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feat: add Liouville–Arnold eval problem#304

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feat: add Liouville–Arnold eval problem#304
kim-em wants to merge 1 commit into
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eval/liouville-arnold

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@kim-em kim-em commented May 23, 2026

This PR adds an eval problem for the Liouville–Arnold theorem on
integrable systems: on a 2n-dimensional symplectic manifold with n
smooth, pointwise linearly independent, pairwise Poisson-commuting first
integrals F₁, …, F_n, every compact connected component of a joint
level set is diffeomorphic to the n-torus T^n. §45 of Knill's
Some Fundamental Theorems in Mathematics.

Formalized on E n := EuclideanSpace ℝ (Fin (2n)) with the standard
symplectic form ω₀ = ∑ᵢ dpᵢ ∧ dqᵢ. Mathlib has EuclideanSpace,
fderiv, AddCircle, Homeomorph, and the smooth-manifold framework,
but no Poisson brackets, no symplectic manifolds beyond
Matrix.symplecticGroup, no first integrals, and no Liouville–Arnold
theorem in any form
(the Liouville files in
Mathlib/Analysis/Complex/ are Liouville's theorem on bounded entire
functions, a different result). The Challenge ships ~1 page of helper
definitions (E, idxP, idxQ, poissonBracket,
IsLiouvilleIntegrable, levelSet).

No formalization found in any major prover. Not on Freek Wiedijk's
100-theorems list.

🤖 Prepared with Claude Code

§45 of Knill's "Some Fundamental Theorems in Mathematics". On a 2n-
dimensional symplectic manifold with n smooth, pointwise linearly
independent, pairwise Poisson-commuting first integrals F₁, …, F_n,
every compact connected component of a joint level set is diffeomorphic
to the n-torus T^n. Formalized on ℝ^{2n} with the standard symplectic
form ω₀ = ∑ᵢ dpᵢ ∧ dqᵢ. Mathlib has the supporting analysis, the
n-torus via AddCircle, and Homeomorph, but no Poisson brackets, no
symplectic manifolds beyond Matrix.symplecticGroup, no first integrals,
and no Liouville–Arnold theorem in any form.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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