Talagrand’s discrete-convexity conjectureOpen Problem
Motivation
High probability under independent coordinate sampling need not give a family any closure under unions. Discrete convexity asks whether a bounded number of its members nevertheless cover most sets in the stronger sense of inexpensive containment certificates. The source is OpenAI's September 2026 manuscript.
Setting
On Bernoulli product space , each coordinate is present independently with probability . For a family , the exceptional family consists of sets contained in no union of members of . A family is -small when it has containment generators with total cost at most .
Formalization targets
For every positive integer N, every density p with 0<p<1, and every family D of subsets of the ground set {0,...,N-1} (an arbitrary family, with no monotonicity assumption), if the product measure of D under independent Bernoulli(p) coordinates, namely the sum over s in D of p^|s|(1-p)^(N-|s|), is at least 1 - 1/2^75, then the family of exceptional sets is small. Here the exceptional family for k=2^75 consists of all subsets S of the ground set that are contained in no union of k members of D, where the k members are given as an arbitrary tuple of exactly k entries of D, repeats allowed and with no disjointness required. A family A is small at density p if there is a family G of generator sets that covers A, meaning every member of A contains some member of G, and whose cost, the sum over I in G of p^|I|, is at most 1/2.
The goal is OAI.TalagrandDiscreteConvexity.talagrand_discrete_convexity.
Significance
The conclusion supplies explicit containment witnesses at the original density. A small probability for the exceptional event alone would not provide such a cover. The manuscript presents a mathematical argument; the attached goal currently has status Open, so the requested contribution is a Lean proof of the displayed formal target.
Difficulty
The family is arbitrary, so monotonicity cannot be used as an extra hypothesis. The same universal number of unions must work for all dimensions and all densities strictly between zero and one.
Formalization scope
Lean uses finite families of finite subsets of Fin N, with and . A tuple has exactly entries; repetitions and overlaps are allowed. The cover cost counts each generator once. The separate two-union density-loss corollary is outside this goal.
The shared definitions are supplied by TalagrandDiscreteConvexity. The target uses Lean 4.33.1 with the pinned Mathlib environment. Contributions should preserve the existing statement and develop reusable supporting lemmas in its definitions.
Selected references
- OpenAI, Talagrand’s discrete-convexity conjecture, preprint, September 2026. Manuscript.
- OpenAI, accompanying Lean statement. Pinned source.