Golden Busemann Coordinate
Abstract
Golden null coefficients carry a nontrivial Busemann rapidity coordinate.
Theorem 1.1 (The golden null basis exposes Busemann rapidity).
Proof. Machine-checked in Lean as D5/S3/Observer/GoldenCoding/GoldenBusemannCoordinate.golden_busemann_coordinate (✓ std3). ∎
Source. Repository-derived.
Commentary.
The real Lorentz form uses the existing sign convention Q_phi(x,y)=x^2-xy-y^2. The golden ratio and its negative conjugate give two null vectors, and direct polarization reduces the form of a v_plus+b v_minus to -5ab.
On the branch a>0 and b<0, the ratio a/(-b) is positive. At unit Lorentz level the coefficient product is a(-b)=1/5, so the half-log definition agrees exactly with log(a sqrt(5)). Differences of this coordinate satisfy the Busemann cocycle law by telescoping.
Reciprocal golden-square scaling preserves the branch and adds 2 log(phi) to rapidity. The points with coefficients (1/sqrt(5),-1/sqrt(5)) and (2/sqrt(5),-1/(2sqrt(5))) both have Lorentz value one, but their rapidities are zero and log(2).
References
- Truth anchor:
D5/S3/Observer/GoldenCoding/GoldenBusemannCoordinate.golden_busemann_coordinate - Dependency: D5/S3/CompletionDynamics/GoldenMobius/GoldenScaleHelix
- Dependency: D5/S3/Observer/GoldenCoding/GoldenLorentzUpdate