Cosmic Parallax in Ellipsoidal Universe

TL;DR

This paper investigates how cosmic parallax measurements could reveal anisotropic expansion in an ellipsoidal universe model, which may explain certain cosmic microwave background observations, but requires significantly improved measurement precision.

Contribution

It analyzes the potential of cosmic parallax to constrain anisotropic cosmological models, specifically the ellipsoidal universe, highlighting the need for enhanced observational accuracy.

Findings

Cosmic parallax can, in principle, detect anisotropic expansion.

Current measurement precision is insufficient to constrain the model.

Future improvements could make such constraints feasible.

Abstract

The detection of a time variation of the angle between two distant sources would reveal an anisotropic expansion of the Universe. We study this effect of "cosmic parallax" within the "ellipsoidal universe" model, namely a particular homogeneous anisotropic cosmological model of Bianchi type I, whose attractive feature is the potentiality to account for the observed lack of power of the large-scale cosmic microwave background anisotropy. The preferred direction in the sky, singled out by the axis of symmetry inherent to planar symmetry of ellipsoidal universe, could in principle be constrained by future cosmic parallax data. However, that will be a real possibility if and when the experimental accuracy will be enhanced at least by two orders of magnitude.