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DM
2002
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13 years 11 months ago
Infinite antichains of matroids with characteristic set {p}
For each prime p, we construct an infinite antichain of matroids in which each matroid has characteristic set {p}. For p = 2, each of the matroids in our antichain is an excluded m...
James G. Oxley, Charles Semple, Dirk L. Vertigan, ...
COMBINATORICS
2000
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13 years 11 months ago
An Infinite Antichain of Permutations
We constructively prove that the partially ordered set of finite permutations ordered by deletion of entries contains an infinite antichain. In other words, there exists an infini...
Daniel A. Spielman, Miklós Bóna