Alphabeta Math
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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.

Gaussian robust risk across dimensions and radii

Example

Assume AC. For an integer d≥2, set σ=d1/4/32 and ϵ=1/4. For the fixed-parameter Gaussian model with ∥θ∥2=d, the class-weighted sample-mean classifier has ℓ∞ robust risk at most 1/100 with training-sample probability at least 1−2e−d/(8(σ2+1)) whenever the integer sample size satisfies n≥4d. In the separate Gaussian-prior experiment Θ∼Nd(0,Id), every Borel learning rule F:(Rd×{−1,+1})n×Rd→{−1,+1} has expected ℓ∞ robust risk at least (1−1/d)/2 whenever n≤d/(131072log⁡d). The first assertion concerns a fixed normalized parameter and an upper bound for one classifier; the second averages over a Gaussian prior and lower-bounds every such Borel learning rule. Expected robust risk in the prior experiment uses outer expectation over the parameter and training sample.

Facts & Assumptions

Given: The Example's Gaussian parameter, radius, and dimension.

[A1]

Assume AC as required by both Gaussian robust-risk bounds. The Axiom of Choice.

[F1]

If σ≤d1/4/32, d≥1, and 1/(4d1/4)≤ϵ≤1/4, then n≥64ϵ2d suffices for the class-weighted mean classifier to have robust risk at most 1/100 with failure probability at most 2e−d/(8(σ2+1)). Robust sample upper bound in the Gaussian model.

[F2]

If d≥2 and n≤ϵ2σ2/(8log⁡d), every Borel learning rule under prior Θ∼Nd(0,Id) has expected robust risk at least (1−1/d)/2. Robust sample lower bound in the Gaussian model.

Proof

1.1givenA1F1algebra

The chosen variance satisfies σ=d1/4/32, and d≥2 makes 1/(4d1/4)≤1/4=ϵ. The upper-bound condition becomes n≥64(1/4)2d=4d. Apply [F1] to obtain the first assertion.

2.1givenA1F2algebra∎

For the lower bound, ϵ2σ2/(8log⁡d)=(1/16)(d/1024)/(8log⁡d)=d/(131072log⁡d). Thus the stated lower sample-size condition is exactly the premise of [F2], which gives the second assertion.

References

Robust sample upper bound in the Gaussian model: supplies the exact one-percent sufficient sample size.

Robust sample lower bound in the Gaussian model: supplies the learner-independent Gaussian-prior necessary sample size.

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