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fpvandoorn/carleson
Source indexedlemma · leanprover/lean4:v4.32.0

MeasureTheory.eLpNorm_withDensity_scale_constant'

Carleson.ToMathlib.MeasureTheory.Function.LpNorm.Misc · Carleson/ToMathlib/MeasureTheory/Function/LpNorm/Misc.lean:46 to 72

Mathematical statement

Exact Lean statement

lemma eLpNorm_withDensity_scale_constant' {f : ℝ≥0 → ℝ≥0∞} (hf : AEStronglyMeasurable f) {p : ℝ≥0∞}
  {a : ℝ≥0} (h : a ≠ 0) :
  eLpNorm (fun t ↦ f (a * t)) p (volume.withDensity (fun (t : ℝ≥0) ↦ t⁻¹))
    = eLpNorm f p (volume.withDensity (fun (t : ℝ≥0) ↦ t⁻¹))

Complete declaration

Lean source

Canonical source
Full Lean sourceLean 4
lemma eLpNorm_withDensity_scale_constant' {f : 0  0∞} (hf : AEStronglyMeasurable f) {p : 0∞}  {a : 0} (h : a  0) :  eLpNorm (fun t  f (a * t)) p (volume.withDensity (fun (t : 0)  t⁻¹))    = eLpNorm f p (volume.withDensity (fun (t : 0)  t⁻¹))  := by  unfold eLpNorm  split_ifs with p_zero p_top  · rfl  · rw [eLpNormEssSup_withDensity (by fun_prop) (by simp),        eLpNormEssSup_withDensity (by fun_prop) (by simp),        eLpNormEssSup_nnreal_scale_constant' h hf]  · symm    rw [eLpNorm'_eq_lintegral_enorm, eLpNorm'_eq_lintegral_enorm,        lintegral_withDensity_eq_lintegral_mul₀' (by measurability)          (aeMeasurable_withDensity_inv ((hf.enorm).pow_const _)),        lintegral_withDensity_eq_lintegral_mul₀' (by measurability)]    rotate_left    · apply aeMeasurable_withDensity_inv        (((AEStronglyMeasurable.comp_aemeasurable _ (by fun_prop)).enorm).pow_const _)      rw [NNReal.map_volume_mul_left h]      apply hf.smul_measure    simp only [enorm_eq_self, Pi.mul_apply, one_div]    rw [ lintegral_nnreal_scale_constant' h,  lintegral_const_mul' _ _ (by simp)]    have :  {t : 0}, (ENNReal.ofNNReal t)⁻¹ = a * (ENNReal.ofNNReal (a * t))⁻¹ := by      intro t      rw [ENNReal.coe_mul, ENNReal.mul_inv (by simp) (by simp),  mul_assoc,          ENNReal.mul_inv_cancel (by simpa) (by simp), one_mul]    simp_rw [ mul_assoc,  this]