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LeanPool.Superdiffusion.Algsuperdiff.Section3.Provider.Diffusivity.ApproximateRecurrence.Closure.Step5InputGradMoment

Step5InputGradMoment #

Ported from scottnarmstrong/Superdiffusion at 7f20476385d4af418f110303085ad0740c9eba46. Module imports, support namespace and local option directives adapted for Lean Pool.

hgradM: the grid fourth moment of the Dirichlet corrector's cube averages #

ABK26, e.nablaw.in.L.eight, read inside Step 5 of l.approximate.recurrence.formula.

Closure.Step5Basket.step5GaugeEndpoint_closureFamilies_of_momentLegs leaves hgradM as the binder

  ( avsum_{R in grid}  E[ |(grad w_D)_R|^4 ] )^{1/2}
      <=  C2 * shom_n^{-2} * h * 3^{2 cgamma (n+h)} .

The route #

The manuscript's own three steps, in order.

  1. The grid step. The grid tiles cu_K, so per-cube Jensen followed by the tiling identity gives, at fixed sample and with no dependence on K,
      avsum_R |(grad w_D)_R|^4  <=  8 ||grad w_D||_{L8bar(cu_K)}^4 ,
    
    which is PrincipalResponseDisplayTwoGrid.descendantsAverage_sq_vecNormSq_add_cubeAverageVec_le at c = 0. The grid fourth moment is a finite average of integrals, so the sample integral may be taken outside.
  2. Calderon--Zygmund. Corrector.exists_cubeEuclideanL8_gradient_sq_sum_le bounds ||grad w_D||^2_{L8bar(cu_K)} by the L^8 norm of the forcing of e.def.w, which Corrector.cubeEuclideanLpNorm_streamForcing_le reads as shom_n^{-1} ||k_{n+h} - k_n||_{L8bar(cu_K)}.
  3. e.km.kn.Lp. Corrector.exists_streamIncrementLpNormSq_head_tail --- the proved frozen theorem --- splits that square into the head C h 3^{2 cgamma (n+h)} and a Gamma_1 tail whose amplitude carries the extra decay 3^{-(K-m)d/8} <= 1. Its second moment is LocalizationEnvelopeMoment.integral_sq_le_of_isBigOWith_gammaSigma_one', so the fourth moment of the L^8 norm is at most an absolute multiple of the head squared, and the square root of the grid moment is the display.

References #

The grid step, at fixed sample #

Per-cube Jensen and the tiling identity, at c = 0. The grid average of the fourth power of the cube averages of a field is at most 8 times the fourth power of its normalized Euclidean L^8 norm on the ambient cube. No dependence on the depth j.

Taking the sample integral outside the grid average #

theorem Algsuperdiff.Section3.Provider.Diffusivity.ApproximateRecurrence.Closure.gridFourthMoment_le_integral_of_cubeFamilyAverage_le {d : ℕ} {Omega : Type u_1} [MeasurableSpace Omega] (mu : MeasureTheory.Measure Omega) (I : Finset (HCPolySupport.TriadicCube d)) (F : HCPolySupport.TriadicCube d → Omega → ℝ) (G : Omega → ℝ) (hFint : ∀ R ∈ I, MeasureTheory.Integrable (fun (omega : Omega) => F R omega ^ 4) mu) (hGint : MeasureTheory.Integrable G mu) (hle : ∀ (omega : Omega), (cubeFamilyAverage I fun (R : HCPolySupport.TriadicCube d) => F R omega ^ 4) ≤ G omega) :
gridFourthMoment mu I F ≤ ∫ (omega : Omega), G omega ∂mu

The grid fourth moment under a pathwise grid bound. The grid is finite, so the sample integral commutes with its average.

The L^8 carrier of e.km.kn.Lp, made measurable #

The volume-normalized L^8 norm of the fresh shell on cu_K is a random variable.

The fourth moment of the fresh-shell L^8 norm on cu_K.

e.km.kn.Lp (the proved frozen theorem) splits ||k_m - k_n||^2_{L8bar(cu_K)} into a head and a Gamma_1 tail whose amplitude carries the factor 3^{-(K-m)d/8} <= 1. Replacing the anchor's tail variable by the measurable positive part max(L^2 - head, 0) --- which the anchor's own bound dominates --- makes the second moment available, and the fourth moment of L follows.

Both the bound and the integrability are produced; no measurability of the anchor's own tail variable is assumed.

hvmem and hgradM at the closure's Dirichlet family #

hvmem and hgradM, proved.

One constant, produced before the model, such that at every admissible pair (n, n+h) and every localization scale K >= n+h the closure's own Dirichlet family satisfies both Step-5 gradient legs: the cube averages are L^4 in the sample, and the square root of their grid fourth moment obeys e.nablaw.in.L.eight in the shape the manuscript reads it.

The depth j is arbitrary: the grid step is the tiling identity, which holds at every depth.

Proved from Corrector.exists_cubeEuclideanL8_gradient_sq_sum_le and ApproximateRecurrence.memLp_eight_grad_freshShellDirichlet, hence from the external Calderon--Zygmund input Algsuperdiff.Frozen.External.calderon_zygmund.