diff --git a/Mathlib/MeasureTheory/Constructions/Prod/Integral.lean b/Mathlib/MeasureTheory/Constructions/Prod/Integral.lean index b57cfa74f5b06..69a1f5da31d44 100644 --- a/Mathlib/MeasureTheory/Constructions/Prod/Integral.lean +++ b/Mathlib/MeasureTheory/Constructions/Prod/Integral.lean @@ -220,17 +220,16 @@ variable [SigmaFinite ν] section +theorem integrable_swap_iff [SigmaFinite μ] {f : α × β → E} : + Integrable (f ∘ Prod.swap) (ν.prod μ) ↔ Integrable f (μ.prod ν) := + measurePreserving_swap.integrable_comp_emb MeasurableEquiv.prodComm.measurableEmbedding +#align measure_theory.integrable_swap_iff MeasureTheory.integrable_swap_iff + theorem Integrable.swap [SigmaFinite μ] ⦃f : α × β → E⦄ (hf : Integrable f (μ.prod ν)) : Integrable (f ∘ Prod.swap) (ν.prod μ) := - ⟨hf.aestronglyMeasurable.prod_swap, - (lintegral_prod_swap _ hf.aestronglyMeasurable.ennnorm : _).le.trans_lt hf.hasFiniteIntegral⟩ + integrable_swap_iff.2 hf #align measure_theory.integrable.swap MeasureTheory.Integrable.swap -theorem integrable_swap_iff [SigmaFinite μ] ⦃f : α × β → E⦄ : - Integrable (f ∘ Prod.swap) (ν.prod μ) ↔ Integrable f (μ.prod ν) := - ⟨fun hf => hf.swap, fun hf => hf.swap⟩ -#align measure_theory.integrable_swap_iff MeasureTheory.integrable_swap_iff - theorem hasFiniteIntegral_prod_iff ⦃f : α × β → E⦄ (h1f : StronglyMeasurable f) : HasFiniteIntegral f (μ.prod ν) ↔ (∀ᵐ x ∂μ, HasFiniteIntegral (fun y => f (x, y)) ν) ∧ @@ -336,13 +335,11 @@ theorem Integrable.integral_prod_right [SigmaFinite μ] ⦃f : α × β → E⦄ /-! ### The Bochner integral on a product -/ - variable [SigmaFinite μ] -theorem integral_prod_swap (f : α × β → E) (hf : AEStronglyMeasurable f (μ.prod ν)) : - ∫ z, f z.swap ∂ν.prod μ = ∫ z, f z ∂μ.prod ν := by - rw [← prod_swap] at hf - rw [← integral_map measurable_swap.aemeasurable hf, prod_swap] +theorem integral_prod_swap (f : α × β → E) : + ∫ z, f z.swap ∂ν.prod μ = ∫ z, f z ∂μ.prod ν := + measurePreserving_swap.integral_comp MeasurableEquiv.prodComm.measurableEmbedding _ #align measure_theory.integral_prod_swap MeasureTheory.integral_prod_swap variable {E' : Type*} [NormedAddCommGroup E'] [CompleteSpace E'] [NormedSpace ℝ E'] @@ -477,7 +474,7 @@ theorem integral_prod : This version has the integrals on the right-hand side in the other order. -/ theorem integral_prod_symm (f : α × β → E) (hf : Integrable f (μ.prod ν)) : ∫ z, f z ∂μ.prod ν = ∫ y, ∫ x, f (x, y) ∂μ ∂ν := by - simp_rw [← integral_prod_swap f hf.aestronglyMeasurable]; exact integral_prod _ hf.swap + rw [← integral_prod_swap f]; exact integral_prod _ hf.swap #align measure_theory.integral_prod_symm MeasureTheory.integral_prod_symm /-- Reversed version of **Fubini's Theorem**. -/