unimpeded: A Public Grid of Nested Sampling Chains for Cosmological Model Comparison and Tension Analysis

TL;DR

The paper introduces 'unimpeded', a Python library with pre-computed chains for cosmological model comparison, revealing that combined data generally favor the standard ΛCDM model and highlighting significant tensions between specific datasets.

Contribution

It provides a public resource for efficient Bayesian analysis across multiple cosmological models and datasets, enabling systematic tension and model comparison studies.

Findings

ΛCDM is most often preferred in combined analyses.

Significant tensions exist between DES and Planck, and SH0ES and Planck datasets.

The Hubble tension persists across models, while the $S_8$ tension is partially resolvable.

Abstract

Bayesian inference is central to modern cosmology, yet comprehensive model comparison and tension quantification remain computationally prohibitive for many researchers. To address this, we release $\texttt{unimpeded}$, a publicly available Python library and data repository providing pre-computed nested sampling and MCMC chains. We apply this resource to conduct a systematic analysis across a grid of eight cosmological models, including $\Lambda$CDM and seven extensions, and 39 datasets, including individual probes and their pairwise combinations. Our model comparison reveals that whilst individual datasets show varied preferences for model extensions, the base $\Lambda$CDM model is most frequently preferred in combined analyses, with the general trend suggesting that evidence for new physics is diluted when probes are combined. Using five complementary statistics, we quantify tensions, finding the most significant to be between DES and Planck ($\sigma=3.57\pm0.10$) and SH0ES and Planck ($\sigma=3.27\pm0.10$) within $\Omega_k\Lambda$CDM. We characterise the $S_8$ tension as high-dimensional ($d_G=4.87\pm0.79$) and partially resolvable in certain extended models, whereas the Hubble tension is low-dimensional and persists across the model space. Caution should be exercised when combining datasets in tension. The $\texttt{unimpeded}$ data products, hosted on Zenodo, provide a powerful resource for reproducible cosmological analysis and underscore the robustness of the $\Lambda$CDM model against this comprehensive benchmark compilation.