Causal Field Theory II: A Unified Framework for Dark Matter, Dark Energy, and the Hubble Tension

In Paper I, we demonstrated that the causal field model explains galactic rotation curves through the saturation of a dimensionless field at _=0. 429, producing gravitational amplification e^2_{}=2. 357 without invoking particle dark matter. Analysis of 1572 measurements from 134 SPARC galaxies confirmed the characteristic speed c₀ = 104. 3 km/s as a new fundamental constant. Building on this empirical foundation, Paper II develops the complete cosmological framework of the causal field theory. Starting from the Principle of Causal Optimality, we derive the full field equations, including modified Einstein equations with an optimality tensor C_, the causal field equation, and the causal potential V () = (e^2 - 1 - 2). Applying these to a homogeneous and isotropic universe yields the causal Friedmann equations, describing cosmic evolution with a dynamical field (t). We show that the same field explaining galactic dynamics also accounts for cosmological phenomena. The field stabilizes at ₕ₀₂ = 0. 3476, giving dark energy density _ = V (ₕ₀₂) = 0. 689₂₀, in exact agreement with Planck observations. The coupling constant = 1. 900 10^-26\ kg/m³ 3. 68 10^-123 M₏₋⁴ is directly derived from observations, not fine-tuned. The environment-dependent coupling () = ₀ e^ with theoretical values ₀ = 5. 65 10^-13 G and = 69. 2 (numerically implemented as ₀ = 2. 74 10^-9 G, = 70 for stability) unifies galactic (₆₀₋₀₂ₓ₈₂ = 4. 40 G) and cosmic (₂₎ₒ₌₈₂ = 0. 0157 G) regimes. The model resolves the Hubble tension through H₋₎₂₀₋/H₂₌₁ = e^₋₎₂₀₋ - ₂₌₁. Numerical integration yields = 0. 0796, predicting H₋₎₂₀₋/H₂₌₁ = 1. 0829, in excellent agreement with the observed 1. 0837. The fine-tuning problem is eliminated because is a coupling constant whose smallness follows from the small Hubble parameter H and moderate ₕ₀₂ = 0. 3476. The coincidence problem is addressed as dark energy domination occurs inevitably when matter density drops below _. The equation of state (z) = -1 + 2̇²/ (3H² + ̇²) deviates from -1 at z 0. 5-1. 0, but these deviations are extremely small (<0. 02\%) and lie below the sensitivity of upcoming surveys like Euclid. The model makes four distinct predictions: (1) evolution of (z) with JWST/ELT; (2) modified gravitational lensing enhanced by e^; (3) gravitational wave speed v₆ₖ = c e^; and (4) the Hubble tension itself. All are falsifiable within 5-15 years. If confirmed, the causal field model unifies dark matter, dark energy, and cosmic structure within a single theoretical framework rooted in a first principle, eliminating the need for separate components while resolving major observational tensions.