Dark Energy Survey: Implications for cosmological expansion models from the final DES baryon acoustic oscillation and supernova data

The Dark Energy Survey (DES) recently released the final results of its two principal probes of the expansion history: Type Ia supernovae (SNe) and baryonic acoustic oscillations (BAO). In this paper, we explore the cosmological implications of these data in combination with external cosmic microwave background (CMB), big bang nucleosynthesis (BBN), and age-of-the-Universe information. The BAO measurement, which is ∼2⁢ away from Planck ’s Λ⁢CDM predictions, pushes for low values of Ωm compared to Planck, in contrast to SN which prefers a higher value than Planck. We identify several tensions among datasets in the Λ⁢CDM model that cannot be resolved by including either curvature (⁢Λ⁢CDM) or a constant dark energy equation of state (⁢CDM). By combining BAO+SN+CMB despite these mild tensions, we obtain Ω =−5.5+4.6 −4.2 ×10−3 in ⁢Λ⁢CDM, and =−0.94⁢8+0.028 −0.027 in ⁢CDM. In ⁢CDM, BAO and SN push again in different directions of parameter space, favoring, respectively, <−1 and >−1. If we open the parameter space to 0⁢⁢CDM [where the equation of state of dark energy varies as ⁡() =0 +(1 −)⁢], all the datasets are mutually more compatible, and we find concordance in the [0 >−1, <0] quadrant, with BAO pushing for <0 and SN for [0 >−1, <0]. For DES BAO and SN in combination with Planck -CMB, we find a 3.2⁢ deviation from Λ⁢CDM, with 0 =−0.67⁢3+0.098 −0.097, =−1.3⁢7+0.51 −0.50, a Hubble constant of 0=67.8⁢1+0.96 −0.86 km s−1 Mpc−1, and an abundance of matter of Ωm =0.310⁢9+0.0086 −0.0099. For the combination of all the background cosmological probes considered (including CMB’s angular acoustic scale ⋆), we still find a deviation of 2.8⁢ from Λ⁢CDM in the 0 − plane. Assuming a minimal neutrino mass, this work provides tentative evidence for non-Λ⁢CDM physics, which is consistent with recent claims in support of evolving dark energy, or a source of unknown systematics.