Section 10: Detection from a local form #
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Formalization of blueprint Section 10, "Detection from a local form" (sec:detection, lines
1418-1479) of blueprint/formalization_blueprint.tex.
Continuous L² embedding from the unit interval into the circle of length sixteen.
Equations
Instances For
The generalized von Neumann inequality on a compact abelian group #
Blueprint lem:von-neumann, lines 1431–1446: three Cauchy–Schwarz steps bound the
progression average by the eighth root of a dilated cube average of the second slot.
All inputs here are bounded; the passage to L² is made later.
The multiplicative difference f(y) conj f(y + s).
Equations
- TrilinearHT.Auto.mulDiff f s y = f y * (starRingEnd ℂ) (f (y + s))
Instances For
First Cauchy–Schwarz step (lem:von-neumann, line 1431).
The square of an inner average as a correlation (lem:von-neumann, line 1433).
Shift and swap: ∫∫ U(u+αt) B(u+βt) V(u+γt) = ∫ B(y) ∫ U(y+(α-β)t) V(y+(γ-β)t).
Cauchy–Schwarz on a product of two probability spaces with a 1-bounded first factor.
Second Cauchy–Schwarz step (lem:von-neumann, lines 1433–1436).
Shift and swap with two factors: ∫∫ U(u+at) V(u+ct) = ∫ V(z) ∫ U(z+(a-c)t).
The square of an inner progression average, integrated: the last differencing step.
Third Cauchy–Schwarz step (lem:von-neumann, lines 1436–1440), with an outer parameter.
The dilated third multiplicative difference average of g.
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- One or more equations did not get rendered due to their size.
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Blueprint lem:von-neumann, lines 1431–1446, for bounded inputs on a compact abelian
group with Haar probability: |Λ|⁸ ≤ ‖R‖₂⁸ · (dilated U³ average of g) when |b|,|c| ≤ 1.
Identification with the Gowers U³ norm (lem:von-neumann, line 1447) #
The order-three cube average as an iterated integral of multiplicative differences.
Integer dilations of the increments do not change the cube average when every nonzero integer multiplication preserves the Haar probability (lem:von-neumann, line 1447).
lem:von-neumann, lines 1431–1447, on a compact abelian group whose nonzero integer
multiplications preserve the Haar probability: |Λ|⁸ ≤ ‖R‖₂⁸ ‖g‖_{U³}⁸ for |b|,|c| ≤ 1.
Lifting a function supported in [0,1) to the torus of length 16.
Equations
- TrilinearHT.Auto.torusLift F = AddCircle.liftIoc 16 (-8) F
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One progression term on the unit cell: Plancherel-free von Neumann bound through the torus.
Affine rescaling of a progression integral over ℝ² to the unit scale.
lem:von-neumann, lines 1427–1429: one kernel character term.
Blueprint lem:von-neumann for bounded inputs: for any ordering of four distinct slots,
|H_I(R,g,b,c)| ≤ C ‖R‖_{2,I} ‖g‖_{U(I)} when |b|,|c| ≤ 1 on I, with C depending
only on the kernel class.
Only the restrictions of the inputs to the cell enter an admissible local form.
An admissible local form vanishes when one input vanishes on the cell.
Integrability of an admissible local progression integrand whose cell
restrictions have finite normalized norms at exponents allowed by eq:absolute.
Blueprint lem:von-neumann, line 1447: passage from bounded inputs to L²
inputs by truncation, for |b|, |c| ≤ 1 on the cell.
Blueprint lem:von-neumann, eq:von-neumann: for any ordering of four distinct
slots, R, g ∈ L²(I) and b, c bounded on I,
|H_I(R,g,b,c)| ≤ C ‖R‖_{2,I} ‖g‖_{U(I)} ‖b‖_∞ ‖c‖_∞.
The constant of lem:von-neumann for the fixed admissible kernel class.
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Blueprint lem:von-neumann, the L¹ assertion: the two-coordinate case of
lem:absolute with R, g ∈ L¹(I) and b, c ∈ L^∞(I).
Tail estimate for norm truncation: for 0 < p ≤ q, the part of f above level B
has L^p norm at most B^(1 - q/p) ‖f‖_q^(q/p).
Additivity of the local form in one input.
Integrability of an admissible local integrand with four normalized L² inputs.
eq:absolute with exponents assigned to four distinct slots.
Blueprint lem:detection, lines 1465-1467: clipping the three opponents of R
at height B changes the local form by at most 3 C C₁ B^{-(q-2)/q}.
Homogeneity of the local form in one input.
Additivity in one slot when every input has finite normalized L² norm.
Linearity in one slot over a finite sum of finite-norm inputs.
The local form only sees an input up to a.e. equality on the cell.
The L² von Neumann bound with the class constant and normalized norms.
The coefficient functions of a finite sum of L² classes.
Blueprint lem:detection, line 1471, one decomposition step: decomposing a
B-bounded input by eq:decomp at accuracy τ and discarding both errors by
eq:von-neumann leaves a single bounded atom in its slot with a large form.
Two distinct real progression slots: the complex form of
real_progression_pair_lintegral, with Jacobian j - i.
eq:absolute for the positive local form, with exponents assigned to four distinct slots.
Blueprint lem:detection, line 1473: expanding an atom pair by lem:separation expands the local form into separated forms, each bounded by the absolute estimate.
Blueprint lem:detection, line 1473: after truncating the shells, some retained term of a large absolutely convergent expansion is large.
Normalized L¹ control of a normalized L² input on the closed cell.
The positive form of real_progression_pair_integral.