Four Null Spacetime Theory IV: Fields on the Four Null Fabric: Light, Matter, Quantum Fields and the Boundary of Lorentz Protection

This is the fourth paper of a series on Four Null Spacetime Theory, in which spacetime is built from finite cells spanned by four lightlike vectors in perfect balance. The first three papers built the cell, the gluing of cells, and the propagation of radiation and gravity; this one places the other fields on the same cells. Fields of form degree p live on the faces of dimension p, so potentials sit on links, field strengths on the six pair bivectors and currents on three dimensional faces, and the vanishing of the boundary of a boundary gives gauge invariance and the Bianchi identity. The scalar and the photon, each given its own most general principal structure, independently select the same light cone, and the Maxwell ratio of electric to magnetic channels is exactly the ratio of the cell’s own channel metric. Matter is native: the Dirac operator is built from the generators, and a massive law follows from one Clifford structure with exact blocking, while an older additive rule is excluded by its exact blocking defect. On the fabric, quantum fields behave as a sound regulator requires: transport preserves entanglement, the nonuniversal area term carries the lattice fingerprint while the universal coefficients lie near the continuum, and every reconnection mesh carries the Einstein kernel. But a fermion kept exact up to a sharp band edge has a nonlocal vacuum, so the realization of the exact law near the cell scale must be local and analytic. Lorentz protection is established for a Euclidean regulator with the symmetry of the F4 lattice, not for a physical crystal of cells, which no finite range operator can make exactly Lorentz invariant. Every result is stated with its status; results computed in the program but not reproducible here are reported as possibilities, never as proved.