A Unified Scalar Dark Photon Framework for Dark Matter, Dark Energy, Electromagnetic Propagation, and Gravitational Dynamics

We present a unified framework in which a single hidden U(1)′ scalar gauge field — the RK field — simultaneously accounts for dark matter, dark energy, and the physical basis of electromagnetic wave propagation. The scalar longitudinal mode of the massive Proca field mediates attractive forces, resolving the spin-1 repulsion problem. We derive flat rotation curves from cored isothermal dark photon halos with velocity-dependent self-interactions that naturally solve the cusp-core problem, and show that the homogeneous vacuum condensate generates dark energy with equation of state w = (1−ξ)/(1+ξ) ≈ −1. Vacuum permittivity ε₀ and permeability μ₀ are shown to emerge from the RK field medium, providing a physical mechanism for the self-sustaining E↔B oscillation cycle. The frequency-dependent medium response predicts a cosmic high-pass filter below the dark plasma frequency. A Coleman-Weinberg seesaw mechanism generates the self-coupling λ ~ 10⁻¹²⁰ without fine-tuning. Cosmological perturbation theory demonstrates sub-percent CMB consistency. Newton’s constant G is derived through dimensional transmutation. Nine falsifiable predictions are identified. The designation “RK particles” honours R. Kaaviyamithran.