Supersaturation via edge-gluing

Fuente: arXiv
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Main Authors: Jin, Zihao, Longbrake, Sean, Yepremyan, Liana
Format: Preprint
Published: 2025
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author Jin, Zihao
Longbrake, Sean
Yepremyan, Liana
author_facet Jin, Zihao
Longbrake, Sean
Yepremyan, Liana
contents In 1984, Erdős and Simonovits conjectured the following: given a bipartite graph $H$, there exist constants $β, C > 0$ such that any graph $G$ on $n$ vertices and $pn^2\geq C \mathrm{ex}(n, H)$ edges contains at least $βn^{\mathrm{v}(H)} p^{\mathrm{e}(H)}$ copies of $H$. We show that edge-gluing preserves the satisfiability of this conjecture under some mild symmetry conditions. Namely, if two graphs $H_1$ and $H_2$ satisfy this conjecture, and if furthermore, gluing them along a fixed edge produces a unique graph then the resulting graph satisfies the conjecture as well. In the same paper, Erdős and Simonovits conjectured a weaker statement: for every $H$, there is some $α, β, C > 0$ such that any graph $G$ on $n$ vertices and $pn^2\geq C n^{1+ α}$ edges contains at least $βn^{\mathrm{v}(H)} p^{\mathrm{e}(H)}$ copies of $H$. We show that if $H$ satisfies this conjecture then by gluing several copies of labeled $H$ along the same copy of a subforest of $H$ produces a graph that also satisfies the conjecture.
format Preprint
id arxiv_https___arxiv_org_abs_2507_16804
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Supersaturation via edge-gluing
Jin, Zihao
Longbrake, Sean
Yepremyan, Liana
Combinatorics
05C35
In 1984, Erdős and Simonovits conjectured the following: given a bipartite graph $H$, there exist constants $β, C > 0$ such that any graph $G$ on $n$ vertices and $pn^2\geq C \mathrm{ex}(n, H)$ edges contains at least $βn^{\mathrm{v}(H)} p^{\mathrm{e}(H)}$ copies of $H$. We show that edge-gluing preserves the satisfiability of this conjecture under some mild symmetry conditions. Namely, if two graphs $H_1$ and $H_2$ satisfy this conjecture, and if furthermore, gluing them along a fixed edge produces a unique graph then the resulting graph satisfies the conjecture as well. In the same paper, Erdős and Simonovits conjectured a weaker statement: for every $H$, there is some $α, β, C > 0$ such that any graph $G$ on $n$ vertices and $pn^2\geq C n^{1+ α}$ edges contains at least $βn^{\mathrm{v}(H)} p^{\mathrm{e}(H)}$ copies of $H$. We show that if $H$ satisfies this conjecture then by gluing several copies of labeled $H$ along the same copy of a subforest of $H$ produces a graph that also satisfies the conjecture.
title Supersaturation via edge-gluing
topic Combinatorics
05C35
url https://arxiv.org/abs/2507.16804