Extended Spherical Collapse and the Accelerating Universe

TL;DR

This paper examines how shear stress and angular momentum influence the nonlinear spherical collapse model in cosmology, revealing their effects on collapse thresholds and virial overdensities within EdS and ΛCDM frameworks.

Contribution

It introduces an extended spherical collapse model incorporating shear and rotation effects, showing their impact on collapse parameters in different cosmological models.

Findings

Shear and rotation increase the linear density threshold for collapse.

Net effects lead to higher virial overdensities at galactic scales.

Shear and rotation modify collapse dynamics compared to standard models.

Abstract

The influence of the shear stress and angular momentum on the nonlinear spherical collapse model is discussed in the framework of the Einstein-de Sitter (EdS) and $\Lambda$CDM models. By assuming that the vacuum component is not clustering within the homogeneous nonspherical overdensities, we show how the local rotation and shear affects the linear density threshold for collapse of the non-relativistic component ($\delta_\mathrm{c}$) and its virial overdensity ($\Delta_\mathrm{V}$). It is also found that the net effect of shear and rotation in galactic scale is responsible for higher values of the linear overdensity parameter as compared with the standard spherical collapse model (no shear and rotation).