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BrownianMotion.StochasticIntegral.DoobLp

Doob's Lᵖ inequality #

theorem ProbabilityTheory.maximal_ineq' {Ω : Type u_2} { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} [MeasureTheory.IsFiniteMeasure P] {𝓕 : MeasureTheory.Filtration } {f : Ω} (hsub : MeasureTheory.Submartingale f 𝓕 P) (hnonneg : 0 f) (ε : NNReal) (n : ) :
ε P.real {ω : Ω | ε (Finset.range (n + 1)).sup' fun (k : ) => f k ω} (ω : Ω) in {ω : Ω | ε (Finset.range (n + 1)).sup' fun (k : ) => f k ω}, f n ω P
theorem ProbabilityTheory.maximal_ineq_finset {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {𝓕 : MeasureTheory.Filtration ι } {Y : ιΩ} [MeasureTheory.IsFiniteMeasure P] (hsub : MeasureTheory.Submartingale Y 𝓕 P) (hnonneg : 0 Y) (ε : NNReal) {n : ι} {J : Finset ι} (hJn : iJ, i n) (hnJ : n J) :
ε P.real {ω : Ω | ε J.sup' fun (i : ι) => Y i ω} (ω : Ω) in {ω : Ω | ε J.sup' fun (i : ι) => Y i ω}, Y n ω P

Auxiliary lemma for maximal_ineq_countable where the index set is a Finset.

theorem ProbabilityTheory.maximal_ineq_countable_ennReal {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {𝓕 : MeasureTheory.Filtration ι } {Y : ιΩ} [MeasureTheory.IsFiniteMeasure P] [Countable ι] (hsub : MeasureTheory.Submartingale Y 𝓕 P) (hnonneg : 0 Y) (ε : NNReal) (n : ι) :
ε P.real {ω : Ω | ε ⨆ (i : ι), ⨆ (_ : i n), ENNReal.ofReal (Y i ω)} (ω : Ω) in {ω : Ω | ε ⨆ (i : ι), ⨆ (_ : i n), ENNReal.ofReal (Y i ω)}, Y n ω P
theorem MeasureTheory.Submartingale.iSup_ofReal_ne_top {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : Measure Ω} {𝓕 : Filtration ι } {Y : ιΩ} [IsFiniteMeasure P] [Countable ι] (hsub : Submartingale Y 𝓕 P) (hnonneg : 0 Y) (n : ι) :
∀ᵐ (ω : Ω) P, ⨆ (i : ι), ⨆ (_ : i n), ENNReal.ofReal (Y i ω)

Alternative form of Submartingale.ae_bddAbove.

theorem MeasureTheory.Submartingale.ae_bddAbove_Iic {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : Measure Ω} {𝓕 : Filtration ι } {Y : ιΩ} [IsFiniteMeasure P] [Countable ι] (hsub : Submartingale Y 𝓕 P) (hnonneg : 0 Y) (n : ι) :
∀ᵐ (ω : Ω) P, BddAbove ((fun (i : ι) => Y i ω) '' Set.Iic n)

Doob's maximal inequality implies that the supremum process of a nonnegative submartingale is a.s. bounded.

theorem ProbabilityTheory.maximal_ineq_countable {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {𝓕 : MeasureTheory.Filtration ι } {Y : ιΩ} [MeasureTheory.IsFiniteMeasure P] [Countable ι] (hsub : MeasureTheory.Submartingale Y 𝓕 P) (hnonneg : 0 Y) (ε : NNReal) (n : ι) :
ε P.real {ω : Ω | ε ⨆ (i : (Set.Iic n)), Y (↑i) ω} (ω : Ω) in {ω : Ω | ε ⨆ (i : (Set.Iic n)), Y (↑i) ω}, Y n ω P

Doob's maximal inequality for a countable index set.

theorem ProbabilityTheory.maximal_ineq_norm_countable {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} [LinearOrder ι] [NormedAddCommGroup E] [NormedSpace E] [CompleteSpace E] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {X : ιΩE} {𝓕 : MeasureTheory.Filtration ι } [MeasureTheory.IsFiniteMeasure P] [Countable ι] (hmar : MeasureTheory.Martingale X 𝓕 P) (ε : NNReal) (n : ι) :
ε P.real {ω : Ω | ε ⨆ (i : (Set.Iic n)), X (↑i) ω} (ω : Ω) in {ω : Ω | ε ⨆ (i : (Set.Iic n)), X (↑i) ω}, X n ω P
theorem ProbabilityTheory.maximal_ineq {ι : Type u_1} {Ω : Type u_2} [LinearOrder ι] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {𝓕 : MeasureTheory.Filtration ι } {Y : ιΩ} [MeasureTheory.IsFiniteMeasure P] [TopologicalSpace ι] [SecondCountableTopology ι] (hsub : MeasureTheory.Submartingale Y 𝓕 P) (hnonneg : 0 Y) (ε : NNReal) (n : ι) :
ε P.real {ω : Ω | ε ⨆ (i : (Set.Iic n)), Y (↑i) ω} (ω : Ω) in {ω : Ω | ε ⨆ (i : (Set.Iic n)), Y (↑i) ω}, Y n ω P
theorem ProbabilityTheory.maximal_ineq_norm {ι : Type u_1} {Ω : Type u_2} {E : Type u_3} [LinearOrder ι] [NormedAddCommGroup E] [NormedSpace E] [CompleteSpace E] { : MeasurableSpace Ω} {P : MeasureTheory.Measure Ω} {X : ιΩE} {𝓕 : MeasureTheory.Filtration ι } [MeasureTheory.IsFiniteMeasure P] [TopologicalSpace ι] [SecondCountableTopology ι] (hmar : MeasureTheory.Martingale X 𝓕 P) (ε : NNReal) (n : ι) :
ε P.real {ω : Ω | ε ⨆ (i : (Set.Iic n)), X (↑i) ω} (ω : Ω) in {ω : Ω | ε ⨆ (i : (Set.Iic n)), X (↑i) ω}, X n ω P