Speaker
Description
"We investigate whether the recent DESI DR2 measurements provide or not evidences for dynamical dark energy by exploring the LambdaCDM model and its extensions. Using a comprehensive MCMC analysis with a wide range of cosmological datasets including DESI DR2 BAO, Lyman alpha data, CMBR, BBN, cosmic chronometers, and multiple Type Ia supernova compilations, we assess the statistical preference for departures from LambdaCDM. We find that neither LambdaCDM nor omega_0-omega_aCDM models reduces the sound horizon by the 7 % required to alleviate the Hubble tension. DESI DR2 consistently favors the quadrant omega_0 > -1 and omega_a < 0, indicating a preference for dynamical dark energy of the Quintom-B type at less 3 sigma level for most dataset combinations, rising to 3.8 sigma only when the DES-SN5Y supernova sample is included. Furthermore, we get neutrino mass constraints. The systematics diagnosis shows that the preference for dynamical dark energy is biased at redshift z<0.1. When these low-z SNe Ia are excluded, our analysis no longer requires a dynamical dark energy and fully restores the LambdaCDM model. The reconstructed evolution of omega(z) shows a transition from the phantom to the quintessence regime by crossing the phantom divide. Overall, DESI DR2 provides valuable new insights into dark energy but does not yet challenge completely the LambdaCDM paradigm. Forthcoming surveys,
including DESI DR3, Rubin Observatory, Euclid, Roman Space Telescope, and the Simons Observatory will be crucial for determining whether these hints of dynamical dark energy persist or are due to statistical fluctuations or residual systematics in low-redshift supernova samples.The talk is based on the review paper:
Phys.Dark Univ. 51 (2026) 102196."