A spherical hydrodynamical model of cosmic voids in {\Lambda}CDM and beyond

TL;DR

This paper introduces a hydrodynamical model for cosmic voids within the DM framework and beyond, enabling more accurate and physically intuitive predictions of void evolution and their sensitivity to cosmological parameters.

Contribution

It presents the first hydrodynamical framework for modeling cosmic voids, including a new method for determining shell-crossing epochs in arbitrary cosmologies.

Findings

Void evolution is most sensitive to rm and w_0, affecting density contrast by 20-30%.

The linear to non-linear density contrast mapping depends on cosmology, aiding dark energy studies.

Varying w_a has smaller but potentially measurable effects on void evolution.

Abstract

Cosmic voids have emerged as powerful probes for cosmology, providing complementary information on the large-scale structure of the universe. We present the first application of a hydrodynamical framework to model the evolution of cosmic voids. This approach offers a physically intuitive characterization of void dynamics and can naturally be applied to non-standard cosmologies. We derive the cosmology-dependent mapping that relates the linear (Lagrangian) and fully non-linear (Eulerian) evolution of the matter density contrast, a central component for accurate theoretical modeling of void statistics. Furthermore, we present a new method for determining the shell-crossing epoch across arbitrary cosmological backgrounds, thereby extending previous treatments restricted to the Einstein-de Sitter universe. Motivated by recent DESI results hinting at dynamical dark energy, we investigate void evolution in $ w_0w_a$CDM cosmologies by varying $ w_0$ and $w_a$. We also consider the impact of varying the matter density parameter, $ \Omega_{\mathrm{m},0}$. We find that the evolution of isolated, spherically symmetric cosmic voids is most sensitive to $ \Omega_{\mathrm{m},0} $ and $ w_0 $, which can alter the non-linear density contrast by up to 20-30%. Variations in $w_a$ have a smaller impact, but may still lead to measurable effects. We also show that the cosmology-dependent mapping between linear and non-linear density contrasts may provide a sensitive probe of dynamical dark energy in precision void analyses.