-- Mathlib/Probability/Martingale/Upcrossing.lean
theorem Submartingale.mul_lintegral_upcrossings_le_lintegral_pos_part [IsFiniteMeasure μ] (a b : ℝ)
    (hf : Submartingale f ℱ μ) : ENNReal.ofReal (b - a) * ∫⁻ ω, upcrossings a b f ω ∂μ ≤
      ⨆ N, ∫⁻ ω, ENNReal.ofReal ((f N ω - a)⁺) ∂μ

Proof state:
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
⊢ ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

Tactic:
intro N

Result:
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
N : ℕ
⊢ ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

Proof state:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ ENNReal.ofReal (b - a) * ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f N a_1) ∂μ ≤
    ⨆ N, ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

Tactic:
rw [(by simp :
    ∫⁻ ω, upcrossingsBefore a b f N ω ∂μ = ∫⁻ ω, ↑(upcrossingsBefore a b f N ω : ℝ≥0) ∂μ),
  lintegral_coe_eq_integral, ← ENNReal.ofReal_mul (sub_pos.2 hab).le]

Result:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ ENNReal.ofReal ((b - a) * ∫ (a_1 : Ω), ↑↑(upcrossingsBefore a b f N a_1) ∂μ) ≤
    ⨆ N, ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

case pos.hfi
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ Integrable (fun x => ↑↑(upcrossingsBefore a b f N x)) μ

Proof state:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ENNReal.ofReal (b - a) * ∫⁻ (ω : Ω), ⨆ N, ↑(upcrossingsBefore a b f N ω) ∂μ ≤
    ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Tactic:
rw [lintegral_iSup']

Result:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ENNReal.ofReal (b - a) * ⨆ n, ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f n a_1) ∂μ ≤
    ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

case pos.hf
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ∀ (n : ℕ), AEMeasurable (fun ω => ↑(upcrossingsBefore a b f n ω)) μ

case pos.h_mono
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ∀ᵐ (x : Ω) ∂μ, Monotone fun n => ↑(upcrossingsBefore a b f n x)

Proof state:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
⊢ ENNReal.ofReal (b - a) * ∫⁻ (ω : Ω), upcrossings a b f ω ∂μ ≤ ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Tactic:
simp_rw [upcrossings]

Result:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
⊢ ENNReal.ofReal (b - a) * ∫⁻ (ω : Ω), ⨆ N, ↑(upcrossingsBefore a b f N ω) ∂μ ≤
    ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Proof state:
case pos.hfi
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ Integrable (fun x => ↑↑(upcrossingsBefore a b f N x)) μ

Tactic:
simp only [NNReal.coe_natCast, hf.adapted.integrable_upcrossingsBefore hab]

Result:
no goals

Proof state:
case f_nn
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
N : ℕ
⊢ 0 ≤ᶠ[ae μ] fun ω => (f N ω - a)⁺

Tactic:
exact Eventually.of_forall fun ω => posPart_nonneg _

Result:
no goals

Proof state:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ∀ (i : ℕ),
    ENNReal.ofReal (b - a) * ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f i a_1) ∂μ ≤
      ⨆ N, ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

Tactic:
intro N

Result:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ ENNReal.ofReal (b - a) * ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f N a_1) ∂μ ≤
    ⨆ N, ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)

Proof state:
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
N : ℕ
⊢ ∫⁻ (ω : Ω), ↑(upcrossingsBefore a b f N ω) ∂μ = ∫⁻ (ω : Ω), ↑↑(upcrossingsBefore a b f N ω) ∂μ

Tactic:
simp

Result:
no goals

Proof state:
case neg
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : ¬a < b
⊢ ENNReal.ofReal (b - a) * ∫⁻ (ω : Ω), upcrossings a b f ω ∂μ ≤ ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Tactic:
rw [not_lt, ← sub_nonpos] at hab

Result:
case neg
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : b - a ≤ 0
⊢ ENNReal.ofReal (b - a) * ∫⁻ (ω : Ω), upcrossings a b f ω ∂μ ≤ ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Proof state:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ENNReal.ofReal (b - a) * ⨆ n, ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f n a_1) ∂μ ≤
    ⨆ N, ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ

Tactic:
simp_rw [this, ENNReal.mul_iSup, iSup_le_iff]

Result:
case pos
Ω : Type u_1
m0 : MeasurableSpace Ω
μ : Measure Ω
f : ℕ → Ω → ℝ
ℱ : Filtration ℕ m0
inst✝ : IsFiniteMeasure μ
a b : ℝ
hf : Submartingale f ℱ μ
hab : a < b
this : ∀ (N : ℕ), ∫⁻ (ω : Ω), ENNReal.ofReal (f N ω - a)⁺ ∂μ = ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)
⊢ ∀ (i : ℕ),
    ENNReal.ofReal (b - a) * ∫⁻ (a_1 : Ω), ↑(upcrossingsBefore a b f i a_1) ∂μ ≤
      ⨆ N, ENNReal.ofReal (∫ (ω : Ω), (f N ω - a)⁺ ∂μ)