There Is No Finite-infinite Duality Pair - Forming Antichains - in the Digraph Poset
نویسندگان
چکیده
Let D denote the partially ordered sets of homomorphism classes of finite directed graphs, ordered by the homomorphism relation. Order theoretic properties of this poset have been studied extensively, and have interesting connections to familiar graph properties and parameters. This paper studies the generalized duality pairs in D: it gives a new, short proof for the Foniok Nešetřil Tardif theorem (characterizing all finite-finite duality pairs in D), and shows, that there is no finite-infinite duality pair where the pairs form antichains in the digraph-poset.
منابع مشابه
No Finite-Infinite Antichain Duality in the Homomorphism Poset of Directed Graphs
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