IV.T162 — sin(theta_23) = 1/(1+iota_tau): Atmospheric Mixing from A-Sector

Numerical result (conjectural): sin(theta_23) = 1/(1+iota_tau) = 0.74554 -> theta_23 = 48.21 degrees, matching PDG 49.1 degrees at -18213 ppm (-1.82%). The formula 1/(1+iota_tau) = kappa_omega / iota_tau (in CKM sector coupling) connects the atmospheric mixing angle to the A-sector holonomy amplitude. Structural interpretation: the (1+iota_tau) factor is the crossing denominator in the A-sector propagator on tau^1. Also note: kappa_D^2 + iota_tau = 0.77518 -> theta_23 = 50.82 deg (+35066 ppm). Best candidate: 1/(1+iota_tau) at -18213 ppm. Scope: conjectural (sub-2% but not sub-1%).