Data Analysis and Phenomenological Cosmology

TL;DR

This paper evaluates a phenomenological two-scale backreaction cosmological model against observational data, finding it less favored than the standard $\\Lambda$CDM model, despite some preference for non-zero spatial curvature.

Contribution

It introduces and tests a two-scale backreaction model with decoupled curvature parameters using recent supernova and BAO data, assessing its viability against standard cosmology.

Findings

Phenomenological models are not favored over $\\Lambda$CDM.

Preference for non-zero, unequal spatial curvatures.

Little evidence for different Hubble scales.

Abstract

In the era of precision cosmology, even percentage level effects are significant on cosmological observables. The recent tension between the local and global values of $H_0$ is much more significant than this, and any possible solution might rely on us going beyond the standard $\Lambda$CDM cosmological model. For much smaller, yet potentially significant effects, spatial curvature from averaging and cosmological backreaction on observational predictions could play a role. This is especially true with the higher precision of new observational data and improved statistical techniques. In this paper, we discuss the observational viability of a class of physically motivated cosmologies which can be parametrized by a phenomenological two-scale backreaction model with decoupled spatial curvature parameters and two Hubble scales. Using the latest JLA Supernovae data together with some of the latest BAO data, we perform a Bayesian model selection analysis and find that the phenomenological models are not favoured over the standard $\Lambda$CDM cosmological model. Although there is still a preference for non-zero and unequal dynamic and geometric spatial curvatures, there is little evidence for differing Hubble scales within these phenomenological template models.