Universal Fusion Law in Constrained Null Geometry: Solar Proton–Proton Fusion and Terrestrial Deuterium–Tritium Fusion

This work develops a universal fusion framework within Constrained Null Geometry and presents two distinct physical realizations derived from the same protected geometric structure. The construction does not begin with fitted nuclear potentials, measured scattering lengths, empirical reaction rates, or phenomenological fusion coefficients. Its starting point is a constrained system of transported null channels, together with positivity, normalization, permutation covariance, protected topology, canonical first loss, and the Fubini–Study geometry of the normalized state space. The logical chain is: constrained null geometry → admissible domain → canonical projector → first-loss map → reconstruction operator → spectrum → physical mass or reaction observable. Physical constants and reaction-specific quantities are not inserted and subsequently reinterpreted geometrically. Previously established CNG quantities enter only as upstream outputs of independent geometric derivations. Reaction data are used only after the calculations as external tests. The first realization is solar proton–proton fusion. The initial proton–proton sector, the deuteron branch, the charged spin–isospin current, the boundary map, the outgoing leptonic branches, Minkowski phase space, and the invariant reaction-rate normalization are compiled into a closed low-energy fusion law. The second realization is the terrestrial reaction deuterium + tritium → alpha particle + neutron. The deuterium–tritium derivation identifies the lowest bright entrance sector, the alpha–neutron final orbital sector, the five-nucleon first-loss projector, the Pauli-admissible triton route space, and the connected transported-null response. The neutron-loss route Gram operator decomposes into a symmetric sector and a two-dimensional standard sector. Pauli antisymmetry removes the symmetric isospin-three-halves direction before the physical transport normalization is performed. The remaining mixed-source pullback produces the triton connected coefficient 5K/4. A canonical Hodge–Plücker identification relates the triton internal space to a spectator dual space tensored with the four-nucleon determinant line. The common Plücker response therefore contributes the same absolute eigenvalue to the triton and alpha sectors and cancels exactly from the deuterium–tritium reaction-energy difference. The resulting CNG reaction-energy theorem is Q_DT = 17.5892978022843 MeV. This value is derived within the explicitly stated cycle-local, Pauli-projected, path-local, and Fubini–Study-normalized five-nucleon action class. The nuclear comparison must be performed using bare nuclear masses. Atomic mass cycles contain additional electronic binding-energy contributions and represent a different observable. The distinction is retained explicitly in the accompanying numerical ledger. The work separates three levels of status: quantities proven from the stated geometric and representation-theoretic premises; results derived within a precisely defined action class; experimental or metrological values used only for external comparison. The accompanying supplement provides machine-readable numerical certificates, calculation ledgers, independent verification scripts, stress tests, scope statements, and cryptographic checksums. No article PDF or LaTeX source is included in the supplement archive. The energy release of the deuterium–tritium reaction is closed in the stated action class. The derivation of the complete second-sheet resonance pole, pole residue, width, energy-dependent entrance kernel, and absolute deuterium–tritium cross section remains a separate dynamical stage and is not inferred from the reaction-energy result. The framework is directly falsifiable. A sufficiently precise bare-nucleus measurement inconsistent with the stated CNG reaction-energy value would reject the displayed five-nucleon realization or one of its explicit geometric premises. Independent measurements of the resonance structure and absolute cross section can test later dynamical extensions without altering the closed energy theorem.