Stable Covariant U(1)grav Polarization Effective Field Theory A Gauge-Invariant Electric-Sector Completion with Coupling Screening, Newtonian Recovery, and Local Stability Domain

This preprint presents version 2.3 of a theoretical framework for a stable covariant (U(1)grav) polarization effective field theory. The work develops a local, gauge-invariant and covariant effective-theory architecture in which MOND-like low-acceleration phenomenology arises from an electric-sector polarization response of a gravitational gauge field. The theory introduces a Stueckelberg-invariant vector (C_μ), an exact gauge-invariant disformal matter metric, and a medium-frame decomposition into positive-semidefinite electric and magnetic invariants. This avoids the global complex-action problem associated with nonlinear functions of the single invariant (E^2-B^2). The nonlinear response is assigned to the electric invariant, while the magnetic sector remains Maxwell-like. Version 2.3 adds a screened matter-coupling function (K(Y,Ξ)), designed to recover the Newtonian limit in high-acceleration or cosmologically screened regimes while preserving the deep-MOND limit in the low-acceleration branch. The paper derives the nonrelativistic force law, the modified Gauss equation, the deep-MOND scaling relation (g=√a_0 g_N), and the baryonic Tully-Fisher relation (v^4=GM_ba_0) under an explicit dimensionless matching condition. The manuscript also provides an isolated electric-sector stability analysis, including no-ghost and subluminality conditions, a Maxwell-limit consistency check, a screened Newtonian recovery argument, and an expanded discussion of remaining work such as full coupled-system stability, lensing, galaxy rotation-curve fits, cluster phenomenology, and cosmological perturbations. This version is intended as a theory-development preprint. It does not claim empirical validation, replacement of dark matter, or completed cosmological phenomenology. Its purpose is to define a mathematically structured local effective-field-theory framework for gravitational polarization and to identify the precise conditions under which it reproduces MOND-like galactic scaling while remaining compatible with a screened Newtonian branch. This preprint is part of the coordinated QVP-G / IRN series, together with:(i) Quantum Vacuum Polarization Gravity (QVP-G): A Unified Effective Field Theory for Dark Matter and Dark Energy;(ii) Microscopic Quantum Vacuum Polarization Gravity (mQVP-G) and its companion paper;(iii) Cosmological Background and Linear Perturbations in QVP-G and QVP-G Cosmology II (Boltzmann-code implementation);(iv) the QVP-G / IRN framework for decoherence and fermion masses;and (v) the hierarchical IRN and quantum-layer papers that address correlation lengths and quantum foundations. The authors gratefully acknowledges the use of a novel multi-agent artificial intelligence system based on iterative Socratic dialogue as a conceptual support tool in the development of this work.