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LeanPool.CaffarelliKohnNirenberg.Leray.CompactnessGradientPairing

Compactness Gradient Pairing #

Supporting estimates for the Navier–Stokes development.

theorem CKN.Leray.tendsto_integral_of_strong_l2 {α : Type u_1} {E : Type u_2} [MeasurableSpace α] [NormedAddCommGroup E] [NormedSpace ℝ E] (μ : MeasureTheory.Measure α) [MeasureTheory.IsFiniteMeasure μ] (F : ℕ → α → E) (G : α → E) (hF : ∀ (n : ℕ), MeasureTheory.MemLp (F n) 2 μ) (hconv : Filter.Tendsto (fun (n : ℕ) => MeasureTheory.eLpNorm (F n - G) 2 μ) Filter.atTop (nhds 0)) :
Filter.Tendsto (fun (n : ℕ) => ∫ (x : α), F n x ∂μ) Filter.atTop (nhds (∫ (x : α), G x ∂μ))

Strong L² convergence on a finite-measure space passes to Bochner integrals.

theorem CKN.Leray.tendsto_integral_mul_test_of_strong_l2 {α : Type u_1} {E : Type u_2} [MeasurableSpace α] [NormedAddCommGroup E] [NormedSpace ℝ E] (μ : MeasureTheory.Measure α) [MeasureTheory.IsFiniteMeasure μ] (F : ℕ → α → E) (G : α → E) (φ : α → ℝ) (hF : ∀ (n : ℕ), MeasureTheory.MemLp (F n) 2 μ) (hφ : MeasureTheory.MemLp φ ⊤ μ) (hconv : Filter.Tendsto (fun (n : ℕ) => MeasureTheory.eLpNorm (F n - G) 2 μ) Filter.atTop (nhds 0)) :
Filter.Tendsto (fun (n : ℕ) => ∫ (x : α), φ x • F n x ∂μ) Filter.atTop (nhds (∫ (x : α), φ x • G x ∂μ))

A bounded scalar multiplier preserves convergence of integrals under strong L² convergence.

theorem CKN.Leray.tendsto_setIntegral_mul_test_of_strong_l2 {α : Type u_1} [MeasurableSpace α] (μ : MeasureTheory.Measure α) [MeasureTheory.IsFiniteMeasure μ] (F : ℕ → α → ℝ) (G φ : α → ℝ) (S : Set α) (hF : ∀ (n : ℕ), MeasureTheory.MemLp (F n) 2 μ) (hφ : MeasureTheory.MemLp φ ⊤ μ) (hS : MeasurableSet S) (hconv : Filter.Tendsto (fun (n : ℕ) => MeasureTheory.eLpNorm (F n - G) 2 μ) Filter.atTop (nhds 0)) :
Filter.Tendsto (fun (n : ℕ) => ∫ (x : α) in S, φ x * F n x ∂μ) Filter.atTop (nhds (∫ (x : α) in S, φ x * G x ∂μ))

A bounded test on a measurable subset preserves strong L² convergence of scalar pairings.