A new null diagnostic customized for reconstructing the properties of dark energy from BAO data

TL;DR

This paper introduces Om3, a new null diagnostic combining BAO and SNIa data that minimally depends on cosmological assumptions, enabling model-independent testing of dark energy properties.

Contribution

The paper proposes Om3, a novel diagnostic that requires no prior knowledge of key cosmological parameters, improving the robustness of dark energy analysis from observational data.

Findings

Om3 is consistent with a cosmological constant.

Om3 can be reconstructed using current SNIa and BAO data.

Future data can refine dark energy constraints using Om and Om3.

Abstract

Baryon Acoustic Oscillations (BAO) provide an important standard ruler which can be used to probe the recent expansion history of our universe. We show how a simple extension of the Om diagnostic, which we call Om3, can combine standard ruler information from BAO with standard candle information from type Ia supernovae (SNIa) to yield a powerful novel null diagnostic of the cosmological constant hypothesis. A unique feature of Om3 is that it requires minimal cosmological assumptions since its determination does not rely upon prior knowledge of either the current value of the matter density and the Hubble constant, or the distance to the last scattering surface. Observational uncertainties in these quantities therefore do not affect the reconstruction of Om3. We reconstruct Om3 using the Union 2.1 SNIa data set and BAO data from SDSS, WiggleZ and 6dFGS. Our results are consistent with dark energy being the cosmological constant. We show how Om and Om3 can be used to obtain accurate model independent constraints on the properties of dark energy from future data sets such as BigBOSS.