Snevily's Conjecture about $\mathcal{L}$-intersecting Families on Set Systems and its Analogue on Vector Spaces

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Main Authors: Liu, Jiuqiang, Yu, Guihai, Feng, Lihua, Wu, Yongjiang
Format: Preprint
Published: 2024
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author Liu, Jiuqiang
Yu, Guihai
Feng, Lihua
Wu, Yongjiang
author_facet Liu, Jiuqiang
Yu, Guihai
Feng, Lihua
Wu, Yongjiang
contents The classical Erdős-Ko-Rado theorem on the size of an intersecting family of $k$-subsets of the set $[n] = \{1, 2, \dots, n\}$ is one of the fundamental intersection theorems for set systems. After the establishment of the EKR theorem, many intersection theorems on set systems have appeared in the literature, such as the well-known Frankl-Wilson theorem, Alon-Babai-Suzuki theorem, and Grolmusz-Sudakov theorem. In 1995, Snevily proposed the conjecture that the upper bound for the size of an $\mathcal{L}$-intersecting family of subsets of $[n]$ is ${{n} \choose {s}}$ under the condition $\max \{l_{i}\} < \min \{k_{j}\}$, where $\mathcal{L} = \{l_{1}, \dots, l_{s}\}$ with $0 \leq l_{1} < \cdots < l_{s}$ and $k_{j}$ are subset sizes in the family. In this paper, we prove that Snevily's conjecture holds for $n \geq {k^{2} \choose {l_{1}+1}}s + l_{1}$, where $k$ is the maximum subset size in the family. We then derive an analogous result for $\mathcal{L}$-intersecting families of subspaces of an $n$-dimensional vector space over a finite field $\mathbb{F}_{q}$.
format Preprint
id arxiv_https___arxiv_org_abs_2403_04139
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Snevily's Conjecture about $\mathcal{L}$-intersecting Families on Set Systems and its Analogue on Vector Spaces
Liu, Jiuqiang
Yu, Guihai
Feng, Lihua
Wu, Yongjiang
Combinatorics
The classical Erdős-Ko-Rado theorem on the size of an intersecting family of $k$-subsets of the set $[n] = \{1, 2, \dots, n\}$ is one of the fundamental intersection theorems for set systems. After the establishment of the EKR theorem, many intersection theorems on set systems have appeared in the literature, such as the well-known Frankl-Wilson theorem, Alon-Babai-Suzuki theorem, and Grolmusz-Sudakov theorem. In 1995, Snevily proposed the conjecture that the upper bound for the size of an $\mathcal{L}$-intersecting family of subsets of $[n]$ is ${{n} \choose {s}}$ under the condition $\max \{l_{i}\} < \min \{k_{j}\}$, where $\mathcal{L} = \{l_{1}, \dots, l_{s}\}$ with $0 \leq l_{1} < \cdots < l_{s}$ and $k_{j}$ are subset sizes in the family. In this paper, we prove that Snevily's conjecture holds for $n \geq {k^{2} \choose {l_{1}+1}}s + l_{1}$, where $k$ is the maximum subset size in the family. We then derive an analogous result for $\mathcal{L}$-intersecting families of subspaces of an $n$-dimensional vector space over a finite field $\mathbb{F}_{q}$.
title Snevily's Conjecture about $\mathcal{L}$-intersecting Families on Set Systems and its Analogue on Vector Spaces
topic Combinatorics
url https://arxiv.org/abs/2403.04139