2025/11/19 by Carloni, Youri, Luongo, Orlando, Biesiada, Marek
Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Statistical Mechanics and Entropy
paper · doi:10.48550/arxiv.2511.15472
In view of the new Dark Energy Spectroscopic Instrument (DESI) 2025 results, we analyze three types of Padé cosmology, based on rational series making use of Padé approximants over the equations of state, namely Padéω (0,1) and Padéω (1,1), plus a Padéq (0,1), i.e., a rational expansion on the dark energy deceleration parameter, in which where the numerator and denominator orders are incorporated into the above brackets. These scenarios appear alternative dark energy parameterizations with respect to the well-known ω0ωaCDM model, claimed as the most viable model by DESI. Accordingly, we perform Monte Carlo Markov chain (MCMC) analyses with the publicly available CLASS Boltzmann code, including the three Padé cosmology, along with the ω0ωaCDM and ΛCDM standard pictures. To this end, we combine independent probes from high to low redshifts to obtain reliable constraints on the cosmological parameters of these models and compare them using statistical selection criteria. Our results show that Padé cosmology is neither statistically excluded nor worse than the ω0ωaCDM parametrization. On the contrary, the Akaike Information Criterion (AIC) identifies Padéq (0,1) as the best-fit model, with weak evidence against the ω0ωaCDM parameterization, while the Deviance Information Criterion (DIC) provides strong evidence against the ω0ωaCDM model, favoring Padé (1,1). Based on our bounds, we further investigate the evolution of the squared sound speed, revealing that the Padéq (0,1) and Padéω (0,1) parameterizations exhibit enhanced stability compared with the other cases here considered and, therefore, describe robust alternatives for the cosmological background.