Posts Tagged ‘string theory’
LHC Reports Failure To Create Black Holes, a Setback For String Theory
At least not yet
Researchers working on the Compact Muon Solenoid team have been crunching numbers to test a form of string theory that calls for the creation and instant evaporation of miniature black holes. They report that the telltale signs of these black holes are disappointingly absent, however.
String theory is the most widely accepted attempt to unify the two major fields of physics, quantum mechanics and relativity. It holds that electrons and quarks are not objects, but one-dimensional strings whose oscillation gives them their observed qualities. It also says the universe has about a dozen dimensions, rather than the usual four (length, width, height and time).
In one version of string theory, if these dimensions exist, gravitons — hypothetical particles that transmit gravity — would leak into them, explaining why gravity is so much weaker than the other forces, as . It’s not really weaker, it just seems weaker, because some of its particles are in another dimension we can’t see. Happily, it takes a lot less energy to test this than it would to actually unify all the forces, and it just so happens it’s is in the energy range that the LHC, the world’s most powerful particle accelerator, is capable of testing.
If this is all true, particles that collided at energies beyond this graviton-leaking energy cutoff would get so close together that gravity would take over, and they would merge to form a tiny black hole. The black holes would instantly decay, so there would be no danger of Earth being swallowed whole, and the decay would be visible as jets of particles. But the researchers have so far seen no jets.
This doesn’t disprove string theory — it just proves that mini black holes can’t be produced at energies between 3.5 and 4.5 trillion electron volts. But they could still theoretically be produced at higher energies, so when the LHC fully fires up in 2013, string theorists will be holding their breath.
Meanwhile, the tests show the LHC is performing supremely well, so physicists aim to keep it running through 2012. This means they might be able to find the elusive Higgs boson sooner than expected.
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Brilliant 10: Raul Rabadan, the Outbreak Sleuth
His skills as a string theorist helped him trace swine flu back to swine and revealed the source of a mysterious salmon plague
Take swine flu. When the frightening influenza strain H1N1 began sweeping the nation last year, Rabadan and his team at Columbia University’s Center for Computational Biology designed algorithms to search massive data sets for clues as to its origin. Whereas most other flu experts limited their search for genetic mutations to the past few months, Rabadan compared H1N1 with the DNA of tens of thousands of influenza samples dating back to 1918. In this way he was able to confirm swine flu’s origin in pigs, not birds or humans, as other scientists had theorized. More important, his work revealed swine to be a dangerous yet underestimated breeding ground for new influenza strains. H1N1, the data showed, had been circulating in swine for 10 years. As a result, public health officials are now tightening surveillance for disease among pigs.
Rabadan’s computational methods are in demand. In May he was tapped by an international team of researchers to help pinpoint the source of a mysterious disease that was killing off farmed Atlantic salmon in Norway. Using a mathematical tool he pioneered called Frequency Analysis of Sequence Data, he and the other researchers looked for RNA sequences in heart and kidney samples taken from the fish, eventually finding evidence of a previously unknown virus. The research could lead to a vaccine to prevent future outbreaks and preserve an important food source. “There are so many unknown viruses out there,” Rabadan says. “It’s fascinating.”
A native of Spain and a former theoretical physicist at the European Organization for Nuclear Research in Switzerland, Rabadan has no regrets about his career change. He enjoyed physics, he says, but takes more satisfaction in the practical applications of computational biology. “I love physics, I love solving problems, but I think biology can have a bigger, more immediate impact.”
Researchers Devise the First Experimental Test of Controversial, Confusing String Theory
String theory elegantly reconciles the otherwise competing rules of quantum mechanics and general relativity. It’s the most widely accepted unified field theory, but it remains controversial. It basically posits that electrons and quarks are not objects, but one-dimensional strings, whose oscillation gives them their observed qualities. The most fun element of string theory is the requirement that the universe has about a dozen dimensions, rather than the usual four (length, width, height and time).
M-theory, the dominant version of string theory, holds that the universe is made up of unfathomably small slices of a 2-dimensional membrane, wriggling in 11-dimensional space.
These bizarre ideas are widely accepted by many theoretical physicists, but the problem is that they can’t be tested — how do you examine an 11th dimension? The field has suffered a backlash in recent years partly for this reason, as some scientists say a theory is not a theory if its predictions can’t be studied in a lab.
Well, now they can, according to of the theoretical physics department at Imperial College London. He is lead author of a paper to be published tomorrow in Physical Review Letters, which explains how string theory math can be used to predict quantum entanglement.
Duff said he was at a conference in Tasmania when a colleague presented some mathematical formulas describing entanglement of multiple quantum bits. The equations looked familiar. Upon returning home, Duff checked his notebooks from a few years earlier, and realized the formulas were the same as those he developed to use string theory to describe black holes.
This is completely unexpected, he said. There is no obvious reason why the insanely complex mathematics underlying string theory can also be used to predict the behavior of entangled quantum systems.
“This may be telling us something very deep about the world we live in, or it may be no more than a quirky coincidence,” he said.
Either way, it’s useful, he added. Using string theory math, Duff predicted the pattern that would occur when four quantum bits are entangled with each other. This can be measured in a lab, and the results will demonstrate whether string theory actually works.
Right now, the best hope for string theory tests comes from CERN’s Large Hadron Collider, which is designed to find the tiniest elementary particles that make up matter. It’s theoretically possible that LHC experiments will uncover supersymmetric particles — one element of string theory — or bounce a graviton into a higher dimension, which could help prove M-theory. But testing the fuzzy math that predicts these behaviors will be much easier.