Primitive-Orbit Interpretation of the Evans Lattice: Formal Model and Geometric Separation

Research Note 39 in the "Geometry of the Critical Line" programme. RN38 proved that the Evans lattice zeta factors as ZEvans (s) = ζ (2s) Zₚrim (s), where Zₚrim sums over coprime lattice pairs. This note investigates the dynamical interpretation of that factorisation. In the WKB picture, the coprime pairs define formal "primitive orbits" on the coupled (σ, θ) submanifold, with complex classical action whose real part is the oscillatory WKB phase and whose imaginary part is the chiral evanescent suppression. However, these primitive orbits are not the prime-translation orbits of the transverse torus. The SCT metric has vanishing cross-components between the (σ, θ) block and the (tR, tI) block: the two classical subsystems are geometrically orthogonal. The Evans dynamical zeta captures the periodic-orbit structure of the carrier subsystem, not of the extractor. This confirms the carrier/extractor separation (RN12) at the classical-orbit level.