Anisotropic expansion and SNIa: an open issue

Understand

We review the appropriateness of using SNIa observations to detect potential signatures of anisotropic expansion in the Universe.

• We focus on Union2 and SNLS3 SNIa datasets and use the hemispherical comparison method to detect possible anisotropic features.
• Unlike some previous works where non-diagonal elements of the covariance matrix were neglected, we use the full covariance matrix of the SNIa data, thus obtaining more realistic and not underestimated errors.
• As a matter of fact, the significance of previously claimed detections of a preferred direction in the Union2 dataset completely disappears once we include the effects of using the full covariance matrix.