The unified bound dark energy--bound dark matter model confronted with DESI DR2, ACT and SPT-3G, and the Unite supernovae measurements

The unified bound dark energy-bound dark matter (BDE-BDM) model derives the whole dark sector from a single supersymmetric SU(3) dark gauge group, whose lightest meson is the dark energy and whose heavier bound states, created with a velocity vc when the group condenses, are the dark matter. Because the condensation scale Λc is fixed by gauge-coupling unification, the dark-energy sector has no free parameter beyond those of $Λ$CDM, and the dark-matter sector adds only vc. We confront the model with DESI DR2 baryon acoustic oscillations (BAO), the Planck, ACT DR6 and SPT-3G D1 CMB spectra, the combined ACT and SPT CMB lensing and the Unite supernovae. The measured condensation scale, Λc=43.74±0.11 eV, lies inside the window 34⁺¹⁶₋₁₁ eV predicted by unification, and the dark energy thaws without ever crossing the phantom divide, reaching w₀=-0.9267±0.0003 today; it thus reproduces the DESI distances that w₀wₐCDM fits with a phantom past. BDE-BDM gives the best fit to the DESI DR2 BAO of the four models, reducing χ²BAO by 20% with respect to $Λ$CDM, more than w₀wₐCDM, and over the full data combination it is statistically equivalent to both $Λ$CDM and w₀wₐCDM, with ln B=-0.50 and $-0.15$, while having two fewer dark-energy parameters than w₀wₐCDM. Within bound dark energy, bound dark matter is moderately preferred over cold dark matter, ln B=+3.2 with Δχ²=-9.0, mostly from the CMB. The data now constrain the bound velocity from both sides, vc=0.37±0.14, which places the free-streaming cutoff of the matter power spectrum at k1/2=1.49\,h Mpc⁻¹ and lowers the amplitude of structure to S₈=0.807±0.007. Future high-redshift and Lyman-$α$ forest data, together with growth and lensing measurements, will therefore provide the decisive tests of the unified dark sector.