PAPER-FBT08A: A Geometric Bridge from Berry–Locked Symplectic Structure to Lorentzian Kinematics

This paper isolates the precise geometric bridge from the six-dimensional Fracture–Berry–Tension (FBT) arena to four-dimensional Lorentzian kinematics. We do not attempt here to derive the full dynamics of special or general relativity. Instead, starting from an admissible 4+2 splitting of the FBT symplectic manifold, Berry readout data on the dual–phase sector, and adistinguished vacuum clock flow, we define an observer–invariant null propagation structure on the effective observable sector M4. The construction of the propagation readout relies on a distinguished vertical evaluation direction. Within the broader FBT programme, this direction is naturally identified with the observable residual phase generator introduced in FBT01B, namely the S-gate. This identification gives a concrete geometric realization of the vertical readout used in the present paper. Its possible algebraic refinement as a central mode is discussed in later work such as FBT02A, but is not required for the present bridge construction. Our central claim is structural rather than dynamical: under natural nondegeneracy, locality, homogeneity, and isotropy assumptions in the Berry–locked vacuum regime, the resulting propagation cone determines a Lorentzian conformal structure on M4, unique up to positive local rescaling. In the flat vacuum sector, this conformal class admits a distinguished representativelocally isometric to Minkowski spacetime. The role of the paper is therefore foundational but limited. It does not derive matter equations, Einstein dynamics, or the numerical value of the physical speed of light. Its purpose is to show how a Lorentzian spacetime kinematics can arise naturally from deeper symplectic–Berry geometry, thereby providing the missing bridge needed for later FBT papers on relativistic fieldequations and gravitational closure.