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LeanPool.HighContrastHomogenization.Support.Deterministic.ConstantCoefficientDirichletBesov.StandardProjectionBoundary

Coarse-graining support: #

Support.Deterministic.ConstantCoefficientDirichletBesov.StandardProjectionBoundary

Imported from the Apache-2.0 CoarseGraining development at commit c7ddd76c08ade64fed1b8d2ca51be14dfee8deb4.

Boundary-crossing centers for projection increments #

For one martingale increment, an overlap cube contributes only if it crosses the standard triadic partition at the increment scale. This file isolates that support reduction. The remaining geometric work is then a finite counting estimate for the crossing centers.

Overlap centers whose overlap cube is not contained in any standard descendant at the increment scale m + 1.

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    If an admissible overlap center is not crossing at the increment scale, then the increment has zero corrected overlap fluctuation on that center.

    The overlap-center sum for one increment may be restricted to the crossing centers. Non-crossing centers contribute zero by local constancy.

    If a fine descendant is one fine scale away from every face of a coarser cube, then its overlap cube is contained in that coarser cube.

    A one-scale-separated descendant cannot be a crossing center for the coarser increment partition.

    Crossing descendants fail the one-fine-scale interior separation from any coarser descendant that contains their center cube. This is the boundary-layer form needed for the cardinality estimate.

    An overlap center at depth j has an ancestor at any increment depth m + 1 ≤ j + 1.

    A crossing overlap center has a coarser increment ancestor, and relative to that ancestor it lies in the one-fine-scale boundary layer.

    Descendants of R at depth n lying in the one-fine-scale boundary layer of R.

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      The boundary layer is exactly the union of the descendants sharing at least one lower or upper coordinate face with the parent cube.

      noncomputable def HCPolySupport.fixedCoordinateFunctionEquiv {α : Type u_1} {β : Type u_2} [DecidableEq α] (i : α) (a : β) :
      { f : α → β // f i = a } ≃ ({ j : α // j ≠ i } → β)

      Remove a fixed coordinate from a function, with inverse given by restoring its prescribed value; used to count face digits.

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        theorem HCPolySupport.cubeCoordLower_child_eq_parent_iff_digit_zero {d : ℕ} (R : TriadicCube d) (digits : Fin d → Fin 3) (i : Fin d) :
        cubeCoordLower { scale := R.scale - 1, index := fun (k : Fin d) => 3 * R.index k + ↑↑(digits k) - 1 } i = cubeCoordLower R i ↔ digits i = 0
        theorem HCPolySupport.cubeCoordUpper_child_eq_parent_iff_digit_two {d : ℕ} (R : TriadicCube d) (digits : Fin d → Fin 3) (i : Fin d) :
        cubeCoordUpper { scale := R.scale - 1, index := fun (k : Fin d) => 3 * R.index k + ↑↑(digits k) - 1 } i = cubeCoordUpper R i ↔ digits i = 2
        noncomputable def HCPolySupport.descendantLowerFaceAtDepth {d : ℕ} (R : TriadicCube d) (n : ℕ) (i : Fin d) :

        Depth-n descendants whose lower ith face coincides with the lower face of R.

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          noncomputable def HCPolySupport.descendantUpperFaceAtDepth {d : ℕ} (R : TriadicCube d) (n : ℕ) (i : Fin d) :

          Depth-n descendants whose upper ith face coincides with the upper face of R.

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            The coordinate-face union containing the boundary layer.

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              Boundary-layer descendants over all increment-scale ancestors.

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                theorem HCPolySupport.incrementBoundaryLayerCentersAtDepth_sum_le_const_mul_ancestor_sum {d : ℕ} (Q : TriadicCube d) (j m : ℕ) (F B : TriadicCube d → ℝ) (hF : ∀ S ∈ incrementBoundaryLayerCentersAtDepth Q j m, 0 ≤ F S) (hB : ∀ R ∈ descendantsAtDepth Q (m + 1), 0 ≤ B R) (hbound : ∀ R ∈ descendantsAtDepth Q (m + 1), ∀ S ∈ descendantBoundaryLayerAtDepth R (j - m), F S ≤ B R) :
                (incrementBoundaryLayerCentersAtDepth Q j m).sum F ≤ 2 * ↑d * (3 ^ (d - 1)) ^ (j - m) * ∑ R ∈ descendantsAtDepth Q (m + 1), B R

                Every crossing center belongs to the boundary layer of its increment-scale ancestor.

                One-increment depth averages are controlled by the corresponding boundary-layer sum. The remaining work is to count that boundary layer.

                theorem HCPolySupport.cubeBesovOverlappingPositiveVectorDepthAverage_cubeIncrementVec_le_const_mul_ancestor_sum {d : ℕ} (Q : TriadicCube d) (u : Vec d → Vec d) {j m : ℕ} (hmj : m ≤ j) (B : TriadicCube d → ℝ) (hB : ∀ R ∈ descendantsAtDepth Q (m + 1), 0 ≤ B R) (hbound : ∀ R ∈ descendantsAtDepth Q (m + 1), ∀ S ∈ descendantBoundaryLayerAtDepth R (j - m), overlapCubeLpNorm S 2 (overlapCubeFluctuationVec S (cubeIncrementVec Q (m + 1) u)) ^ 2 ≤ B R) :
                cubeBesovOverlappingPositiveVectorDepthAverage Q (cubeIncrementVec Q (m + 1) u) j ≤ (↑(overlapCentersAtDepth Q j).card)⁻¹ * (2 * ↑d * (3 ^ (d - 1)) ^ (j - m) * ∑ R ∈ descendantsAtDepth Q (m + 1), B R)

                One-increment overlap averages are controlled by any nonnegative increment-ancestor budget which bounds each boundary-layer center of that ancestor. This is the counted form of the boundary reduction: the only remaining analytic work is to provide the pointwise ancestor budget.

                theorem HCPolySupport.overlappingPositiveDepthAverage_increment_le_ancestorSum {d : ℕ} (Q : TriadicCube d) (u : Vec d → Vec d) {j m : ℕ} (hmj : m ≤ j) (B : TriadicCube d → ℝ) (hB : ∀ R ∈ descendantsAtDepth Q (m + 1), 0 ≤ B R) (hbound : ∀ R ∈ descendantsAtDepth Q (m + 1), ∀ S ∈ descendantBoundaryLayerAtDepth R (j - m), overlapCubeLpNorm S 2 (overlapCubeFluctuationVec S (cubeIncrementVec Q (m + 1) u)) ^ 2 ≤ B R) :
                cubeBesovOverlappingPositiveVectorDepthAverage Q (cubeIncrementVec Q (m + 1) u) j ≤ (↑((3 ^ d) ^ j))⁻¹ * (2 * ↑d * (3 ^ (d - 1)) ^ (j - m) * ∑ R ∈ descendantsAtDepth Q (m + 1), B R)

                Lowering the overlap-center normalization to the explicit standard cardinality lower bound gives the scale-separated counted form of the one-increment boundary estimate.