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LeanPool.HighContrastHomogenization.Provider.Quenched.RowTailSumConstruction

High-contrast homogenization: Provider.Quenched.RowTailSumConstruction #

Imported from the Apache-2.0 HighContrastHomogenization development at commit 7a13dbcd8d6609264a713373f5c69ceeac870472.

A measurable representative of the weighted row series #

The weighted tail series of e.random.adapted.sum need not converge off the support of the law, so the endgame carries it as a measurable function agreeing almost everywhere with the raw series. This file constructs that representative from measurability of the rows and almost-everywhere summability alone.

theorem HCPolySupport.HighContrast.Quenched.exists_measurable_weighted_rowTailSum {Ω : Type u_1} [MeasurableSpace Ω] {P : MeasureTheory.Measure Ω} {B : ℕ → Ω → ℝ} {kappa : ℝ} (hB : ∀ (m : ℕ), Measurable (B m)) (hsummable : ∀ᵐ (ω : Ω) ∂P, ∀ (k : ℕ), Summable fun (j : ℕ) => 3 ^ (kappa * ↑j) * B (k + j) ω) :
∃ (F : ℕ → Ω → ℝ), (∀ (k : ℕ), Measurable (F k)) ∧ ∀ᵐ (ω : Ω) ∂P, ∀ (k : ℕ), HasSum (fun (j : ℕ) => 3 ^ (kappa * ↑j) * B (k + j) ω) (F k ω)

An almost-everywhere summable weighted row family has a measurable tail-sum representative at every generation.