Model- and calibration-independent test of cosmic acceleration

Abstract

We present a calibration-independent test of the acceleratedexpansion of the universe using supernova type Ia data. The test isalso model-independent in the sense that no assumptions about thecontent of the universe or about the parameterization of thedeceleration parameter are made and that it does not assume anydynamical equations of motion. Yet, the test assumes the universe and the distribution of supernovae to bestatistically homogeneous and isotropic. A significant reduction of systematic effects, as compared to ourprevious, calibration-dependent test, is achieved.Accelerated expansion is detected at significant level (4.3σin the 2007 Gold sample, 7.2σ 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, forwhich the assumption of statistical isotropy and homogeneity is lesswell established.