* Astronomy

Members Login
Post Info
TOPIC: Dark matter


L

Posts: 131433
Date:
RE: Dark matter
Permalink  
 


Title: Decaying Hidden Gauge Boson and the PAMELA and ATIC/PPB-BETS Anomalies
Authors: Chuan-Ren Chen, Fuminobu Takahashi, T. T. Yanagida
(Version v2)

We show that the PAMELA anomaly in the positron fraction as well as the ATIC/PPB-BETS excesses in the e^- + e^+ flux are simultaneously explained in our scenario that a hidden U(1)H gauge boson constitutes dark matter of the Universe and decays into the standard-model particles through a kinetic mixing with an U(1)B-L gauge boson. Interestingly, the B-L charge assignment suppresses an antiproton flux in consistent with the PAMELA and BESS experiments, while the hierarchy between the B-L symmetry breaking scale and the weak scale naturally leads to the right lifetime of O(10^26) seconds.

Read more (80kb, PDF)

__________________


L

Posts: 131433
Date:
Permalink  
 

Scientists who launched a balloon-borne instrument over Antarctica have discovered a large clump of mysterious dark matter only 3,000 light-years from Earth.
The NASA-funded device was carried to an altitude of about 24 miles, using a helium-filled balloon as big as the interior of a large sports stadium.
It detected a source of high energy cosmic rays within 18,000 trillion miles - nearby in space terms - to our solar system.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

New Theories May Shed Light on Dark Matter
If current theories prove correct, ordinary matterall that we can see, smell and touchmakes up just a fraction, maybe 4 percent, of the universe. The rest comes from the so-called dark sector: dark matter and dark energy, a mysterious and pervasive energy that is suspected of speeding the universe's expansion. Dark matter, so known because it refuses to emit or interact with light in a way that we can see, is nearly six times as prevalent as ordinary matter. But, for all its ubiquity, it is often tagged as being fairly bland, a sort of galactic deadweight that only reveals itself through its gravitational pull.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Giant simulation could solve mystery of "dark matter"
The search for a mysterious substance which makes up most of the Universe could soon be at an end, according to new research.
Dark matter is believed to account for 85 per cent of the Universes mass but has remained invisible to telescopes since scientists inferred its existence from its gravitational effects more than 75 years ago.
Now the international Virgo Consortium, a team of scientists including cosmologists at Durham University, has used a massive computer simulation showing the evolution of a galaxy like the Milky Way to see gamma-rays given off by dark matter.
They say their findings, published in the prestigious scientific journal Nature (Thursday, November 6), could help NASAs Fermi Telescope in its search for the dark matter and open a new chapter in our understanding of the Universe.
The Virgo Consortium looked at dark matter halos structures surrounding galaxies which contain a trillion times the mass of the Sun.
Their simulations called The Aquarius Project - showed how the galaxys halo grew through a series of violent collisions and mergers between much smaller clumps of dark matter that emerged from the Big Bang.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Title: Can Dark Matter Decay in Dark Energy?
Authors: S. H. Pereira, J. F. Jesus

We analyse the interaction between Dark Energy and Dark Matter from a thermodynamical perspective. By assuming they have different temperatures, we study the possibility of occurring a decay from Dark Matter into Dark Energy, characterised by a negative parameter Q. We find that, if at least one of the fluids has non vanishing chemical potential, for instance \mu_x<0 and \mu_{dm}=0 or \mu_x=0 and \mu_{dm}>0, the decay is possible, where \mu_x and \mu_{dm} are the chemical potentials of Dark Energy and Dark Matter, respectively. Using recent cosmological data, we find that, for a fairly general interaction, the Dark Matter decay is favoured with a probability of ~ 87% over the Dark Energy decay.

Read more (105kb, PDF)

__________________


L

Posts: 131433
Date:
Permalink  
 

Israeli astronomers cast new light on dark matter
No one knows how the universe is structured but physicists and astronomers alike believe that the thing called "dark matter" plays a central role. In physics and astronomy, dark matter and its companion dark energy, account for most of the universe's mass. Its presence is implied in the rotation of the galaxies, their orbits in clusters and temperature distribution between them, and the evidence suggests that there is far more matter that does not interact with the electromagnetic force, meaning dark matter, than that which does. In other words, you can feel it, but you can't see it. At least until now.


Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Dark matter may shine with invisible 'dark light'
Mysterious dark matter could be shining with its own private kind of light. This "dark radiation" would be invisible to us, but could still have visible effects.
Astronomers usually assume that dark matter particles barely interact with each other.
Lotty Ackerman and colleagues at Caltech in Pasadena decided to test this assumption by supposing there is a force between dark matter particles that behaves in the same way as the electromagnetic force. That would imply a new form of radiation that is only accessible to dark matter.
Their calculations showed that it could have as much as 1% of the strength of the electromagnetic force and not conflict with any observations.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Galaxy survey casts doubt on cold dark matter
The physical properties of most galaxies in the universe can be explained in terms of just a single parameter. Thats the controversial conclusion of a team of astronomers in the UK and US, who have studied some 200 galaxies using radio and optical telescopes. The team believes that their discovery could mean that cold dark matter an invisible substance that some astrophysicists have invoked to explain the formation and motion of galaxies does not exist. However, not all astrophysicists are convinced.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Dark matter the mysterious stuff that doesnt emit light, and doesnt appear to interact with normal matter much if at all outmasses normal matter in the Universe by a comfortable amount. We know its out there, and we even have a decent grasp of what its doing, but, maddeningly, we dont know what it is.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Israeli astronomers find a dark matter filament close to the Milky Way

Read more (Doc) (13 Aug 2008)

New observations from the 40-inch Wise Observatory telescope in Israel has revealed more than a dozen galaxies lined up along a bridge of dark matter inside a region of nearly empty space, which is being called as 'bridge to nowhere' by astronomers.
According to a report in New Scientist, this 'bridge to nowhere' could shed light on how small galaxies formed in the early universe.

Read more

__________________
«First  <  121 22 23 24 2543  >  Last»  | Page of 43  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard