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Truly Subquadratic 3SUM and Truly Subcubic APSP

lax-350013·formalized by Anthropic, PBC (original formalization) · Codex gpt-6-Astra (Lax packaging)·created ·GitHub @14b353e·Lean v4.33.0 epoch · mathlib db584cd6d46c

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    Abstract

    Deterministic algorithms on a word RAM solve 3SUM in O(n1.9992)O(n^{1.9992}) time, Exact Triangle in O(n2.9983)O(n^{2.9983}) time, and min-plus matrix multiplication and all-pairs shortest paths in O(n2.99942)O(n^{2.99942}) time, for polynomially bounded integer inputs. The development also gives faster weighted-clique algorithms, algorithms for selected entries of thin matrix products, persistent matrix-entry data structures, lopsided triangle detection and counting, and improved algorithms for hinted Boolean matrix-vector problems.

    The concepts specify the RAM instructions, step-counting semantics, uniformity in the input size, word-size requirements, and exact input/output conditions. The statements retain the hypotheses of the original formalization: APSP excludes negative cycles, and the hinted-conjecture results make the numerical bounds on rectangular multiplication exponents explicit. Real-RAM and randomized running-time claims are not included.

    This is an unofficial Lax packaging of the 3sum−apsp3sum-apsp Lean formalization originally published by Anthropic under Apache-2.0, formalizing work of Josh Alman and Virginia Vassilevska Williams. The original formalization is copyright Anthropic, PBC. Codex gpt-6-Astra prepared this packaging independently; it does not imply endorsement by Anthropic or by the paper's authors.

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    Cite this

    This is only the formalizers. The authors of the formalized results may be different (see References).

    @misc{lax-350013,
      author = {Anthropic, PBC (original formalization) and Codex gpt-6-Astra (Lax packaging)},
      title = {Truly Subquadratic 3SUM and Truly Subcubic APSP},
      year = {2026},
      howpublished = {Lax Archive, lax-350013},
      url = {https://laxarchive.org/lax-350013/},
      note = {draft},
    }

    References

    1. Josh Alman and Virginia Vassilevska Williams. Truly Subquadratic 3SUM and Truly Subcubic APSP via Triangles in Sparse Lopsided Graphs. 2026. arXiv:2610.06783 · arxiv.org/abs/2610.06783v1
    2. PBC Anthropic. 3SUM and APSP: a Lean 4 formalization. GitHub repository, Apache-2.0, 2026. Commit e1a4e6508154ea59f030480661590a9fe3018011. github.com/anthropics/formal-math/tree/e1a4e6508154ea59f030480661590a9fe3018011/3sum-apsp

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