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Project-declaredLean 4.31.0 · mathlib@fabf563a7c95

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.

Exact Lean statement

theorem antiSerreDerPos {F : ℍ → ℂ} {k : ℤ} (hMD : MDifferentiable 𝓘(ℂ) 𝓘(ℂ) F)
    (hSDF : ResToImagAxis.Pos (serre_D k F))
    (hF : ResToImagAxis.EventuallyPos F) : ResToImagAxis.Pos F

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem antiSerreDerPos {F : ℍ  ℂ} {k : } (hMD : MDifferentiable 𝓘(ℂ) 𝓘(ℂ) F)    (hSDF : ResToImagAxis.Pos (serre_D k F))    (hF : ResToImagAxis.EventuallyPos F) : ResToImagAxis.Pos F := by  obtain _, hSDF_pos := hSDF  obtain hF_real, t₀, ht₀_pos, hF_pos := hF  refine hF_real, fun t ht => ?_  have key :  s, 0 < s  0 < (F.resToImagAxis s).re := by    refine  pos_of_deriv_neg_at_zeros ?_ ht₀_pos hF_pos ?_    · intro s hs      exact (continuous_re.continuousAt.comp        (ResToImagAxis.Differentiable F hMD s hs).continuousAt).continuousWithinAt    · intro s hs _ hgs      have hda := hasDerivAt_resToImagAxis_re hMD hs      rw [hda.deriv]      have h_ria : F.resToImagAxis s = F I * s, by simp [hs] := by        simp [resToImagAxis, ResToImagAxis, dif_pos hs]      have hz : F (I * s, by simp [hs] : ℍ) = 0 := by        apply Complex.ext        · rw [zero_re,  h_ria]; exact hgs        · rw [zero_im,  h_ria]; exact (hF_real s hs)      have : 0 < ((D F).resToImagAxis s).re := by        simpa [resToImagAxis, ResToImagAxis, dif_pos hs,          serre_D_apply, hz, mul_zero, sub_zero] using hSDF_pos s hs      nlinarith [pi_pos]  exact key t ht
Project
Sphere Packing in Dimension 8
License
Apache-2.0
Commit
acfc6204e65a
Source
SpherePacking/ModularForms/Derivative.lean:928-952

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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

Cusp Form rpow mul res To Imag Axis tendsto zero

cuspForm_rpow_mul_resToImagAxis_tendsto_zero

Plain-language statement

For a cusp form f of level Γ(n), we have t^s * f(it) → 0 as t → ∞ for any real power s. This follows from the exponential decay of cusp forms at infinity: f = O(exp(-2π τ.im / n)).

sphere packingFourier analysismodular forms

Source project: Sphere Packing in Dimension 8

Person-level attribution pending.

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