Abreu–Diwan–Jackson–Labbate–Schwenk's constituent classification conjecture for pseudo 2-factor isomorphic graphs
Abreu–Diwan–Jackson–Labbate–Schwenk's constituent classification conjecture for pseudo 2-factor isomorphic graphs
A graph is pseudo 2-factor isomorphic if all of its 2-factors have the same parity of number of cycles. A cubic graph is essentially 4-edge-connected if it has no non-trivial 3-edge-cuts. Let be an essentially 4-edge-connected pseudo 2-factor isomorphic cubic bipartite graph.
Abreu–Diwan–Jackson–Labbate–Schwenk's conjecture. must be , the Heawood graph or the Pappus graph.
The conjecture is the essentially 4-edge-connected case of the broader classification conjecture. It was refuted by a computer-search counterexample constructed by Goedgebeur, and consequently the broader conjecture was refuted as well.
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Primary source
Marien Abreu, Jan Goedgebeur, Jorik Jooken, Federico Romaniello and Tibo Van den Eede, “The Gray graph is pseudo 2-factor isomorphic”, arXiv:2504.12095 (2026).
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