Re acceleration of the Universe

In summary, researchers Michele Moresco, Lucia Pozzetti, Andrea Cimatti, Raul Jimenez, Claudia Maraston, Licia Verde, Daniel Thomas, Annalisa Citro, Rita Tojeiro, and David Wilkinson have submitted a paper to the Journal of Cosmology and Astroparticle Physics (JCAP) detailing a 6% measurement of the Hubble parameter at a redshift of approximately 0.45. This measurement, based on data from the Baryon Oscillation Spectroscopic Survey (BOSS), provides evidence for the epoch of cosmic re-acceleration and is independent of assumptions on cosmological models. The data also supports the concept of a transition epoch from decelerated to accelerated
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wolram
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Just thought i would flag this up.

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 http://www.physics-astronomy.unibo.it/en/research/areas/astrophysics/cosmology-with-cosmic-chronometers
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
 
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Yes, I found that paper interesting. Particularly the emphasis on being able 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". (emphasis mine)

Notice their statement:
Once combined, these measurements yield a 6% accuracy constraint of H(z=0.4293)=91.8[itex]\pm[/itex]5.3 km/s/Mpc.

If you plot this value on my diagram of the 'H(z) v z' expansion history of the universe,
https://www.physicsforums.com/threa...n-from-type-ia-sne.817386/page-3#post-5137199, the error bars straddle the R =ct solid line but just miss the [itex]\Lambda[/itex]CDM red dashed line.

Note: those lines were based on a h0 = 0.67, the 'R = ct' plot would be exactly over the 'H(z=0.4293)=91.8[itex]\pm[/itex]5.3 km/s/Mpc' data point, if h0 was lower, say ~ 0.65.

upload_2015-7-14_14-37-37-png.85944.png


Just a thought,
Garth
 
Last edited:

1. What is the concept of "Re acceleration of the Universe"?

The "Re acceleration of the Universe" refers to the observed phenomenon where the expansion of the universe, which was previously thought to be slowing down, is now accelerating. This phenomenon was first discovered in the late 1990s through observations of distant supernovae.

2. What is causing the "Re acceleration of the Universe"?

The cause of the "Re acceleration of the Universe" is still not fully understood, but it is believed to be driven by a mysterious force called dark energy. Dark energy is thought to make up about 70% of the total energy in the universe and its repulsive nature is causing the expansion of the universe to accelerate.

3. How does the "Re acceleration of the Universe" impact our understanding of the universe?

The "Re acceleration of the Universe" challenges our current understanding of the universe and its evolution. It has prompted scientists to revise their theories and models to account for the presence and behavior of dark energy. It also raises questions about the fate of the universe and whether it will continue to expand forever or eventually collapse.

4. Are there any experiments or observations being conducted to further study the "Re acceleration of the Universe"?

Yes, there are ongoing experiments and observations being conducted to better understand the "Re acceleration of the Universe". These include studies of distant supernovae, measurements of the cosmic microwave background radiation, and experiments using large-scale structures in the universe. These efforts aim to provide more data and evidence to help explain the phenomenon of dark energy and its role in the acceleration of the universe.

5. Is there a possibility that the "Re acceleration of the Universe" could reverse in the future?

There is currently no evidence or theoretical basis to suggest that the "Re acceleration of the Universe" will reverse in the future. The expansion of the universe is expected to continue to accelerate due to the presence of dark energy. However, our understanding of dark energy and its behavior is still evolving, so it is possible that new discoveries may change our understanding of the future of the universe.

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