Back Reaction from Walls

TL;DR

This paper investigates how the presence of walls and underdense regions in the universe affects the distance-redshift relation, showing it remains similar to Friedmann models under certain conditions but can vary widely with arbitrary density contrasts.

Contribution

It demonstrates that in a universe with walls and underdense regions, the distance-redshift relation can be closely approximated or significantly altered depending on density contrasts.

Findings

Distance-redshift relation remains close to Friedmann models with small density contrasts.

Arbitrary distance-redshift relations can be reproduced with models allowing large density contrasts.

The scale of underdense regions relative to the Hubble scale influences the relation's behavior.

Abstract

We study the distance-redshift relation in a universe filled with 'walls' of pressure-less dust separated by under dense regions. We show that as long as the density contrast of the walls is small, or the diameter of the under dense regions is much smaller than the Hubble scale, the distance-redshift relation remains close to what is obtained in a Friedmann universe. However, when arbitrary density contrasts are allowed, every prescribed distance-redshift relation can be reproduced with such models.