Isomorphism Between PFUS and General Relativity Spacetime and Proof of the Origin of Gravity

Based on the Pythagorean Frustum Unified System (PFUS), this paper rigorously proves that the 45° coaxial double-cone frustum geometry of PFUS admits a rigid, global, and contradiction-free structural isomorphism with the spacetime of Einstein’s General Relativity. Starting from primitive geometry, this paper proves that PFUS naturally satisfies all core axioms: pseudo-Riemannian metric, curvature-matter coupling, geodesic motion, gravitational equivalence, spacetime curvature, and energy-momentum constraints. The global operator β₁ and scale factor π₁ together determine spacetime curvature, dynamical equilibrium, and structural stability, corresponding precisely to the essence of gravity as spacetime curvature in General Relativity. This paper establishes a complete one-to-one correspondence between PFUS and General Relativity, proving that PFUS is the unique primitive ontological realization of General Relativity in the universe. It provides a unified and closed primordial explanation for the origin of gravity, spacetime structure, equivalence principle, cosmic expansion, singularity resolution, and the unification of gravity and quantum theory. No external assumptions, free parameters, or logical gaps are introduced; the work is complete, rigorous, and fully self-consistent.