# Cosmic Voids in Evolving Dark Sector Cosmologies: the Low Redshift Universe

## TL;DR

This study compares void properties in standard and alternative dark sector cosmologies using simulations, finding that void volume distributions differ in coupled models and void densities vary with dark sector physics, while shape statistics are insensitive.

## Contribution

It introduces a comparative analysis of void properties across different dark sector models, highlighting observable differences in void volume and density distributions.

## Key findings

- Void volume distribution differs in coupled dark sector models.
- Void shape distributions are similar across models.
- Void densities vary, with emptiest in quintessence and densest in $\\Lambda$CDM.

## Abstract

We present a comparison of void properties between the standard model of cosmology, $\Lambda$ Cold Dark Matter ($\Lambda$CDM), and two alternative cosmological models with evolving and interacting dark sectors: a quintessence model ($\phi$CDM) and a Coupled Dark Matter-Dark Energy (CDE) model. Using $N$-body simulations of these models, we derive several measures of void statistics and properties, including distributions of void volume, ellipticity, prolateness, and average density. We find that the volume distribution derived from the CDE simulation deviates from the volume distribution derived from the $\Lambda$CDM simulation in the present-day universe, suggesting that the presence of a coupled dark sector could be observable through this statistic. We also find that the distributions of void ellipticity and prolateness are practically indistinguishable among the three models over the redshift range $z=0.0-1.0$, indicating that simple void shape statistics are insensitive to small changes in dark sector physics. Interestingly, we find that the distributions of average void density measured in each of the three simulations are distinct from each other. In particular, voids on average tend to be emptiest under a quintessence model, and densest under the $\Lambda$CDM model. Our results suggest that it is the scalar field present in both alternative models that causes emptier voids to form, while the coupling of the dark sector mitigates this effect by slowing down the evacuation of matter from voids.