paper

What are and diagnostics telling us in light of data?

arXiv:1604.07910 · doi:10.3847/0004-637X/825/1/17

Abstract

Two-point diagnostics and have been introduced as an interesting tool for testing the validity of the CDM model. Quite recently, Sahni, Shafieloo Starobinsky (2014) combined two independent measurements of from BAO data with the value of the Hubble constant , and used the second of these diagnostics to test the CDM model. Their result indicated a considerable tension between observations and predictions of the CDM model. Since reliable data concerning expansion rates of the Universe at different redshifts are crucial for the successful application of this method, we investigate both two-point diagnostics on the most comprehensive set of measurements of coming from the BAO and differential ages (DA) of passively evolving galaxies. We discuss the uncertainties of two-point diagnostics and find that they are strongly non-Gaussian and follow the patterns deeply rooted in their very construction. Therefore we propose that non-parametric median statistics is the most appropriate way of treating this problem. Our results support the claims that CDM is in tension with data according to the two-point diagnostics developed by Shafieloo, Sahni and Starobinsky. However, other alternatives to the CDM, such as wCDM or CPL models perform even worse. We also notice that there are serious systematic differences between BAO and DA methods which ought to be better understood before measurements can become competitive to the other probes.

19 pages, 10 figures, 5 tables. Accepted for publication in the ApJ

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