Module: Mathlib.Probability.Kernel.IonescuTulcea.Traj

Goal state before:
pp: X : ℕ → Type u_1
inst✝⁴ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝³ : ∀ (n : ℕ), IsMarkovKernel (κ n)
E : Type u_2
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
a b c : ℕ
hab : a ≤ b
hbc : b ≤ c
x₀ : (i : ↥(Iic a)) → X ↑i
f : ((n : ℕ) → X n) → E
i_cf : Integrable ((traj κ a) x₀)[f | ↑piLE c] ((traj κ a) x₀)
mcf : StronglyMeasurable ((traj κ a) x₀)[f | ↑piLE c]
x : (n : ℕ) → X n
h1 : ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x = ((traj κ a) x₀)[f | ↑piLE b] x
h2 :
  ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x =
    ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x)
⊢ ((traj κ a) x₀)[f | ↑piLE b] x =
    ∫ (y : (i : ↥(Iic c)) → X ↑i),
      ((traj κ a) x₀)[f | ↑piLE c] (updateFinset x (Iic c) y) ∂(partialTraj κ b c) (frestrictLe b x)

Tactic:
rw [← h1, h2, ← traj_map_frestrictLe, Kernel.map_apply, integral_map]

Goal state after:
X : ℕ → Type u_1
inst✝⁴ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝³ : ∀ (n : ℕ), IsMarkovKernel (κ n)
E : Type u_2
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
a b c : ℕ
hab : a ≤ b
hbc : b ≤ c
x₀ : (i : ↥(Iic a)) → X ↑i
f : ((n : ℕ) → X n) → E
i_cf : Integrable ((traj κ a) x₀)[f | ↑piLE c] ((traj κ a) x₀)
mcf : StronglyMeasurable ((traj κ a) x₀)[f | ↑piLE c]
x : (n : ℕ) → X n
h1 : ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x = ((traj κ a) x₀)[f | ↑piLE b] x
h2 :
  ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x =
    ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x)
⊢ ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x) =
    ∫ (x_1 : (n : ℕ) → X n),
      ((traj κ a) x₀)[f | ↑piLE c] (updateFinset x (Iic c) (frestrictLe c x_1)) ∂(traj κ b) (frestrictLe b x)

case hφ
X : ℕ → Type u_1
inst✝⁴ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝³ : ∀ (n : ℕ), IsMarkovKernel (κ n)
E : Type u_2
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
a b c : ℕ
hab : a ≤ b
hbc : b ≤ c
x₀ : (i : ↥(Iic a)) → X ↑i
f : ((n : ℕ) → X n) → E
i_cf : Integrable ((traj κ a) x₀)[f | ↑piLE c] ((traj κ a) x₀)
mcf : StronglyMeasurable ((traj κ a) x₀)[f | ↑piLE c]
x : (n : ℕ) → X n
h1 : ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x = ((traj κ a) x₀)[f | ↑piLE b] x
h2 :
  ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x =
    ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x)
⊢ AEMeasurable (frestrictLe c) ((traj κ b) (frestrictLe b x))

case hfm
X : ℕ → Type u_1
inst✝⁴ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝³ : ∀ (n : ℕ), IsMarkovKernel (κ n)
E : Type u_2
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
a b c : ℕ
hab : a ≤ b
hbc : b ≤ c
x₀ : (i : ↥(Iic a)) → X ↑i
f : ((n : ℕ) → X n) → E
i_cf : Integrable ((traj κ a) x₀)[f | ↑piLE c] ((traj κ a) x₀)
mcf : StronglyMeasurable ((traj κ a) x₀)[f | ↑piLE c]
x : (n : ℕ) → X n
h1 : ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x = ((traj κ a) x₀)[f | ↑piLE b] x
h2 :
  ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x =
    ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x)
⊢ AEStronglyMeasurable (fun y ↦ ((traj κ a) x₀)[f | ↑piLE c] (updateFinset x (Iic c) y))
    (Measure.map (frestrictLe c) ((traj κ b) (frestrictLe b x)))

case hf
X : ℕ → Type u_1
inst✝⁴ : (n : ℕ) → MeasurableSpace (X n)
κ : (n : ℕ) → Kernel ((i : ↥(Iic n)) → X ↑i) (X (n + 1))
inst✝³ : ∀ (n : ℕ), IsMarkovKernel (κ n)
E : Type u_2
inst✝² : NormedAddCommGroup E
inst✝¹ : NormedSpace ℝ E
inst✝ : CompleteSpace E
a b c : ℕ
hab : a ≤ b
hbc : b ≤ c
x₀ : (i : ↥(Iic a)) → X ↑i
f : ((n : ℕ) → X n) → E
i_cf : Integrable ((traj κ a) x₀)[f | ↑piLE c] ((traj κ a) x₀)
mcf : StronglyMeasurable ((traj κ a) x₀)[f | ↑piLE c]
x : (n : ℕ) → X n
h1 : ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x = ((traj κ a) x₀)[f | ↑piLE b] x
h2 :
  ((traj κ a) x₀)[((traj κ a) x₀)[f | ↑piLE c] | ↑piLE b] x =
    ∫ (y : (n : ℕ) → X n), ((traj κ a) x₀)[f | ↑piLE c] y ∂(traj κ b) (frestrictLe b x)
⊢ Measurable (frestrictLe c)