The unified Bound Dark Energy--Bound Dark Matter model: theory and constraints from DESI DR2

The unified Bound Dark Energy--Bound Dark Matter (BDE-BDM) model derives both the dark energy and the whole of the dark matter from a single supersymmetric SU(3) gauge group with N f=6 flavors. Gauge-coupling unification predicts the scale at which it condenses, =34+16-11 eV, before any cosmological data are used, so the dark-energy sector adds no parameter to those of and the dark-matter sector adds only one. Fitting DESI DR2 BAO, Planck CMB, Planck+ACT DR6 CMB lensing, and three supernova compilations (PantheonPlus, Union3.1, DES-Dovekie) gives, for Union3.1, =43.67 plus or minus0.13 eV, inside the predicted range: a high-energy prediction met by a late-time measurement. The equation of state evolves to w 0=-0.9262 plus or minus0.0005 and never crosses the phantom divide. Relative to the model lowers the DESI BAO χ squared by 2.95 -- 3.67 and the supernova χ squared by 2.53 -- 4.07, recovering 57% -- 71% of the total reduction that obtains by fitting two dark-energy parameters to the same data, and reaching the lower BAO χ squared of the two models for two of the three compilations. Its Δ DIC against is strong for every compilation, -8.28 to-7.47, varying by 0.81 where that of varies by 4.8. Because the dark-energy sector adds no parameter to those of, the likelihood gain survives the Occam penalty: B=+4.09, +4.12, and +4.83 against, where gives-2.11, -0.26, and-0.56. Among six models pairing a cosmological constant, the parametrization or bound dark energy with cold or bound dark matter, BDE-BDM has the largest Bayesian evidence.