A Structural Closure of a Unified Field Theory

Conventional approaches to unified field theory have sought to merge the four fundamental interactions at the level of dynamics, equations of motion, or field content, with persistent structural failure.This work proposes a different closure principle: unification is not a problem of force combination, but of admissible state structure. Building on earlier results (Papers A–C) concerning the impossibility of closed prediction operators and the necessity of selection horizons, an existence equation is introduced that relates transition, inertia, and a single invariant frame constant CCC.This equation does not describe dynamics.Instead, it defines the boundary of physically admissible states. It is shown that all four fundamental interactions—electromagnetic, gravitational, weak, and strong—are constrained by the same structural relation, differing only in how transition and inertia are instantiated.Within this framework, the speed of light appears not as a property of photons, but as a universal frame constant governing admissibility across all interactions. Unified field theory is thereby completed as a structural closure: not a synthesis of forces, but a demonstration that no physically realizable state can violate the same existence bound.Any alternative notion of unification that neglects this constraint is shown to be structurally untenable. AI Usage Declaration: The core concepts and mathematical intuitions of this paper were conceived by the author (Byeong-Young Oh). The technical formalization of the mathematical framework and the English drafting process were performed in collaboration with Artificial Intelligence (AI) models. The author takes full responsibility for the contents and logical integrity of this work. This work is part of an ongoing independent research program. Official research index :https://jingyu-papa.github.io/publications/