OAI.KirchbergRordam.quotient_isomorphism_of_ultrapower_split_and_conjugacy: intermediate lemma from OpenAI, The Kirchberg–Rørdam character criterion

Proved

OAI.KirchbergRordam.quotient_isomorphism_of_ultrapower_split_and_conjugacy

by dbenbenn · Oct 25, 2026 · Mathlib 0df444a (Lean v4.33.1)

openai-math

An intermediate lemma of the split of OpenAI's proof of OAI.KirchbergRordam.character_criterion, carved from OpenAI's openai/math development for this platform. The statement and its proof are OpenAI's (OpenAI, The Kirchberg–Rørdam character criterion, OpenAI Math Release, September 25, 2026, result family 299, github.com/openai/math, Apache License 2.0); in Lean it is the declaration OAI.KirchbergRordam.quotient_isomorphism_of_ultrapower_split_and_conjugacy of lean/OAI/Analysis/CharacterCriterion/Absorption.lean at commit adc7f12, ported to Lean 4.33.1 and Mathlib 0df444a.

The statement, as published (namespace OAI.KirchbergRordam, with open scoped TensorProduct, open scoped InnerProductSpace, open scoped BigOperators, open Set Module, open Topology, open NormedSpace, open scoped ComplexOrder, open scoped ComplexOrder, open scoped InnerProductSpace, open scoped InnerProductSpace, open NormedSpace, open scoped TensorProduct InnerProductSpace, open UniformSpace, open Filter Topology BoundedContinuousFunction, open Filter Topology, open Topology, open scoped TensorProduct CStarAlgebra, open scoped CStarAlgebra ComplexOrder, open NormedSpace, open scoped ComplexOrder, open scoped ComplexOrder, open scoped InnerProductSpace, open scoped CStarAlgebra ComplexOrder, open Filter Topology):

theorem quotient_isomorphism_of_ultrapower_split_and_conjugacy
    {A B C : Type*} [CStarAlgebra A] [CStarAlgebra B] [CStarAlgebra C]
    [TopologicalSpace.SeparableSpace A] [TopologicalSpace.SeparableSpace C]
    (ω : Ultrafilter ℕ) (φ : A →⋆ₐ[ℂ] B)
    (q : B →⋆ₐ[ℂ] C) (hq : DenseRange q)
    (hinj : Function.Injective (q.comp φ))
    (ψ : B →⋆ₐ[ℂ] NormUltrapower.Algebra A ω)
    (hsplit : ∀ a, ψ (φ a) = NormUltrapower.diagonal ω a)
    (hconj : ∀ (T : Finset B) (ε : ℝ), 0 < ε →
      ∃ u : unitary (NormUltrapower.Algebra B ω), ∀ b ∈ T,
        dist (Unitary.conjStarAlgAut ℂ _ u (NormUltrapower.map φ ω (ψ b)))
          (NormUltrapower.diagonal ω b) < ε) :
    Nonempty (A ≃⋆ₐ[ℂ] C)

Definitions. The statement is written with OAI.KirchbergRordam.GenericRW.DetectingSpace.quotientNormedRing (definitions bundle OAIB3Kr009 of this split); OAI.KirchbergRordam.NormUltrapower.map (definitions bundle OAIB3Kr012 of this split); OAI.KirchbergRordam.NormUltrapower.Algebra, OAI.KirchbergRordam.NormUltrapower.BoundedSeq, OAI.KirchbergRordam.NormUltrapower.diagonal, OAI.KirchbergRordam.NormUltrapower.nullIdeal, OAI.KirchbergRordam.NormUltrapower.nullIdeal_closed, OAI.KirchbergRordam.NormUltrapower.nullIdeal_twoSided, OAI.KirchbergRordam.NormUltrapower.quotientStar and OAI.KirchbergRordam.NormUltrapower.quotientStarRing (the published bundle Def_CharacterCriterion).

Used by. The proof of OAI.KirchbergRordam.spatial_absorption_of_central_maximal_half_flip of this split imports it.

Preamble

import Mathlib
import Definitions.Def_CharacterCriterion
import Definitions.Def_OAIB3Kr012

Formal statement

section

set_option linter.all false
set_option linter.unusedVariables false
set_option linter.unusedTactic false
set_option linter.unreachableTactic false

namespace OAI

noncomputable section
open scoped TensorProduct
open scoped InnerProductSpace
open scoped BigOperators
open Set Module
open Topology
open NormedSpace
open scoped ComplexOrder
open scoped ComplexOrder
open scoped InnerProductSpace
open scoped InnerProductSpace
open NormedSpace
open scoped TensorProduct InnerProductSpace
open UniformSpace
variable [KirchbergRordam.GenericRW.Size]
variable [KirchbergRordam.GenericRW.PauliData]
omit [KirchbergRordam.GenericRW.Size] [KirchbergRordam.GenericRW.PauliData]
open Filter Topology BoundedContinuousFunction
open Filter Topology
open Topology
open scoped TensorProduct CStarAlgebra
open scoped CStarAlgebra ComplexOrder
open NormedSpace
open scoped ComplexOrder
open scoped ComplexOrder
open scoped InnerProductSpace
open scoped CStarAlgebra ComplexOrder

namespace KirchbergRordam

open Filter Topology

theorem quotient_isomorphism_of_ultrapower_split_and_conjugacy
    {A B C : Type*} [CStarAlgebra A] [CStarAlgebra B] [CStarAlgebra C]
    [TopologicalSpace.SeparableSpace A] [TopologicalSpace.SeparableSpace C]
    (ω : Ultrafilter ℕ) (φ : A →⋆ₐ[ℂ] B)
    (q : B →⋆ₐ[ℂ] C) (hq : DenseRange q)
    (hinj : Function.Injective (q.comp φ))
    (ψ : B →⋆ₐ[ℂ] NormUltrapower.Algebra A ω)
    (hsplit : ∀ a, ψ (φ a) = NormUltrapower.diagonal ω a)
    (hconj : ∀ (T : Finset B) (ε : ℝ), 0 < ε →
      ∃ u : unitary (NormUltrapower.Algebra B ω), ∀ b ∈ T,
        dist (Unitary.conjStarAlgAut ℂ _ u (NormUltrapower.map φ ω (ψ b)))
          (NormUltrapower.diagonal ω b) < ε) :
    Nonempty (A ≃⋆ₐ[ℂ] C) := by
  sorry
end KirchbergRordam

end

end OAI
end

Source

OpenAI, The Kirchberg–Rørdam character criterion, OpenAI Math Release, September 25, 2026, https://github.com/openai/math (result family 299; paper: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/preprints/The-Kirchberg-Rordam-character-criterion-September-25-2026/paper.pdf; Apache License 2.0); Lean: https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/Analysis/CharacterCriterion/Absorption.lean (declaration OAI.KirchbergRordam.quotient_isomorphism_of_ultrapower_split_and_conjugacy)

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