Cosmic Parallax: possibility of detecting anisotropic expansion of the universe by very accurate astrometry measurements

TL;DR

This paper explores how precise astrometry can detect anisotropic expansion of the universe via cosmic parallax, providing a new method to test cosmological isotropy and constrain models like LTB with future satellite data.

Contribution

It introduces the concept of cosmic parallax as a real-time test for cosmic anisotropy and evaluates its potential to constrain LTB cosmologies with upcoming astrometry missions.

Findings

Future missions like Gaia could set competitive limits on off-center positions in LTB models.

Cosmic parallax offers a novel, real-time consistency test of the FRW metric.

Constraints from astrometry could complement CMB dipole measurements.

Abstract

Refined astrometry measurements allow us to detect large-scale deviations from isotropy through real-time observations of changes in the angular separation between sources at cosmic distances. This "cosmic parallax" effect is a powerful consistency test of FRW metric and may set independent constraints on cosmic anisotropy. We apply this novel general test to LTB cosmologies with off-center observers and show that future satellite missions such as Gaia might achieve accuracies that would put limits on the off-center distance which are competitive with CMB dipole constraints.