A Closed Coherence–Decoherence Field Theory of Cosmology Emergent Dark Sector Dynamics from Coherence Memory

We develop a closed cosmological field theory in which the dark sector emerges dynamically from the history of coherence loss in the universe, rather than from fundamental dark matter particles or an externally imposed cosmological constant. The theory rests on a dual-domain ontology: a coherence domain in which quantum superposition is exact and atemporality holds, and a decoherence domain in which classical localisation, spacetime geometry, and gravitational embedding arise. Cosmological evolution is the macroscopic expression of the universe's progressive transition between these domains. The theory is built from two coupled scalar fields: a coherence phase field σ (x, t) parametrising local coherence state, and a cosmological scale field r (t) encoding the universe's position along its dynamical cycle. The dynamics are governed by a fixed Lagrangian with stable interaction potential V (σ, r) = Λ₀ (1 + ηr) sin² (σ/2) + αr cosσ + εr² sin⁴ (σ/2) The dark sector is not introduced phenomenologically but generated dynamically through a nonlocal memory closure law, yielding the history-dependent dark-sector density Λ (r) = ∫₀˃ e^−μ (r−r') κ sin² (σ (r') /2) dr'. In this framework, apparent dark matter and dark energy correspond to accumulated decoherence energy stored within the cosmological evolution itself. The theory contains only five free parameters and predicts, without halo-by-halo fitting: nearly flat galactic rotation curves with universal residual deviations; lensing centroids systematically offset from baryonic mass distributions; an age-dependent effective dark matter strength testable with high-redshift surveys; and a four-phase cosmological cycle (coherence, matter formation, decoherence dominance, recoherence). The framework is sharply falsifiable through existing and forthcoming surveys including Euclid, the Vera Rubin Observatory, and the James Webb Space Telescope.