English

Supersaturation via edge-gluing

Combinatorics 2025-10-30 v2

Abstract

In 1984, Erd\H{o}s and Simonovits conjectured the following: given a bipartite graph HH, there exist constants β,C>0\beta, C > 0 such that any graph GG on nn vertices and pn2Cex(n,H)pn^2\geq C \mathrm{ex}(n, H) edges contains at least βnv(H)pe(H)\beta n^{\mathrm{v}(H)} p^{\mathrm{e}(H)} copies of HH. We show that edge-gluing preserves the satisfiability of this conjecture under some mild symmetry conditions. Namely, if two graphs H1H_1 and H2H_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, Erd\H{o}s and Simonovits conjectured a weaker statement: for every HH, there is some α,β,C>0\alpha, \beta, C > 0 such that any graph GG on nn vertices and pn2Cn1+αpn^2\geq C n^{1+ \alpha} edges contains at least βnv(H)pe(H)\beta n^{\mathrm{v}(H)} p^{\mathrm{e}(H)} copies of HH. We show that if HH satisfies this conjecture then by gluing several copies of labeled HH along the same copy of a subforest of HH produces a graph that also satisfies the conjecture.

Keywords

Cite

@article{arxiv.2507.16804,
  title  = {Supersaturation via edge-gluing},
  author = {Zihao Jin and Sean Longbrake and Liana Yepremyan},
  journal= {arXiv preprint arXiv:2507.16804},
  year   = {2025}
}

Comments

17 pages

R2 v1 2026-07-01T04:13:50.592Z