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New bounds for a hypergraph bipartite Turán problem
Journal of Combinatorial Theory Series A ( IF 0.9 ) Pub Date : 2020-07-22 , DOI: 10.1016/j.jcta.2020.105299
Beka Ergemlidze , Tao Jiang , Abhishek Methuku

Let t be an integer such that t2. Let K2,t(3) denote the triple system consisting of the 2t triples {a,xi,yi}, {b,xi,yi} for 1it, where the elements a,b,x1,x2,,xt, y1,y2,,yt are all distinct. Let ex(n,K2,t(3)) denote the maximum size of a triple system on n elements that does not contain K2,t(3). This function was studied by Mubayi and Verstraëte [9], where the special case t=2 was a problem of Erdős [1] that was studied by various authors [3], [9], [10].

Mubayi and Verstraëte proved that ex(n,K2,t(3))<t4(n2) and that for infinitely many n, ex(n,K2,t(3))2t13(n2). These bounds together with a standard argument show that g(t):=limnex(n,K2,t(3))/(n2) exists and that2t13g(t)t4. Addressing the question of Mubayi and Verstraëte on the growth rate of g(t), we prove that as t,g(t)=Θ(t1+o(1)).



中文翻译:

超图二部图兰问题的新界

t为一个整数,使得Ť2。让ķ2Ť3表示由2 t三元组组成的三元组系统{一种X一世ÿ一世}{bX一世ÿ一世} 对于 1个一世Ť,其中的元素 一种bX1个X2XŤÿ1个ÿ2ÿŤ都是截然不同的。让ñķ2Ť3表示不包含n个元素的三元系统的最大大小ķ2Ť3。Mubayi和Verstraëte[9]研究了此功能,其中特例Ť=2 是Erdős[1]的问题,已被多位作者[3],[9],[10]研究。

Mubayi和Verstraëte证明了 ñķ2Ť3<Ť4ñ2并且对于无穷多个ññķ2Ť32Ť-1个3ñ2。这些界限与标准参数一起表明GŤ=ññķ2Ť3/ñ2 存在,那2Ť-1个3GŤŤ4 解决穆巴伊和韦斯特拉特的增长率问题 GŤ,我们证明 ŤGŤ=ΘŤ1个+Ø1个

更新日期:2020-07-22
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