feat: add Brouwer fixed-point theorem eval problem#286
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This PR adds the Brouwer fixed-point theorem (§33 of Knill's "Some Fundamental Theorems in Mathematics", and #36 on Freek's 100 list) as a new eval problem: every continuous self-map of a nonempty compact convex K ⊆ ℝᵈ has a fixed point. Mathlib has the Banach fixed-point theorem (strictly weaker — needs Lipschitz < 1); Brouwer is formalized in Lean outside mathlib, in Isabelle/AFP, HOL Light, and Coq. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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This PR adds the Brouwer fixed-point theorem as a new lean-eval challenge problem — §33 of Oliver Knill's Some Fundamental Theorems in Mathematics, and theorem #36 on Freek Wiedijk's Formalizing 100 Theorems list.
Every continuous self-map of a nonempty compact convex
K ⊆ ℝᵈhas a fixed point.mathlib has only the Banach fixed-point theorem (strictly weaker — requires a Lipschitz constant
< 1). Brouwer is formalized in Lean outside mathlib (perdocs/100.yaml'slinksentry for #36), in Isabelle/AFP, HOL Light, and Coq.🤖 Prepared with Claude Code