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: NIST seeks calibration methodologies for determining the accuracy of micro-flows

Related Stories

SLAC gears up for dark matter hunt with LUX-ZEPLIN

May 21, 2015

Researchers have come a step closer to building one of the world's best dark matter detectors: The U.S. Department of Energy (DOE) recently signed off on the conceptual design of the proposed LUX-ZEPLIN (LZ) ...

Fresh theories about dark matter

May 15, 2015

Tom Broadhurst, the Ikerbasque researcher in the Department of Theoretical Physics of the UPV/EHU, together with Sandor Molnar of the National Taiwan University and visiting Ikerbasque researcher at the UPV/EHU ...

What shape is the universe?

May 12, 2015

The universe. It's the only home we've ever known. Thanks to its intrinsic physical laws, the known constants of nature, and the heavy-metal-spewing fireballs known as supernovae we are little tiny beings ...

Recommended for you

Researchers prove magnetism can control heat, sound

7 hours ago

Phonons—the elemental particles that transmit both heat and sound—have magnetic properties, according to a landmark study supported by Ohio Supercomputer Center (OSC) services and recently published by ...

How researchers listen for gravitational waves

16 hours ago

A century ago, Albert Einstein postulated the existence of gravitational waves in his General Theory of Relativity. But until now, these distortions of space-time have remained stubbornly hidden from direct ...

What's fair?: New theory on income inequality

May 27, 2015

The increasing inequality in income and wealth in recent years, together with excessive pay packages of CEOs in the U.S. and abroad, is of growing concern, especially to policy makers. Income inequality was ...

Scientists one step closer to mimicking gamma-ray bursts

May 27, 2015

Using ever more energetic lasers, Lawrence Livermore researchers have produced a record high number of electron-positron pairs, opening exciting opportunities to study extreme astrophysical processes, such ...

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". :)

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.