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Statement

Let X1,…,XnX_1,\ldots,X_n be independent nonnegative random variables with EXi≤1\mathbb{E}X_i \le 1, and let SS be their sum. Is P(S<ES+1)≥1/e\mathbb{P}(S < \mathbb{E}S + 1) \ge 1/e? Feige proved the constant 1/131/13 and conjectured the sharp 1/e1/e. Three independent July 2026 proofs settle it, both building on the Vlassis-Thomas calibration theorem; the sharper one determines the optimal small-deviation bound for every deviation δ≥1\delta \ge 1.

Record

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  1. proof attempt · #1

    ChatGPT 5.6 Pro, GPT-5.6 Sol, Codex, with Weibo Fu, Yanjun Han, Guanyang Wang, Jun Yan, Peng Zhang, Zhengqing Zhou, Zipei Nie, Jiaye Wei and Mark Stander

    The record says a model found this and names the people who worked on it. No ProbXiv account is credited for it, and nobody has answered for it here.

    AI involvement
    ai discovered
    — the result was found by a model.

    The primary paper states plainly that the proof was found by ChatGPT 5.6 Pro, combining the Vlassis-Thomas Dirichlet calibration theorem with Grünbaum-type convex geometry; the authors checked, revised and rewrote the argument, and the accompanying Lean formalization was developed with Codex. The independent second proof by Nie and Wei was obtained with the assistance of GPT-5.6 Sol. A further independent proof was found by Stander.

  2. Machine-checked by Lean on #1 · not a person

    lean: correctLean

    scope Lean formalization of the result

    An end-to-end Lean formalization of the e−1e^{-1} conjecture accompanies the primary paper, formalizing the Vlassis-Thomas theorem, Grünbaum's centroid theorem and the combining argument. Three independent AI-assisted proofs appeared within days; neither preprint is peer-reviewed yet.

    Lean checked the formalisation, not that it says the same thing as the statement above.

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