The weak mixing angle sin²θW = 3/8 at the GUT scale is derived as an exact theorem from the mode dimension ratio of the face Laplacian of the truncated octahedron (Kelvin cell). The T₂g sector (dim=3) gives SU (3) c, the T₁u sector (dim=3) gives SU (2) L, and the A₁g sector (dim=1) gives U (1) Y. The ratio sin²θW = 3/8 follows from the hypercharge assignments of these sectors. The 2-loop self-consistent GUT calculation using all foam-derived beta coefficients gives MGUT = 1. 50×10¹⁶ GeV, αGUT = 1/46, and reproduces αₛ (MZ) = 0. 1179 exactly from the GUT chain.
Luke Alexander Martin (Tue,) studied this question.