If you believe the headline of a press release issued today by Northeastern University, its researchers have found evidence of extra dimensions. The actual text of the press release tells a different story, that they haven’t found evidence of extra dimensions. One can’t blame the headline writer too much though, because the text itself is full of enough hype and nonsense about string theory and extra dimensions to confuse most people.
According to the press release text:
Researchers at Northeastern University and the University of California, Irvine say that scientists might soon have evidence for extra dimensions and other exotic predictions of string theory.
… IceCube, now under construction, could provide the first evidence for string theory and other theories that attempt to build upon our current understanding of the universe…
“To find clues to support string theory and other bold, new theories, we need to study how matter interacts at extreme energies,” said Anchordoqui…
In recent decades, new theories have developed – such as string theory, extra dimensions and supersymmetry – to bridge the gap between the two most successful theories of the 20th century, general relativity and quantum mechanics…
Anchordoqui and his colleagues say that extragalactic sources can serve as the ultimate cosmic accelerator, and that neutrinos from these sources smacking into protons can release energies in the realm where the first clues to string theory could be revealed….
“String theory and other possibilities can distort the relative numbers of ‘down’ and ‘up’ neutrinos,” said Jonathan Feng.
The half a dozen references to string theory in the short press release might lead the gullible to think that we’re about to be provided with evidence for the “exotic predictions of string theory”, but that has little relationship to the reality here, one aspect of which of course is that there are no “predictions of string theory” about any of this.
The occasion of the press release is the appearance in Physical Review Letters of a paper by Anchordoqui, Feng and Goldberg entitled Particle Physics on Ice: Constraints on Neutrino Interactions Far Above the Weak Scale. The authors discuss the possibility of using the difference between up and down observed rates for collisions of ultra-high energy cosmic ray neutrinos to get information about neutrino cross-sections at around 6 Tev center of mass energy, far above the energy scale for which we now have data about these cross-sections. They conclude that the data from the AMANDA array operating at the South Pole since 2000 already provide some constraints, and that IceCube, the next generation array now being installed there, could at 90% confidence level rule out a 40% enhancement of the neutrino cross-section over the Standard Model values.
What’s interesting here is not that extra dimensions have been found, but rather the opposite. AMANDA results show no evidence of the kind of enhanced cross-sections you might expect from some extra-dimensional scenarios, and it seems possible that IceCube will rule out such extra dimensions at energies accessible by the LHC even before the LHC comes on line. For a similar but earlier argument of this kind, see a discussion by Jacques Distler a year and a half ago concerning an earlier paper by these same authors that argues that the Pierre Auger Observatory, another cosmic ray observatory now taking data, may also be able to rule out extra dimensions observable at LHC energies before the LHC is turned on.
There’s also some mention of this over at Lubos Motl’s blog, with half the posting devoted to scatological attacks on this blog and its readers. I really think he’s losing it. Note that following current arXiv policy, a trackback linking to Lubos’s posting has appeared at the arXiv listing for the Anchordoqui et. al. paper, but no such trackback will be allowed to appear to the posting you are now reading.
Update: One of the problems with the endless number of absurdly overhyped press releases about string theory is that they get widely distributed.
Update: The Slashdot article does contain a useful extended comment from someone working for AMANDA/IceCube.
Update: The headline on the press release has been changed by the people at Northeastern. It now reads “NU researchers say South Pole detector could yield signs of extra dimensions “.