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LeanPool.Malliavin.ClarkOconeSolution

Malliavin calculus through the Clark--Ocone formula #

This statement gives explicit Mathlib-only meanings to the Cameron--Martin space, the smooth Malliavin derivative, its graph closure, predictable projection, and the natural predictable process space. The theorem supplies the time realization and Brownian Itô isometry and states martingale representation together with the Clark--Ocone identity on the closed graph. The explicit boundary definitions support independent statement auditing; named bridges transfer their witnesses to the shared library API.

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Square-integrable real random variables.

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    Square-integrable real processes on time times sample space.

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      Predictable square-integrable processes.

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        The measurable space generated by a process's coordinates.

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          The process coordinates generate the ambient measurable space.

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            The constant L² representative of a random variable's expectation.

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              The identity random variable centered by its Bochner mean.

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                A continuous linear functional as its centered Cameron--Martin class.

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                  The rank-one H-valued random variable w ↦ G(w)h.

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                    Bounded C¹ functionals with uniformly bounded derivative.

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                      Convert the independent statement boundary to the library's smoothness predicate.

                      A smooth functional as a scalar L² class.

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                        (F, η) belongs to the closure of the smooth Malliavin graph.

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                          Transfer the independently stated graph closure to the library graph closure.

                          The predictable sigma-algebra lies below the ambient product sigma-algebra.

                          Orthogonal projection onto predictable processes.

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                            theorem PalomarClarkOcone.generated_clark_ocone {W : Type u} [NormedAddCommGroup W] [NormedSpace ℝ W] [CompleteSpace W] [MeasurableSpace W] [BorelSpace W] [SecondCountableTopology W] {P : MeasureTheory.Measure W} [ProbabilityTheory.IsGaussian P] {B : NNReal → W → ℝ} (hB : ProbabilityTheory.IsPreBrownianReal B P) (coordinate : NNReal → StrongDual ℝ W) (coordinate_apply : ∀ (t : NNReal) (w : W), B t w = (coordinate t) w) (generated : IsWienerGenerated B) (hsm : ∀ (t : NNReal), MeasureTheory.StronglyMeasurable (B t)) {filtration : MeasureTheory.Filtration NNReal inst✝} (hnat : filtration = MeasureTheory.Filtration.natural B hsm) :
                            ∃ (timeDerivative : ↥(MeasureTheory.Lp (↥(CameronMartin.Space P)) 2 P) →ₗᵢ[ℝ] ↥(TimeProcessL2 P)) (itoIntegral : ↥(PredictableProcessL2 filtration P) →L[ℝ] ↥(RandomL2 P)), (∀ (h : ↥(CameronMartin.Space P)), (∀ (t : NNReal), inner ℝ h ((CameronMartin.ofDual P) (coordinate t)) = 0) → h = 0) ∧ (∀ (t : NNReal) (G : ↥(RandomL2 P)), ↑↑(timeDerivative ((smulLp ((CameronMartin.ofDual P) (coordinate t))) G)) =ᵐ[nonnegativeLebesgueMeasure.prod P] fun (p : NNReal × W) => (Set.Ioc 0 t).indicator 1 p.1 * ↑↑G p.2) ∧ (∀ (U : ↥(PredictableProcessL2 filtration P)), ‖itoIntegral U‖ = ‖U‖) ∧ (∀ (U : ↥(PredictableProcessL2 filtration P)), ∫ (w : W), ↑↑(itoIntegral U) w ∂P = 0) ∧ (∀ {a b : NNReal}, a ≤ b → ∀ (Z : ↥(MeasureTheory.lpMeas ℝ ℝ (↑filtration a) 2 P)), ∃ (U : ↥(PredictableProcessL2 filtration P)), (↑↑↑U =ᵐ[nonnegativeLebesgueMeasure.prod P] fun (p : NNReal × W) => (Set.Ioc a b).indicator 1 p.1 * ↑↑↑Z p.2) ∧ ↑↑(itoIntegral U) =ᵐ[P] fun (w : W) => ↑↑↑Z w * (B b w - B a w)) ∧ (∀ (G : ↥(RandomL2 P)), ∃ (U : ↥(PredictableProcessL2 filtration P)), G = expectationL2 G + itoIntegral U) ∧ ∀ {F : ↥(RandomL2 P)} {η : ↥(MeasureTheory.Lp (↥(CameronMartin.Space P)) 2 P)}, InGraphClosure P F η → ∃ (G : NNReal × W → ℝ), MeasureTheory.StronglyMeasurable G ∧ ↑↑↑((predictableProjection filtration) (timeDerivative η)) =ᵐ[nonnegativeLebesgueMeasure.prod P] G ∧ (∀ᵐ (t : NNReal) ∂nonnegativeLebesgueMeasure, 0 < t → (fun (w : W) => G (t, w)) =ᵐ[P] P[fun (w : W) => ↑↑(timeDerivative η) (t, w) | ↑filtration t]) ∧ F = expectationL2 F + itoIntegral ((predictableProjection filtration) (timeDerivative η))

                            Generated-space martingale representation and textbook Clark--Ocone. For a generating pre-Brownian process with continuous linear coordinates on a separable real Gaussian Banach space, using its natural filtration, there are a time realization of the closed Malliavin derivative and a Brownian Itô isometry such that every terminal L² variable has a stochastic-integral representation. For every pair in the closed Malliavin graph, the predictable projection of the derivative has a representative whose time sections are the conditional expectations for almost every positive time in the Clark--Ocone identity. The Brownian coordinate directions are total in the Cameron--Martin space, so the displayed generator law determines the continuous time realization.