Galaxy correlations and the BAO in a void universe: structure formation as a test of the Copernican Principle

Sean February, Chris Clarkson, Roy Maartens

Research output: Contribution to journalArticlepeer-review


A suggested solution to the dark energy problem is the void model, where accelerated expansion is replaced by Hubble-scale inhomogeneity. In these models, density perturbations grow on a radially inhomogeneous background. This large scale inhomogeneity distorts the spherical Baryon Acoustic Oscillation feature into an ellipsoid which implies that the bump in the galaxy correlation function occurs at different scales in the radial and transverse correlation functions. We compute these for the first time, under the approximation that curvature gradients do not couple the scalar modes to vector and tensor modes. The radial and transverse correlation functions are very different from those of the concordance model, even when the models have the same average BAO scale. This implies that if void models are fine-tuned to satisfy average BAO data, there is enough extra information in the correlation functions to distinguish a void model from the concordance model. We expect these new features to remain when the full perturbation equations are solved, which means that the radial and transverse galaxy correlation functions can be used as a powerful test of the Copernican Principle.
Original languageEnglish
Article number023
Pages (from-to)023
JournalJournal of Cosmology and Astroparticle Physics
Issue number3
Early online date19 Mar 2013
Publication statusPublished - Mar 2013


  • galaxy clustering
  • baryon acoustic oscillations
  • cosmological perturbation theory


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