Is there evidence for dark energy evolution?

Abstract

Recently, Sahni, Shafielo o & Starobinsky (2014) combined two independent measurements of $H(z)$ from BAO data with the value of the Hubble constant $H_0=H(z=0)$, in order to test the cosmological constant hypothesis by means of an improved version of the $Om$ diagnostic. Their result indicated a considerable tension between observations and predictions of the $\Lambda$CDM model. However, such strong conclusion was based only on three measurements of $H(z)$. This motivated us to repeat similar work on a larger sample. By using a comprehensive data set of 29 $H(z)$, we find that discrepancy indeed exists. Even though the value of ${\Omega }_{m,0}{h}^2$ inferred from $Om{h}^2$ diagnostic depends on the way one chooses to make a summary statistics (weighted mean or the median), the persisting discrepancy supports the claims of Sahni, Shafielo o & Starobinsky (2014) that $\Lambda$CDM model may not be the best description of our Universe.

8 pages, 2 figures. Accepted for publication in the ApJL

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