New model postulates existence of shape-shifting 'chameleon' particle

Published: Saturday, May 30, 2009, 11:45 [IST]

London, May 30 (ANI): Cosmologists have come up with a model postulating the existence of a 'chameleon' particle, which would change its mass depending on its environment, and might be used to explain the accelerating expansion of the Universe.

According to a report in Nature News, a new research has claimed to have spotted signs of this elusive particle, whose existence was first postulated in 2003 to explain the accelerating expansion of the Universe, which has been attributed to some unknown 'dark energy'.

The changing mass of a chameleon particle would modify the range at which its force can act, thus possibly explaining why whatever causes the Universe's acceleration hasn't been detected on Earth.

On Earth, the chameleon would be too heavy to create any noticeable force, but in the tracts of empty space, its effect would be huge.

In theory, photons that travel through magnetic fields can turn into chameleons, reducing the amount of light that reaches Earth from distant sources.

The amount of dimming depends on the light's frequency.

By comparing light emitted across a range of frequencies from the luminous centres of 77 active galaxies, Douglas Shaw at Queen Mary University of London and his colleagues have found what they call "good evidence" that some photons have gone missing in transit.

"It's absolutely an interesting way of looking for (exotic) particles, and the results are certainly intriguing," said Frank Wilczek, a particle physicist at the Massachusetts Institute of Technology (MIT) in Cambridge.

By themselves, the observations of dimmed light by Shaw and his colleagues can't distinguish between models that rely on chameleons and models in which photons turn into other 'axion-like' particles.

Either "would be an interesting discovery," said Shaw.

However, only the chameleon model predicts that the photons' polarizations should be aligned with the magnetic fields they traversed.

So far, the team has studied data on light from three stars in the Milky Way galaxy and in each case found the required polarization.

As part of the research into the Chameleon particle, Amanda Weltman at the University of Cambridge, UK, along with the GammeV group at the Fermi National Accelerator Laboratory in Batavia, Illinois, is attempting to shine laser light through a tube with windows at either end that is immersed in a magnetic field.

The chameleon model predicts that some photons should convert to chameleon particles. When the laser is switched off, the chameleons should slowly turn back to photons and create a faint afterglow.

The experiment has completed its first phase without seeing any signs of a chameleon.

However, the team has not yet searched for the chameleons with parameters that match those possibly sighted by Shaw's team.

The GammeV group is now preparing to test for chameleons in that "interesting range," said Weltman. (ANI)

 

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