Model- and calibration-independent test of cosmic acceleration

TL;DR

This paper introduces a calibration-independent, model-independent test for cosmic acceleration using supernova data, confirming acceleration with high significance under certain assumptions.

Contribution

It develops a new test that does not rely on calibration or specific cosmological models, improving robustness over previous methods.

Findings

Detection of cosmic acceleration at 4.3 sigma (2007 data)

Detection at 7.2 sigma (2008 data)

Results depend on low-redshift supernovae assumptions

Abstract

We present a calibration-independent test of the accelerated expansion of the universe using supernova type Ia data. The test is also model-independent in the sense that no assumptions about the content of the universe or about the parameterization of the deceleration parameter are made and that it does not assume any dynamical equations of motion. Yet, the test assumes the universe and the distribution of supernovae to be statistically homogeneous and isotropic. A significant reduction of systematic effects, as compared to our previous, calibration-dependent test, is achieved. Accelerated expansion is detected at significant level (4.3 sigma in the 2007 Gold sample, 7.2 sigma in the 2008 Union sample) if the universe is spatially flat. This result depends, however, crucially on supernovae with a redshift smaller than 0.1, for which the assumption of statistical isotropy and homogeneity is less well established.