Origin of unresolved cosmological tensions (including the H0 tension)

Ascertain the physical origin of unresolved statistical tensions among cosmological parameter inferences from independent datasets, particularly the H0 tension in which the present-day Hubble parameter H0 inferred from Planck 2018 cosmic microwave background observations assuming the ΛCDM model is inconsistent with late-time distance-ladder measurements based on Type Ia supernovae and Cepheids.

Background

The paper develops a generalized estimator to quantify statistical tensions among multiple cosmological datasets in a shared parameter space, addressing limitations of pairwise metrics like Q_DM and one-dimensional rule-of-thumb Nσ measures. This framework highlights that interpreting probability-to-exceed values in higher-dimensional spaces requires care and proposes a geometric interpretation for two- and three-dataset cases.

Within this context, the authors note that several well-known discrepancies persist in current cosmology, most notably the H0 tension, where the H0 value inferred from CMB data under ΛCDM disagrees with late-time determinations from distance-ladder methods using Type Ia supernovae and Cepheids. Despite extensive investigation, the origin of these tensions remains unresolved, motivating the development of robust tools and further inquiry into their causes.