Rademacher–Menshov estimates and nested projection products #
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The finite Rademacher–Menshov argument decomposes variable prefixes into
dyadic blocks and combines orthogonal block energy with the triangle inequality.
We develop its Hilbert-space row formulation, for finite families of bounded
linear maps whose squared output norms sum to at most the squared input norm.
The intended applications are noncommuting products of nested orthogonal
projections and their disjoint-interval jumps, as in blueprint lem:prefix.
All statements and local definitions are independent of the column construction.
The classical logarithmic maximal inequality is recorded in Terence Tao,
247A Lecture Notes 2, page 31, exercises Q14–Q15:
https://www.math.ucla.edu/~tao/247a.1.06f/notes2.pdf.
The exact row/product formulation and constants follow
blueprint/formalization_blueprint.tex, lines 508–535.
The explicit logarithmic horizon and numerical restart bounds implement
lem:compression, lines 567 and 579, for arbitrary real budgets and layer counts.
The Hilbertian norm of a finite family of outputs, also for normed outputs.
Equations
Instances For
Removing rows preserves their square-sum contraction estimate.
Finite Pythagoras for the orthogonal vectors used in dyadic blocks.
The two half-prefixes occupy disjoint rows; completing the left half costs one additional unit of the dyadic logarithmic bound.
Binary splitting is the recursive form of one dyadic block at each length.
The finite row version of Rademacher–Menshov for a power-of-two horizon.
The binary induction implements the dyadic decomposition in lem:prefix.
Arbitrary finite prefixes have the exact dyadic logarithmic row bound. Zero-padding to the next power of two leaves every relevant vector and energy unchanged.
The initial projection followed by successive projection differences.
Equations
- TrilinearHT.Auto.projectionIncrement P 0 = P 0
- TrilinearHT.Auto.projectionIncrement P n.succ = P (n + 1) - P n
Instances For
The exact constant L_T = 1 + ceil(log₂(T+1)) in the source.
Equations
- TrilinearHT.Auto.projectionPrefixConstant T = ↑(Nat.clog 2 (T + 1)) + 1
Instances For
The single-layer nested-projection row estimate with arbitrary row times,
the first case of blueprint eq:prefix, lines 508–514.
Products are ordered with layer zero on the right; different layers need not commute.
Equations
- TrilinearHT.Auto.nestedProjectionProduct P 0 x✝ = ContinuousLinearMap.id 𝕜 H
- TrilinearHT.Auto.nestedProjectionProduct P m.succ x✝ = P m x✝ ∘SL TrilinearHT.Auto.nestedProjectionProduct P m x✝
Instances For
Blueprint eq:prefix: the logarithmic row estimate for arbitrary
noncommuting products of nested orthogonal projection layers.
Product telescoping with Bessel difference rows. The dyadic prefix estimate controls each right-hand product; left-hand factors are contractions.
The exact square-sum jump constant once the layer differences are Bessel rows.
Successive differences of a nested orthogonal projection family are Bessel rows.
Blueprint eq:product-jump, lines 515–519: the square sum of successive
product jumps is at most m² L_T^(2(m-1)) times the input energy.
Differences over disjoint index intervals are Bessel rows, including empty intervals.
The source transition horizon for a real column budget and a natural
number of projection layers (lem:compression, lines 567 and 579).
Instances For
Blueprint lem:compression, line 579: the prescribed transition
horizon makes the common restart contraction factor strictly less than one half.
Blueprint lem:compression, line 597: the exact restart horizon has
prefix constant at most a cubic layer-count factor times log (2D).
An ordered subproduct, omitting the factors selected as false.
Equations
- TrilinearHT.Auto.operatorSubproduct P σ 0 = ContinuousLinearMap.id 𝕜 H
- TrilinearHT.Auto.operatorSubproduct P σ n.succ = if σ n = true then P n ∘SL TrilinearHT.Auto.operatorSubproduct P σ n else TrilinearHT.Auto.operatorSubproduct P σ n
Instances For
An ordered product with any designated factors replaced by their complements.
Equations
- TrilinearHT.Auto.operatorComplementProduct P θ 0 = ContinuousLinearMap.id 𝕜 H
- TrilinearHT.Auto.operatorComplementProduct P θ n.succ = (if θ n = true then ContinuousLinearMap.id 𝕜 H - P n else P n) ∘SL TrilinearHT.Auto.operatorComplementProduct P θ n
Instances For
Blueprint lem:compression, line 597: expanding complements costs
at most 2^m in the finite row norm. Only a uniform bound for all ordered
subproducts is required; no commutation of the factors is assumed.