Can Cosmic Parallax Distinguish Between Anisotropic Cosmologies?

TL;DR

This paper investigates whether cosmic parallax measurements can differentiate between various anisotropic cosmological models, focusing on Bianchi type I universes, and assesses the potential of upcoming astrometry missions to detect such effects.

Contribution

It analyzes cosmic parallax in Bianchi type I models to determine if observations can distinguish between different anisotropic universe evolutions.

Findings

Cosmic parallax varies with anisotropic models.

Upcoming astrometry missions may detect anisotropic effects.

Cosmic parallax can potentially differentiate between anisotropic cosmologies.

Abstract

In an anisotropic universe, observers not positioned at a point of special symmetry should observe cosmic parallax - the relative angular motion of test galaxies over cosmic time. It was recently argued that the non-observance of this effect in upcoming precision astrometry missions such as Gaia may be used to place strong bounds on the position of off-center observers in a void-model universe described by the Lemaitre-Tolman-Bondi metric. We consider the analogous effect in anisotropic cosmological models described by an axisymmetric homogeneous Bianchi type I metric and discuss whether any observation of cosmic parallax would distinguish between different anisotropic evolutions.