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Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

Norm tsum log Deriv expo le of norm le

norm_tsum_logDeriv_expo_le_of_norm_le

Plain-language statement

Monotone version of norm_tsum_logDeriv_expo_le: if ‖q‖ ≤ r < 1, then ‖∑ n·qⁿ/(1-qⁿ)‖ ≤ r/(1-r)³. Useful when we have a uniform bound on ‖q‖.

Exact Lean statement

lemma norm_tsum_logDeriv_expo_le_of_norm_le {q : ℂ} {r : ℝ} (hqr : ‖q‖ ≤ r) (hr : r < 1) :
    ‖∑' n : ℕ+, (n : ℂ) * q ^ (n : ℕ) / (1 - q ^ (n : ℕ))‖ ≤ r / (1 - r) ^ 3

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma norm_tsum_logDeriv_expo_le_of_norm_le {q : ℂ} {r : } (hqr : ‖q‖  r) (hr : r < 1) :    ‖∑' n : +, (n : ℂ) * q ^ (n : ) / (1 - q ^ (n : ))‖  r / (1 - r) ^ 3 := by  have hq : ‖q‖ < 1 := lt_of_le_of_lt hqr hr  have hr_nonneg : 0  r := le_trans (norm_nonneg _) hqr  calc ‖∑' n : +, (n : ℂ) * q ^ (n : ) / (1 - q ^ (n : ))‖       ‖q‖ / (1 - ‖q‖) ^ 3 := norm_tsum_logDeriv_expo_le hq    _  r / (1 - r) ^ 3 := by        have := sub_pos.mpr hr        have := sub_pos.mpr hq        gcongr
Project
Sphere Packing in Dimension 8
License
Apache-2.0
Commit
acfc6204e65a
Source
SpherePacking/ModularForms/Eisenstein.lean:449-458

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Related declarations

Project-declaredLean 4.31.0

Anti Der Pos

antiDerPos

Plain-language statement

If FF is a modular form where F(it)F(it) is positive for sufficiently large tt (i.e. constant term is positive) and the derivative is positive, then FF is also positive.

sphere packingFourier analysismodular forms

Source project: Sphere Packing in Dimension 8

Person-level attribution pending.

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Project-declaredLean 4.31.0

Anti Serre Der Pos

antiSerreDerPos

Plain-language statement

Let F:HCF : \mathbb{H} \to \mathbb{C} be a holomorphic function where F(it)F(it) is real for all t>0t > 0. Assume that Serre derivative kF\partial_k F is positive on the imaginary axis. If F(it)F(it) is positive for sufficiently large tt, then F(it)F(it) is positive for all t>0t > 0.

sphere packingFourier analysismodular forms

Source project: Sphere Packing in Dimension 8

Person-level attribution pending.

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