Baryon Asymmetry as Embedding Segregation in the Absolute Frame Theory: Matter Dominance and the Arrow of Time as a Single Topological Boundary Condition

Version of June 2nd, 2026, following the technical development in the Absolute Frame Theory programme. We propose, within the Absolute Frame Theory (AFT), that the observed matter--antimatter asymmetry is not generated dynamically but segregated structurally. The four-dimensional observable manifold M is continuously embedded in an N-dimensional Euclidean substratum A; the directions transverse to the embedding form an inaccessible fiber F. We show that a thermodynamic arrow alone cannot source a baryon asymmetry, because baryon number is even under time reversal; the required charge asymmetry is supplied instead by the orientation of the embedding's normal complex structure, which the fourth axiom (informational irreversibility) selects together with the arrow of time. In this reading the global state is charge symmetric with vanishing total baryon number---matter in M balanced by antimatter in the fiber F, a configuration structurally analogous to the CPT--symmetric universe; CPT is thereby respected, and the construction bypasses, rather than realizes, the Sakharov conditions. The net baryon number accessible in M is identified with a topological index: the instanton number of the emergent normal-bundle connection, whose sign is fixed by the fourth axiom. This quantity vanishes for a homogeneous background, and a nonzero asymmetry therefore requires a topologically nontrivial embedding at the onset, giving a topological characterization of the low-entropy ``past hypothesis''. The magnitude of the baryon-to-photon ratio is recast as an entropy-per-baryon ratio and left, with the onset winding number, as the principal open quantity.