OAI/Analysis/Unitarizability/CompactMean.lean

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Weak-star compactness for positive normalized invariant means.

  1. theorem OAI.Dixmier.amenable_of_approximate_means line 16

    Source documentation

    Approximate positive normalized means, with all finite translation tests, have a positive normalized invariant weak-star cluster point.

    theorem amenable_of_approximate_means
        (h : ∀ (S : Finset G) (ε : ℝ), 0 < ε →
          ∃ m : (G →ᵇ ℂ) →L[ℂ] ℂ,
            ‖m‖ ≤ 1 ∧ m (BoundedContinuousFunction.const G (1 : ℂ)) = 1 ∧
            (∀ b : G →ᵇ ℂ, (∀ x, 0 ≤ (b x).re ∧ (b x).im = 0) →
              0 ≤ (m b).re ∧ (m b).im = 0) ∧
            ∀ g ∈ S, ∀ b : G →ᵇ ℂ, ‖m (leftTranslate g b) - m b‖ ≤ ε * ‖b‖) :
        Amenable G := by
    …

    Mentions: OAI.Dixmier.leftTranslate, OAI.Dixmier.Amenable