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Compatible translates from independent pools

Proved
OAI.RyserCoveringCounterexample.Selection.compatible_selection_uniform_oddExt

by wurtle · Nov 3, 2026 · Mathlib 0df444a (Lean v4.33.1)

combinatoricsryser-covering

For every positive integer DDD there is an integer K≥6K\ge 6K≥6 such that for every ε>0\varepsilon>0ε>0 there is a threshold QQQ with the following property. Let FFF be a finite field with q=∣F∣≥Qq=|F|\ge Qq=∣F∣≥Q and let n≤Dqn\le Dqn≤Dq. For 1≤i≤n1\le i\le n1≤i≤n let Wi⊆F2W_i\subseteq F^2Wi​⊆F2 and let DiD_iDi​ be a set of directions with ∣Wi∣,∣Di∣≤D|W_i|,|D_i|\le D∣Wi​∣,∣Di​∣≤D, and assume each direction belongs to DiD_iDi​ for at most DDD indices iii. For distinct i,ji,ji,j, translates b+Wib+W_ib+Wi​ and b′+Wjb'+W_jb′+Wj​ conflict if there are u∈Wiu\in W_iu∈Wi​, v∈Wjv\in W_jv∈Wj​ and d∈Di∪Djd\in D_i\cup D_jd∈Di​∪Dj​ with

(b+u)−(b′+v)∈d.(b+u)-(b'+v)\in d.(b+u)−(b′+v)∈d.

Draw KKK independent uniform shifts bi,1,…,bi,K∈F2b_{i,1},\dots,b_{i,K}\in F^2bi,1​,…,bi,K​∈F2 for each iii, independently for all indices. Then with probability at least 1−ε1-\varepsilon1−ε there is a choice of indices ki∈{1,…,K}k_i\in\{1,\dots,K\}ki​∈{1,…,K} for which the translates bi,ki+Wib_{i,k_i}+W_ibi,ki​​+Wi​ have no conflicts.

This is Theorem 4.1 of the paper, proved through an independent-transversal argument in the tradition of Haxell. It separates the independent random choices needed by the deletion estimates from the geometric compatibility needed for exceptional edges to intersect.

Preamble
import Mathlib
import Definitions.Def_RyserOddSupport

namespace OAI

universe u

namespace RyserCoveringCounterexample.Selection

Formal statement
theorem compatible_selection_uniform_oddExt (D : ℕ) (hD : 1 ≤ D) :
    ∃ K : ℕ, 6 ≤ K ∧
      ∀ ε : ℝ, 0 < ε → ∃ Q : ℕ,
        ∀ (F : Type u) [Field F] [Fintype F] [DecidableEq F]
          (n : ℕ) (data : Data F n),
          Bounded D data → Q ≤ Fintype.card F →
            1 - ε ≤ (poolLaw F n K).prob
              (fun pool => HasCompatibleChoice data pool) := by
  sorry

end RyserCoveringCounterexample.Selection
end OAI
Source
OpenAI, A counterexample to Ryser's covering conjecture, OpenAI Math Release, September 23, 2026, https://github.com/openai/math (paper: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/preprints/A-Counterexample-to-Rysers-Covering-Conjecture-September-23-2026/paper.pdf; Apache License 2.0); Theorem 4.1. Lean: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/Combinatorics/Ryser/Selection/Main.lean#L13 (declaration OAI.RyserCoveringCounterexample.Selection.compatible_selection_uniform; suffix _oddExt added for name uniqueness)

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