Theorem: MeasureTheory.measurable_stoppedValue
File: Mathlib/Probability/Process/Stopping.lean

Proof steps:
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
⊢ Measurable (stoppedValue u τ)
state_after: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
⊢ Measurable (stoppedValue u τ)
tactic: have h_str_meas : ∀ i, StronglyMeasurable[f i] (stoppedValue u fun ω => min (τ ω) i) := fun i =>
    stronglyMeasurable_stoppedValue_of_le hf_prog (hτ.min_const i) fun _ => min_le_right _ _
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
⊢ Measurable (stoppedValue u τ)
state_after: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
⊢ MeasurableSet (stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i})
tactic: intro t ht i
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
⊢ MeasurableSet (stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i})
state_after: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
⊢ stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i} = (stoppedValue u fun ω => min (τ ω) i) ⁻¹' t ∩ {ω | τ ω ≤ i}
tactic: suffices stoppedValue u τ ⁻¹' t ∩ {ω : Ω | τ ω ≤ i} =
      (stoppedValue u fun ω => min (τ ω) i) ⁻¹' t ∩ {ω : Ω | τ ω ≤ i} by
    rw [this]; exact ((h_str_meas i).measurable ht).inter (hτ.measurableSet_le i)
state_before: Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
⊢ stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i} = (stoppedValue u fun ω => min (τ ω) i) ⁻¹' t ∩ {ω | τ ω ≤ i}
state_after: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
⊢ ω ∈ stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i} ↔ ω ∈ (stoppedValue u fun ω => min (τ ω) i) ⁻¹' t ∩ {ω | τ ω ≤ i}
tactic: ext1 ω
state_before: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
⊢ ω ∈ stoppedValue u τ ⁻¹' t ∩ {ω | τ ω ≤ i} ↔ ω ∈ (stoppedValue u fun ω => min (τ ω) i) ⁻¹' t ∩ {ω | τ ω ≤ i}
state_after: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
⊢ τ ω ≤ i → (u (τ ω) ω ∈ t ↔ u (min (τ ω) i) ω ∈ t)
tactic: simp only [stoppedValue, Set.mem_inter_iff, Set.mem_preimage, Set.mem_setOf_eq,
    and_congr_left_iff]
state_before: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
⊢ τ ω ≤ i → (u (τ ω) ω ∈ t ↔ u (min (τ ω) i) ω ∈ t)
state_after: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
h : τ ω ≤ i
⊢ u (τ ω) ω ∈ t ↔ u (min (τ ω) i) ω ∈ t
tactic: intro h
state_before: case h
Ω : Type u_1
β : Type u_2
ι : Type u_3
m : MeasurableSpace Ω
inst✝⁹ : LinearOrder ι
inst✝⁸ : MeasurableSpace ι
inst✝⁷ : TopologicalSpace ι
inst✝⁶ : OrderTopology ι
inst✝⁵ : SecondCountableTopology ι
inst✝⁴ : BorelSpace ι
inst✝³ : TopologicalSpace β
u : ι → Ω → β
τ : Ω → ι
f : Filtration ι m
inst✝² : MetrizableSpace β
inst✝¹ : MeasurableSpace β
inst✝ : BorelSpace β
hf_prog : ProgMeasurable f u
hτ : IsStoppingTime f τ
h_str_meas : ∀ (i : ι), StronglyMeasurable (stoppedValue u fun ω => min (τ ω) i)
t : Set β
ht : MeasurableSet t
i : ι
ω : Ω
h : τ ω ≤ i
⊢ u (τ ω) ω ∈ t ↔ u (min (τ ω) i) ω ∈ t
state_after: no goals
tactic: rw [min_eq_left h]