Abstract
LetX be ann-element set and ℱ a family of its subsets. Considering the setsF∩(X - {x}) for a given x ∈X, there might be some coincidences, namely, ifF and G differ only in x, then they have the same intersection withX - {x}. It is proved that if |ℱ| ≤ 65n/14, then for an appropriatex ∈X, the number of coincidences is at most 9. Several similar, best possible bounds are obtained, continuing previous research by Bondy, Bollobás and the authors.
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Watanabe, M., Frankl, P. Some best possible bounds concerning the traces of finite sets. Graphs and Combinatorics 10, 283–292 (1994). https://doi.org/10.1007/BF02986678
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DOI: https://doi.org/10.1007/BF02986678