Locally integrable, class D, class DL #
The condition that the running supremum process (t, ω) ↦ sup_{s ≤ t} ‖X s ω‖ is strongly
measurable as a function on the product.
Equations
- ProbabilityTheory.HasStronglyMeasurableSupProcess X = MeasureTheory.StronglyMeasurable fun (tω : ι × Ω) => ⨆ (s : ι), ⨆ (_ : s ≤ tω.1), ‖X s tω.2‖ₑ
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A stochastic process has integrable supremum if the function (t, ω) ↦ sup_{s ≤ t} ‖X s ω‖
is strongly measurable and if for all t, the random variable ω ↦ sup_{s ≤ t} ‖X s ω‖
is integrable.
Equations
- ProbabilityTheory.HasIntegrableSup X P = (ProbabilityTheory.HasStronglyMeasurableSupProcess X ∧ ∀ (t : ι), MeasureTheory.Integrable (fun (ω : Ω) => ⨆ (s : ι), ⨆ (_ : s ≤ t), ‖X s ω‖ₑ) P)
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A stochastic process has locally integrable supremum if it satisfies locally the property that
for all t, the random variable ω ↦ sup_{s ≤ t} ‖X s ω‖ is integrable.
Equations
- ProbabilityTheory.HasLocallyIntegrableSup X 𝓕 P = ProbabilityTheory.Locally (fun (x : ι → Ω → E) => ProbabilityTheory.HasIntegrableSup x P) 𝓕 X P
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A stochastic process $(X_t)$ is of class D (or in the Doob-Meyer class) if it is adapted and the set $\{X_\tau \mid \tau \text{ is a finite stopping time}\}$ is uniformly integrable.
- progMeasurable : MeasureTheory.ProgMeasurable 𝓕 X
- uniformIntegrable : MeasureTheory.UniformIntegrable (fun (τ : ↑{T : Ω → WithTop ι | MeasureTheory.IsStoppingTime 𝓕 T ∧ ∀ (ω : Ω), T ω ≠ ⊤}) => MeasureTheory.stoppedValue X ↑τ) 1 P
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A stochastic process $(X_t)$ is of class DL if it is adapted and for all $t$, the set $\{X_\tau \mid \tau \text{ is a stopping time with } \tau \le t\}$ is uniformly integrable.
- progMeasurable : MeasureTheory.ProgMeasurable 𝓕 X
- uniformIntegrable (t : ι) : MeasureTheory.UniformIntegrable (fun (τ : ↑{T : Ω → WithTop ι | MeasureTheory.IsStoppingTime 𝓕 T ∧ ∀ (ω : Ω), T ω ≤ ↑t}) => MeasureTheory.stoppedValue X ↑τ) 1 P
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Class D implies Class DL.
If {stoppedValue X T : T is a bounded stopping time} is uniformly integrable, then X is
of class D.
A nonnegative right-continuous submartingale is of class DL.
A nonnegative right-continuous submartingale is of class D iff it is uniformly integrable.
A martingale with right-continuous paths is of class DL.
If the index type has a top element, then class DL implies class D.
The class of processes that are jointly measurable is stable.
The class of processes with integrable supremum is stable.
The class of processes with locally integrable supremum is stable.
The Class D is stable.
The Class DL is stable.
A process of class DL is locally of class D.
A right-continuous, nonnegative submartingale is locally of class D.
A nonnegative local submartingale is locally of class D.