The U-Cell Model and the CMB Acoustic Scale: Self-Consistent Analysis of the l_a Constraint

A self-consistent numerical analysis of the Planck 2018 CMB shift parameters (R, l_a) for the U-Cell Model (UCM) parameters (Omega_m=0.3166, w=−1) using identical Eisenstein–Hu approximations for both UCM and ΛCDM. The UCM–ΛCDM difference in l_a is 1.8σ — a factor 2.3 smaller than a previous naive estimate of 4.2σ. Full consistency with l_a=301.471 is achieved at Omega_b h²=0.02246, which is 0.6σ from Planck and 0.5σ from BBN. This value constitutes a new falsifiable UCM prediction testable by CMB-S4 and Simons Observatory.