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LeanPool.Superdiffusion.Algsuperdiff.Section4.Provider.ExcessDecay.EdFinalInputs

EdFinalInputs #

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

The interior branch's three carried inputs, discharged #

The interior route (EdBridgeInteriorClause) delivers the two-leg one-step contraction off the harmonic-approximation anchor, but carries three items as binders:

This module discharges all three.

1. The gate, from z ∈ □_{m-1} #

image_add_subset_openCubeSet_of_mem_inner: for z ∈ □_{m-1} and j ≤ m-1 the translated cube z + □_j sits inside □_m — the coordinates satisfy |z_i| < 3^{m-1}/2 and |w_i| < 3^j/2 ≤ 3^{m-1}/2, so |z_i + w_i| < 3^{m-1} = 3^m/3 < 3^m/2. Since □_m is open it is disjoint from its own frontier, so the frozen statement's gate follows (inter_frontier_eq_empty_of_subset), and so does the one-step's interior inclusion (the same lemma at j - 2). This is exactly the implication disclosed as "the terminal consumer supplies it from z ∈ □_{m-1}", now formalized: the connectedness detour is not needed, the coordinate computation is direct.

2. The harmonic replacement pair, at every scale #

exists_harmonicReplacementPair: on any open bounded convex nonempty window V and for any H¹(V) datum Φ there are v : H¹(V) weakly harmonic and w : H¹₀(V) with

   v = Φ − w      and      ∇v = ∇Φ − ∇w        (both POINTWISE, as the anchor demands) .

The construction is the proved ResidualCorrectorExistence route run at the datum's own force +∇Φ (rather than −∇Φ), so that the solution enters with the sign the anchor's clauses want and both clauses are H1Function.sub_toFun / H1Function.sub_grad. Reading the packaged ResidualCorrectorExistence.exists_weaklyHarmonicOn_of_datum instead would deliver only the toFun clause: its MemH10 witness is existentially bound, and pointwise gradient equality does not follow from pointwise value equality.

exists_harmonicReplacementPair_movedCube instantiates it at the anchor's own moved replacement cube y + □_{n-2}, y = wellPlacedCentre z m (n-2), using the identity (y + □_{n-2}) = truncatedWindow y m (n-2) (the clamped cube already sits inside □_m).

3. The contraction absorption at the interior ratio #

exists_edFinalStep is EdBridgeFolds.exists_edBridgeStep read on the interior branch: there is no W' → U_0 re-index there, so the quasi-monotonicity price κ(d,1) is not paid and the target ratio is θ^k = 3^{-k/4} rather than θ^{k+1}. Both simplifications are strict weakenings of the proved statement (1 ≤ κ(d,1) and 3^{-(k+1)/4} ≤ 3^{-k/4}), so the interior step size is the proved k₀(d) unchanged.

References #

1. The gate from z ∈ □_{m-1} #

The interior gate, from the printed indicator's own condition. For z ∈ □_{m-1} and j ≤ m-1 the translated cube z + □_j sits inside □_m.

The frozen interior clause's frontier-empty gate, from any inclusion in □_m: an open set is disjoint from its own frontier.

The frozen interior clause's gate at the printed indicator's own condition.

2. The harmonic replacement pair #

The harmonic replacement pair exists on every admissible window.

v weakly harmonic, w ∈ H¹₀(V), and BOTH clauses the anchor's interior slot demands: v = Φ − w and ∇v = ∇Φ − ∇w, pointwise. The Dirichlet solve is run at the datum's own force +∇Φ, so the pair is (Φ − ρ, ρ) with ρ the zero-trace solution.

The anchor's moved replacement cube IS a truncated window at the clamped centre.

The harmonic replacement pair at the anchor's own moved replacement cube, at every scale n with n - 2 ≤ m: the interior route's carried item (c), discharged from the solution u alone.

3. The contraction absorption at the interior ratio #

1 ≤ κ(d,j) for j ≥ -1: the volume-ratio constant is at least one.

theorem Algsuperdiff.Section4.Provider.ExcessDecay.exists_edFinalStep (d : ℕ) [NeZero d] :
∃ (k₀ : ℕ), 3 ≤ k₀ ∧ ∀ (k : ℕ), k₀ ≤ k → taylorContractionConst d * Schauder.schauderWindowConst d * windowRatioConst d 2 * (3 ^ (-↑k)) ^ (1 / 2) ≤ 1 / 2 * 3 ^ (-(1 / 4) * ↑k)

The contraction absorption on the interior branch. There is a step size k₀(d) ≥ 3 beyond which the one-step's contraction prefactor is absorbed into HALF of the iteration anchor's own ratio θ^k = 3^{-k/4} — no κ(d,1), and no shift to θ^{k+1}, because the interior clause reads its oscillation on the contraction's own window.