A model independent null test on the cosmological constant

TL;DR

This paper employs the Om statistic and Genetic Algorithms to perform a model-independent null test on the flat $\Lambda$CDM model, reconstructing the universe's expansion history and checking for deviations.

Contribution

It introduces a novel combination of Genetic Algorithms and the Om statistic for a model-independent test of the cosmological constant.

Findings

$\Lambda$CDM is consistent within 2$\sigma$

Some low-redshift deviations from $\Lambda$CDM are possible

Reconstruction of $H(z)$ is model-independent

Abstract

We use the Om statistic and the Genetic Algorithms (GA) in order to derive a null test on the spatially flat cosmological constant model $\Lambda$CDM. This is done in two steps: first, we apply the GA to the Constitution SNIa data in order to acquire a model independent reconstruction of the expansion history of the Universe $H(z)$ and second, we use the reconstructed $H(z)$ in conjunction with the Om statistic, which is constant only for the $\Lambda$CDM model, to derive our constraints. We find that while $\Lambda$CDM is consistent with the data at the $2\sigma$ level, some deviations from $\Lambda$CDM model at low redshifts can be accommodated.