Paper 80: Periodic Anisotropy in the Low-ℓ CMB: Cuboctahedral Symmetry, Forbidden Modes, and the Coherence Horizon

This study presents evidence that the low-multipole angular spectrum of the cosmic microwave background (CMB) exhibits structured, periodic anisotropy inconsistent with statistical isotropy. Using rotation-resolved correlation analysis of Planck 2018 SMICA data, we identify harmonic modes ell = 3, 4, 8, 12, 16) that align with a cuboctahedral tiling template derived from Holosphere Theory. These modes display distinct angular periodicities (180°, 90°, 45°, 30°, 22.5°), while other multipoles ell = 5, 7, 10, 11) show exact nulls, consistent with destructive geometric interference. The pattern of constructive, forbidden, and degraded harmonic responses provides falsifiable evidence for a finite coherence horizon and discrete geometric selection rules in the CMB. These results support a non-isotropic interpretation of primordial structure governed by polyhedral angular strain symmetry.