The effect of interacting dark energy on local measurements of the Hubble constant

TL;DR

This study investigates how interacting dark energy models influence local measurements of the Hubble constant, revealing increased variance and uncertainty in these measurements due to cosmic variance effects in such models.

Contribution

The paper provides the first detailed analysis of local Hubble constant variations in coupled dark energy models using N-body simulations, highlighting increased measurement uncertainties.

Findings

Variance in local flows is larger in coupled models.

Higher $\sigma_8$ values contribute to increased variance.

Cosmological models with interacting dark energy affect local Hubble measurements.

Abstract

In the current state of cosmology, where cosmological parameters are being measured to percent accuracy, it is essential to understand all sources of error to high precision. In this paper we present the results of a study of the local variations in the Hubble constant measured at the distance scale of the Coma Cluster, and test the validity of correcting for the peculiar velocities predicted by gravitational instability theory. The study is based on N-body simulations, and includes models featuring a coupling between dark energy and dark matter, as well as two $\Lambda$CDM simulations with different values of $\sigma_8$. It is found that the variance in the local flows is significantly larger in the coupled models, which increases the uncertainty in the local measurements of the Hubble constant in these scenarios. By comparing the results from the different simulations, it is found that most of the effect is caused by the higher value of $\sigma_8$ in the coupled cosmologies, though this cannot account for all of the additional variance. Given the discrepancy between different estimates of the Hubble constant in the universe today, cosmological models causing a greater cosmic variance is something that we should be aware of.