Model independent inference of the expansion history and implications for the growth of structure

TL;DR

This paper uses a model-independent Gaussian Process approach to analyze the Universe's expansion history, combining multiple datasets, and examines implications for dark energy, growth of structure, and the Hubble tension.

Contribution

It introduces a model-independent method to constrain the expansion history and dark energy evolution, avoiding assumptions of specific cosmological models.

Findings

CMB, LRG, Lyα, and JLA data are consistent with ΛCDM.

H0 measurements are moderately inconsistent with other data.

Growth of structure approximates Ω_m^0.55 under current precision.

Abstract

We model the expansion history of the Universe as a Gaussian Process and find constraints on the dark energy density and its low-redshift evolution using distances inferred from the Luminous Red Galaxy (LRG) and Lyman-alpha (Ly$\alpha$) datasets of the Baryon Oscillation Spectroscopic Survey, supernova data from the Joint Light-curve Analysis (JLA) sample, Cosmic Microwave Background (CMB) data from the Planck satellite, and local measurement of the Hubble parameter from the Hubble Space Telescope ($\mathsf H0$). Our analysis shows that the CMB, LRG, Ly$\alpha$, and JLA data are consistent with each other and with a $\Lambda$CDM cosmology, but the ${\mathsf H0}$ data is inconsistent at moderate significance. Including the presence of dark radiation does not alleviate the ${\mathsf H0}$ tension in our analysis. While some of these results have been noted previously, the strength here lies in that we do not assume a particular cosmological model. We calculate the growth of the gravitational potential in General Relativity corresponding to these general expansion histories and show that they are well-approximated by $\Omega_{\rm m}^{0.55}$ given the current precision. We assess the prospects for upcoming surveys to measure deviations from $\Lambda$CDM using this model-independent approach.