Absorbing any extra generator from the distinguished one
ProvedOAI.FreeGroupFactorMain.InfiniteGeneration.one_step_extra_of_noneThroughout, is the group von Neumann algebra of a discrete group acting on , with canonical trace , left-regular unitaries , and . Let and . Let for be the initial tuple, and for let be the extra generators. The orbit is the set of tuples for -preserving -automorphisms of . Assume that for every there are a -preserving automorphism fixing each , , and a word with and . Then for every and there are a -preserving automorphism fixing each , , and a word with
This reduces the absorption of an arbitrary extra generator to the distinguished one.
Formalization Note The statement is verbatim from OpenAI's Lean development, with the listed Definitions imported in place of the upstream modules; the definitions are supporting code for this statement.
import Mathlib import Definitions.Def_FreeGroupFactorProof18 namespace OAI noncomputable section universe uA uG uι open Set Metric Filter open scoped NNReal Topology BigOperators ContDiff ENNReal attribute [local instance] Classical.propDecidable namespace FreeGroupFactorMain.Generation end FreeGroupFactorMain.Generation namespace FreeGroupFactorMain.InfiniteGeneration open Generation
theorem one_step_extra_of_none
(hone : ∀ ε : ℝ, 0 < ε → ∃ α : M ≃⋆ₐ[ℂ] M,
(∀ T, canonicalTrace (α T) = canonicalTrace T) ∧
(∀ k : ℕ, α (extra (some k) : M) = (extra (some k) : M)) ∧
∃ w : FreeGroup (Fin 3),
(∀ i, ‖α (initial i : M)-(initial i : M)‖ < ε) ∧
twoNorm (α (word initial w)-(extra none : M)) < ε)
(q : Option ℕ) {ε : ℝ} (hε : 0 < ε) :
∃ α : M ≃⋆ₐ[ℂ] M, (∀ T, canonicalTrace (α T) = canonicalTrace T) ∧
(∀ r : Option ℕ, r ≠ q → α (extra r : M) = (extra r : M)) ∧
∃ w : FreeGroup (Fin 3),
(∀ i, ‖α (initial i : M)-(initial i : M)‖ < ε) ∧
twoNorm (α (word initial w)-(extra q : M)) < ε := by
sorry
end FreeGroupFactorMain.InfiniteGeneration
end
end OAI