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Project-declaredLean 4.29.0-rc6 · mathlib@5c8398df5281

Ae eq of tendsto e Lp Norm sub

BareFunction.ae_eq_of_tendsto_eLpNorm_sub

Plain-language statement

Lp limit uniqueness: if f_n → g₁ and f_n → g₂ in eLpNorm, then g₁ =ᵐ g₂.

Exact Lean statement

theorem ae_eq_of_tendsto_eLpNorm_sub
    {p : ℝ≥0∞} (hp : 1 ≤ p)
    {f : ℕ → α → E} {g₁ g₂ : α → E}
    (hf_aesm : ∀ n, AEStronglyMeasurable (f n) μ)
    (hg₁ : AEStronglyMeasurable g₁ μ) (hg₂ : AEStronglyMeasurable g₂ μ)
    (h1 : Tendsto (fun n => eLpNorm (f n - g₁) p μ) atTop (nhds 0))
    (h2 : Tendsto (fun n => eLpNorm (f n - g₂) p μ) atTop (nhds 0)) :
    g₁ =ᵐ[μ] g₂

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
theorem ae_eq_of_tendsto_eLpNorm_sub    {p : 0∞} (hp : 1  p)    {f :   α  E} {g₁ g₂ : α  E}    (hf_aesm :  n, AEStronglyMeasurable (f n) μ)    (hg₁ : AEStronglyMeasurable g₁ μ) (hg₂ : AEStronglyMeasurable g₂ μ)    (h1 : Tendsto (fun n => eLpNorm (f n - g₁) p μ) atTop (nhds 0))    (h2 : Tendsto (fun n => eLpNorm (f n - g₂) p μ) atTop (nhds 0)) :    g₁ =ᵐ[μ] g₂ := by  -- eLpNorm(g₁ - g₂) is constant, bounded by eLpNorm(g₁ - f n) + eLpNorm(f n - g₂) → 0  have hzero : eLpNorm (g₁ - g₂) p μ = 0 := le_antisymm (by    have hbound :  n, eLpNorm (g₁ - g₂) p μ         eLpNorm (f n - g₁) p μ + eLpNorm (f n - g₂) p μ := by      intro n      calc eLpNorm (g₁ - g₂) p μ          = eLpNorm ((g₁ - f n) + (f n - g₂)) p μ := by            congr 1; ext x; simp [sub_add_sub_cancel]        _  eLpNorm (g₁ - f n) p μ + eLpNorm (f n - g₂) p μ :=            eLpNorm_add_le (hg₁.sub (hf_aesm n)) ((hf_aesm n).sub hg₂) hp        _ = eLpNorm (f n - g₁) p μ + eLpNorm (f n - g₂) p μ := by            congr 1            rw [show g₁ - f n = -(f n - g₁) from by                  ext x                  simp [sub_eq_add_neg],                eLpNorm_neg]    -- Constant ≤ sum → 0, so constant = 0    have hsum_tendsto : Tendsto (fun n => eLpNorm (f n - g₁) p μ + eLpNorm (f n - g₂) p μ)        atTop (nhds 0) := by simpa [add_zero] using h1.add h2    exact ge_of_tendsto hsum_tendsto (Filter.Eventually.of_forall hbound)) bot_le  have hae_zero := (eLpNorm_eq_zero_iff (hg₁.sub hg₂)    (ne_of_gt (lt_of_lt_of_le (by simp : (0 : 0∞) < 1) hp))).mp hzero  -- g₁ - g₂ =ᵐ 0 → g₁ =ᵐ g₂  exact hae_zero.mono fun x hx => by simpa [sub_eq_zero] using hx
Project
DeGiorgi
License
Apache-2.0
Commit
4c1b3077d378
Source
DeGiorgi/LpFunctionToolkit.lean:85-116

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Related declarations

Project-declaredLean 4.29.0-rc6

E Lp Norm pi le sum component

BareFunction.eLpNorm_pi_le_sum_component

Plain-language statement

Vector eLpNorm ≤ sum of component eLpNorms for Pi-valued functions. Uses eLpNorm_mono_real for the pointwise bound together with eLpNorm_sum_le for ℝ-valued functions, avoiding Pi instance synthesis.

partial differential equationsregularity theoryanalysis

Source project: DeGiorgi

Person-level attribution pending.

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Project-declaredLean 4.29.0-rc6

Mem Lp of tendsto e Lp Norm

BareFunction.memLp_of_tendsto_eLpNorm

Plain-language statement

If f n → g in eLpNorm and each f n ∈ Lp, then g ∈ Lp, provided g is AEStronglyMeasurable. Avoids the Lp type entirely. The key observation: eLpNorm (f n - g) → 0 means eLpNorm (f N - g) < 1 for some N. Then eLpNorm g ≤ eLpNorm (f N - g) + eLpNorm (f N) < ∞.

partial differential equationsregularity theoryanalysis

Source project: DeGiorgi

Person-level attribution pending.

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Project-declaredLean 4.29.0-rc6

Scalar cauchy to limit

BareFunction.scalar_cauchy_to_limit

Plain-language statement

Scalar Cauchy → limit. Generic over codomain E and domain α.

partial differential equationsregularity theoryanalysis

Source project: DeGiorgi

Person-level attribution pending.

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