Imports
/- Copyright (c) 2025 Joseph Tooby-Smith. All rights reserved. Released under Apache 2.0 license as described in the file LICENSE. Authors: Joseph Tooby-Smith -/ module public import Physlib.Units.UnitDependent public import Mathlib.MeasureTheory.Integral.Bochner.Basic

Dimensional invariance of the integral

In this module we prove that the dimensional properties of the integral.

@[expose] public sectionlemma scaleUnit_measure (u1 u2 : LTMCTUnitChoices) (μ : MeasureTheory.Measure M) : scaleUnit u1 u2 μ = μ.map (fun m => scaleUnit u1 u2 m) := M:Typeinst✝⁴:NormedAddCommGroup Minst✝³:NormedSpace ℝ Minst✝²:HasDim Minst✝¹:MeasurableSpace Minst✝:MeasurableConstSMul ℝ Mu1:LTMCTUnitChoicesu2:LTMCTUnitChoicesμ:Measure M⊢ scaleUnit u1 u2 μ = Measure.map (fun m => scaleUnit u1 u2 m) μ All goals completed! 🐙

The statement that for a measure μ of dimension d, and a function f : M → G of dimension (CarriesDimension.d G * d⁻¹) (where CarriesDimension.d G is the dimension associated with terms of type G), then ∫ x, f x ∂μ has the correct dimension, namely CarriesDimension.d G.

In other words, the function:

fun (μ : DimSet (MeasureTheory.Measure M) d)
    (f : DimSet (M → G) (CarriesDimension.d G * d⁻¹)) ↦ ∫ x, f.1 x ∂μ.1

is dimensionally correct.

M:Typeinst✝⁷:NormedAddCommGroup Minst✝⁶:NormedSpace ℝ Minst✝⁵:HasDim Minst✝⁴:MeasurableSpace Minst✝³:MeasurableConstSMul ℝ MG:Typeinst✝²:NormedAddCommGroup Ginst✝¹:NormedSpace ℝ Ginst✝:HasDim Gd:Dimension LTMCTDimensionBaseu1:LTMCTUnitChoicesu2:LTMCTUnitChoicesμ:Measure Mhμ:μ ∈ DimSet (Measure M) df:M → Ghf:f ∈ DimSet (M → G) (dim G * d⁻¹)⊢ (u1.dimScale u2) (dim G) * (u2.dimScale u1) d * ((u2.dimScale u1) (dim G) * (u1.dimScale u2) d) = (u1.dimScale u2) (dim G) * (u2.dimScale u1) (dim G) * ((u2.dimScale u1) d * (u1.dimScale u2) d) All goals completed! 🐙 _ = ∫ (x : M), f x ∂ μ := M:Typeinst✝⁷:NormedAddCommGroup Minst✝⁶:NormedSpace ℝ Minst✝⁵:HasDim Minst✝⁴:MeasurableSpace Minst✝³:MeasurableConstSMul ℝ MG:Typeinst✝²:NormedAddCommGroup Ginst✝¹:NormedSpace ℝ Ginst✝:HasDim Gd:Dimension LTMCTDimensionBaseu1:LTMCTUnitChoicesu2:LTMCTUnitChoicesμ:Measure Mhμ:μ ∈ DimSet (Measure M) df:M → Ghf:f ∈ DimSet (M → G) (dim G * d⁻¹)⊢ ((u1.dimScale u2) (dim G) * (u2.dimScale u1) (dim G) * ((u2.dimScale u1) d * (u1.dimScale u2) d)) • ∫ (x : M), f x ∂μ = ∫ (x : M), f x ∂μ All goals completed! 🐙