Implications of DES 5YR SNe Dataset for $\Lambda$CDM

Understand

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 (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 $\Omega_m \leq 1$ 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.