Documentation

BrownianMotion.StochasticIntegral.Locally

Local properties of processes #

theorem ProbabilityTheory.locally_and_of_isStable {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [Zero E] [TopologicalSpace ι] [LinearOrder ι] [OrderBot ι] [OrderTopology ι] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} {p q : (ιΩE)Prop} (hp : IsStable 𝓕 p) (hpX : p X) (hqX : Locally q 𝓕 X P) :
Locally (fun (Y : ιΩE) => p Y q Y) 𝓕 X P
theorem ProbabilityTheory.locally_of_ae {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [𝓕.IsComplete P] {p : (ιE)Prop} (hpX : ∀ᵐ (ω : Ω) P, p fun (x : ι) => X x ω) (hp₀ : p 0) :
Locally (fun (X : ιΩE) => ∀ (ω : Ω), p fun (x : ι) => X x ω) 𝓕 X P

If the filtration satisfies the usual conditions, then a property of the paths of a process that holds almost surely holds locally.

theorem ProbabilityTheory.Locally.rightContinuous {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] (hX : Locally (fun (X : ιΩE) => ∀ (ω : Ω), Function.IsRightContinuous fun (x : ι) => X x ω) 𝓕 X P) :
∀ᵐ (ω : Ω) P, Function.IsRightContinuous fun (x : ι) => X x ω
theorem ProbabilityTheory.Locally.left_limit {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] (hX : Locally (fun (X : ιΩE) => ∀ (ω : Ω) (x : ι), ∃ (l : E), Filter.Tendsto (fun (x : ι) => X x ω) (nhdsWithin x (Set.Iio x)) (nhds l)) 𝓕 X P) :
∀ᵐ (ω : Ω) P, ∀ (x : ι), ∃ (l : E), Filter.Tendsto (fun (x : ι) => X x ω) (nhdsWithin x (Set.Iio x)) (nhds l)
theorem ProbabilityTheory.Locally.isCadlag {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] (hX : Locally (fun (X : ιΩE) => ∀ (ω : Ω), IsCadlag fun (x : ι) => X x ω) 𝓕 X P) :
∀ᵐ (ω : Ω) P, IsCadlag fun (x : ι) => X x ω
theorem ProbabilityTheory.isStable_rightContinuous {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } [TopologicalSpace E] :
IsStable 𝓕 fun (X : ιΩE) => ∀ (ω : Ω), Function.IsRightContinuous fun (x : ι) => X x ω

The processes with right-continuous paths are a stable class.

theorem ProbabilityTheory.isStable_left_limit {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } [TopologicalSpace E] :
IsStable 𝓕 fun (X : ιΩE) => ∀ (ω : Ω) (x : ι), ∃ (l : E), Filter.Tendsto (fun (x : ι) => X x ω) (nhdsWithin x (Set.Iio x)) (nhds l)

The processes with left limits are a stable class.

theorem ProbabilityTheory.isStable_isCadlag {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } [TopologicalSpace E] :
IsStable 𝓕 fun (X : ιΩE) => ∀ (ω : Ω), IsCadlag fun (x : ι) => X x ω

The càdlàg processes are a stable class.

theorem ProbabilityTheory.locally_rightContinuous_iff {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] [𝓕.IsComplete P] :
Locally (fun (X : ιΩE) => ∀ (ω : Ω), Function.IsRightContinuous fun (x : ι) => X x ω) 𝓕 X P ∀ᵐ (ω : Ω) P, Function.IsRightContinuous fun (x : ι) => X x ω
theorem ProbabilityTheory.locally_left_limit_iff {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] [𝓕.IsComplete P] :
Locally (fun (X : ιΩE) => ∀ (ω : Ω) (x : ι), ∃ (l : E), Filter.Tendsto (fun (x : ι) => X x ω) (nhdsWithin x (Set.Iio x)) (nhds l)) 𝓕 X P ∀ᵐ (ω : Ω) P, ∀ (x : ι), ∃ (l : E), Filter.Tendsto (fun (x : ι) => X x ω) (nhdsWithin x (Set.Iio x)) (nhds l)
theorem ProbabilityTheory.locally_isCadlag_iff {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [LinearOrder ι] [OrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [Zero E] {𝓕 : MeasureTheory.Filtration ι } {X : ιΩE} [TopologicalSpace E] [𝓕.IsComplete P] :
Locally (fun (X : ιΩE) => ∀ (ω : Ω), IsCadlag fun (x : ι) => X x ω) 𝓕 X P ∀ᵐ (ω : Ω) P, IsCadlag fun (x : ι) => X x ω
theorem ProbabilityTheory.locally_isCadlag_iff_locally_ae {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [ConditionallyCompleteLinearOrderBot ι] [TopologicalSpace ι] [OrderTopology ι] [SecondCountableTopology ι] [DenselyOrdered ι] [NoMaxOrder ι] [NormedAddCommGroup E] [MeasureTheory.IsFiniteMeasure P] {𝓕 : MeasureTheory.Filtration ι } [𝓕.IsComplete P] [𝓕.IsRightContinuous] {X : ιΩE} :
Locally (fun (X : ιΩE) => ∀ (ω : Ω), IsCadlag fun (x : ι) => X x ω) 𝓕 X P Locally (fun (X : ιΩE) => ∀ᵐ (ω : Ω) P, IsCadlag fun (x : ι) => X x ω) 𝓕 X P
theorem ProbabilityTheory.rightContinuous_indicator {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} [LinearOrder ι] [NormedAddCommGroup E] {X : ιΩE} [TopologicalSpace ι] (hC : ∀ (ω : Ω), Function.IsRightContinuous fun (x : ι) => X x ω) (s : Set Ω) (ω : Ω) :
Function.IsRightContinuous fun (t : ι) => s.indicator (X t) ω
theorem ProbabilityTheory.stronglyAdapted_indicator {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} [LinearOrder ι] [NormedAddCommGroup E] {X : ιΩE} {𝓕 : MeasureTheory.Filtration ι } [OrderBot ι] (hX : MeasureTheory.StronglyAdapted 𝓕 X) {τ : ΩWithTop ι} ( : MeasureTheory.IsStoppingTime 𝓕 τ) :
MeasureTheory.StronglyAdapted 𝓕 fun (i : ι) => {ω : Ω | < τ ω}.indicator (X i)
theorem ProbabilityTheory.isStronglyProgressive_indicator {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} { : MeasurableSpace Ω} [LinearOrder ι] [NormedAddCommGroup E] {X : ιΩE} {𝓕 : MeasureTheory.Filtration ι } [OrderBot ι] [MeasurableSpace ι] (hX : MeasureTheory.IsStronglyProgressive 𝓕 X) {τ : ΩWithTop ι} ( : MeasureTheory.IsStoppingTime 𝓕 τ) :
MeasureTheory.IsStronglyProgressive 𝓕 fun (i : ι) => {ω : Ω | < τ ω}.indicator (X i)

The class of strongly progressive processes is stable.