Challenging the ω 0 ω a CDM parametrization through rational expansions in view of the DESI DR2

In view of the new Dark Energy Spectroscopic Instrument 2025 results, we analyze three types of , based on rational series making use of Padé approximants over the equations of state, namely Padé ω (0, 1) and Padé (1, 1), plus a Padé q (0, 1), i.e., a rational expansion on the dark energy deceleration parameter, in which the numerator and denominator orders are incorporated into the above brackets. These scenarios appear as alternative dark energy parametrizations with respect to the well-known ω 0 ω a CDM model. Accordingly, we perform Monte Carlo Markov chain analyses with the publicly available Boltzmann code, including the three Padé parametrizations, along with the ω 0 ω a CDM and Λ CDM 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 ω 0 ω a CDM parametrization is not significantly preferred over the Padé cosmology. On the contrary, the deviance information criterion identifies Padé (1, 1) as along with the ω 0 ω a CDM parametrization. Based on our bounds, we further investigate the evolution of the squared sound speed, revealing that the Padé q (0, 1) and Padé ω (0, 1) parametrizations exhibit enhanced stability compared with the other cases here considered and, therefore, describe robust alternatives for the cosmological background.