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 July 25th, 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 instanton number ν of the emergent normal-bundle connection counts B+L, which electroweak sphalerons erase in equilibrium; the surviving asymmetry therefore resides in B−L, which is anomaly-free and admits no topological source. What the framework fixes is the sign of that asymmetry, through the orientation selected by the fourth axiom (the C-odd choice J → −J), and not its magnitude, which is that of standard leptogenesis. The orientation vanishes for a homogeneous background, so a nonzero asymmetry requires an oriented onset, giving a characterization of the low-entropy "past hypothesis" in terms of the embedding rather than of a winding number. The magnitude of the baryon-to-photon ratio is left as an open quantity: the onset density is diluted by the subsequent inflation, whence the magnitude is set by post-inflationary leptogenesis, while the boundary orientation fixes the sign.