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Uniform smallness of a normal positive orbit on orthogonal projections

Proved
OAI.BoundedHochschild.KadisonRingrose.normal_positive_uniform_orbit_hull

by wurtle · Nov 4, 2026 · Mathlib 0df444a (Lean v4.33.1)

bounded-hochschild-cohomologyoai-math

Throughout, MMM is a unital C*-algebra with a partial order making it star-ordered, XXX is a complex Banach space, and e:X∗→Me:X^*\to Me:X∗→M is an isometric conjugate-linear isomorphism, so MMM is a von Neumann algebra with predual XXX (the Lean hypothesis e). Let MMM be finite and ψ\psiψ a positive functional in the predual. Let (qn)(q_n)(qn​) be pairwise orthogonal projections and ε>0\varepsilon>0ε>0. Then, for all large nnn, every functional GGG in the norm-closed convex hull of the unitary pullbacks of ψ\psiψ (unitaryOrbitHull, with pullback a↦ψ(uau∗)a\mapsto\psi(uau^*)a↦ψ(uau∗)) satisfies

∣G(qn)∣<ε.|G(q_n)|<\varepsilon.∣G(qn​)∣<ε.

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. Only the keyword lemma, where used upstream, becomes theorem, and a leading include ... in or omit ... in moves to the preamble. It is a step of the Lean proof of the vanishing of higher bounded Hochschild cohomology.

Preamble
import Mathlib
import Definitions.Def_KadisonRingroseSupport2

namespace OAI

noncomputable section

open Filter Topology
open scoped ComplexOrder

namespace BoundedHochschild
namespace KadisonRingrose

open HochschildNormalPart

universe u

variable {M X : Type u} [CStarAlgebra M] [PartialOrder M] [StarOrderedRing M]
  [NormedAddCommGroup X] [NormedSpace ℂ X] [CompleteSpace X]

Formal statement
theorem normal_positive_uniform_orbit_hull (e : StrongDual ℂ X ≃ₗᵢ⋆[ℂ] M)
    (hfinite : FiniteAlgebra M) (ψ : M →ₚ[ℂ] ℂ) (hψ : TraceInPredual e ψ)
    (q : ℕ → M) (hq : ∀ n, IsStarProjection (q n))
    (horth : ∀ i j, i ≠ j → q i * q j = 0) (ε : ℝ) (hε : 0 < ε) :
    ∀ᶠ n in atTop, ∀ G ∈ unitaryOrbitHull (positiveFunctionalCLM ψ), ‖G (q n)‖ < ε := by
  sorry

end KadisonRingrose
end BoundedHochschild
end
end OAI
Source
OpenAI, Vanishing of higher bounded Hochschild cohomology, September 23, 2026, https://github.com/openai/math (paper: preprints/Vanishing-of-higher-bounded-Hochschild-cohomology-September-23-2026/paper.pdf; Apache License 2.0); Lean declaration `OAI.BoundedHochschild.KadisonRingrose.normal_positive_uniform_orbit_hull`, https://github.com/openai/math/blob/adc7f1241b42e322a6451854ab7e4b4c146bf78a/lean/OAI/Analysis/BoundedHochschild/NormalOrbitHull.lean#L106

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