Implications of DES 5YR SNe Dataset for ΛCDM

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 $\mathrm{\Lambda }$CDM model. Here we shift the focus of DES data to the pressureless matter sector in the $\mathrm{\Lambda }$CDM model by studying the matter density parameter ${\mathrm{\Omega }}_m$. Employing primarily frequentist profile likelihoods, supported by complementary Bayesian methods, we demonstrate that ${\mathrm{\Omega }}_m$ 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 ${\mathrm{\Omega }}_m\le 1$ prior to demonstrate negative DE densities ${\mathrm{\Omega }}_m>1$ at the highest effective redshift probed. Nevertheless, the largest discrepancy with Planck occurs for profile likelihoods and posteriors peaked at ${\mathrm{\Omega }}_m<1$ in the traditional $\mathrm{\Lambda }$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 ${\mathrm{\Omega }}_k$ decreases with effective redshift disfavouring a flat Universe in higher redshift DES SNe at $>3\sigma$. Our choice of ${\mathrm{\Omega }}_k$ prior leads to an underestimation of the tension with a flat Universe.