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Birkhoff Retrograde Lean

Lean 4 + Mathlib formalization toward Birkhoff's retrograde periodic orbit in the planar circular restricted three-body problem. It covers the energy-component geometry, Levi-Civita regularization and the shooting argument, with 116 machine-checked proofs and reductions. Two end lemmas are still…

Description excerpted from the original listing, which is linked below.

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Facts

Published: 25 Sep 2026 (23d ago)
Medium: web
Language: English (the page says so itself)
First seen: 25 Sep 2026, 19:45 UTC

Built with

Claude Code: confirmed
the agent's own trailer in the repository's commit history

What we can see

80 hygiene score

Certificate issued by Certainly Intermediate R1, 19 days remaining
Cookie attributes no cookies set
Credentials and payment does not ask for either
No strict transport security
Served over HTTPS
Mail authentication sender policy and authentication published
Loads insecure resources 3 resources
Redirects none
Security headers 2 of 5 set
Third-party origins 24
Transport security TLS 1.3

Observed 25 Sep 2026 by fetching the page as a browser would. This describes hygiene and transparency, not safety: a missing header does not make a site dangerous, and a complete set does not make it trustworthy.

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For a README (Markdown)

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Changes we have seen

25 Sep 2026 first indexed

Birkhoff Retrograde Lean

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