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How statement and proof provenance work

The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.

  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
  • AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.

These labels describe origin, not correctness: citations and verification chips remain separate evidence.

Clustered sources and absolute l1 error

Statement

Let 0<δ<1/4, take the one-dimensional type-1 data x0=1/4,x1=1/4+δ,c0=1,c1=−1, and include mode k=1. For every real δ in this range, ∥c∥1=2 while F1=e−πi/2(1−e−2πiδ),∣F1∣≤2πδ. Thus this exact Fourier coefficient tends to zero as the source points cluster, although the coefficient l1 norm remains 2. The dyadic subfamily, for example δ=2−n with n≥3, consists of admissible exact input coordinates and also tends to zero. For any such dyadic datum for which the algorithm has a successful run, the theorem gives an absolute l1-scaled error certificate; the exact family has no positive lower bound on ∣F1∣ from which that certificate alone yields a relative-error guarantee.

Facts & Assumptions

Given: 0<δ<1/4, the displayed two-source type-1 data, and a mode box with K1≥1.

[A1]

The Axiom of Countable Choice (ACω): the successful-run error theorem assumes Countable Choice through the Gaussian Poisson-summation supplier.

[F1]

Type-1, type-2, and type-3 nonuniform Fourier transforms: F1=∑jcje−2πixj.

[F2]

Certified type-1 Gaussian gridding error and type-2 adjoint bound: for any successful type-1 run on admissible finite dyadic data, the error is bounded absolutely by ϵana∥c∥1+Bround; success is conditional on the supplied candidate and arithmetic controls.

[F5]

Elementary factorial and geometric series converge uniformly, Real elementary functions and their domains, and The second fundamental theorem: if G is differentiable on [a,b] with G′=f and f is integrable, then ∫abf=G(b)−G(a): cosine is continuous and integrable on each compact interval, the integral obeys ∣∫abh∣≤∣b−a∣max⁡∣h∣, and integrating the derivative of sine gives sin⁡t=∫0tcos⁡s ds.

[F6]

Real elementary functions and their domains: π=4∫01(1+s2)−1 ds≥2>0.

[F7]

Finite complex-array norms used by the NUFFT certificates: ∥c∥1=∑j∣cj∣ for the displayed two-entry array.

Proof

1.1givenF1F7algebra

Since c0=1 and c1=−1, [F7] gives ∥c∥1=∣1∣+∣−1∣=2. For mode 1, substitute the source locations into [F1] to obtain F1=e−2πi/4−e−2πi(1/4+δ)=e−πi/2(1−e−2πiδ). This is a direct factorization of the exact two-term sum.

2.1A1F2F3F4F5F6F7F8step 1.1algebra∎

Put t=πδ. By the complex exponential addition law and [F3], 1−e−2it=e−it(eit−e−it)=e−it(2isin⁡t), so ∣1−e−2it∣=2∣sin⁡t∣ by [F3] and [F8]. From [F3]–[F5], for t≥0 we have ∣sin⁡t∣=∣∫0tcos⁡s ds∣≤tmax⁡0≤s≤t∣cos⁡s∣≤t. Since t=πδ>0 by [F6] and ∣e−πi/2∣=1, step 1.1 yields ∣F1∣≤2t=2πδ. Taking the dyadic sequence δ=2−n with n≥3 shows that admissible exact input coefficients can have ∣F1∣ arbitrarily small while step 1.1 keeps ∥c∥1=2 by [F7]. Whenever a successful run is available for one of these inputs, [F2] gives an absolute bound without division by ∣F1∣; thus the certificate alone supplies no uniform relative-error estimate without an additional lower bound on the exact output.

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