Abstract
The aim of this paper is to prove the following extension of the Folkman-Rado-Sanders Finite Union Theorem: For every positive integersr andk there exists a familyL of sets having the following properties:
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i)
ifS 1,S 2, ...,S k + 1 are distinct pariwise disjoint elements ofL then there exists nonemptyI ⊂ {1, 2, ...,k + 1} with ∪ i∈I S i ⋃L
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ii)
ifL =L 1 ⋃...⋃L r is an arbitrary partition then there existsj ≤ r and pairwise disjoint setsS 1,S 2, ...,S k ∈L j , such thatL i∈I S i ∈L j for every nonemptyI ⊂ {1, 2, ...,k}.
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Nešetřil, J., Rödl, V. Finite union theorem with restrictions. Graphs and Combinatorics 2, 357–361 (1986). https://doi.org/10.1007/BF01788110
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DOI: https://doi.org/10.1007/BF01788110