Classification of Finite Simple Groups Formalized in Lean

(cfsg.axiommath.ai)

155 points | by pfdietz 7 hours ago

16 comments

  • Davidzheng 31 minutes ago
    Makes me sad that the homotopical foundation people never got their shit together and now formalization is so mature but it's still done in set theoretic foundations.
  • mlmonkey 7 hours ago
    Out of curiosity: is it possible to take a frontier model and just let it loose on all math textbooks out there, converting each and every proof/theorem/lemma/etc. into Lean? A frontier model should be able to do that, right? And it's a one-time task: do it once and it's there for eternity, available as a library to be used in other proofs.

    Maybe my understanding of Lean is wrong; I'm thinking of it as a programming language but for Math.

    • jonath_laurent 6 hours ago
      Axiom MTS here. What you describe is pretty close to how we formalised this proof, which is scattered across more than 500 articles and books: a swarm of agents was tasked with going through all these sources.

      One challenge is assembling everything into a coherent whole, since the same informal concept can be formalised in slightly different but incompatible ways.

      • p11p 2 hours ago
        [flagged]
        • penteract 2 hours ago
          Producing a formalized proof from a non-formalized proof in a paper or book should not be considered a violation of copyright.
          • pfdietz 1 hour ago
            Indeed; one cannot copyright mathematical ideas, only their expression. And the formalization is a different expression.
    • bananaflag 6 hours ago
      Yes, but thing is, for a lot of basic stuff there are myriad ways in which it is formulated, so humans have to decide which of them goes in the library. Of course you can include two or five or ten equivalent formulations (like textbooks sometimes do) but still, not everything under the sun.

      Probably this will be done in some form in the coming months.

      • thaumasiotes 5 hours ago
        > Of course you can include two or five or ten equivalent formulations (like textbooks sometimes do) but still, not everything under the sun.

        Note that mathlib currently includes duplicates of many theorems; I believe deduplication is an active goal (if not one seeing much labor right now).

    • aureianimus 5 hours ago
      Yes and no. With enough compute, probably, but doing this does not necessarily yield a reusable library. See https://xenaproject.wordpress.com/2026/10/16/how-to-formaliz...
    • Someone 3 hours ago
      _If_ you have formalized a provable theorem in Lean, a simple bread-first search can prove it. It will take lots (and lots, and lots, and lots…) of time, though (https://en.wikipedia.org/wiki/General_Problem_Solver).

      LLMs can do smarter searches, and will likely find proofs for most of them, but are not guaranteed to find a proof.

    • tyromaniac 6 hours ago
      Write a few proofs with it and then come back to this
    • QuesnayJr 6 hours ago
      I think people assume that it would end up not being usable by humans without a lot of hand-holding. Though maybe that's wrong, and somebody should try it.
  • sebzim4500 7 hours ago
    This seems like a very good use of auto-formalization, because in the past mathematicians have incorrectly believed that they were finished with the classification only discover a missing class/sporadic group.

    The original proof was a collaboration of ~100 mathematicians, if Tao is correct then we should expect to see more such collaborations in the future like we do in e.g. physics.

    • QuesnayJr 6 hours ago
      They didn't discover a missing sporadic group. The big gap in the proof (the quasithin case) happened because it was covered in a 600-page unpublished manuscript that under further investigation turned out to be incomplete.
  • compacct27 3 hours ago
    Groups were my gateway drug into abstract algebra. A friend clued me into symmetry being everywhere and Groups are how symmetry is formalized, and it’s been a crazy journey understanding all that. The frontier models can tie those abstract concepts to plain English examples and answer questions decently well, it’s never been a better time to pick up the field solo and see what it has to offer us
  • sleepyams 1 hour ago
    Somehow the classification of finite simple groups makes me feel uneasy as a mathematician, but I suppose this helps quell that feeling.

    https://en.wikipedia.org/wiki/Monster_group

  • vessenes 1 hour ago
    Note they found one gap (and filled it) in the previously accepted 1,000+ page proof. So that's pretty cool.
  • senderista 4 hours ago
    Filling in well-known gaps like this is the kind of thing the AI companies should be doing, not trying to scoop research in progress.
  • pfdietz 7 hours ago
    The formalization is 43.1M lines of Lean.
    • bwestergard 6 hours ago
      Is that going to be mathematically useful?
      • sebzim4500 6 hours ago
        It's nice to know that they didn't miss anything. The natural language proof is 10,000 pages and they have missed groups in the past.
        • cvoss 1 hour ago
          Indeed, this formalization effort spotted a flawed argument in one of the original publications and worked around it to repair the result.
        • Panoramix 4 hours ago
          How do we know the formalization itself doesn't have any errors? AFAIK it's very far from trivial to formalize something.
          • kenferry 1 hour ago
            Well, the point of the _computer_ formalization is that it's checkable.

            An error in the formalization would be a bug in lean. Which, as we know, certainly seems plausible (I've mused on if these giant proofs are incentivizing LLMs to find lean bugs to exploit), but at least it's a smaller surface area.

          • sebzim4500 4 hours ago
            In general checking that the definitions are correct isn't that hard and assuming at least one of the lean kernels you verify with is correct (which tbf is an assumption, the implementations are based on each other so could have a common bug) that's all you need to verify.

            In this case the statement is unusually complicated but still much much easier to verify than the proof itself.

      • pfdietz 5 hours ago
        The proof was of such complexity and length there were lingering doubts. This dispels them.
      • curt15 6 hours ago
        More so if Lean uncovers logical errors. Note also there is already an ongoing 2nd generation proof.
    • cubefox 4 hours ago
      I suppose this is the longest Lean proof by a wide margin.
      • pfdietz 3 hours ago
        It's possibly the longest open source project of any kind (depending on whether you count comments and white space in Linux).
        • cubefox 2 hours ago
          I wonder whether humans could have realistically finished it without AI by 2100.
          • sebzim4500 36 minutes ago
            Depends if you include a few decades of improvements in lean itself. Non-AI proof automation is much better than it was even a year ago and so some fiddly results can now be done with `by grind`.

            Also don't discount the fact that people would learn how to do this kind of project, currently no one really knows how to decide what definitions work best, what should be reducible, what should be part of a public api and what should be local to a module, etc.

          • cvoss 1 hour ago
            I would bet no. Because the original proof is so distributed, with parts of it being very old, and with parts of it being, as a first attempt, not the most concise or lucid route to the result, we were rapidly approaching a world where the empirical knowledge of how/why the result holds was literally dying.

            The article refers to its use of the "first-generation proof". It would seem this proof is too large to be truly known by one person, and the group of people who "collectively knew" it grew old and started to die. Since its original formulation, mathematicians began to compile, consolidate, and revise the proof into a 2nd generation digested form (estimated to be 5000 pages instead of tens of thousands). But that effort was still so monumental in its own right that a 3rd gen proof project began to digest the 2nd gen proof before the 2nd gen proof was even finished. I believe both the 2nd and 3rd gen projects are still ongoing.

            It will be interesting to see how small the proof gets once we finish learning how to obtain these results "efficiently" with the benefit of hindsight.

    • gggg_g_g__g 1 hour ago
      Holy shit.
    • claudismusa 30 minutes ago
      [dead]
  • vatsachak 6 hours ago
    LLM formalization is not as useful as human formalization, but nice to know that the Classification is correct
  • pixl97 7 hours ago
    Page has some kind of redirect bug that steals the back button, may want to open it in a new tab to avoid that.
  • QuesnayJr 6 hours ago
    I'm surprised they only found one gap. I would have expected multiple (fixable) gaps would have been uncovered, especially since the result was spread over many papers by many different people.
  • esafak 3 hours ago
    Looking at the visualizations made me wonder if the embeddings themselves can be used to suggest, if not derive, mathematical results. I realize it depends on the quality of the embeddings.
  • Salparvezml 6 hours ago
    [flagged]
  • v3ai 6 hours ago
    based if true