The Vacuum Saturation Model: Phenomenological Constraints and Predictions for Dynamical Dark Energy

A scalar field coupled to free-streaming radiation through a scalar-fluid interaction extracts energy from photons and neutrinos, accumulating it as dark energy. At recombination, supersaturation of the neutrino channel triggers a condensation that produces dark matter. The model has two coupling constants measured from Planck observations. From these, a coupled ODE system produces Omega_DE = 0.685, Omega_DM = 0.265, H_0 = 67.4 km/s/Mpc, sigma_8 = 0.813, and w_eff(z=0) = -0.984. The dark matter condensation rate is derived from nucleation kinetics with no additional fitting. The equation of state satisfies w > -1 at all redshifts, consistent with DESI DR2 evidence for dynamical dark energy. Cosmic chronometer H(z) data across 31 measurements are fit comparably to LCDM (chi-squared per degree of freedom of 0.50 versus 0.48). A parameter scan over the CMB TT power spectrum shows that the VSM expansion history accommodates the Planck peak measurements with a peak chi-squared of 0.52, compared to 0.99 for LCDM. The model predicts a non-monotonic w(z) trajectory with a feature at z ~ 5, a spatial correlation between cosmic void properties and local dark matter density, and a sigma_8 consistent with Planck that alleviates the tension present in LCDM.