Testing the Copernican Principle via Cosmological Observations

TL;DR

This paper evaluates whether current cosmological observations can distinguish between homogeneous dark energy models and inhomogeneous models that violate the Copernican Principle, highlighting the potential of future surveys to resolve this question.

Contribution

It demonstrates that existing data cannot rule out inhomogeneous models violating the Copernican Principle and discusses how upcoming surveys could test this.

Findings

Current observations cannot exclude inhomogeneous anti-Copernican models.

Future baryonic acoustic oscillation surveys will be decisive in testing the Copernican Principle.

Inhomogeneous models can explain supernova data without dark energy.

Abstract

Observations of distances to Type-Ia supernovae can be explained by cosmological models that include either a gigaparsec-scale void, or a cosmic flow, without the need for Dark Energy. Instead of invoking dark energy, these inhomogeneous models instead violate the Copernican Principle. we show that current cosmological observations (Supernovae, Baryon Acoustic Oscillations and estimates of the Hubble parameters based on the age of the oldest stars) are not able to rule out inhomogeneous anti-Copernican models. The next generation of surveys for baryonic acoustic oscillations will be sufficiently precise to either validate the Copernican Principle or determine the existence of a local Gpc scale inhomogeneity.