Discrete Mathematics - First Japan Conference on Graph Theory and Applications
Matchings, cutsets, and chain partitions in graded posets
Discrete Mathematics
Sperner theory
Partitioning the Boolean lattice into chains of large minimum size
Journal of Combinatorial Theory Series A
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Let 2[n] denote the Boolean lattice of order n, that is, the poset of subsets of {1,..., n} ordered by inclusion. Extending our previous work on a question of Füredi, we show that for any c 1, there exist functions e(n) ∼ √n/2 and f(n)∼ c√n log n and an integer N (depending only on c) such that for all n , there is a chain decomposition of the Boolean lattice 2[n] into (n ⌊n/2⌋) chains, all of which have size between e(n) and f(n). (A positive answer to Füredi's question would imply that the same result holds for some e(n) ∼ √π/2 √n and f(n) = e(n) + 1.) The main tool used is an apparently new observation about rank-collection in normalized matching (LYM) posets.