fpvandoorn/carleson
Source indexedlemma · leanprover/lean4:v4.32.0
MeasureTheory.trunc_Lp_Lq_higher
Carleson.ToMathlib.RealInterpolation.Misc · Carleson/ToMathlib/RealInterpolation/Misc.lean:790 to 810
Source documentation
If f is in Lp, the truncation is element of Lq for q ≥ p.
Exact Lean statement
lemma trunc_Lp_Lq_higher (hpq : p ∈ Ioc 0 q) {f : α → ε} (hf : MemLp f p μ) (ht : t ≠ ∞) :
MemLp (trnc ⊤ f t) q μComplete declaration
Lean source
Full Lean sourceLean 4
lemma trunc_Lp_Lq_higher (hpq : p ∈ Ioc 0 q) {f : α → ε} (hf : MemLp f p μ) (ht : t ≠ ∞) : MemLp (trnc ⊤ f t) q μ := by refine ⟨aestronglyMeasurable_trnc hf.1, ?_⟩ rcases (eq_or_ne q ⊤) with q_eq_top | q_ne_top · rw [q_eq_top, eLpNorm_exponent_top] simp only [trnc] calc _ _ ≤ max 0 t := trunc_eLpNormEssSup_le t _ < ∞ := by finiteness · have p_ne_top := ne_top_of_le_ne_top q_ne_top hpq.2 rw [← rpow_lt_top_iff_of_pos (toReal_pos (hpq.1.trans_le hpq.2).ne' q_ne_top)] apply lt_of_le_of_lt (estimate_eLpNorm_trunc q_ne_top hpq hf.1) apply mul_lt_top ?_ ?_ · by_cases ht'' : t = 0 · rw [ht''] apply ENNReal.rpow_lt_top_of_nonneg (h := by finiteness) simp only [sub_nonneg] rw [toReal_le_toReal p_ne_top q_ne_top] exact hpq.2 · finiteness · exact (rpow_lt_top_iff_of_pos (toReal_pos hpq.1.ne' p_ne_top)).mpr hf.2