OAI/GroupTheory/PolycyclicRecognition/Geometry/WeightedWordBound.lean

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Word-length control by a weighted norm

Short-cost factors are accumulated until they leave a small identity ball. Each completed block has bounded word length and pays for that length.

  1. theorem OAI.PolycyclicRecognition.seminorm_product_cost_bound line 22

    Source documentation

    The residual factor stays in the small ball; every flushed block is charged against the accumulated cost.

    theorem seminorm_product_cost_bound
        (p w : GroupSeminorm G) (c : G → ℝ≥0) {δ : ℝ}
        (hδ : 0 < δ) (hδ1 : δ ≤ 1)
        (hpc : ∀ g, p g ≤ c g)
        (hlocal : ∀ g, p g ≤ δ → w g ≤ 1)
        (hwc : ∀ g, w g ≤ max 1 (c g : ℝ))
        (l : List G) :
        w l.prod ≤ (4 / δ) * (productCost c l : ℝ) + 1 := by
    …

    Mentions: OAI.PolycyclicRecognition.productCost