* Astronomy

Blobrana · L

RE: Dark matter

Blobrana · L

Physicists remain sceptical about claims made last week that dark matter has been detected at a laboratory in Italy, insisting that the data need to be backed up by further experiments. The Italian team, which made the claims at a meeting in Venice, says it has strong evidence that dark matter takes the form of weakly interacting particles.
Read more

Blobrana · L

An Italian team on Wednesday renewed its claim to have discovered evidence for the existence of dark matter, the invisible material that makes up the bulk of the universe.
Critics say the University of Rome team has answered some of the objections to their earlier findings but not all of them, leaving their claims still a subject of great controversy.

Read more

Blobrana · L

For the second time in eight years, an Italian research collaboration is claiming to see a clear signature of dark matter the massive, rarely interacting particles that are thought to fill the universe.
Rita Bernabei, a physicist at the University of Rome Tor Vergata and the National Institute for Nuclear Physics, presented the results at a conference on Wednesday in Venice. They confirm a seasonal variation in dark matter detections, which, the researchers claim, is generated by Earth passing through the halo of dark matter that envelops the Milky Way.

Read more

Blobrana · L

Title: Cosmological constraint on unparticle dark matter
Authors: Yan Gong, Xuelei Chen

In unparticle dark matter (unmatter) model, the equation of state of the unmatter is given by p=
ho/(2d_U+1), where d_U is the scaling factor. Unmatter of such equation of state has significant impacts on the expansion history of the Universe. We use the type Ia supernovae (SNIa) and the shift parameter of the cosmic microwave background (CMB) to put constraint on such unmatter models. We find that if only the SNIa data is used, the constraint is weak, but with the CMB shift parameter data added strong constraints can be obtained. For the $\Lambda$UDM model, in which unmatter is the sole dark matter, we find that d_U > 30 at 95% C.L., rendering it practically indistinguishable from cold dark matter. For the \Lambda CUDM model, in which unmatter co-exists with cold dark matter, we found that the unmatter can at most make up a few percent of the total cosmic density if d_U<10.

Read more (52kb, PDF)

Blobrana · L

First 3D map of the Universe's Dark Matter scaffolding.

Click to Play | View Details

Blobrana · L

Two mysterious streams of radiation are emanating from the heart of our galaxy, and dark matter could explain them both. The question is: what kind of dark matter?
In 2003, data from the Wilkinson Microwave Anisotropy Probe (WMAP) revealed a "haze" of unexplained microwave radiation at the centre of the Milky Way. A year earlier, the satellite INTEGRAL found an unusual stream of gamma rays coming from the same region.
Various theories have attempted to explain these anomalies. Now two groups have come up with different explanations of how dark matter, the stuff thought to make up most of the universe's mass, could be behind them both.

Read more

Blobrana · L

Physicists have again returned empty-handed from a search for the 'dark matter' that is thought to fill the cosmos. But the latest null result hasn't dimmed their enthusiasm or their plans for a new generation of detectors.
Since the 1970s, theorists have predicted the existence of massive particles that rarely, if ever, interact with normal matter. This dark matter is believed to be responsible for slowing the rotation of galaxies and makes up about 85% of matter in the Universe. Physicists have devised a host of experiments to find dark matter, but to date, nobody has been able to detect it directly.

Read more

Blobrana · L

Waiting for dark matter in a mine, with the world's best detectors
A half-mile down in an old iron ore mine in Minnesota, incredibly sensitive detectors have been waiting for a particle of dark matter, an invisible substance that may form the skeleton of galaxies, to make itself known.
A consortium of research scientists, including Stanford physicist Blas Cabrera, anticipated the detection of a predicted-but-undiscovered dark particle known as a weakly interacting massive particle, or WIMP. The hope was that several WIMPs would travel through space and a half-mile of Earth to plunk themselves into the nuclei of germanium atoms in the detectors, each collision creating a vibration and a tiny puff of heat that would signal the WIMP's existence.
WIMPs are leading candidates for dark matter, the unseen stuff that accounts for 85 percent of the entire mass of the universe. Billions of WIMPs may be passing unnoticed through the bodies of humans every second.
The Cryogenic Dark Matter Search was somewhat like waiting for a phone call from the early moments of the universe, when dark matter was formed. But in this case, the phone never rang. The detectors in the clean room at the bottom of the mine, cooled within a whisper of absolute zero, recorded no WIMPS.

Read more

Blobrana · L

UCLA's Dark Matter 2008 meeting was held Wednesday through Friday, Feb. 20-22, 2008 at the Marriott Hotel in Marina del Rey, California, just a few miles from the UCLA campus. If you attended or gave a talk at the meeting, we're most grateful for your participation.

Read more

First results from the 5-Tower WIMP Search presented at DM 2008.

Read more (450kb, PDF)