One orbit step toward a transported tuple, rank at least two
ProvedOAI.FreeGroupFactorMain.Generation.orbit_step_ge_twoThroughout, is the group von Neumann algebra of a discrete group acting on , with canonical trace , left-regular unitaries , and . Let , and let the orbit be the set of tuples as runs over the -preserving -automorphisms of . For a tuple of unitaries, is the evaluation of the word and . Tuples carry the metric in the operator norm. Let be the free generators of . Let , let be a -preserving -automorphism of , and . There are in the orbit with and a word such that
Thus, after a small move in the orbit, a word in the -tuple approximates the transported extra generator.
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 namespace FreeGroupFactorMain noncomputable section open Set Metric Filter open scoped NNReal Topology BigOperators ContDiff attribute [local instance] Classical.propDecidable open UnitaryEvaluation namespace Generation
theorem orbit_step_ge_two (n : ℕ) (hn : 2 ≤ n)
(Φ : Ambient n ≃⋆ₐ[ℂ] Ambient n)
(ht : ∀ T, canonicalTrace (Φ T) = canonicalTrace T) {θ : ℝ} (hθ : 0 < θ) :
∃ V ∈ orbit n, dist V (mapTuple Φ (initial n)) < θ ∧
∃ w : FreeGroup (Fin n), ∀ j : Option (Fin n),
twoNorm ((wordTuple V (fun j => j.elim w FreeGroup.of) j : Ambient n) -
(mapTuple Φ generatorUnitary j : Ambient n)) < θ := by
sorry
end Generation
end
end FreeGroupFactorMain
end OAI