Orateur
Description
In this work we introduce a high-redshift cosmographic framework based on a new Padé expansion, providing improved accuracy at $z \gtrsim 1$. We estimate the cosmographic parameters $ H(z), \,q(z),\, j(z),\,s(z) $ at different fixed redhsift values by combining DESI BAO data (calibrated with Planck’s sound horizon scale $r_d$), the Pantheon Plus and DESy5 Type Ia supernova samples, and cosmic-chronometer measurements of $H(z)$. Our analysis yields precise constraints on cosmographic parameters and highlights deviations from the $\Lambda$CDM model. We also reconstruct the deceleration parameter $q(z)$, from which we obtain information about the dark-energy equation of state $w(z)$ in a fully model-independent way. These measurements provide a powerful tool to test cosmological models and to investigate the late-time expansion history of the Universe and the nature of dark energy.
