{\it Gauging} the cosmic acceleration with recent type Ia supernovae data sets

TL;DR

This paper evaluates a model-independent method for detecting cosmic acceleration using supernova data, testing its reliability and applying it to recent datasets to confirm the universe's accelerated expansion.

Contribution

It introduces and assesses a model-independent estimator for cosmic acceleration, analyzing its robustness and limitations with mock data and applying it to recent supernova samples.

Findings

The estimator can sometimes falsely indicate no acceleration in accelerating universes.

Recent supernova data strongly supports the universe's accelerated expansion.

The estimator's dependence on the Hubble constant is discussed.

Abstract

We revisit a model-independent estimator for cosmic acceleration based on type Ia supernovae distance measurements. This approach does not rely on any specific theory for gravity, energy content or parameterization for the scale factor or deceleration parameter and is based on falsifying the {\it null hypothesis} that the Universe never expanded in an accelerated way. By generating mock catalogues of known cosmologies we test the robustness of this estimator establishing its limits of applicability. We detail the pros and cons of such approach. For example, we find that there are specific counterexamples in which the estimator wrongly provides evidence against acceleration in accelerating cosmologies. The dependence of the estimator on the $H_0$ value is also discussed. Finally, we update the evidence for acceleration using the recent UNION2.1 and JLA samples. Contrary to recent claims, available data strongly favors an accelerated expansion of the Universe in complete agreement with the standard $\Lambda$CDM model.