Matter-Antimatter Asymmetry from UD Duality: A First-Principles Resolution

We present a first-principles resolution of the matter-antimatter asymmetry from UD theory. The asymmetry is shown to be a necessary consequence of the three UD axioms. Antimatter is derived as a phase-flipped configuration of matter, produced only when the critical condition $(m_0^2/2)|\langle D_u|D_d\rangle| = \alpha\langle D_u|U_d|D_u\rangle$ is satisfied. This is an instantaneous crossing in the evolving $U$–$D$ competition. The $1:1$ initial symmetry assumed in standard cosmology is absent; antimatter is a derivative of matter. Its extreme rarity follows from the stringency of the critical condition and the efficient annihilation channels that eliminate antimatter upon contact with ordinary matter. In the baryonic sector, both proton and antiproton are absolutely stable in isolation by CPT symmetry; the asymmetry originates entirely from the production threshold and environmental annihilation. The cosmological evolution is traced from the early universe to the present epoch. A comparison with $\Lambda$CDM and Standard Model baryogenesis is provided. All conclusions are derived from the UD field equations.