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A linear hypergraph extension of the bipartite Turán problem
European Journal of Combinatorics ( IF 1.0 ) Pub Date : 2020-12-15 , DOI: 10.1016/j.ejc.2020.103269
Guorong Gao , An Chang

An r-uniform hypergraph is linear if every two edges intersect in at most one vertex. Given a family of r-uniform hypergraphs F, the linear Turán number exrlin(n,F) is the maximum number of edges of a linear r-uniform hypergraph on n vertices that does not contain any member of F as a subhypergraph.

Given a graph F and a positive integer r2, the r-expansion of F is the r-graph F+ obtained from F by enlarging each edge of F with r2 new vertices disjoint from V(F) such that distinct edges of F are enlarged by distinct vertices. For ts2, we prove the following extension of Kővári–Sós–Turán’s theorem exrlin(n,Ks,t+)(t1)1sr(r1)n21s+O(n22s). Specially, for s=2, r=3, we prove that ex3lin(n,K2,t+)=1+ot(1)16t1n32, which is an improvement of Gerbner, Methuku and Vizer’s result (Gerbner et al., 2019). Moreover, we also prove some sharp bounds for the linear Turán number of Ks,t+.



中文翻译:

二分法Turán问题的线性超图扩展

一个 [R如果每两个边缘最多相交一个顶点,则均匀超图是线性的。给定一个家庭[R-一致超图 F,线性图兰数ex[R一世ññF 是线性的最大边数 [R一致超图 ñ 不包含的任何成员的顶点 F 作为超图。

给定图 F 和一个正整数 [R2[R-扩展 F 是个 [R-图形 F+ 从...获取 F 通过扩大每个边缘 F[R-2 新顶点不相交 VF 这样 F被不同的顶点放大。对于Ťs2,我们证明了Kővári–Sós–Turán定理的以下扩展 ËX[R一世ññķsŤ+Ť-1个1个s[R[R-1个ñ2-1个s+Øñ2-2s 特别是 s=2[R=3,我们证明 ËX3一世ññķ2Ť+=1个+ØŤ1个1个6Ť-1个ñ32这是Gerbner,Methuku和Vizer结果的改进(Gerbner et al。,2019)。此外,我们还证明了线性图兰数的一些尖锐边界ķsŤ+

更新日期:2020-12-15
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