II.D73 — The Physics Quadrant Matrix

2x2 classification of mathematical frameworks by PDE type (elliptic/hyperbolic) and metric type (Archimedean/non-Archimedean). QFT in (H,A), GR locally in (E,A), Category tau in (H,nA). The fourth quadrant (H,nA) is the only quadrant where the Unification Obstruction does not apply.