fpvandoorn/carleson
Source indexedlemma · leanprover/lean4:v4.32.0
ENNReal.exists_biSup_le_enorm_add_eps
Carleson.ToMathlib.Data.ENNReal · Carleson/ToMathlib/Data/ENNReal.lean:110 to 124
Mathematical statement
Exact Lean statement
lemma exists_biSup_le_enorm_add_eps
{f : ι → E} {ε : ℝ≥0} (εpos : 0 < ε) (hs : s.Nonempty) (hf : IsBounded (f '' s)) :
∃ x ∈ s, ⨆ z ∈ s, ‖f z‖ₑ ≤ ‖f x‖ₑ + εComplete declaration
Lean source
Full Lean sourceLean 4
lemma exists_biSup_le_enorm_add_eps {f : ι → E} {ε : ℝ≥0} (εpos : 0 < ε) (hs : s.Nonempty) (hf : IsBounded (f '' s)) : ∃ x ∈ s, ⨆ z ∈ s, ‖f z‖ₑ ≤ ‖f x‖ₑ + ε := by by_contra! H have M : ⨆ z ∈ s, ‖f z‖ₑ + ε ≤ ⨆ z ∈ s, ‖f z‖ₑ := by simpa only [iSup_le_iff] using fun i hi ↦ (H i hi).le have nt : ⨆ z ∈ s, ‖f z‖ₑ ≠ ⊤ := by -- boundedness of `f` used here rw [ne_eq, iSup₂_eq_top]; push Not obtain ⟨C, pC, hC⟩ := hf.exists_pos_norm_le; lift C to ℝ≥0 using pC.le simp_rw [mem_image, forall_exists_index, and_imp, forall_apply_eq_imp_iff₂] at hC exact ⟨C, coe_lt_top, mod_cast hC⟩ obtain ⟨B, eB⟩ : ∃ B : ℝ≥0, ⨆ z ∈ s, ‖f z‖ₑ = B := Option.ne_none_iff_exists'.mp nt rw [← biSup_add hs, eB] at M norm_cast at M exact lt_irrefl _ (M.trans_lt (lt_add_of_pos_right B εpos))