Extremal number of cliques of given orders in graphs with a forbidden clique minor

Fuente: arXiv
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Autores principales: Shi, Ruilin, Wei, Fan
Formato: Preprint
Publicado: 2024
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author Shi, Ruilin
Wei, Fan
author_facet Shi, Ruilin
Wei, Fan
contents Alon and Shikhelman initiated the systematic study of a generalization of the extremal function. Motivated by algorithmic applications, the study of the extremal function $\text{ex}(n, K_k, K_t\text{-minor})$, i.e., the number of cliques of order $k$ in $K_t$-minor free graphs on $n$ vertices, has received much attention. In this paper, we determine essentially sharp bounds on the maximum possible number of cliques of order $k$ in a $K_t$-minor free graph on $n$ vertices. More precisely, we determine a function $C(k,t)$ such that for each $k < t$ with $t-k\gg \log_2 t$, every $K_t$-minor free graph on $n$ vertices has at most $ n C(k, t)^{1+o_t(1)}$ cliques of order $k$. We also show this bound is sharp by constructing a $K_t$-minor-free graph on $n$ vertices with $C(k, t) n$ cliques of order $k$. This bound answers a question of Wood and Fox-Wei asymptotically up to $o_t(1)$ in the exponent except the extreme values when $k$ is very close to $t$.
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id arxiv_https___arxiv_org_abs_2408_12082
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publishDate 2024
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spellingShingle Extremal number of cliques of given orders in graphs with a forbidden clique minor
Shi, Ruilin
Wei, Fan
Combinatorics
Alon and Shikhelman initiated the systematic study of a generalization of the extremal function. Motivated by algorithmic applications, the study of the extremal function $\text{ex}(n, K_k, K_t\text{-minor})$, i.e., the number of cliques of order $k$ in $K_t$-minor free graphs on $n$ vertices, has received much attention. In this paper, we determine essentially sharp bounds on the maximum possible number of cliques of order $k$ in a $K_t$-minor free graph on $n$ vertices. More precisely, we determine a function $C(k,t)$ such that for each $k < t$ with $t-k\gg \log_2 t$, every $K_t$-minor free graph on $n$ vertices has at most $ n C(k, t)^{1+o_t(1)}$ cliques of order $k$. We also show this bound is sharp by constructing a $K_t$-minor-free graph on $n$ vertices with $C(k, t) n$ cliques of order $k$. This bound answers a question of Wood and Fox-Wei asymptotically up to $o_t(1)$ in the exponent except the extreme values when $k$ is very close to $t$.
title Extremal number of cliques of given orders in graphs with a forbidden clique minor
topic Combinatorics
url https://arxiv.org/abs/2408.12082