The Euclidean MST-ratio for Bi-colored Lattices

Fuente: arXiv
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Main Authors: di Montesano, Sebastiano Cultrera, Draganov, Ondřej, Edelsbrunner, Herbert, Saghafian, Morteza
Format: Preprint
Published: 2024
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_version_ 1866910671812165632
author di Montesano, Sebastiano Cultrera
Draganov, Ondřej
Edelsbrunner, Herbert
Saghafian, Morteza
author_facet di Montesano, Sebastiano Cultrera
Draganov, Ondřej
Edelsbrunner, Herbert
Saghafian, Morteza
contents Given a finite set, $A \subseteq \mathbb{R}^2$, and a subset, $B \subseteq A$, the \emph{MST-ratio} is the combined length of the minimum spanning trees of $B$ and $A \setminus B$ divided by the length of the minimum spanning tree of $A$. The question of the supremum, over all sets $A$, of the maximum, over all subsets $B$, is related to the Steiner ratio, and we prove this sup-max is between $2.154$ and $2.427$. Restricting ourselves to $2$-dimensional lattices, we prove that the sup-max is $2.0$, while the inf-max is $1.25$. By some margin the most difficult of these results is the upper bound for the inf-max, which we prove by showing that the hexagonal lattice cannot have MST-ratio larger than $1.25$.
format Preprint
id arxiv_https___arxiv_org_abs_2403_10204
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The Euclidean MST-ratio for Bi-colored Lattices
di Montesano, Sebastiano Cultrera
Draganov, Ondřej
Edelsbrunner, Herbert
Saghafian, Morteza
Computational Geometry
Combinatorics
52C05, 05C10
G.2
Given a finite set, $A \subseteq \mathbb{R}^2$, and a subset, $B \subseteq A$, the \emph{MST-ratio} is the combined length of the minimum spanning trees of $B$ and $A \setminus B$ divided by the length of the minimum spanning tree of $A$. The question of the supremum, over all sets $A$, of the maximum, over all subsets $B$, is related to the Steiner ratio, and we prove this sup-max is between $2.154$ and $2.427$. Restricting ourselves to $2$-dimensional lattices, we prove that the sup-max is $2.0$, while the inf-max is $1.25$. By some margin the most difficult of these results is the upper bound for the inf-max, which we prove by showing that the hexagonal lattice cannot have MST-ratio larger than $1.25$.
title The Euclidean MST-ratio for Bi-colored Lattices
topic Computational Geometry
Combinatorics
52C05, 05C10
G.2
url https://arxiv.org/abs/2403.10204