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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 + ε

Complete declaration

Lean source

Canonical source
Full Lean sourceLean 4
lemma exists_biSup_le_enorm_add_eps    {f : ι  E} {ε : 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 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 : 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))