OAI/GroupTheory/PolycyclicRecognition/Geometry/ExponentialHaarMultiplier.lean
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The exact Haar multiplier of an exponential-coordinate automorphism
- theorem
OAI.PolycyclicRecognition.exponentialConjugate_map_measureline 25Source documentation
The pushforward multiplier is the reciprocal absolute determinant. Consequently the multiplier of image volumes is the absolute determinant.
theorem exponentialConjugate_map_measure (F : L ≃ₗ⁅ℝ⁆ L) : Measure.map (exponentialConjugate e Exp hbij F) (Measure.map ((Exp ∘ e) ∘ b.equivFun.symm) volume) = ENNReal.ofReal |(LinearMap.det F.toLinearEquiv.toLinearMap)⁻¹| • Measure.map ((Exp ∘ e) ∘ b.equivFun.symm) volume := by …