Implications of DES 5YR SNe Dataset for \(\Lambda \)CDM

Abstract

Dark Energy Survey 5-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 (DE) deviation from the \(\Lambda \)CDM model. Here we shift the focus of DES data to the pressureless matter sector in the \(\Lambda \)CDM model by studying the matter density parameter \(\Omega _m\). Employing primarily frequentist profile likelihoods, supported by complementary Bayesian methods, we demonstrate that \(\Omega _m\) increases with effective redshift in the DES data up to a point that there is a \(2.5 \sigma \) discrepancy with Planck. We relax the traditional \(\Omega _m \le 1\) prior to demonstrate negative DE densities \(\Omega _m > 1\) at the highest effective redshift probed. Nevertheless, the largest discrepancy with Planck occurs for profile likelihoods and posteriors peaked at \(\Omega _m < 1\) in the traditional \(\Lambda \)CDM regime. 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 \(\Omega _k\) decreases with effective redshift disfavouring a flat Universe in higher redshift DES SNe at \(> 3 \sigma \). Our choice of \(\Omega _k\) prior leads to an underestimation of the tension with a flat Universe.