OAI/NumberTheory/EgyptianFractions/LogWeightedSums.lean

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Logarithmic weights in finite exponential sums

Abel summation transfers a uniform bound for all prefixes of a sequence to its logarithmically weighted sum. This supplies the inner logarithmic weight in the first Type I term of Vaughan's identity; no estimate over primes is assumed here.

  1. theorem OAI.Problem337.Vaughan.norm_sum_smul_le_two_mul_of_monotone line 20

    Source documentation

    An increasing nonnegative real weight costs at most twice its endpoint when all unweighted prefix sums are bounded by B.

    theorem norm_sum_smul_le_two_mul_of_monotone
        {E : Type*} [NormedAddCommGroup E] [NormedSpace ℝ E]
        (f : ℕ → ℝ) (z : ℕ → E) (N : ℕ) (B : ℝ)
        (hf : Monotone f) (hf0 : 0 ≤ f 0)
        (hprefix : ∀ k ≤ N + 1, ‖∑ j ∈ Finset.range k, z j‖ ≤ B) :
        ‖∑ j ∈ Finset.range (N + 1), f j • z j‖ ≤ 2 * f N * B := by
    …
  2. theorem OAI.Problem337.Vaughan.norm_log_weighted_range_le line 53

    Source documentation

    Logarithmic weights on positive indices, in shifted-range form. The result also holds for N = 0 and N = 1, when the weighted sum is zero.

    theorem norm_log_weighted_range_le
        (z : ℕ → ℂ) (N : ℕ) (B : ℝ)
        (hprefix : ∀ k ≤ N, ‖∑ j ∈ Finset.range k, z (j + 1)‖ ≤ B) :
        ‖∑ j ∈ Finset.range N, (Real.log (j + 1 : ℕ) : ℂ) * z (j + 1)‖ ≤
          2 * Real.log N * B := by
    …
  3. lemma OAI.Problem337.Vaughan.sum_Icc_one_eq_shifted_range line 71
  4. theorem OAI.Problem337.Vaughan.norm_log_weighted_Icc_le line 79

    Source documentation

    Positive-interval formulation of the logarithmic Abel estimate.

    theorem norm_log_weighted_Icc_le
        (z : ℕ → ℂ) (N : ℕ) (B : ℝ)
        (hprefix : ∀ k ≤ N, ‖∑ j ∈ Finset.Icc 1 k, z j‖ ≤ B) :
        ‖∑ j ∈ Finset.Icc 1 N, (Real.log j : ℂ) * z j‖ ≤
          2 * Real.log N * B := by
    …