Branch-Local Particle Genesis and Matter-Sector Emergence

SCQG Paper 11 of 28 This paper explains how particles can form within each of the two time orientations of the reciprocal universe. The reciprocal endpoint condition relates allowed terminal data in one orientation to allowed initial data in the other. It sets boundary conditions for fields and states prepared and evolved locally within each orientation. The construction begins with an algebra of local field observables and a positive state. It gives causal scalar and spinor equations, separate bosonic and fermionic particle-production calculations, and the conservation equations for energy and momentum exchanged between local sectors. A particle-number description uses a specified state, mode basis and time interval. Spectral conditions determine when an excitation remains identifiable, and kinetic evolution determines how much of the produced population survives. Explicit two-mode models show how a prepared mode can lose an initial disturbance and later receive it back from a complementary mode. The paper derives bounds on this return for stationary couplings, changing backgrounds and repeated interactions with fresh modes. The complementary modes, their physical effects and the finite resources needed to prepare them remain part of the calculation. The paper also specifies how one common boundary action and state preparation determine local observables and a physical length scale. A capacity-allocation theorem bounds the endpoint-conditioned contribution to initial support and the number of disjoint family carriers it can accommodate. Detector records and their thermodynamic costs enter through actual writing, retention and readout operations. This is Paper 11 of the Semantic Commitment / Quantum Gravity series.