OAI/GroupTheory/PolycyclicRecognition/Analysis/SublinearScaleOffsets.lean

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Vanishing offsets from the local comparison of adjacent scales

  1. theorem OAI.PolycyclicRecognition.uniform_sublinear_of_contractive_increments line 18

    Source documentation

    The scale-comparison estimate in the height argument forces its offsets to be uniformly sublinear. Only finitely many contractions are needed for each prescribed error, so no regularity of the offset as a function of scale is required.

    theorem uniform_sublinear_of_contractive_increments
        {P W : Type*} [NormedAddCommGroup W]
        (s : P → ℝ → W) {q C : ℝ} (hq : 0 < q) (hq1 : q < 1)
        (hbound : ∀ p r, 1 ≤ r → ‖s p r‖ ≤ C * r)
        (hincrement : ∀ ε : ℝ, 0 < ε → ∃ R : ℝ, 1 ≤ R ∧
          ∀ p r, R ≤ r → ‖s p r - s p (q * r)‖ ≤ ε * r) :
        ∀ ε : ℝ, 0 < ε → ∃ R : ℝ, 1 ≤ R ∧
          ∀ p r, R ≤ r → ‖s p r‖ ≤ ε * r := by
    …