A complex form of mathematical symmetry linked to string theory has been glimpsed in the real world for the first time, in laboratory experiments on exotic crystals.
Mathematicians discovered a complex 248-dimensional symmetry called E8 in the late 1800s. The dimensions in the structure are not necessarily spatial, like the three dimensions we live in, but they correspond to mathematical degrees of freedom, where each dimension represents a different variable.
In the 1970s, the symmetrical form turned up in calculations related to string theory, a candidate for the "theory of everything" that might explain all the forces in the universe. But string theory still awaits experimental proof.
The structure is also the basis for another proposed theory of everything advanced
Now, physicists have detected the signature of E8 in a very different realm – experiments on super-chilled crystals.
Radu Coldea of the University of Oxford and his colleagues chilled a crystal made of cobalt and niobium to 0.04 °C above absolute zero. Atoms in the crystal are arranged in long, parallel chains. Because of a quantum property called spin, electrons attached to the atom chains act like tiny bar magnets, each of which can only point up or down.
Strange things occurred when the experimenters applied a powerful 5.5-Tesla magnetic field perpendicular to the direction of these electron "magnets". Patterns appeared spontaneously in the electron spins in the chains – in a simplified example with three electrons, the spins could read up-up-down or down-up-down, among other possibilities. Each distinct pattern has a different energy associated with it.
The ratio of these different energy levels showed that the electron spins were ordering themselves according to mathematical relationships in E8 symmetry.
Alexander Zamolodchikov, currently at Rutgers University in Piscataway, New Jersey, pointed out in 1989 that the theoretically predicted energies of such systems match expectations from E8 symmetry.
But the underlying reason why is still mysterious. Robert Konik of Brookhaven National Laboratory in Upton, New York, who was not involved in the experiment, says the fact that such a simple system – essentially consisting of one-dimensional chains of magnets – should display such complex symmetry is surprising.
"Just sort of looking at the system, you wouldn't necessarily expect it to occur," he told New Scientist. It is "remarkable" to see this rather exotic piece of mathematics appear in the real world, he adds.
Although E8 does show up in string theory calculations, observing the symmetry in magnetic crystal experiments does not provide any evidence for string theory itself, Konik says.
"The fact that you see this particular symmetry in this spin chain doesn't say anything about string theory per se," he says. "The existence of this symmetry in a sense is sort of separate from any [particular] physical phenomenon."
For the same reason, the experiments also provide no backing for Lisi's proposed theory of everything, which is based on E8, he adds.
Journal reference: Science (DOI: 10.1126/science.1180085)
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The Kazakh and Belarusian crew of a plane caught transporting arms from North Korea may face the death penalty, a Thai paper said on Wednesday, citing police.
The Il-76 cargo plane, carrying about 40 tons of weaponry, was seized after landing for refueling at Bangkok's Don Muang airport on December 12. Officials said the weapons included missiles and rocket-propelled grenades.
The paper quoted a senior police official as saying that the crew would be charged with the illegal possession of explosives, punishable by "from two years to death."
The plane's five crew members, one Belarus national and four Kazakhs, were taken to Bangkok's Klong Prem Central Prison after their arrest.
The Bangkok Post quoted investigators as saying the crew were planning to offload part of their cargo in Sri Lanka and the Middle East. However, the suspects reportedly refused to name the buyers or locations.
The plane's Belarusian commander earlier said that the plane had flown from Ukraine, and claimed that neither he nor the other crewmembers knew of the military nature of the cargo.
Mikhail Petukhov was earlier quoted by the Thai news agency TNA as saying the aircraft refueled in Azerbaijan, then in the United Arab Emirates, and then in Thailand while en route to Pyongyang. The plane's commander said the aircraft was scheduled to refuel in Thailand and Sri Lanka on its way back, after which the cargo was expected to be delivered to Ukraine.
Australia intends to introduce filters which will ban access to websites containing criminal content.
The banned sites will be selected by an independent classification body guided by complaints from the public, said Communications Minister Stephen Conroy.
A seven month trial in conjunction with internet service providers found the technology behind the filter to be 100% effective.
However, there has been opposition from some internet users.
Twitter users have been voicing their disapproval by adding the search tag "nocleanfeed" to their comments about the plans.
"Successful technology isn't necessarily successful policy," said Colin Jacobs, a spokesperson for Electronic Frontiers Australia, a non-profit organisation that campaigns for online freedom.
"We're yet to hear a sensible explanation of what this policy is for, who it will help, and why it is worth spending so much taxpayers' money on."
Mr Conroy said the filters included optional extras such as a ban on gambling sites which ISPs could choose to implement in exchange for a grant.
"Through a combination of additional resources for education and awareness, mandatory internet filtering of RC (refused classification)-rated content, and optional ISP-level filtering, we have a package that balances safety for families and the benefits of the digital revolution," he said.
The filter laws will be introduced in parliament in August 2010 and will take a year to implement.
'noble aims'
"Historical attempts to put filters in place have been effective up to a point," Dr Windsor Holden, principal analyst at Juniper Research, told BBC News.
The "noble aims" of the filter could be lost in its implementation, he warned.
"Clearly there is a need to protect younger and more vulnerable users of the net, but one concern is that it won't just be illegal websites that will be blocked," he added.
"You have to take extreme caution in how these things are rolled out and the uses to which they're put."
(From BBC)
