OAI/NumberTheory/Ostmann/ZeroDensity/FiniteInverseSquareDensity.lean

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Inverse-square summability from a three-halves counting bound

  1. theorem OAI.Ostmann.finite_exp_three_halves_sum line 12

    Source documentation

    Sorting by height converts the counting bound into a convergent 4/3-series.

    theorem finite_exp_three_halves_sum {ι : Type*} (S : Finset ι)
        (y : ι → ℝ) (B : ℝ) (hB : 0 ≤ B)
        (hy : ∀ i ∈ S, 0 ≤ y i)
        (hc : ∀ t : ℝ, 0 ≤ t →
          ((S.filter (fun i => y i ≤ t)).card : ℝ) ≤ B * Real.exp ((3 / 2) * t)) :
        (∑ i ∈ S, Real.exp (-2 * y i)) ≤ B ^ (4 / 3 : ℝ) *
          ∑ j ∈ Finset.range S.card, ((j + 1 : ℕ) : ℝ) ^ (-4 / 3 : ℝ) := by
    …