Anisotropy in a Nonsingular Bounce

TL;DR

This paper investigates the evolution of anisotropies in a nonsingular bouncing cosmology model, demonstrating that anisotropies decrease during Ekpyrotic contraction and can remain small through the bounce, aligning with observations.

Contribution

It provides a detailed analysis of anisotropy behavior in a model combining Ekpyrotic contraction with a Galileon bounce, showing anisotropies can be controlled.

Findings

Anisotropies decrease during Ekpyrotic contraction.

Anisotropies can be constrained to remain small during the bounce.

Derived conditions for Ekpyrotic phase to match current anisotropy bounds.

Abstract

Following recent claims relative to the question of large anisotropy production in regular bouncing scenarios, we study the evolution of such anisotropies in a model where an Ekpyrotic phase of contraction is followed by domination of a Galileon-type Lagrangian which generates a non-singular bounce. We show that the anisotropies decrease during the phase of Ekpyrotic contraction (as expected) and that they can be constrained to remain small during the non-singular bounce phase (a non-trivial result). Specifically, we derive the e-folding number of the phase of Ekpyrotic contraction which leads to a present-day anisotropy in agreement with current observational bounds.