Dilaton could affect abundance of dark matter particles

Oct 02, 2007

The amount of dark matter left over from the early universe may be less than previously believed. Research published in the open access journal PMC Physics A shows that the "relic abundance" of stable dark matter particles such as the neutralino may be reduced as compared to standard cosmology theories due to the effects of the "dilaton"', a particle with zero spin in the gravitational sector of strings.

Nikolaos Mavromatos of King's College London and colleagues in Athens and Texas obtained their result by studying a special "off-shell" time-dependent term (due to the dilaton) in the Boltzmann equation that describes the evolution of hot matter density as the Universe cooled down. "The formalism that this work used was developed in partial collaboration with John Ellis of CERN and Vasiliki Mitsou of IFIC, Valencia, and is a version of 'non-critical string theory'", said Mavromatos.

All the matter and radiation in the universe is thought to have been created by the Big Bang. The radiation stopped interacting with the matter some 400,000 years later -- when the universe had cooled down enough for electrons and protons to form hydrogen atoms. The density of dark matter particles such as the neutralino (a dark matter candidate favoured by many of the current "supersymmetric" approaches to particle physics) was therefore "frozen" at this time -- the so-called relic abundance.

The researchers say that the neutralino relic abundance is reduced by as much as a factor of ten in their models due to dilaton effects, as compared to standard cosmology theories. In contrast, the relic abundance of "ordinary" matter, which makes up stars, planets and humans, is only slightly diluted. The new model also agrees with the established model of nucleosynthesis (the way in which light elements were created during the first few minutes of the universe).

The new result is important for both cosmology and particle physics, says Mavromatos. Indeed, such non-equilibrium string cosmology models are on an equal footing with the standard cosmological cold dark matter model (called Lambda-CDM). For particle physics, the findings are relevant for future supersymmetric searches in colliders such as the Large Hadron Collider, due to come on-line at CERN early next year. The supersymmetric theory, one of the facets of string theory, postulates that every particle has a massive "shadow" particle partner.

Dark matter is fundamentally different from normal, luminous matter and is invisible to modern telescopes, giving off no light or heat. It appears to interact with normal matter only through gravity. Most cosmologists believe dark matter, currently thought to make up 95% of all matter in the universe, plays a crucial role in how large structures such as galaxies emerged after the Big Bang.

Citation: Dilaton and off-shell (non-critical string) effects in Boltzmann equation for species abundances, A.B. Lahanas et al. PMC Physics A (in press)
www.physmathcentral.com/pmcphysa/

Source: BioMed Central

Explore further: First in-situ images of void collapse in explosives

add to favorites email to friend print save as pdf

Related Stories

Results from CERN presented at ICHEP

Jul 08, 2014

Speaking at press conference held during the 37th International Conference on High Energy Physics, ICHEP, in Valencia, Spain this morning CERN Director General Rolf Heuer gave a resume of results from CERN that are being ...

Reinterpreting dark matter

Jul 02, 2014

Tom Broadhurst, an Ikerbasque researcher at the University of the Basque Country (UPV/EHU), has participated alongside scientists of the National Taiwan University in a piece of research that explores cold ...

Higgs quest deepens into realm of 'New Physics'

Jul 02, 2014

Two years after making history by unearthing the Higgs boson, the particle that confers mass, physicists are broadening their probe into its identity, hoping this will also solve other great cosmic mysteries.

Recommended for you

First in-situ images of void collapse in explosives

6 hours ago

While creating the first-ever images of explosives using an x-ray free electron laser in California, Los Alamos researchers and collaborators demonstrated a crucial diagnostic for studying how voids affect ...

New approach to form non-equilibrium structures

Jul 24, 2014

Although most natural and synthetic processes prefer to settle into equilibrium—a state of unchanging balance without potential or energy—it is within the realm of non-equilibrium conditions where new possibilities lie. ...

Nike krypton laser achieves spot in Guinness World Records

Jul 24, 2014

A set of experiments conducted on the Nike krypton fluoride (KrF) laser at the U.S. Naval Research Laboratory (NRL) nearly five years ago has, at long last, earned the coveted Guinness World Records title for achieving "Highest ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

LearmSceince
not rated yet Oct 02, 2007
LOL!
It's incredible that people cling to ideas even after evidence is in.
JohnSawyer
not rated yet Oct 03, 2007
LearmSceince:

Your statement would be better received if you learned to spell the words "learn" and "science". :)