# Cosmic voids as cosmological laboratories

**Authors:** Carlos Mauricio Correa  
**arXiv:** [2210.17459](https://arxiv.org/abs/2210.17459)  
**Date:** 2022-10-31  
**Summary page:** https://www.summarizepaper.com/en/paper/2210.17459v1/

## Key points

- Cosmic voids are valuable for studying dark energy and alternative theories of gravity
- New galaxy spectroscopic surveys have increased attention on cosmic voids
- Void size function characterizes the abundance of voids
- Void-galaxy cross-correlation function provides information about density and velocity fields within voids
- Accurate interpretation requires understanding of geometrical and dynamical distortions
- Anisotropic patterns have been observed, emphasizing the need for accurate modeling
- The thesis presents a theoretical and statistical framework encompassing all relevant effects in cosmic void studies
- The framework lays the foundation for reliable modeling of statistics related to cosmic voids
- A novel cosmological test based on two perpendicular projections of the correlation function is introduced
- This test does not rely on fiducial-cosmology assumptions and reduces the number of mock catalogues needed for estimation of covariances.

## Summary

Cosmic voids have emerged as valuable cosmological laboratories for investigating the nature of dark energy and alternative theories of gravity. With the advent of new galaxy spectroscopic surveys, which cover an unprecedented volume and redshift range, cosmic voids are receiving increased attention. Two primary statistics in void studies are the void size function, which characterizes the abundance of voids, and the void-galaxy cross-correlation function, which provides information about the density and velocity fields within these regions. However, accurately interpreting these statistics requires a comprehensive understanding of the effects of both geometrical (Alcock-Paczynski effect) and dynamical (Kaiser effect) distortions around cosmic voids. Failure to properly model these effects can lead to biased cosmological constraints. Observational measurements have revealed prominent anisotropic patterns that further emphasize the need for accurate modeling. To address this challenge, this thesis presents a theoretical and statistical framework based on dynamical and cosmological foundations. This framework encompasses all relevant effects involved in cosmic void studies: the expansion effect (t-RSD), off-centering effect (v-RSD), AP-volume effect, and ellipticity effect (e-RSD). By studying the mapping of voids between real space and redshift space, this framework lays the foundation for a reliable modeling of aforementioned statistics. In addition to developing a comprehensive framework, this thesis introduces a novel cosmological test based on two perpendicular projections of the correlation function. This method is free from fiducial-cosmology assumptions, allowing it to effectively break any potential degeneracy between cosmological parameters. Furthermore, it significantly reduces the number of mock catalogues required to estimate covariances. Overall, this work by Carlos Mauricio Correa provides an extensive exploration of cosmic voids as cosmological laboratories. It offers a theoretical and statistical framework that accounts for various effects impacting void studies while introducing a new cosmological test that enhances accuracy and efficiency of cosmological parameter estimation.