* Astronomy

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RE: Dark matter

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Title: Dark matter and dark gauge fields
Authors: D. V. Ahluwalia, Cheng-Yang Lee, D. Schritt, T. F. Watson (University of Canterbury, New Zealand)

Following the unexpected theoretical discovery of a mass dimension one fermionic quantum field of spin one half, we now present first results on two _local_ versions. The Dirac and Majorana fields of the standard model of particle physics are supplemented by their natural counterparts in the dark matter sector. The possibility that a mass dimension transmuting symmetry may underlie a new standard model of particle physics is briefly suggested.

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The Mystery of the Missing Mass

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Title: Dark Matter Candidates: A Ten-Point Test
Authors: Marco Taoso, Gianfranco Bertone, Antonio Masiero

An extraordinarily rich zoo of non-baryonic Dark Matter candidates has been proposed over the last three decades. Here we present a 10-point test that a new particle has to pass, in order to be considered a viable DM candidate:
I.) Does it match the appropriate relic density?
II.) Is it cold?
III.) Is it neutral?
IV.) Is it consistent with BBN?
V.) Does it leave stellar evolution unchanged?
VI.) Is it compatible with constraints on self-interactions?
VII.) Is it consistent with direct DM searches?
VIII.) Is it compatible with gamma-ray constraints?
IX.) Is it compatible with other astrophysical bounds?
X.) Can it be probed experimentally?

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Supercomputer cosmological simulations prove that indeed, this problem can be resolved. Researchers modelled the formation of a dwarf galaxy to illustrate the very violent processes galaxies suffer at their births, a process in which dense gas clouds in the galaxy form massive stars, which, at the ends of their lives, blow up as supernovae.

"These huge explosions push the interstellar gas clouds back and forth in the centre of the galaxy. Our high-resolution model did extremely accurate simulations, showing that this 'sloshing' effect, similar to water in a bathtub, kicks most of the dark matter out of the centre of the galaxy" - Sergey Mashchenko, research associate in the Department of Physics and Astronomy at McMaster University.

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Blobrana · L

Researchers at McMaster University (Hamilton, Ontario) now claim to have located the missing dark matter in a halo around galaxies. Using a supercomputer to create the most accurate model yet of galaxy formation, the researchers claim the missing matter was there all along, just not where researchers expected it to be.
The key to finding the missing matter was adding more detail to the models used to explain the violent formation of new galaxies, in particular the relationship between interstellar gas and dark matter. The current model dubbed, "cold dark matter cosmology," is correct, but needed a more detailed simulation, according to Sergey Mashchenko, a research associate in the Department of Physics & Astronomy at McMaster University. He said the problem is in the model's prediction that much more dark matter should be concentrated in the centre of distant galaxies than is observed.

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Three quarters of our universe is made up of some weird, gravitationally repulsive substance that was only discovered ten years ago dark energy. This month in Physics World, Eric Linder and Saul Perlmutter, both at the University of California at Berkeley, reveal how little we know about dark energy and describe what advances in our knowledge of dark energy we can expect in the coming decade from a series of planned space missions.

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Title: Dark matter's X-files
Authors: Alexander Kusenko
(Version v2)

Sterile neutrinos with keV masses can constitute all or part of the cosmological dark matter. The electroweak-singlet fermions, which are usually introduced to explain the masses of active neutrinos, need not be heavier than the electroweak scale; if one of them has a keV-scale mass, it can be the dark-matter particle, and it can also explain the observed pulsar kicks. The relic sterile neutrinos could be produced by several different mechanisms. If they originate primarily from the Higgs decays at temperatures of the order of 100 GeV, the resulting dark matter is much ``colder'' than the warm dark matter produced in neutrino oscillations. The signature of this form of dark matter is the spectral line from the two-body decay, which can be detected by the X-ray telescopes. The same X-rays can have other observable manifestations, in particular, though their effects on the formation of the first stars.

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Title: Direct Detection of Cold Dark Matter
Authors: Laura Baudis

We know from cosmological and astrophysical observations that more than 80% of the matter density in the Universe is non-luminous, or dark. This non-baryonic dark matter could be composed of neutral, heavy particles, which were non-relativistic, or 'cold', when they decoupled from ordinary matter. I will review the direct detection methods of these hypothetical particles via their interactions with nuclei in ultra-low background, deep underground experiments. The emphasis is on most recent results and on the status of near future projects.

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Title: Coloured dark matter
Authors: Vladimir Dzhunushaliev

The idea is presented that a classical non-Abelian gauge field can be considered as a dark matter candidate. It is shown that Yang-Mills equations have solutions with such distribution of the mass density that it is possible to describe a rotational curve of spiral galaxies. The conditions necessary for such consideration are considered.

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