Derivation of the Activation Invariant ξ_c — Public Domain Release (2026)

This project contains the public-domain 2026 derivation of the cross‑domain Activation Invariant ξ₍c₎, a dimensionless geometric strain variable that emerges only after O(6)-symmetric normalization of heterogeneous datasets. Independent physical domains—atomic spectroscopy, Casimir forces, orbital shear, galactic rotation, cluster dispersion, and cosmic shear—collapse onto a universal OFF→ON threshold at ξ₍c₎ ≈ 0.56. All materials (PDF, DOCX, overview, figures) are released under Public Domain / CC BY 4.0.