Featured Research

from universities, journals, and other organizations

Toward A Unified Description Of Dark Energy And Dark Matter

Date:
April 9, 2007
Source:
Observatory of Paris
Summary:
From various independent observations, cosmologists have established that ordinary matter, made of protons and neutrons, accounts for only 4% of the total energy content of the Universe. The remaining 96% is made of puzzling ingredients Dark Matter and Dark Energy. Researchers at the Laboratory Universe and Theories from the Observatory of Paris and the Belgian Fonds de la Recherche Scientifique have recently suggested the Abnormally Weighting Energy (AWE) Hypothesis to describe the dark side of the Universe as a revolutionary aspect of gravitational physics.

Likelihood of various cosmological parameters for the AWE dark matter model (from SNLS data). The maximum likelihood is obtained for an age of about 16 billion years (against 13 billions for the concordance model), and corresponds to a model with ©m=0.05, ©AWE=0.14 et ©DE=0.76. This result allows identifying from supernovae alone, and a posteriori, ordinary matter to baryons, AWE to cold dark matter and dark energy to terms resulting from the variation of the gravitational strength.
Credit: Image courtesy of Observatory of Paris

From various independent observations, cosmologists have established that ordinary matter, made of protons and neutrons, accounts for only 4% of the total energy content of the Universe. The remaining 96% is made of puzzling ingredients Dark Matter and Dark Energy. Researchers at the Laboratory Universe and Theories from the Observatory of Paris and the Belgian Fonds de la Recherche Scientifique have recently suggested the Abnormally Weighting Energy (AWE) Hypothesis to describe the dark side of the Universe as a revolutionary aspect of gravitational physics.

Related Articles


In the past decade, cosmology has entered an era of high precision, and in the future it may become a unique laboratory to test theories of fundamental physics, from gravitation laws to microphysics. Amongst the many questions raised by this science in turmoil, one of the most important is indisputably the one of the energy content of the Universe. Knowing what the Universe is precisely made of, and in which proportions, allows not only to determine its age but also to reconstruct the history, to predict its past and future. In fact in the attempt to solve this question cosmologists have made two of the most promising discoveries in the history of modern physics: the existence of dark matter and dark energy.

While dark matter is unavoidable to explain at the same time the angular fluctuations of the cosmic microwave background and the formation and the properties of galaxies, dark energy has been originally invoked to account for the observed recent acceleration of the cosmic expansion. The so-called concordance model of cosmology assumes that this dark energy is in fact the cosmological constant once introduced by Einstein himself as an attempt to incorporate Mach’s principle within general relativity.

However, the usual interpretation of the cosmological constant in terms of quantum vacuum fluctuations is in disagreement with observed value by a few dozens orders of magnitude! Furthermore, as the vacuum energy is assumed constant everywhere at all times, it is hard to explain how it became dominant only a few billion years ago. This would mean that we live in a very particular, and even privileged, epoch of cosmic history… Is this an extraordinary coincidence? Yet this anthropic consideration is quite deceiving for scientists.

To overcome these difficulties, the authors, Jean-Michel Alimi and Andrι Fόzfa, have proposed the AWE Hypothesis (« Abnormally Weighting Energy ») in which the dark sector of cosmic matter violates the equivalence principle on cosmological scales. This principle, as well introduced by Einstein, assumes that all kinds of energies produce and undergo the same form of gravity. This principle is extremely well tested (to a part out of a thousand billion) in laboratories, i.e. at local scales, in contrast what would happen if violation of the equivalence principle would be scale-dependant. In other words, what would happen if the equivalence principle was rigorously verified at local scales, where dark matter and dark energy are present in tiny amount, but is violated on cosmological scales where dark matter and dark energy are dominant?

The authors have precisely shown that this could naturally happen if some particles, those of dark matter for instance, do not couple to gravitation in the same way as ordinary matter. These particles would therefore see gravitational fields with a gravitational strength different from ordinary matter. The authors have answered these questions by showing how at a given scale the gravitational strength becomes dependent on dark matter concentration…

If the amount of dark matter at sub-galactic scales is negligible, so is the amplitude of this effect. This is not the case on cosmological scales where dark matter dominates the energy content of the Universe. The team has shown that over such cosmic distances, ordinary matter has experienced a stronger cosmic expansion, as its own gravitational coupling strength has been adapting to the dark matter domination. This change in the matter gravitational coupling results in an accelerating cosmic expansion until equilibrium is reached such that the gravitational coupling on cosmological scales stabilizes at a value which differs from the one measured in our Solar system.

The resulting dark energy mechanism exhibits key features which appear very promising. (i) First, it does not require the existence of negative pressures such as in the case of the cosmological constant or other proposed models like quintessence. (ii) It allows explaining naturally the cosmic coincidence as result of the stabilization mechanism of the gravitational constant during the matter-dominated era. (iii) It fairly accounts for the Hubble diagram of type Ia supernovae by predicting independently the amount of ordinary matter and dark matter as obtained by the detailed analysis of cosmic microwave background anisotropies. This suggests an explanation to the remarkable adequacy of the concordance model while predicting an age of the Universe which is compatible with existing observations. Finally, (iv) in the future this mechanism leads to a decelerated cosmic expansion described by the well-known Einstein-de Sitter cosmological model. Most important is the AWE hypothesis allows reducing dark energy as a new property of gravitation: the anomalous gravity of dark matter.


Story Source:

The above story is based on materials provided by Observatory of Paris. Note: Materials may be edited for content and length.


Cite This Page:

Observatory of Paris. "Toward A Unified Description Of Dark Energy And Dark Matter." ScienceDaily. ScienceDaily, 9 April 2007. <www.sciencedaily.com/releases/2007/04/070407175959.htm>.
Observatory of Paris. (2007, April 9). Toward A Unified Description Of Dark Energy And Dark Matter. ScienceDaily. Retrieved January 28, 2015 from www.sciencedaily.com/releases/2007/04/070407175959.htm
Observatory of Paris. "Toward A Unified Description Of Dark Energy And Dark Matter." ScienceDaily. www.sciencedaily.com/releases/2007/04/070407175959.htm (accessed January 28, 2015).

Share This


More From ScienceDaily



More Space & Time News

Wednesday, January 28, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Asteroid's Moon Spotted During Earth Flyby

Asteroid's Moon Spotted During Earth Flyby

Rumble (Jan. 27, 2015) — Scientists working with NASA&apos;s Deep Space Network antenna at Goldstone, California discovered an unexpected moon while observing asteroid 2004 BL86 during its recent flyby past Earth. Credit to &apos;NASA JPL&apos;. Video provided by Rumble
Powered by NewsLook.com
Water Fleas Prepare for Space Voyage

Water Fleas Prepare for Space Voyage

Reuters - Innovations Video Online (Jan. 26, 2015) — Scientists are preparing a group of water fleas for a unique voyage into space. The aquatic crustaceans, known as Daphnia, can be used as a miniature model for biomedical research, and their reproductive and swimming behaviour will be tested for signs of stress while on board the International Space Station. Jim Drury went to meet the team. Video provided by Reuters
Powered by NewsLook.com
Mars Rover Opportunity Celebrates 11-Year Anniversary

Mars Rover Opportunity Celebrates 11-Year Anniversary

Rumble (Jan. 26, 2015) — Eleven years ago NASA&apos;s Opportunity rover touched down on Mars for what was only supposed to be a 90-day mission. Since then it has traveled 25.9 miles (41.7 kilometers), further than any other off-Earth surface vehicle has ever driven. Credit to &apos;NASA&apos;. Video provided by Rumble
Powered by NewsLook.com
NASA's On Course To Take Pluto's Best Photo Ever

NASA's On Course To Take Pluto's Best Photo Ever

Newsy (Jan. 25, 2015) — NASA&apos;s New Horizons probe is en route to snap a picture of Pluto this summer, but making sure it doesn&apos;t miss its one chance to do so starts now. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins