Implications of DES 5YR SNe Dataset for ΛCDM

Dark Energy Survey five-year supernovae data (DES 5YR SNe) in conjunction with Planck CMB and Dark Energy Spectroscopic Instrument (DESI) BAO data has detected a strong dynamical dark energy deviation from the ΛCDM model. Here, we shift the focus of DES data to the pressureless matter sector in the ΛCDM model by studying the matter density parameter Ωₘ. Employing frequentist profile likelihoods, we demonstrate that Ωₘ increases with effective redshift in the DES dataset at up to 2.5 σ level. At the highest redshifts, one encounters negative dark energy densities Ωₘ > 1. Our findings corroborate earlier observations in Pantheon and Pantheon+ datasets with an independent SNe dataset with a higher effective redshift. In an appendix, we confirm that curvature Ωₖ decreases with effective redshift disfavouring a flat Universe in higher redshift DES SNe at > 3 σ. Our choice of Ωₖ prior leads to an underestimation of the tension with a flat Universe.