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arXiv · 2301.10740

Testing $\Lambda$CDM cosmology in a binned universe: anomalies in the deceleration parameter

Erick Pastén·Victor Cárdenas
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Abstract

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.

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Erick Pastén, Victor Cárdenas. 2023-01-25. Testing $\Lambda$CDM cosmology in a binned universe: anomalies in the deceleration parameter. https://doi.org/10.1016/j.dark.2023.101224

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