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Non-trivial d-wise intersecting families
Journal of Combinatorial Theory Series A ( IF 1.1 ) Pub Date : 2020-11-26 , DOI: 10.1016/j.jcta.2020.105369
Jason O'Neill , Jacques Verstraëte

For an integer d2, a family F of sets is d-wise intersecting if for any distinct sets A1,A2,,AdF, A1A2Ad, and non-trivial if AFA=. Hilton and Milner conjectured that for kd2 and large enough n, the extremal (i.e. largest) non-trivial d-wise intersecting family of k-element subsets of [n] is, up to isomorphism, one of the following two families:A(k,d)={A([n]k):|A[d+1]|d}H(k,d)={A([n]k):[d1]A,A[d,k+1]}{[k+1]{i}:i[d1]}. The celebrated Hilton-Milner Theorem states that H(k,2) is the unique, up to isomorphism, extremal non-trivial intersecting family for k>3. We prove the conjecture and prove a stability theorem, stating that any large enough non-trivial d-wise intersecting family of k-element subsets of [n] is a subfamily of A(k,d) or H(k,d).



中文翻译:

非平凡的d交集家庭

对于整数 d2, 一个家庭 F如果有任何不同的集合,则集合的d方向相交一种1个一种2一种dF一种1个一种2一种d,并且如果不重要一种F一种=。希尔顿和米尔纳猜想是ķd2并且足够大的n,是的k个元素子集的极(即最大)非平凡d方向相交族[ñ] 直到同构,是以下两个家族之一:一种ķd={一种[ñ]ķ|一种[d+1个]|d}Hķd={一种[ñ]ķ[d-1个]一种一种[dķ+1个]}{[ķ+1个]{一世}一世[d-1个]} 著名的希尔顿-米尔纳定理指出: Hķ2 是唯一的,直至同构的极端非平凡相交家族 ķ>3。我们证明了这个猜想,并证明了一个稳定性定理,指出任何足够大的非平凡d-相交族的k-子集[ñ] 是的一个亚科 一种ķd 要么 Hķd

更新日期:2020-11-27
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