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feat: add Cauchy–Kovalevskaya theorem eval problem#272

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feat: add Cauchy–Kovalevskaya theorem eval problem#272
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eval/cauchy-kovalevskaya

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@kim-em kim-em commented May 19, 2026

This PR adds the Cauchy–Kovalevskaya theorem as a new lean-eval challenge problem — §32 of Oliver Knill's Some Fundamental Theorems in Mathematics.

For real-analytic data F, f, u₀, the quasi-linear scalar Cauchy problem uₜ = F·∇ₓu + f, u(·,0) = u₀ has a unique local analytic solution near every point of the initial hypersurface.

The statement uses only off-the-shelf mathlib (AnalyticOnNhd, fderiv, EuclideanSpace) — no new definitions. The PDE is encoded through the Fréchet derivative: fderiv ℝ u p (0,1) is the time derivative and fderiv ℝ u p (v,0) the spatial directional derivative. Locality and uniqueness are folded into one ∀ x₀, ∃ U … statement. Mathlib has no Cauchy–Kovalevskaya theorem, and a search found no formalization of it in any other proof assistant.

🤖 Prepared with Claude Code

@kim-em kim-em force-pushed the eval/cauchy-kovalevskaya branch from 46859bd to ff39072 Compare May 19, 2026 11:00
This PR adds the Cauchy-Kovalevskaya theorem (§32 of Knill's "Some
Fundamental Theorems in Mathematics") as a new eval problem: the
quasi-linear scalar Cauchy problem with real-analytic data has a unique
local analytic solution. The statement uses only off-the-shelf mathlib,
encoding the PDE through the Fréchet derivative; mathlib has no
Cauchy-Kovalevskaya theorem.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
@kim-em kim-em force-pushed the eval/cauchy-kovalevskaya branch from ff39072 to 2ae2cc5 Compare May 19, 2026 12:24
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