File: Mathlib/Analysis/Fourier/PoissonSummation.lean

full_name: Real.fourierCoeff_tsum_comp_add
code: /-- The key lemma for Poisson summation: the `m`-th Fourier coefficient of the periodic function
`∑' n : ℤ, f (x + n)` is the value at `m` of the Fourier transform of `f`. -/
theorem Real.fourierCoeff_tsum_comp_add {f : C(ℝ, ℂ)}
    (hf : ∀ K : Compacts ℝ, Summable fun n : ℤ => ‖(f.comp (ContinuousMap.addRight n)).restrict K‖)
    (m : ℤ) : fourierCoeff (Periodic.lift <| f.periodic_tsum_comp_add_zsmul 1) m = 𝓕 f m 
goal: fourierCoeff ⋯.lift m = 𝓕 ⇑f ↑m

full_name: Real.tsum_eq_tsum_fourierIntegral
code: /-- **Poisson's summation formula**, most general form. -/
theorem Real.tsum_eq_tsum_fourierIntegral {f : C(ℝ, ℂ)}
    (h_norm :
      ∀ K : Compacts ℝ, Summable fun n : ℤ => ‖(f.comp <| ContinuousMap.addRight n).restrict K‖)
    (h_sum : Summable fun n : ℤ => 𝓕 f n) (x : ℝ) :
    ∑' n : ℤ, f (x + n) = ∑' n : ℤ, 𝓕 f n * fourier n (x : UnitAddCircle) 
goal: ∑' (n : ℤ), f (x + ↑n) = ∑' (n : ℤ), 𝓕 ⇑f ↑n * (fourier n) ↑x

full_name: isBigO_norm_Icc_restrict_atTop
code: /-- If `f` is `O(x ^ (-b))` at infinity, then so is the function
`fun x ↦ ‖f.restrict (Icc (x + R) (x + S))‖` for any fixed `R` and `S`. -/
theorem isBigO_norm_Icc_restrict_atTop {f : C(ℝ, E)} {b : ℝ} (hb : 0 < b)
    (hf : f =O[atTop] fun x : ℝ => |x| ^ (-b)) (R S : ℝ) :
    (fun x : ℝ => ‖f.restrict (Icc (x + R) (x + S))‖) =O[atTop] fun x : ℝ => |x| ^ (-b) 
goal: (fun x => ‖ContinuousMap.restrict (Set.Icc (x + R) (x + S)) f‖) =O[Filter.atTop] fun x => |x| ^ (-b)

full_name: isBigO_norm_Icc_restrict_atBot
code: theorem isBigO_norm_Icc_restrict_atBot {f : C(ℝ, E)} {b : ℝ} (hb : 0 < b)
    (hf : f =O[atBot] fun x : ℝ => |x| ^ (-b)) (R S : ℝ) :
    (fun x : ℝ => ‖f.restrict (Icc (x + R) (x + S))‖) =O[atBot] fun x : ℝ => |x| ^ (-b) 
goal: (fun x => ‖ContinuousMap.restrict (Set.Icc (x + R) (x + S)) f‖) =O[Filter.atBot] fun x => |x| ^ (-b)

full_name: isBigO_norm_restrict_cocompact
code: theorem isBigO_norm_restrict_cocompact (f : C(ℝ, E)) {b : ℝ} (hb : 0 < b)
    (hf : f =O[cocompact ℝ] fun x : ℝ => |x| ^ (-b)) (K : Compacts ℝ) :
    (fun x => ‖(f.comp (ContinuousMap.addRight x)).restrict K‖) =O[cocompact ℝ] (|·| ^ (-b)) 
goal: (fun x => ‖ContinuousMap.restrict (↑K) (f.comp (ContinuousMap.addRight x))‖) =O[Filter.cocompact ℝ] fun x => |x| ^ (-b)

full_name: Real.tsum_eq_tsum_fourierIntegral_of_rpow_decay_of_summable
code: /-- **Poisson's summation formula**, assuming that `f` decays as
`|x| ^ (-b)` for some `1 < b` and its Fourier transform is summable. -/
theorem Real.tsum_eq_tsum_fourierIntegral_of_rpow_decay_of_summable {f : ℝ → ℂ} (hc : Continuous f)
    {b : ℝ} (hb : 1 < b) (hf : IsBigO (cocompact ℝ) f fun x : ℝ => |x| ^ (-b))
    (hFf : Summable fun n : ℤ => 𝓕 f n) (x : ℝ) :
    ∑' n : ℤ, f (x + n) = ∑' n : ℤ, 𝓕 f n * fourier n (x : UnitAddCircle) 
goal: ∑' (n : ℤ), f (x + ↑n) = ∑' (n : ℤ), 𝓕 f ↑n * (fourier n) ↑x

full_name: Real.tsum_eq_tsum_fourierIntegral_of_rpow_decay
code: /-- **Poisson's summation formula**, assuming that both `f` and its Fourier transform decay as
`|x| ^ (-b)` for some `1 < b`. (This is the one-dimensional case of Corollary VII.2.6 of Stein and
Weiss, *Introduction to Fourier analysis on Euclidean spaces*.) -/
theorem Real.tsum_eq_tsum_fourierIntegral_of_rpow_decay {f : ℝ → ℂ} (hc : Continuous f) {b : ℝ}
    (hb : 1 < b) (hf : f =O[cocompact ℝ] (|·| ^ (-b)))
    (hFf : (𝓕 f) =O[cocompact ℝ] (|·| ^ (-b))) (x : ℝ) :
    ∑' n : ℤ, f (x + n) = ∑' n : ℤ, 𝓕 f n * fourier n (x : UnitAddCircle) 
goal: ∑' (n : ℤ), f (x + ↑n) = ∑' (n : ℤ), 𝓕 f ↑n * (fourier n) ↑x

full_name: SchwartzMap.tsum_eq_tsum_fourierIntegral
code: /-- **Poisson's summation formula** for Schwartz functions. -/
theorem SchwartzMap.tsum_eq_tsum_fourierIntegral (f g : SchwartzMap ℝ ℂ) (hfg : 𝓕 ⇑f = ⇑g) (x : ℝ) :
    ∑' n : ℤ, f (x + n) = (∑' n : ℤ, g n * fourier n (x : UnitAddCircle)) 
goal: ∑' (n : ℤ), f (x + ↑n) = ∑' (n : ℤ), g ↑n * (fourier n) ↑x