Structural Cosmology v2.3: Toward Nonlinear Structure Formation in the Structural Cosmology Framework

Structural Cosmology v2. 3 extends the linear perturbation framework developed in v2. 2 into the nonlinear regime of cosmic structure formation. Starting from the linearized structural field equation and the scale-dependent effective gravitational coupling Geff (k, z) G₄₅₅ (k, z) Geff (k, z), this work develops an illustrative nonlinear perturbation framework incorporating mode coupling, self-interactions, matter-structural coupling, and environment-dependent damping of the structural field. The framework introduces: nonlinear structural field dynamics with self-interaction and screening effects, modified halo mass function predictions, nonlinear matter power spectrum corrections, an illustrative N-body simulation prescription, a nonlinear Generalized Green's Function Perturbation Theory (GGPT) framework, and five new falsifiability criteria (C36–C40). This release integrates the complete development path from: v2. 0 Effective Field Formulation, v2. 1 Covariant Field Equations, v2. 2 Linear Perturbation Theory, to the new nonlinear structure formation framework of v2. 3. The paper contains 45 figures, including the full EFT foundation, covariant field equations, perturbation framework, and nonlinear extensions. All results are presented as illustrative theoretical framework development and are not intended as precision cosmological inference.