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Project-declaredLean 4.32.0 · mathlib@249c48c2

Add Equiv Add Haar Char eq ring Haar Char det diagonal

MeasureTheory.addEquivAddHaarChar_eq_ringHaarChar_det_diagonal

Plain-language statement

A diagonal matrix scales addHaar with its determinant

Exact Lean statement

lemma addEquivAddHaarChar_eq_ringHaarChar_det_diagonal [SecondCountableTopology F]
    (ρ : (ι → F) ≃L[F] (ι → F)) {D : ι → F}
    (h : ρ.toLinearMap.toMatrix' = Matrix.diagonal D) :
    addEquivAddHaarChar ρ.toContinuousAddEquiv = ringHaarChar ρ.toLinearEquiv.det

Formal artifact

Lean source

Canonical source
Full Lean sourceLean 4
lemma addEquivAddHaarChar_eq_ringHaarChar_det_diagonal [SecondCountableTopology F]    (ρ : (ι  F) ≃L[F] (ι  F)) {D : ι  F}    (h : ρ.toLinearMap.toMatrix' = Matrix.diagonal D) :    addEquivAddHaarChar ρ.toContinuousAddEquiv = ringHaarChar ρ.toLinearEquiv.det := by  have feq : ρ.toLinearMap = Matrix.toLin' (Matrix.diagonal D) := by    rw [ h, Matrix.toLin'_toMatrix']  have fdet : ρ.toLinearMap.det = ∏ i, D i := by rw [feq, LinearMap.det_toLin', det_diagonal]  have hu (i : ι) : IsUnit (D i) := by    refine IsUnit.prod_univ_iff.1 ?_ i    rw [ fdet]    exact LinearEquiv.isUnit_det' ρ.toLinearEquiv  -- `ρ` acts coordinatewise as left multiplication by the units `D i`, so both sides equal  -- `∏ i, ringHaarChar (D i)`: the left via `piCongrRight`, the right since `det ρ = ∏ i, D i`.  have hρ : ρ.toContinuousAddEquiv = .piCongrRight fun i  .mulLeft (hu i).unit := by    ext x i    calc ρ.toContinuousAddEquiv x i = Matrix.toLin' (Matrix.diagonal D) x i := by rw [ feq]; rfl      _ = D i * x i := mulVec_diagonal D x i  have hdet : ρ.toLinearEquiv.det = ∏ i, (hu i).unit := by    apply Units.val_inj.1    simpa [LinearEquiv.coe_det] using fdet  rw [hρ, addEquivAddHaarChar_piCongrRight, hdet, map_prod]  rfl
Project
Fermat's Last Theorem
License
Apache-2.0
Commit
8dd808888295
Source
FLT/HaarMeasure/HaarChar/FiniteDimensional.lean:64-85

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Plain-language statement

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Source project: Fermat's Last Theorem

Person-level attribution pending.

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Plain-language statement

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Person-level attribution pending.

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