Packing nearly-disjoint sets
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De Bruijn and Erdős proved that ifA1, ...,Ak are distinct subsets of a set of cardinalityn, and |Ai ∩Aj|≦1 for 1≦in, then some two ofA1, ...,Ak have empty intersection. We prove a strengthening, that at leastk /n ofA1, ...,Ak are pairwise disjoint. This is motivated by a well-known conjecture of Erdőds, Faber and Lovász of which it is a corollary.
[1] de Ng Dick Bruijn. A combinatorial problem , 1946 .
[2] David E. Woolbright. On the Size of Partial Parallel Classes in Steiner Systems , 1980 .
[3] Neil Hindman,et al. On a Conjecture of Erdös, Faber, and Lovász about n-Colorings , 1981, Canadian Journal of Mathematics - Journal Canadien de Mathematiques.