ΛCDM model against cosmography: a possible deviation after DESI 2024

Abstract

In this study, we present an analysis of the standard flat-CDM (Lambda cold dark matter) model using a cosmographic approach, incorporating recent Dark Energy Survey Instrument (DESI) baryon acoustic oscillation (BAO) observations and Type Ia Supernova (SNIa) catalogues, including Dark Energy Survey Supernova 5 Year Release (DES-SN5YR) and Pantheon + compilations. We find full consistency between the standard model and the cosmographic approach when considering DESI BAO and SNIa catalogues independently. When combining DESI BAO with SNIa data, we examine the impact of the Planck prior on the sound horizon at the drag epoch, rd , and the Cepheid prior on the absolute magnitude, M. Applying the Planck prior on rd alone yields an H0 value consistent with the Planck measurement, while applying the Cepheid prior on M alone results in an H0 value consistent with the SH0ES measurement. Without any priors, the H0 value obtained has a large error margin, reconciling the Planck and SH0ES measurements. In all cases where individual priors are applied, we observe no significant tension between the flat-CDM model and the cosmographic approach. However, when both Planck and Cepheid priors are applied simultaneously, significant tensions arise between the model and cosmography. This tension is even more pronounced when excluding LRG1 and LRG2 from the DESI measurements. These results indicate that the standard model cannot simultaneously reconcile high-redshift Planck cosmic microwave background observations and local Cepheid measurements. This discrepancy supports the possibility of new physics beyond the standard model or, alternatively, the presence of unrecognized systematic errors in the observational data.