E8 Corridor Dipole as Affine Character at Level 1 — Coxeter-Orbit Selection Rule — E8 Intelligence Research

The phi-deformed Cartan partition function Z(β) = Tr(exp(-βH_φ)) is identified as the character of the E8^(1) affine Lie algebra at level 1, with modular invariance arising from the Weyl-Kac denominator formula. The 132/108 corridor dipole selects exactly two of the twelve 20-root Coxeter orbits — those stabilized by the φ-scaled involution C_φ = φ·C where C is the Coxeter element — yielding a 40-root sublattice whose theta series matches the corridor's spectral density. The 30-fold Coxeter number enters as the quantum parameter q = exp(2πi/30), placing the deformation at the 30th root of unity where the quantum group U_q(E8) becomes modular. Author: Andrew Stewart Caldin, Independent Researcher, UK. Part of the E8 Intelligence Research series. Platform: e8intelligence.com