Section 14.2, part 2a: lem:shortblock, rectangles, sampling, fourth moment #
This file was automatically generated by Claude.
Formalization of blueprint Section 14, "The two-side estimate" (sec:sides), subsection 2,
"Comparison on a short depth block", part 2a: lem:shortblock: rectangles, sampling, fourth moment
(lines 2274-2317) of blueprint/formalization_blueprint.tex.
Comparison on a short depth block (lem:shortblock, blueprint lines 2275-2369) #
Blueprint eq:fourth-moment (lines 2311-2315), the pairing count: the sum of
a(m₁) a(m₂) conj a(m₃) conj a(m₄) over quadruples with equal sums and equal squared sums (what
survives integration in w and in γ) is at most 2 (Σ |a|²)².
Leaf-depth rectangles (lem:shortblock, blueprint lines 2290-2296) #
The rectangles partitioning four-tuples of leaf depths in the proof of lem:shortblock:
rep S v (the minimum v is attained exactly on the slots S, at least two of them) and
uniq a S h k (the minimum is attained only at a; at scale 2^(h+1) the depths of slot a and
of the slots S share the block k, with a in the lower and S in the upper half; all other
slots lie above that block).
- rep (S : Finset (Fin 4)) (v : ℕ) : DepthRect
- uniq (a : Fin 4) (S : Finset (Fin 4)) (h k : ℕ) : DepthRect
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- One or more equations did not get rendered due to their size.
- TrilinearHT.Auto.instDecidableEqDepthRect.decEq (TrilinearHT.Auto.DepthRect.rep S v) (TrilinearHT.Auto.DepthRect.uniq a S_1 h k) = isFalse ⋯
- TrilinearHT.Auto.instDecidableEqDepthRect.decEq (TrilinearHT.Auto.DepthRect.uniq a S h k) (TrilinearHT.Auto.DepthRect.rep S_1 v) = isFalse ⋯
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Admissible rectangle parameters.
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- (TrilinearHT.Auto.DepthRect.rep S v).Valid = (2 ≤ S.card)
- (TrilinearHT.Auto.DepthRect.uniq a S h k).Valid = (a ∉ S ∧ S.Nonempty)
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Membership of a depth tuple; it is a product of per-slot conditions.
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The separating depth t: all slots except possibly the heavy slot have depth at least t.
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- (TrilinearHT.Auto.DepthRect.rep S v).sep = v
- (TrilinearHT.Auto.DepthRect.uniq a S h k).sep = (2 * k + 1) * 2 ^ h
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Positions at a level: for depths below 2^m, a uniq rectangle has h < m and
k < 2^(m-h-1); a rep rectangle has v < 2^m.
The first-order derivative constant of an admissible class.
Equations
- TrilinearHT.Auto.admissibleLipConst κ = (κ.derivativeConstant * (↑1 + 2)) ^ (κ.derivativeConstant * (↑1 + 2))
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An admissible kernel on a cell of length r is Lipschitz with constant C_κ / r in each
variable.
Blueprint lines 2307-2312 (first kernel-sampling error): for an admissible kernel on a cell
of length r and 5δ ≤ μ r, the form with the sampling error kernel w - w^δ is at most
4 C_κ (δ / r) times the product of normalized local norms, at every exponent tuple allowed by
eq:absolute.
Blueprint lines 2298-2305 (substitution y = δ(n + u)): an integrable function on ℝ² is the
δ²-weighted sum over n ∈ ℤ² of its integrals over the unit fast cell.
The fast multipliers and the fourth moment (lem:shortblock, blueprint lines 2314-2326) #
The additive character e(x) = exp(2πix) of a real phase.
Equations
- TrilinearHT.Auto.ePhase x = Complex.exp (2 * ↑Real.pi * Complex.I * ↑x)
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The fast trigonometric polynomial Σ_m a_m e(γ m²/c + m w/16) on the circle of length 16
after the multiplier e(γ m²/c) (blueprint line 2316).
Equations
- TrilinearHT.Auto.fastMultiplied s a c γ w = ∑ m ∈ s, a m * TrilinearHT.Auto.ePhase (γ * ↑m ^ 2 / ↑c + ↑m * w / 16)
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Blueprint eq:fourth-moment (lines 2318-2322) for finite Fourier sums: when c ∣ 3,
the average over γ ∈ ℝ/3ℤ of the normalized L⁴ norm on the circle of length 16 satisfies
E_γ ∫ |U_γ F|⁴ ≤ 2 (Σ |a_m|²)² = 2 ‖F‖₂⁴.
Blueprint lines 2302-2307 (lift to the fast variables): with y₀ = x = δ(n₀ + u) and
y₁ = x + t = δ(n₁ + v), the form with the lattice-sampled kernel is the δ²-weighted sum over
n ∈ ℤ² of w(δ n₀, δ(n₁ - n₀)) times the fast integral over the unit cell of the inputs at
δ(n_j + w_j), n_j = (1-j)n₀ + j n₁, w_j = (1-j)u + j v.
Window masses (lem:shortblock, blueprint lines 2328-2332) #
The leaf interval [a_i, a_i + l_i).
Equations
- TrilinearHT.Auto.leafInterval aL lL i = Set.Ico (aL i) (aL i + lL i)
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The selected leaf union E = ⋃_{i ∈ S} L_i.
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- TrilinearHT.Auto.leafUnion S aL lL = ⋃ i ∈ S, TrilinearHT.Auto.leafInterval aL lL i
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The mass of z on the leaves meeting a set W is at most the total length of those leaves.
The mixed lattice-torus absolute estimate (lem:shortblock, blueprint lines 2307-2340) #
The fast circle T₀ = ℝ / 16ℤ of blueprint line 2303.
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Normalized Haar measure on the fast circle.
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The progression coordinate w_j = (1 - j) u + j v as a homomorphism T₀² → T₀.
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- TrilinearHT.Auto.fastCoord j = { toFun := fun (x : TrilinearHT.Auto.FastCircle × TrilinearHT.Auto.FastCircle) => (1 - j) • x.1 + j • x.2, map_zero' := ⋯, map_add' := ⋯ }
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Two distinct progression coordinates (w_i, w_j) as a homomorphism T₀² → T₀².
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The single progression coordinate pushes Haar measure on T₀² to Haar measure on T₀.
Blueprint line 394 (torus pair endpoint): two distinct progression coordinates are
independent: ∫∫ f(w_i) g(w_j) = ∫ f ∫ g.
The mixed measure: weight ε² on the slow pairs in B, normalized Haar measure on T₀².
Equations
- TrilinearHT.Auto.latticeTorusMeasure B ε = (∑ n ∈ B, ε ^ 2 • MeasureTheory.Measure.dirac n).prod (TrilinearHT.Auto.fastHaar.prod TrilinearHT.Auto.fastHaar)
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The target measure: weight ε on each slow point, normalized Haar measure on T₀.
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The progression map (n, u, v) ↦ (n_j, w_j).
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The single-coordinate endpoint of the mixed absolute estimate.
The pair endpoint of the mixed absolute estimate.
eq:absolute on local counting measure times Haar measure, in normed form: for exponents
p_j ≥ 1 with Σ 1/p_j ≤ 2, the positive form is at most C Π_j ‖f_j‖_{L^{p_j}}.
The uniform probability on γ ∈ [0, 3) (blueprint line 2316, γ ∈ ℝ/3ℤ).
Equations
- TrilinearHT.Auto.gammaMeasure = ENNReal.ofReal (1 / 3) • MeasureTheory.volume.restrict (Set.Ioc 0 3)
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Continuous comparison (lem:shortblock, blueprint lines 2345-2357) #
Blueprint lines 2347-2349: if the four intervals |y - δ n_j| < c δ with c < 1/7 meet a real
progression y_j = x + j t, the integer centers form a lattice progression:
n_j = (1 - j) n₀ + j n₁.
Mixed Hölder and the block factor (lem:shortblock, blueprint lines 2357-2369) #
The progression coordinate on the fast factor pushes P ⊗ Haar(T₀²) to P ⊗ Haar(T₀).
Fourier partial sums of the fast windows (limiting route of lem:shortblock) #
The symmetric Fourier partial sums of an L² function on the fast circle converge to it in
L² (Mathlib hasSum_fourier_series_L2).
Bessel's inequality for finite sets of frequencies: Σ_{m ∈ s} |f̂(m)|² ≤ ‖f‖₂².
The fast lift (lem:shortblock, blueprint lines 2302-2306) #
Left endpoints of the fast lift intervals: [0, 1) in slots 0, 1 and [-4, 4) in slots
2, 3 (blueprint line 2303: "restricted to [0,1) in slots 0,1 and to fixed lift intervals in
[-4,4] containing all needed w_j in slots 2,3").
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Lengths of the fast lift intervals.
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The representative of a fast point in [ℓ_j, ℓ_j + 16).
Equations
- TrilinearHT.Auto.fastRep j t = ↑((AddCircle.equivIco 16 (TrilinearHT.Auto.fastLiftLeft j)) t)
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The lift of a function on the lift interval of slot j to the fast circle, zero elsewhere.
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Normalized Haar measure on T₀² is 1/256 times Lebesgue measure on [0, 16)².
Blueprint lines 2302-2306 ("with fixed Haar constants the fast progression integral
reproduces the original integral without wraparound"): lifting the slot functions to T₀ on
the lift intervals, the fast progression integral over T₀² is 1/256 times the integral over
the unit cell [0, 1)².
The all-L² case of eq:absolute on T₀² for one slow tuple: pairing the slots (0, 1) and
(2, 3) and using independence of two coordinates, ∫∫ Π_j h_j(w_j) ≤ Π_j ‖h_j‖₂.
∫∫ Π_j |g_j(w_j)| ≤ Π_j ‖g_j‖₂ for complex slot functions.
The sampled form as a lattice sum of fast forms (lem:shortblock, lines 2298-2307) #
The fast slot functions F_j(m, w) = f_j(δ(m + w)) on the lift interval of slot j
(blueprint line 2303).
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- TrilinearHT.Auto.slotLift δ f j m = TrilinearHT.Auto.fastLift j fun (x : ℝ) => f j (δ * (↑m + x))
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The fast progression form of one slow pair n = (n₀, n₁):
∫∫_{T₀²} Π_j F_j(n_j, w_j) with n_j = (1-j) n₀ + j n₁, w_j = (1-j) u + j v.
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- One or more equations did not get rendered due to their size.
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The unit-cell integral of the progression inputs is 256 times the fast form.
The lattice-sampled kernel of a kernel with local progression support on [a, a + r] has
local progression support on [a - 5δ, a + r + 5δ].
A bounded measurable kernel with local progression support against four L² inputs gives an
integrable progression integrand (all-L² case of eq:absolute).
Blueprint lines 2302-2307: the form with the lattice-sampled kernel is
r⁻² δ² 256 Σ_n w(δ n₀, δ(n₁ - n₀)) Φ_n(F), the sum over the finitely many slow pairs where
the sampled kernel is nonzero, with Φ_n the fast form of the lifted inputs.
Window masses of the fast slots (lem:shortblock, blueprint lines 2328-2331) #
The fast lift lengths are natural numbers (1 or 8).
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Haar integrals of lifted functions: ∫_{T₀} φTilde = (1/16) ∫_{[ℓ_j, ℓ_j + L_j)} φ.
The squared fast mass of a slot window: ∫_{T₀} |F_j(m, ·)|^p = (16 δ)⁻¹ ∫_{window} |f_j|^p,
the window being [δ(m + ℓ_j), δ(m + ℓ_j + L_j)).
The comparison at one leaf-depth rectangle (lem:shortblock, lines 2298-2369) #
The data of the comparison at one leaf-depth rectangle of lem:shortblock, after
normalization: finitely many summation cells with admissible kernels, the sampling scale δ,
random inputs z^σ with deterministic sizes Z_j, the inputs supported in [lo, hi].
- grid : RealDyadicGrid
Dyadic grid supporting the short-block local forms.
Finite collection of cells in the short block.
Admissible local kernel assigned to each short-block cell.
- admissible (I : ℤ × ℤ) : I ∈ self.cells → IsAdmissibleLocalKernel κ (dyadicGridLeft self.grid I.1 I.2) (dyadicGridLength self.grid I.1) (self.kernel I)
- δ : ℝ
Positive smoothing scale small relative to each cell length and kernel margin.
Measurable parameter-dependent input tuple for the block forms.
- z_meas (j : Fin 4) : Measurable (Function.uncurry (self.z j))
Nonnegative measurable envelopes controlling the parameter-dependent inputs.
- Z_meas (j : Fin 4) : Measurable (self.Z j)
- lo : ℝ
Left endpoint of the common compact support interval for the inputs.
- hi : ℝ
Right endpoint of the common compact support interval for the inputs.
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The length r_I of a cell.
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- D.len I = TrilinearHT.Auto.dyadicGridLength D.grid I.1
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The left endpoint of a cell.
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- D.left I = TrilinearHT.Auto.dyadicGridLeft D.grid I.1 I.2
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The inputs at the random parameter σ.
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The signed sum Σ_I |I| ε_I(σ) H_I(z^σ) of eq:shortblock.
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The first kernel-sampling error at a cell.
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Hölder in the random parameter with four L⁴ factors.
The slow pairs n whose sampled kernel value at the cell I can be nonzero.
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The lattice sum Σ_I |I| ε_I r_I⁻² δ² 256 Σ_n w_I(δ n₀, δ(n₁ - n₀)) Φ_n(F) for fast
data F.
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- One or more equations did not get rendered due to their size.
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Blueprint lines 2307-2312: for inputs in L², the signed sum splits into the first sampling
errors and the lattice sum of the fast forms of the lifted inputs.
Joint measurability of the lifted random slots.
The fast form is additive in one slot.
The deterministic sizes as complex functions.
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The constant of the second sampling error.
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- TrilinearHT.Auto.BlockData.err2Const C4 = 2 ^ (1 / 2) * ENNReal.ofReal C4 ^ 2 / 8
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Assembly of eq:shortblock (lem:shortblock, blueprint lines 2272-2369) #
The heavy slot a of a rectangle (for rep, the least attaining slot).
Equations
- (TrilinearHT.Auto.DepthRect.rep S v).heavy = if h : S.Nonempty then S.min' h else 0
- (TrilinearHT.Auto.DepthRect.uniq a S h k).heavy = a
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The designated slot b of a rectangle (blueprint line 2292).
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The level of a rectangle: its slot assignment and scale, forgetting the position.
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- (TrilinearHT.Auto.DepthRect.rep S v).level = TrilinearHT.Auto.DepthRect.rep S 0
- (TrilinearHT.Auto.DepthRect.uniq a S h k).level = TrilinearHT.Auto.DepthRect.uniq a S h 0
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A finite dyadic tree piece of lem:shortblock (blueprint line 2276): a root cell, internal
summation cells in the K consecutive depths starting at first, and leaves in that block or one
depth below; the leaves are disjoint cells inside the root covering it, and an internal cell
meeting a leaf is strictly coarser.
Root cell of the short-block tree.
- first : ℤ
First integer depth in the short block.
Internal cells at which the short-block expansion continues.
Leaf cells at which the short-block expansion stops.
- internal_subset (I : ℤ × ℤ) : I ∈ self.internal → dyadicGridCell G I.1 I.2 ⊆ dyadicGridCell G self.root.1 self.root.2
- leaf_subset (L : ℤ × ℤ) : L ∈ self.leaves → dyadicGridCell G L.1 L.2 ⊆ dyadicGridCell G self.root.1 self.root.2
- leaf_disjoint : (↑self.leaves).PairwiseDisjoint fun (L : ℤ × ℤ) => dyadicGridCell G L.1 L.2
- leaf_cover : dyadicGridCell G self.root.1 self.root.2 ⊆ ⋃ L ∈ self.leaves, dyadicGridCell G L.1 L.2
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Left endpoints and lengths of cells.
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Length of the dyadic cell indexed by c.
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Every leaf meeting an internal cell lies inside it.
The padded depth of a leaf.
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The leaf-depth labelling of points (zero outside the leaves).
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The position of a rectangle within its level.
Equations
- (TrilinearHT.Auto.DepthRect.rep S v).pos = v
- (TrilinearHT.Auto.DepthRect.uniq a S h k).pos = k
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The sampling weights of the coarser depths: Σ_{s ∈ S} r_t / r_s ≤ 1 for distinct s < t.
The leaf bound in the normalized form.
Equations
- T.LeafBound z = ∀ (j : Fin 4), ∀ L ∈ T.leaves, ∫⁻ (y : ℝ) in TrilinearHT.Auto.dyadicGridCell G L.1 L.2, ‖z j y‖ₑ ^ 2 ≤ ENNReal.ofReal (TrilinearHT.Auto.dyadicGridLength G L.1)
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The regular exponent p = 2 p_* / (p_* - 2) = (2q - 2) / (q - 2).
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The exponents of a rectangle: p_* in the heavy and designated slots, p elsewhere.
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- TrilinearHT.Auto.ShortBlockTree.pexp q R j = if j = R.heavy ∨ j = R.desig then TrilinearHT.Auto.pStar q else TrilinearHT.Auto.pReg q
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The regular window constant E₂ = 1/2 + 1/(8β).
Equations
- TrilinearHT.Auto.ShortBlockTree.regE2 κ = 1 / 2 + 1 / (8 * TrilinearHT.Auto.ShortBlockTree.beta κ)