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LeanPool.Superdiffusion.Algsuperdiff.Section5.Trace.GoodCubeCrossing

GoodCubeCrossing #

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

Good cubes met by a crossing of the annulus #

The chains-of-good-cubes estimate counts the sites of a crossing of the annulus between □_{m-1} and the complement of □_m at which the event Q(z + □_n, ε) occurs. It reads a crossing as a function x : ℕ → ℤ^d on {0, …, N} and counts with qSiteCount, while the pre-exit cube trace of a continuous path is a list of strictly adjacent sites whose good vertices are counted with Finset.filter. This file converts the first count into the second at the crossing index (m - n).toNat of the lattice 3^{n-1} ℤ^d, and carries the resulting bound to the trace of a continuous path stopped on leaving □_m.

Main definitions #

Main results #

1. The two embeddings of the site lattice #

The embedding z ↦ 3^{n-1} z used by the good cube events is the embedding used by the path estimate.

2. From the crossing count to the good-vertex count #

theorem Algsuperdiff.Section5.Trace.le_card_filter_of_isPathFrom {d : ℕ} (M : Section3.ABKModel d) (Creg Cinj : ℝ) (m n : ℤ) (ep : ℝ) (omega : Section3.Cutoff.CutoffSample d) (Good : Percolation.Site d → Prop) [DecidablePred Good] (hGood : ∀ (z : Percolation.Site d), Good z ↔ omega ∈ Support.qEvent M Creg Cinj n (Support.rescaledLatticePoint n z) ep) (hcrossing : ∀ (N : ℕ) (x : ℕ → Fin d → ℤ), Section3.Provider.Percolation.IsLatticePath x N → x 0 ∈ Section3.Provider.Percolation.cubeAt (m - n).toNat 0 → x N ∉ Section3.Provider.Percolation.cubeAt ((m - n).toNat + 1) 0 → 3 / 4 * 3 ^ (m - n).toNat ≤ ↑(Support.qSiteCount M Creg Cinj n ep (Percolation.pathSites N x) omega)) (Xi : List (Percolation.Site d)) (hXi : Percolation.IsPathFrom (m - n).toNat Xi) :
3 / 4 * 3 ^ (m - n).toNat ≤ ↑(Finset.filter Good Xi.toFinset).card

The good-vertex count along a list crossing. The crossing bound supplied for the functional reading of a crossing of the annulus at index (m - n).toNat bounds the number of good vertices of every list crossing at the same index.

theorem Algsuperdiff.Section5.Trace.natThreshold_le_card_filter_of_isPathFrom {d : ℕ} (M : Section3.ABKModel d) (Creg Cinj : ℝ) (m n : ℤ) (ep : ℝ) (omega : Section3.Cutoff.CutoffSample d) (Good : Percolation.Site d → Prop) [DecidablePred Good] (hGood : ∀ (z : Percolation.Site d), Good z ↔ omega ∈ Support.qEvent M Creg Cinj n (Support.rescaledLatticePoint n z) ep) (hcrossing : ∀ (N : ℕ) (x : ℕ → Fin d → ℤ), Section3.Provider.Percolation.IsLatticePath x N → x 0 ∈ Section3.Provider.Percolation.cubeAt (m - n).toNat 0 → x N ∉ Section3.Provider.Percolation.cubeAt ((m - n).toNat + 1) 0 → 3 / 4 * 3 ^ (m - n).toNat ≤ ↑(Support.qSiteCount M Creg Cinj n ep (Percolation.pathSites N x) omega)) (Xi : List (Percolation.Site d)) (hXi : Percolation.IsPathFrom (m - n).toNat Xi) :
3 * 3 ^ (m - n).toNat / 4 ≤ (Finset.filter Good Xi.toFinset).card

The good-vertex count with a natural-number threshold. This is the form the trace of a continuous path consumes.

3. The pre-exit cube trace at a general threshold #

A pre-exit cube trace with the crossing count of its scale. A path starting in the closed cube □_{n+k} and leaving □_{n+k+1} in finite positive time has a uniformly sampled scale-n cube trace, all of whose vertices are visited strictly before the exit, with at least L - 2 d good vertices whenever every crossing of the discrete annulus at index k has at least L of them. The two vertices lost are the endpoint corrections that turn the trace into a crossing; neither of them is claimed to be visited.

4. The trace vertices, and their enumeration #

A scale-n cell that meets □_{n+k+1} is indexed by a site of the centered cube of index k + 1. The cell of a site with 2 |z i| = 3^{k+1} + 1 already lies outside, and both sides being integers with 3^{k+1} odd, the strict inequality 2 |z i| < 3^{k+1} follows by parity.

The good sites of the centered lattice cube of index k.

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    An injective enumeration of the good sites of the centered lattice cube of index k.

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    • One or more equations did not get rendered due to their size.
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      theorem Algsuperdiff.Section5.Trace.exists_goodSiteEnum_eq {d k : ℕ} (Good : Percolation.Site d → Prop) [DecidablePred Good] {z : Percolation.Site d} (hz : Percolation.inCube k z) (hgood : Good z) :
      ∃ (j : Fin (goodSites k Good).card), (goodSiteEnum k Good) j = z

      Every good site of the centered lattice cube of index k is enumerated.