A companion note showed that the cosmological constant follows from horizon thermodynamics with no free parameters. Here we extend the framework to the matter content and gauge structure of the Standard Model. The metric on any two-sphere decomposes under SO(3) as a rank-2 tensor: 1⊗1 = 0⊕1⊕2, yielding 1, 3, and 5 degrees of freedom for the ℓ = 0, 1, and 2 sectors respectively. The metric symmetry gµν = gνµ suppresses ℓ = 1; the unfilled thermal capacity of the horizon splits between ℓ = 0 (baryonic matter, 1 dof) and ℓ = 2 (dark matter, 5 dof), predicting Ωdm/Ωb = 5 exactly. The suppressed ℓ = 1 residual maps to three neutrino flavors with small masses. When the Planck-area patches of the horizon are quantized, the real SO(3) algebra complexifies into SU(3)×SU(2)×U(1) with 1 + 3 + 8 = 12 generators. The Cartan decomposition requires SU(2) ⊂ SU(3)—the strong interaction cannot close without the weak. The real sectors (ℓ = 0, ℓ = 2) give the long-range forces; the complexified sectors are intrinsically short-range. Quantization and time evolution act as dual operations on the horizon algebra: complexification creates gauge structure, decomplexification creates classical reality. If confirmed by forthcoming data, both the matter content and the gauge forces are outputs of the rank-2 tensor geometry of the cosmological horizon.
Yaroslav Ryabov (Sun,) studied this question.