From UD Theory to the Weak Interaction: Bifurcated Unification and the W/Z Mass Ratio

We derive the electroweak sector from the UD action, based on the bifurcated electroweak unification. The four UD fields are classified by attribute action into the condensate channel $(U_d, D_d)$ and the expansive channel $(U_u, D_u)$. Both channels possess non-zero static stiffness, but the gauge fields of the weak interaction couple exclusively to the condensate channel, acquiring mass and rendering the weak force short-range. The photon, as the gauge field of the expansive channel, does not couple to the condensate stiffness and remains massless. The parameter-free ratio $m_W/m_Z = \cos\theta_W$ is derived directly from diagonalization of the condensate mass matrix, with $\theta_W$ defined through the gauge couplings that are themselves related to the UD structural constant $m_0$. The chiral V–A structure emerges from the exclusive coupling of weak bosons to the $D_d$ component of the fermion, with right-handed coupling suppressed by the external $U_d$ field disrupting the $D_d$-$D_u$ bound state. The Higgs boson is identified as a dynamical scalar excitation of the condensate stiffness, with tree-level self-couplings $\lambda_3 = 0$ and $\lambda_4 = 0$, and mass $m_h^2 = 2m_0^2$, derived from diagonalization of the full $4 \times 4$ stiffness matrix. All derivations are self-contained and proceed from the UD axioms.