# Dark energy evolution

1. Mar 18, 2015

### wolram

Is Dark Energy a constant ?

arXiv:1503.04923 [pdf, ps, other]
Is there evidence for dark energy evolution?
Xuheng Ding, Marek Biesiada, Shuo Cao, Zhengxiang Li, Zong-Hong Zhu
Comments: 8 pages, 2 figures. Accepted for publication in the ApJL
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

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 $Omh^2$ 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.

2. Mar 18, 2015

### Chalnoth

Seems to me that what they're really showing is a significant discrepancy between the differential age (DA) measurements and the BAO/CMB measurements. This will naturally show up as a deviation from a cosmological constant as long as the DA measurements have a different redshift distribution than the BAO measurements (which they do).