimensions
Ho, Boon Suan
Combinatorics
Metric Geometry
52C10
Erdős asked whether every $n$-point set in Euclidean space whose $\binom{n}{2}$ pairwise distances are mutually at least $1$ apart must have diameter at least $(1+o(1))n^2$. We disprove this statement by constructing for every prime power $q$ a set $\mathcal X_q\subset \mathbb R^{q^2+q}$ of $n=q+1$ points such that all pairwise distances in $\mathcal X_q$ are mutually at least $1$ apart, while $$\operatorname{diam}(\mathcal X_q)\le\Bigl(1-\frac{1}{π^2}+o(1)\Bigr)n^2.$$ The proof is fully formalized in Lean 4.
title Erdős's diameter conjecture for separated distances fails in high dimensions
topic Combinatorics
Metric Geometry
52C10
url https://arxiv.org/abs/2604.15305