Testing ΛCDM cosmology in a binned universe: Anomalies in the deceleration parameter

• DOI: 10.1016/j.dark.2023.101224
• Publication Date: 2023-04-05T23:30:57Z
• Authors: Erick Pastén; Víctor H. Cárdenas
• Keywords: Luminosity distance

We study the reconstructed deceleration parameter splitting the data in different redshift bins, fitting both a cosmographic luminosity distance and also assuming a flat $\Lambda$CDM model, using the Pantheon+ sample of type Ia supernova data (SNIA). We observe tensions $\sim 2\sigma-3\sigma$ for different redshift and distance indicators if the full sample is used. However, those tensions disappear when the SNIA at $z<0.008$ are removed. If the data is splitted in 2 hemispheres according to our movement w.r.t CMB, a strange $3.8 \sigma$ tension appears in one of the samples between particular redshift bins. Finally, considering posterior distribution as Gaussian, general linear model prefers a positive slope for $q_0$ across redshift bins opposed to a zero slope expected in a $\Lambda$CDM universe. We discuss possible explanations for our results and the influence of lowest redshift SNIA data in cosmological analysis.<br/>Comment: Published version in Physics of the Dark Universe journal<br/>