On path partitions and colourings in digraphs
نویسنده
چکیده
We provide a new proof of a theorem of Saks which is an extension of Greene’s Theorem to acyclic digraphs, by reducing it to a similar, known extension of Greene and Kleitman’s Theorem. This suggests that the Greene-Kleitman Theorem is stronger than Greene’s Theorem on posets. We leave it as an open question whether the same holds for all digraphs, that is, does Berge’s conjecture concerning path partitions in digraphs imply the extension of Greene’s theorem to all digraphs (conjectured by Aharoni, Hartman and Hoffman)?
منابع مشابه
Colourings, homomorphisms, and partitions of transitive digraphs
We investigate the complexity of generalizations of colourings (acyclic colourings, (k, `)colourings, homomorphisms, and matrix partitions), for the class of transitive digraphs. Even though transitive digraphs are nicely structured, many problems are intractable, and their complexity turns out to be difficult to classify. We present some motivational results and several open problems.
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