Rational values of the weak saturation limit

Fuente: arXiv
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Auteurs principaux: Ascoli, Ruben, He, Xiaoyu
Format: Preprint
Publié: 2025
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author Ascoli, Ruben
He, Xiaoyu
author_facet Ascoli, Ruben
He, Xiaoyu
contents Given a graph $F$, a graph $G$ is weakly $F$-saturated if all non-edges of $G$ can be added in some order so that each new edge introduces a copy of $F$. The weak saturation number $\operatorname{wsat}(n, F)$ is the minimum number of edges in a weakly $F$-saturated graph on $n$ vertices. Bollobás initiated the study of weak saturation in 1968 to study percolation processes, which originated in biology and have applications in physics and computer science. It was shown by Alon that for each $F$, there is a constant $w_F$ such that $\operatorname{wsat}(n, F) = w_Fn + o(n)$. We characterize all possible rational values of $w_F$, proving in particular that $w_F$ can equal any rational number at least $\frac 32$.
format Preprint
id arxiv_https___arxiv_org_abs_2501_15686
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Rational values of the weak saturation limit
Ascoli, Ruben
He, Xiaoyu
Combinatorics
05C35
Given a graph $F$, a graph $G$ is weakly $F$-saturated if all non-edges of $G$ can be added in some order so that each new edge introduces a copy of $F$. The weak saturation number $\operatorname{wsat}(n, F)$ is the minimum number of edges in a weakly $F$-saturated graph on $n$ vertices. Bollobás initiated the study of weak saturation in 1968 to study percolation processes, which originated in biology and have applications in physics and computer science. It was shown by Alon that for each $F$, there is a constant $w_F$ such that $\operatorname{wsat}(n, F) = w_Fn + o(n)$. We characterize all possible rational values of $w_F$, proving in particular that $w_F$ can equal any rational number at least $\frac 32$.
title Rational values of the weak saturation limit
topic Combinatorics
05C35
url https://arxiv.org/abs/2501.15686