Dark Energy Evolution: Is $\Lambda$CDM Model the Best?

In summary, a study by Ding, Biesiada, Cao, Li, and Zhu (2014) found a discrepancy between observations and predictions of the cosmological constant hypothesis. This was based on a larger sample of 29 measurements of $H(z)$, indicating that the $\Lambda$CDM model may not be the most accurate description of the Universe. This discrepancy was attributed to a difference in redshift distribution between the differential age measurements and the BAO/CMB measurements.
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wolram
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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.
 
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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).
 

FAQ: Dark Energy Evolution: Is $\Lambda$CDM Model the Best?

What is dark energy?

Dark energy is a hypothetical form of energy that is believed to be responsible for the observed accelerating expansion of the universe. It is thought to make up about 68% of the total energy of the universe.

What is the $\Lambda$CDM model?

The $\Lambda$CDM (Lambda Cold Dark Matter) model is the current standard model of cosmology, which describes the evolution of the universe. It includes the presence of dark energy, cold dark matter, and the cosmological constant.

How does dark energy affect the evolution of the universe?

Dark energy is thought to be responsible for the accelerated expansion of the universe. It counteracts the gravitational pull of matter and causes the expansion of the universe to accelerate over time.

Is the $\Lambda$CDM model the best explanation for dark energy evolution?

The $\Lambda$CDM model is currently the most widely accepted model for explaining the observed expansion of the universe. However, there are alternative theories that attempt to explain dark energy without the need for a cosmological constant.

How is dark energy being studied and tested?

Dark energy is being studied through various methods, including observations of the cosmic microwave background, the large-scale structure of the universe, and the expansion rate of the universe. Scientists are also conducting experiments to try and detect the presence of dark energy directly.

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