Living in a Void: Testing the Copernican Principle with Distant Supernovae

TL;DR

This paper proposes testing the Copernican Principle by analyzing supernovae data to distinguish between dark energy and a local void as explanations for cosmic acceleration, using redshift dependence of luminosity distances.

Contribution

It introduces a method to test the Copernican Principle by examining the local redshift dependence of supernovae luminosity distances, offering an alternative to dark energy explanations.

Findings

Redshift dependence of luminosity distance can discriminate between void models and dark energy.

Future supernova surveys in the 0.1-0.4 redshift range are ideal for testing the Copernican Principle.

The approach can determine the validity of the Copernican Principle on large scales.

Abstract

A fundamental presupposition of modern cosmology is the Copernican Principle; that we are not in a central, or otherwise special region of the Universe. Studies of Type Ia supernovae, together with the Copernican Principle, have led to the inference that the Universe is accelerating in its expansion. The usual explanation for this is that there must exist a `Dark Energy', to drive the acceleration. Alternatively, it could be the case that the Copernican Principle is invalid, and that the data has been interpreted within an inappropriate theoretical frame-work. If we were to live in a special place in the Universe, near the centre of a void where the local matter density is low, then the supernovae observations could be accounted for without the addition of dark energy. We show that the local redshift dependence of the luminosity distance can be used as a clear discriminant between these two paradigms. Future surveys of Type Ia supernovae that focus on a redshift range of ~0.1-0.4 will be ideally suited to test this hypothesis, and hence to observationally determine the validity of the Copernican Principle on new scales, as well as probing the degree to which dark energy must be considered a necessary ingredient in the Universe.