l3lab/ntp-mathlib huggingface dataset:
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      

Proof state:
case pos
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this✝ : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∈ s
this : Set.indicator s (fun _x => ⊤) x ≤ g1 x
⊢ ↑(f x) < (fun x => g0 x + g1 x) x

Next tactic:
simp only [h, Set.indicator_of_mem, top_le_iff] at this
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      

Proof state:
case pos
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this✝ : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∈ s
this : g1 x = ⊤
⊢ ↑(f x) < (fun x => g0 x + g1 x) x

Next tactic:
simp [this]
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · 

Proof state:
case neg
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∉ s
⊢ ↑(f x) < (fun x => g0 x + g1 x) x

Next tactic:
have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by 

Proof state:
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∉ s
⊢ f x = AEMeasurable.mk f fmeas x

Next tactic:
rw [Set.compl_subset_comm] at hs
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; 

Proof state:
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : sᶜ ⊆ {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∉ s
⊢ f x = AEMeasurable.mk f fmeas x

Next tactic:
exact hs h
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
      

Proof state:
case neg
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this✝ : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∉ s
this : f x = AEMeasurable.mk f fmeas x
⊢ ↑(f x) < (fun x => g0 x + g1 x) x

Next tactic:
rw [this]
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
      rw [this]
      

Proof state:
case neg
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this✝ : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
x : α
h : x ∉ s
this : f x = AEMeasurable.mk f fmeas x
⊢ ↑(AEMeasurable.mk f fmeas x) < (fun x => g0 x + g1 x) x

Next tactic:
exact (f_lt_g0 x).trans_le le_self_add
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
      rw [this]
      exact (f_lt_g0 x).trans_le le_self_add
  · 

Proof state:
case intro.intro.intro.intro.intro.intro.intro.intro.intro.refine'_2
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
⊢ ∫⁻ (x : α), (fun x => g0 x + g1 x) x ∂μ ≤ ∫⁻ (x : α), ↑(f x) ∂μ + ε

Next tactic:
calc
      ∫⁻ x, g0 x + g1 x ∂μ = (∫⁻ x, g0 x ∂μ) + ∫⁻ x, g1 x ∂μ :=
        lintegral_add_left g0_cont.measurable _
      _ ≤ (∫⁻ x, f x ∂μ) + ε / 2 + (0 + ε / 2) := by
        refine' add_le_add _ _
        · convert g0_int using 2
          exact lintegral_congr_ae (fmeas.ae_eq_mk.fun_comp _)
        · convert g1_int
          simp only [smeas, μs, lintegral_const, Set.univ_inter, MeasurableSet.univ,
            lintegral_indicator, mul_zero, restrict_apply]
      _ = (∫⁻ x, f x ∂μ) + ε := by simp only [add_assoc, ENNReal.add_halves, zero_add]
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
      rw [this]
      exact (f_lt_g0 x).trans_le le_self_add
  · calc
      ∫⁻ x, g0 x + g1 x ∂μ = (∫⁻ x, g0 x ∂μ) + ∫⁻ x, g1 x ∂μ :=
        lintegral_add_left g0_cont.measurable _
      _ ≤ (∫⁻ x, f x ∂μ) + ε / 2 + (0 + ε / 2) := by
        

Proof state:
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
⊢ ∫⁻ (x : α), g0 x ∂μ + ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), ↑(f x) ∂μ + ε / 2 + (0 + ε / 2)

Next tactic:
refine' add_le_add _ _
/-- Given an almost everywhere measurable function `f` with values in `ℝ≥0` in a sigma-finite space,
there exists a lower semicontinuous function `g > f` with integral arbitrarily close to that of `f`.
Formulation in terms of `lintegral`.
Auxiliary lemma for Vitali-Carathéodory theorem `exists_lt_lower_semicontinuous_integral_lt`. -/
theorem exists_lt_lowerSemicontinuous_lintegral_ge_of_aemeasurable [SigmaFinite μ] (f : α → ℝ≥0)
    (fmeas : AEMeasurable f μ) {ε : ℝ≥0∞} (ε0 : ε ≠ 0) :
    ∃ g : α → ℝ≥0∞,
      (∀ x, (f x : ℝ≥0∞) < g x) ∧ LowerSemicontinuous g ∧ (∫⁻ x, g x ∂μ) ≤ (∫⁻ x, f x ∂μ) + ε := by
  have : ε / 2 ≠ 0 := (ENNReal.half_pos ε0).ne'
  rcases exists_lt_lowerSemicontinuous_lintegral_ge μ (fmeas.mk f) fmeas.measurable_mk this with
    ⟨g0, f_lt_g0, g0_cont, g0_int⟩
  rcases exists_measurable_superset_of_null fmeas.ae_eq_mk with ⟨s, hs, smeas, μs⟩
  rcases exists_le_lowerSemicontinuous_lintegral_ge μ (s.indicator fun _x => ∞)
      (measurable_const.indicator smeas) this with
    ⟨g1, le_g1, g1_cont, g1_int⟩
  refine' ⟨fun x => g0 x + g1 x, fun x => _, g0_cont.add g1_cont, _⟩
  · by_cases h : x ∈ s
    · have := le_g1 x
      simp only [h, Set.indicator_of_mem, top_le_iff] at this
      simp [this]
    · have : f x = fmeas.mk f x := by rw [Set.compl_subset_comm] at hs; exact hs h
      rw [this]
      exact (f_lt_g0 x).trans_le le_self_add
  · calc
      ∫⁻ x, g0 x + g1 x ∂μ = (∫⁻ x, g0 x ∂μ) + ∫⁻ x, g1 x ∂μ :=
        lintegral_add_left g0_cont.measurable _
      _ ≤ (∫⁻ x, f x ∂μ) + ε / 2 + (0 + ε / 2) := by
        refine' add_le_add _ _
        · 

Proof state:
case refine'_1
α : Type u_1
inst✝⁴ : TopologicalSpace α
inst✝³ : MeasurableSpace α
inst✝² : BorelSpace α
μ : Measure α
inst✝¹ : WeaklyRegular μ
inst✝ : SigmaFinite μ
f : α → ℝ≥0
fmeas : AEMeasurable f
ε : ℝ≥0∞
ε0 : ε ≠ 0
this : ε / 2 ≠ 0
g0 : α → ℝ≥0∞
f_lt_g0 : ∀ (x : α), ↑(AEMeasurable.mk f fmeas x) < g0 x
g0_cont : LowerSemicontinuous g0
g0_int : ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(AEMeasurable.mk f fmeas x) ∂μ + ε / 2
s : Set α
hs : {x | (fun x => f x = AEMeasurable.mk f fmeas x) x}ᶜ ⊆ s
smeas : MeasurableSet s
μs : ↑↑μ s = 0
g1 : α → ℝ≥0∞
le_g1 : ∀ (x : α), Set.indicator s (fun _x => ⊤) x ≤ g1 x
g1_cont : LowerSemicontinuous g1
g1_int : ∫⁻ (x : α), g1 x ∂μ ≤ ∫⁻ (x : α), Set.indicator s (fun _x => ⊤) x ∂μ + ε / 2
⊢ ∫⁻ (x : α), g0 x ∂μ ≤ ∫⁻ (x : α), ↑(f x) ∂μ + ε / 2

Next tactic:
convert g0_int using 2