SRCD–GPT v4.0: Unification of the Four Fundamental Interactions through a Single Elastic Ratio Coordinate

This work presents SRCD–GPT v4.0, a unified structural framework in which the four fundamental interactions—strong, weak, electromagnetic, and gravitational—are organized within a single elastic ratio coordinate. The central premise of SRCD is that the fundamental descriptive quantity of nature is not absolute length, energy, mass, or force, but a dimensionless ratio. All physical observables are first reduced to ratios with respect to a data-derived reference scale and then mapped into a bounded elastic coordinate σ=Rα1+Rα,R=xxref.\sigma = \frac{R^{\alpha}}{1+R^{\alpha}}, \qquad R = \frac{x}{x_{\mathrm{ref}}}.σ=1+RαRα,R=xrefx. In this formulation, physical meaning is carried by relative saturation and confinement, not by absolute magnitudes. Within this framework, interaction strength is interpreted as a manifestation of elastic confinement regimes along the bounded coordinate σ\sigmaσ. Near saturation (σ→1\sigma \to 1σ→1), strong short-range confinement dominates; near the relaxed baseline (σ≈0.5\sigma \approx 0.5σ≈0.5), gravity emerges as a weak but universal response. Electromagnetic and weak interactions arise as intermediate and transition-localized regimes, respectively, rather than as secondary byproducts of other forces. Unification is therefore not achieved at a single point or energy scale, but across a finite transition interval (void region) in which elastic descriptions overlap and force identities become ambiguous. This avoids the need for force-to-force conversion, parameter tuning, or new fundamental constants. SRCD–GPT does not replace General Relativity, Quantum Mechanics, or the Standard Model. Instead, it provides an organizational and interpretive layer explaining why different interactions occupy distinct regimes while remaining comparable within a single geometric structure. The framework is parameter-minimal, scale-invariant, and falsifiable through structural coherence tests across arithmetic, atomic, astrophysical, and cosmological datasets.