Thomassen's theorem on the two-linkage problem in acyclic digraphs: a shorter proof

Fuente: arXiv
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Autor principal: Seymour, Paul
Formato: Preprint
Publicado: 2024
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author Seymour, Paul
author_facet Seymour, Paul
contents Let G be an acyclic digraph, and let a, b, c, d be vertices, where a, b are sources, c, d are sinks, and every other vertex has in-degree and out-degree at least two. In 1985, Thomassen showed that there do not exist disjoint directed paths from a to c and from b to d, if and only if G can be drawn in a closed disc with a, b, c, d drawn in the boundary in order. We give a shorter proof.
format Preprint
id arxiv_https___arxiv_org_abs_2409_09758
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Thomassen's theorem on the two-linkage problem in acyclic digraphs: a shorter proof
Seymour, Paul
Combinatorics
05C10
Let G be an acyclic digraph, and let a, b, c, d be vertices, where a, b are sources, c, d are sinks, and every other vertex has in-degree and out-degree at least two. In 1985, Thomassen showed that there do not exist disjoint directed paths from a to c and from b to d, if and only if G can be drawn in a closed disc with a, b, c, d drawn in the boundary in order. We give a shorter proof.
title Thomassen's theorem on the two-linkage problem in acyclic digraphs: a shorter proof
topic Combinatorics
05C10
url https://arxiv.org/abs/2409.09758