منابع مشابه
An intersection theorem for four sets
Fix integers n, r ≥ 4 and let F denote a family of r-sets of an n-element set. Suppose that for every four distinct A,B,C,D ∈ F with |A∪B ∪C ∪D| ≤ 2r, we have A∩B ∩C ∩D 6= ∅. We prove that for n sufficiently large, |F| ≤ ( n−1 r−1 ) , with equality only if ⋂ F∈F F 6= ∅. This is closely related to a problem of Katona and a result of Frankl and Füredi [10], who proved a similar statement for thre...
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It is known from a previous paper [3] that Katona’s Intersection Theorem follows from the Complete Intersection Theorem by Ahlswede and Khachatrian via a Comparison Lemma. It also has been proved directly in [3] by the pushing–pulling method of that paper. Here we add a third proof via a new (k,k+1)-shifting technique, whose impact will be exploared elsewhere. The fourth and last of our proofs ...
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ژورنال
عنوان ژورنال: Advances in Mathematics
سال: 2007
ISSN: 0001-8708
DOI: 10.1016/j.aim.2006.11.013