Dimensional Deployment Theory (DDT) within the FDM Framework

We present Dimensional Deployment Theory (DDT), a self-contained field-theoretic framework in which observable $3+1$-dimensional spacetime is not a primary structure but the condensed phase of a dynamical $2+1$-dimensional substrate (M₃, gab), accessed through a geometrically controlled deployment map D2 → 3. The framework is built on four pillars: (I) A unique canonical action coupling a scalar deployment field X² non-minimally to the $2+1$D curvature, with all field equations derived by explicit variation. (II) A variational derivation of dissipative dynamics from the Keldysh influence functional, yielding emergent dimensional viscosity ηdim = DDv2D² = Ω⁻¹ free of independent bath parameters. (III) A constructive existence and stability proof for propagating dimensional fronts X² ∝ (r - vD t/λD) with velocity and width derived entirely from the substrate potential curvature. (IV) A complete, self-contained operational calculus—the canonical implementation pipeline with formally declared axioms, admissibility gates, and a strict protocol—that defines unambiguously what constitutes a valid DDT computation, independently of any classical GR or FLRW machinery. All fundamental constants (κDDT = 2, ΦF = √2 - 1, RF ≈ 1.0987) are mathematically shielded against continuous reparametrization by algebraic identities and topological constraints. The theory predicts: A universal 9.87% enhancement of strong-lensing time-delay distances. Spatially correlated H₀ variations at ~5% correlated with the deployment front topology ΣD. An extended high-redshift cosmic timeline (+19% at $z = 10$). Five strict Popperian falsification criteria—each with a declared numerical threshold and target dataset—are provided. The paper is entirely self-contained: no auxiliary document is required to execute, evaluate, or falsify a DDT prediction.