Bang-Jensen and Wang's conjecture on branchings in semicomplete split digraphs

Let DD be a semicomplete split digraph, meaning a split digraph whose relevant semicomplete structure has no pair of non-adjacent vertices. It is 22-arc-strong if deleting any one arc leaves a strong digraph. A good (u,v)(u,v)-pair is a pair of arc-disjoint out-branching and in-branching rooted at uu and vv, respectively.

Bang-Jensen and Wang's conjecture. Every 22-arc-strong semicomplete split digraph DD contains a good (u,v)(u,v)-pair for every choice of vertices u,vu,v in DD.

This conjecture narrows the general branching problem to semicomplete split digraphs. The source describes related counterexamples for general 22-arc-strong split digraphs but gives no resolution of this semicomplete case.

Sources & referencesView supporting material

Primary source

Jiangdong Ai, Yiming Hao, Zhaoxiang Li and Qi Shao, “Arc-disjoint in- and out-branchings in semicomplete split digraphs”, arXiv:2410.12575 (2024).

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