The Union-Closed Sets Conjecture for Small Families
نویسندگان
چکیده
منابع مشابه
Union-closed families of sets
A family of sets is union-closed if it contains the union of any two of its elements. Some years ago, Reimer gave a lower bound for the average size of an element of a union-closed family consisting of m sets and, two years ago, Czédli did the same under the additional condition that our sets are contained in a set with n elements. Recently Tom Eccles and I have determined the minimum average s...
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The union-closed sets conjecture states that if a finite family of sets A 6 = {∅} is union-closed, then there is an element which belongs to at least half the sets in A. In 2001, D. Reimer showed that the average set size of a union-closed family, A, is at least 1 2 log2 |A|. In order to do so, he showed that all union-closed families satisfy a particular condition, which in turn implies the pr...
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Let F be a union-closed family of subsets of an m-element set A. Let n = |F| ≥ 2 and for a ∈ A let s(a) denote the number of sets in F that contain a. Frankl’s conjecture from 1979, also known as the union-closed sets conjecture, states that there exists an element a ∈ A with n − 2s(a) ≤ 0. Strengthening a result of Gao and Yu [7] we verify the conjecture for the particular case when m ≥ 3 and ...
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We survey the state of the union-closed sets conjecture.
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In 1979 Frankl conjectured that in a finite non-trivial union-closed collection of sets there has to be an element that belongs to at least half the sets. We show that this is equivalent to the conjecture that in a finite non-trivial graph there are two adjacent vertices each belonging to at most half of the maximal stable sets. In this graph formulation other special cases become natural. The ...
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ژورنال
عنوان ژورنال: Graphs and Combinatorics
سال: 2016
ISSN: 0911-0119,1435-5914
DOI: 10.1007/s00373-016-1701-3