Unification of Gravity and Electromagnetism in Four-Dimensional Spacetime Based on Qi-Yuan Field Theory

This paper proposes a new framework for the unification of fields based on the traditional Chinese philosophy of "Qi-Yuan" (Qi-Unitism). We construct a single fundamental field—the "Wu-Nei Field" (Wu-Nei Field) $\Phi_\mu$—in flat four-dimensional spacetime, which possesses an intrinsic $O(3)$ symmetry. Through rigorous derivations in quantum field theory, we demonstrate that this field naturally emerges as the Maxwell electromagnetic field (spin-1) in the linear limit. In the high-order nonlinear correlation regime, using the Hubbard-Stratonovich transformation, we precisely derive the linearized Einstein-Hilbert action (spin-2). The core finding of this work is that the specific antisymmetric self-coupling structure of the Wu-Nei field naturally leads to the Einstein-Æther coefficient $c_\theta$ being algebraically zero. Consequently, the theory passes the modern rigorous tests of GW170817 (gravitational wave speed) and Cassini (Post-Newtonian parameter $\gamma$) without any parameter fine-tuning. Furthermore, we calculate the 1-loop $\beta$-function to determine the validity range of the effective field theory and link the background density $\rho$ of "Qi" with dark energy density, predicting an upper bound for the nonlinear coupling $\beta \lesssim 10^{-6} \text{ eV}^{-1}$. This model is the first to tightly integrate Zhuangzi's ontological concept of "Small One" with modern physics, providing a candidate scheme for unified field theory that is consistent with experimental constraints and possesses profound philosophical connotations.