Measurement of the Weyl potential evolution from the first three years of Dark Energy Survey data

TL;DR

This study measures the Weyl potential evolution over four redshift bins using Dark Energy Survey data, revealing deviations from Lambda Cold Dark Matter predictions and contributing to the tension in matter clustering parameters.

Contribution

First measurement of the Weyl potential evolution from DES data that is model-independent and tests gravity theories beyond General Relativity.

Findings

Measured Weyl potential is below ΛCDM predictions at low redshifts.

Tension in σ8 persists without CMB data.

Dark Energy Survey data favor high primordial fluctuations and slow Weyl potential evolution.

Abstract

The Weyl potential, which is the sum of the spatial and temporal distortions of the Universe's geometry, provides a direct way of testing the theory of gravity and the validity of the $\Lambda$CDM (Lambda Cold Dark Matter) model. Here we present measurement of the Weyl potential at four redshifts bins using data from the first three years of observations of the Dark Energy Survey. We find that the measured Weyl potential is 2$\sigma$, respectively 2.8$\sigma$, below the $\Lambda$CDM predictions in the two lowest redshift bins. We show that these low values of the Weyl potential are at the origin of the tension between Cosmic Microwave Background measurements and weak lensing measurements, regarding the parameter $\sigma_8$ which quantifies the clustering of matter. Interestingly, we find that the tension remains if no information from the Cosmic Microwave Background is used. Dark Energy Survey data on their own prefer a high value of the primordial fluctuations, together with a slow evolution of the Weyl potential. An important feature of our method is that the measurements of the Weyl potential are model-independent and can therefore be confronted with any theory of gravity, allowing efficient tests of models beyond General Relativity.