OAI/Analysis/KadisonKastler/QuantitativePolarPath.lean

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Quantitative continuous polar paths from two approximate inverses

  1. theorem OAI.KadisonKastler.exists_continuous_polar_path line 16

    Source documentation

    The smoothing estimates produce a continuous unitary family with explicit errors in both factors. Only the first family needs continuity.

    theorem exists_continuous_polar_path (a c : X → A) (ha : Continuous a)
        {r : ℝ} (hr : 0 ≤ r) (hrsmall : r < 1 / 8)
        (hanorm : ∀ x, ‖a x‖ ≤ 1 + r) (hcnorm : ∀ x, ‖c x‖ ≤ 1 + r)
        (hac : ∀ x, ‖a x * c x - 1‖ ≤ r) (hca : ∀ x, ‖c x * a x - 1‖ ≤ r) :
        ∃ v : X → unitary A, Continuous v ∧
          (∀ x, ‖(v x : A) - a x‖ ≤ 4 * r) ∧
          (∀ x, ‖star (v x : A) - c x‖ ≤ 10 * r) := by
    …