Lax Lean Archive

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Graphs without a 3-Connected Subgraph are 4-Colourable

lax-10·formalized by Édouard Bonnet·created 2026-08-02·GitHub @7b348ba·Lean v4.30.0 epoch · mathlib c5ea00351c28

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    Abstract

    This submission formalizes the main proof of Bonnet, Feghali, Nguyen, Scott, Seymour, Thomassé, and Trotignon available at https://arxiv.org/abs/2402.06338. It internally proves the technical Theorem 3. Only its consequence, Theorem 2, and the result claimed in the title are exposed.

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    Cite this

    @misc{lax-10,
  author = {Édouard Bonnet},
  title = {Graphs without a 3-Connected Subgraph are 4-Colourable},
  year = {2026},
  howpublished = {Lax Archive, lax-10},
  url = {https://laxarchive.org/lax-10/},
  note = {draft},
}

    References

    1. Edouard Bonnet, Carl Feghali, Tung Nguyen, Alex Scott, Paul Seymour, Stephan Thomasse and Nicolas Trotignon. Graphs without a 3-Connected Subgraph are 4-Colourable. Electronic Journal of Combinatorics 32(1):P1.26, 2025. doi:10.37236/13181

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