Abstract
We consider the maximal size of families of k-element subsets of an n element set [. n] that satisfy the properties that every r subsets of the family have non-empty intersection, and no ℓ subsets contain [. n] in their union. We show that for large enough n, the largest such family is the trivial one of all (n-2k-1) subsets that contain a given element and do not contain another given element. Moreover we show that unless such a family is such that all subsets contain a given element, or all subsets miss a given element, then it has size at most 9(n-2k-1).We also obtain versions of these statements for weighted non-uniform families.
Original language | English |
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Pages (from-to) | 128-138 |
Number of pages | 11 |
Journal | European Journal of Combinatorics |
Volume | 33 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2012 |