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
Full Lean sourceLean 4
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)) := 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 : ℝ≥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]