Random Turán Problems for Hypergraph Expansions

Fuente: arXiv
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Autores principales: Nie, Jiaxi, Spiro, Sam
Formato: Preprint
Publicado: 2024
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author Nie, Jiaxi
Spiro, Sam
author_facet Nie, Jiaxi
Spiro, Sam
contents Given an $r_0$-uniform hypergraph $F$, we define its $r$-uniform expansion $F^{(r)}$ to be the hypergraph obtained from $F$ by inserting $r-r_0$ distinct vertices into each edge of $F$, and we define $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ to be the largest $F^{(r)}$-free subgraph of the random hypergraph $G_{n,p}^r$. We initiate the first systematic study of $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ for general hypergraphs $F$. Our main result essentially resolves this problem for large $r$ by showing that $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ goes through three predictable phases whenever $F$ is Sidorenko and $r$ is sufficiently large, with the behavior of $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ being provably more complex whenever $F$ has no Sidorenko expansion. Moreover, our methods unify and generalize almost all previously known results for the random Turán problem for degenerate hypergraphs of uniformity at least 3.
format Preprint
id arxiv_https___arxiv_org_abs_2408_03406
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Random Turán Problems for Hypergraph Expansions
Nie, Jiaxi
Spiro, Sam
Combinatorics
05D40, 05C35, 05C65, 05C80
Given an $r_0$-uniform hypergraph $F$, we define its $r$-uniform expansion $F^{(r)}$ to be the hypergraph obtained from $F$ by inserting $r-r_0$ distinct vertices into each edge of $F$, and we define $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ to be the largest $F^{(r)}$-free subgraph of the random hypergraph $G_{n,p}^r$. We initiate the first systematic study of $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ for general hypergraphs $F$. Our main result essentially resolves this problem for large $r$ by showing that $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ goes through three predictable phases whenever $F$ is Sidorenko and $r$ is sufficiently large, with the behavior of $\mathrm{ex}(G_{n,p}^r,F^{(r)})$ being provably more complex whenever $F$ has no Sidorenko expansion. Moreover, our methods unify and generalize almost all previously known results for the random Turán problem for degenerate hypergraphs of uniformity at least 3.
title Random Turán Problems for Hypergraph Expansions
topic Combinatorics
05D40, 05C35, 05C65, 05C80
url https://arxiv.org/abs/2408.03406