First-Loss Proton–Proton Fusion in Constrained Null Geometry

This work develops a parameter-free proton–proton fusion model within Constrained Null Geometry (CNG). The reaction is formulated as a rank-changing transition from a six-channel entrance configuration to the discrete five-channel X5 deuteron stratum. Starting from the canonical six-channel reconstruction operator, the construction derives the normalized first-loss invariant, the exchange-odd AAB reconstruction trace, the connected entrance interaction, and the unique radial Riesz scale. The resulting proton–proton entrance Hamiltonian consists of the repulsive Coulomb operator supplemented by a geometrically fixed rank-one singlet kernel. The derived entrance parameters are: g_tr = 1/2 beta = gamma_X = sqrt(2 mu_pn B_X5) / (hbar c) A trace-preserving first-loss lock maps the removed internal direction into a residual reconstruction trace rather than discarding it. Within the primitive local quadratic CNG action, gauge covariance, radial-domain uniqueness, and multiplicity-one spin–isospin coupling determine the leading charged-current transition and exclude an independent constant transverse boundary vertex at threshold. The Coulomb-resolvent completion gives: Lambda_65 strong at zero energy = 1.70008535725480 This leads to the threshold prediction: S_pp(0) = 2.74004468156394 × 10^-22 keV b The accompanying supplement contains theorem audits, numerical ledgers, symbol and unit tables, falsification criteria, reproducibility scripts, reaction-rate utilities, and machine-readable CSV and JSON outputs. The model is explicitly testable through the microscopic AAB singlet matrix element, the connected-polarization sign, radial-domain uniqueness, the absence of a diproton pole, and the possible emergence of additional microscopic boundary degrees of freedom.