Just thought i would flag this up.(adsbygoogle = window.adsbygoogle || []).push({});

arXiv:1601.01701 [pdf, ps, other]

A 6% measurement of the Hubble parameter at $z\sim0.45$: direct evidence of the epoch of cosmic re-acceleration

Michele Moresco, Lucia Pozzetti, Andrea Cimatti, Raul Jimenez, Claudia Maraston, Licia Verde, Daniel Thomas, Annalisa Citro, Rita Tojeiro, David Wilkinson

Comments: 30 pages, 9 figures, 5 tables, submitted to JCAP. The H(z) data can be downloaded at this http URL

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

Deriving the expansion history of the Universe is a major goal of modern cosmology. To date, the most accurate measurements have been obtained with Type Ia Supernovae and Baryon Acoustic Oscillations, providing evidence for the existence of a transition epoch at which the expansion rate changes from decelerated to accelerated. However, these results have been obtained within the framework of specific cosmological models that must be implicitly or explicitly assumed in the measurement. It is therefore crucial to obtain measurements of the accelerated expansion of the Universe independently of assumptions on cosmological models. Here we exploit the unprecedented statistics provided by the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 9 to provide new constraints on the Hubble parameter $H(z)$ using the em cosmic chronometers approach. We extract a sample of more than 130000 of the most massive and passively evolving galaxies, obtaining five new cosmology-independent $H(z)$ measurements in the redshift range $0.3<z<0.5$, with an accuracy of $\sim$11-16\% incorporating both statistical and systematic errors. Once combined, these measurements yield a 6\% accuracy constraint of $H(z=0.4293)=91.8\pm5.3$ km/s/Mpc. The new data are crucial to provide the first cosmology-independent determination of the transition redshift at high statistical significance, measuring $z_{t}=0.4\pm0.1$, and to significantly disfavor the null hypothesis of no transition between decelerated and accelerated expansion at 99.9\% confidence level. This analysis highlights the wide potential of the cosmic chronometers approach: it permits to derive constraints on the expansion history of the Universe with results competitive with standard probes, and most importantly, being the estimates independent of the cosmological model, it can constrain cosmologies beyond -and including- the $\Lambda$CDM model

**Physics Forums - The Fusion of Science and Community**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Re acceleration of the Universe

Loading...

Similar Threads - acceleration Universe | Date |
---|---|

B Accelerated expansion of the universe | Feb 12, 2018 |

I Will the acceleration of the expansion of universe ever decrease? | Dec 6, 2017 |

I How does the speed of light affect expansion acceleration? | Nov 16, 2017 |

A Observational evidence for accelerating universe | Mar 15, 2017 |

B Is the universe expanding at an accelerating rate | Oct 31, 2016 |

**Physics Forums - The Fusion of Science and Community**