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The Turán Number of Berge-$K_4$ in 3-Uniform Hypergraphs
SIAM Journal on Discrete Mathematics ( IF 0.8 ) Pub Date : 2020-07-01 , DOI: 10.1137/20m1315269
Hui Zhu , Liying Kang , Zhenyu Ni , Erfang Shan

SIAM Journal on Discrete Mathematics, Volume 34, Issue 3, Page 1485-1492, January 2020.
For a graph $G=(V,E)$, a hypergraph $H$ is called a Berge-$G$ if there is a bijection $f:E(G)\mapsto E(H)$ such that $e\subseteq f(e)$ for all $e\in E(G)$. The family of Berge-$G$ hypergraphs is denoted by $\mathcal{B}(G)$. The maximum number of edges in an $n$-vertex $r$-graph with no subhypergraph isomorphic to any Berge-$G$ is denoted by $ex_r(n, \mathcal{B}(G))$. Gyárfás [SIAM J. Discrete Math., 33 (2019), pp. 383--392] showed that for $n\geq 6$, $ex_3(n,\mathcal{B}(K_4))=\lfloor\frac{n}{3}\rfloor\lfloor\frac{n+1}{3}\rfloor\lfloor\frac{n+2}{3}\rfloor$. However, we found an error in the proof of the result when $n\ge 7$. A recent result due to Gerbner, Methuku, and Palmer [European J. Combin., 86 (2020), 103082] implies that for $n\geq 9$, $ex_3(n,\mathcal{B}(K_4))=\lfloor\frac{n}{3}\rfloor\lfloor\frac{n+1}{3}\rfloor\lfloor\frac{n+2}{3}\rfloor$. In this paper we prove the remaining cases $n=7$ and $n=8$ for the completeness of the conclusion.


中文翻译:

3均匀超图中的TuránBerge- $ K_4 $

SIAM离散数学杂志,第34卷,第3期,第1485-1492页,2020年1月。
对于图$ G =(V,E)$,如果存在双射$ f:E(G)\ mapsto E(H)$,则超图$ H $被称为Berge- $ G $,使得$ e \ E(G)$中所有$ e \的subseteq f(e)$。Berge- $ G $超图族由$ \ mathcal {B}(G)$表示。在$ n $-顶点$ r $-图中没有与任何Berge- $ G $同构的亚超图的最大边数用$ ex_r(n,\ mathcal {B}(G))$表示。Gyárfás[SIAM J.Discrete Math。,33(2019),pp.383--392]显示,对于$ n \ geq 6 $,$ ex_3(n,\ mathcal {B}(K_4))= \ lfloor \ frac {n} {3} \ rfloor \ lfloor \ frac {n + 1} {3} \ rfloor \ lfloor \ frac {n + 2} {3} \ rfloor $。但是,当$ n \ ge 7 $时,我们在结果证明中发现了一个错误。Gerbner,Methuku和Palmer的最新结果[European J. Combin。,86(2020),103082]暗示对于$ n \ geq 9 $,$ ex_3(n,\ mathcal {B}(K_4))= \ lfloor \ frac {n} {3} \ rfloor \ lfloor \ frac {n + 1} {3} \ rfloor \ lfloor \ frac {n + 2} {3} \ rfloor $。在本文中,我们为证明结论的完整性,证明了其余情况$ n = 7 $和$ n = 8 $。
更新日期:2020-07-01
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