Weak Jackson–Thomassen orientation conjecture

A digraph DD is kk-strong if it has at least k+1k+1 vertices and remains strongly connected after the deletion of any set of at most k1k-1 vertices. An orientation of a digraph is an oriented spanning subdigraph obtained by deleting precisely one arc from every directed 2-cycle. Weak Jackson–Thomassen conjecture. There exists a function f(k)f(k) so that every f(k)f(k)-strong digraph on at least 2k+12k+1 vertices contains a spanning kk-strong oriented graph. This natural weakening is open for general digraphs already when k=2k=2, although it holds for symmetric digraphs for all kk.

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Primary source

Jia Zhou, Jørgen Bang-Jensen, Tong Zhou and Jin Yan, “Highly connected spanning oriented subdigraphs in generalizations of semicomplete digraphs”, arXiv:2607.17150 (2026).

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