The dark-matter rumour mill

Any WIMPs in here?

You shouldn’t believe everything you read in the blogs (except this one of course).

Yesterday, the rumour mill was in overdrive as the Resonaances blog said a paper was due to be released a week on Friday in the journal Nature about a possible detection of dark matter.

What constitutes dark matter, which is thought to make up around 90% of the material in the universe, is a hot topic of research these days with researchers vying to be the first to provide direct evidence of it. If true, it would perhaps be the discovery of the year.

The new rumours are based on the latest results from the Cryogenic Dark Matter Search (CDMS) located in the Soudan Underground Laboratory in Minnesota, which is searching for weakly interacting massive particles or WIMPs — a prime candidate for dark matter.

We were a little suspicious of the rumours as Nature is published on Thursday with embargos for news items about its papers on Wednesday evening at 6pm GMT. However, the paper could have been an advanced online publication in Nature or perhaps was due to be published in Science, which is published every Friday.

The rumours were also backed by a series of talks being given by various members of the CDMSteam at labs such as CERN on 18 December - the same date as the paper would be published.

However, Leslie Sage, a senior editor at Nature, wrote to Resonaances saying there was no suchNature paper and the rumours were unfounded.

I contacted Priscilla Cushman from the CDMS collaboration and based at the University of Minnesota, who confirmed to me that indeed they have not submitted a paper to Nature.

So why are they presenting the results at different labs on the same day? “Since there is no major conference at this time in which to present them we are coordinating our talks,” Cushman toldphysicsworld.com.

CDMS researchers will, however, be publishing an arXiv paper on the morning of Friday 18 December about their latest results, so we will have to wait until then.

Cushman says the group were quite taken aback by the rumours going around. “It is certainly an interesting social phenomena [sic],” says Cushman. But ultimately it was “lots of smoke and not much fire”.

Taking an author’s ‘literary fingerprint’

Billy S A king of infinite space

Imagine this: a much-celebrated author locks himself away to begin work on his masterpiece, a novel called The Meta Book that will comprise an infinite number of words all strung together in the writer’s unique literary style. While this may sound like the plotline to a short-story by one of the great magical realist authors of Latin America, it is actually the idea of a trio of physicists in Sweden.

Sebastian Bernhardsson and his colleagues at Umeå University are interested in the unique “literary fingerprint” left by famous authors. They conceptualize a writer’s use of language as a complex system in the same way that scientists model the climate, the economy or ant colonies.

By feeding an author’s entire oeuvre into their calculations, they find that each writer creates a unique curve on a graph representing the number of different words used as a function of the total number of words. What’s more, this signature curve can be detected in every single work of a particular author regardless of what they are writing about.

Publishing their findings in New Journal of Physics the authors create curves for the works of Thomas Hardy, DH Lawrence and Herman Melville. “It is like everything an author can think of writing is processed by a mental pipeline which imposes a unique fingerprint on an authors’ infinite meta-book,” says Bernhardsson. I think, what he means by this is that (statistically speaking) there is a common thread running through everything these authors wrote — as if they were plucking extracts from their infinite corpus.

Now, the literary purists out there may be reading this and seething at yet another example of uncouth physicists trying to impose rigid mathematical frameworks onto works of unquantifiable beauty, or of “unweaving the rainbow” as Keats famously accused Newton. If anything, however, the results of this research reveal the opposite. For 75 years, language analysts have assumed that all literature, regardless of author, follows the same statistical pattern when viewed as a whole. This was based on the law proposed by American linguist George Kingsley Zipf stating that the frequency of a word is inversely proportional to its occurrence.

In this new view of fiction, however, each author defines their own unique law based on non-trivial mathematics. “It shows that, even statistically speaking, our personality is not drowned by the general rules, and structure of the language itself,” says Bernhardsson.

The researchers intend to develop their work by testing their meta book concept for more authors and languages other than English. So who knows — maybe the magical literary worlds of Borges and Márquez will be next in line to have their curves exposed.

On Her Majesty’s Space Service

Agency men: Drayson and Scolese

The UK’s science minister Paul Drayson was licensed to thrill yesterday when he turned up at the Rutherford Appleton Laboratory to announce that the UK will set up its own executive space agency. Lord Drayson hinted that it might be called “Her Majesty’s Space Service”, and said it would provide “a unified approach to ensure the UK gains a bigger share of the global space market”.

Drayson was speaking to researchers at the 5th Appleton Space Science Conference, and the announcement was met with warm applause. Not surprising, because space scientists have been waiting at least 20 years for the news!

Space science funding is currently done by six government departments and two research councils — and it is not clear whether the new agency will coordinate these activities, or take over funding altogether.

However, Drayson was very clear that the overall spend on space science research will not change. And he was also adamant that the UK space community has long been at a disadvantage for not having an executive agency to negotiate its participation in international projects.

Although the UK is a leader in space science and technology, the government had not been particularly keen on space. The country has shunned manned space missions and the 1986 Space Act makes it very difficult for a private company to launch anything into space from British soil. The reason, believe it or not, is that firms cannot afford adequate insurance to comply with the indemnity requirements of the act.

But then Gordon Brown came to power in 2007 — and apparently Brown loves space science, or so I was told by a leading space scientist at the post-conference drinks reception. It seems that when Brown was Chancellor of the Exchequer he asked his minions to identify up-and-coming industry sectors and guess what was at the top of the list?

Indeed, in his speech Drayson said that 20,000 Britons are employed directly by the space industry, which is worth £6.8bn per year.

“It’s a recession proof industry” he claimed, citing 9% growth every year for the last decade. And the good news is set to continue, with 5% growth forecast for the next decade.

Drayson’s speech was followed by the Appleton Lecture by Chris Scolese, who is associate administrator of NASA. I wonder if the second in command of the world’s most famous space agency gave Drayson any tips on setting up an agency?

The A to Z of the AB effect

Electrons (blue) passing either side of a current-carrying solenoid shows the Aharonov-Bohm effect in action.

The Aharonov-Bohm effect is one of those weird, counter-intuitive consequences of quantum mechanics that makes physics the fascinating subject it is.

Discovered 50 years ago by Yakir Aharonov and the late David Bohm at the University of Bristol in the UK, the AB effect, as it is known to insiders, is being celebrated today at a special conferenceat Bristol.

In case you weren’t aware, the AB effect describes the fact that an electrically charged particle passing through a region where both the magnetic and electric fields are zero is nevertheless affected by the electromagnetic potential in that region.

It can best be understood by considering a beam of electrons passing through two slits and then around either side of a current-carrying solenoid, as shown by the blue lines in the picture above.

Although there is no magnetic field outside the solenoid, the potential is different on the two sides, which means that the wavefunction of the electrons travelling past one side of the solenoid are phase-shifted by a different amount compared with the electrons travelling past the other.

The AB effect can be verified by allowing the electron beams to interfere: the resulting fringe patterns shift depending on whether the solenoid is on or off.

The conference, which also marks the 25th anniversary of Michael Berry’s discovery of the related “Berry phase”, has attracted a crowd of specialists from around the world, including Aharonov himself.

I went to the conference dinner at the university’s Georgian-period Goldney Hall, where guests were treated to a marvellous menu of roast asparagus with goat’s cheese mousse and Serrano ham crisps, slow-cooked rump of lamb with quince sauce, and confit of raspberries.

Spotted among the guests were Bob Chambers, who confirmed the AB effect experimentally back in 1960, former Brookhaven chairman Michael Hart and independent physicist Julian Barbour, author of The End of Time.

Today’s first lecture session back at the university’s physics department was chaired by Murray Peshkin from Argonne National Laboratory in the US, who introduced Sir Michael by saying “he is a man of few words but many syllables — so listen carefully”.

Berry’s lecture was entitled “Semifluxon degeneracy choreography” and he duly proceded to use a fair few long-syllabled words, including “Gaussian random simulation”, “traceless real symmetric 2×2 matrices” and “rearrangements of nodal domains”.

The talk was a bit over my head, but on such occasions I take comfort in Richard Feynman’s famous phrase that “nobody really understands quantum mechanics”.

Closing in on dark matter

The physics blogosphere has been wild with rumour in recent days that researchers in the Cryogenic Dark Matter Search (CDMS) in the US may have obtained the first direct evidence for dark matter in the form of Weakly Interacting Massive Particles.

The CDMS group gave simultaneous lectures at SLAC and Fermilab late on Thursday evening UK time that would, or would not, announce major new findings, depending on whose blog you read

My colleague Michael Banks has been listening in to the webcasts and emailed me to say that “the outcome is that it is not conclusive evidence of dark matter, but they did have two events on a background of 0.5… so some signal, but not the five events needed for a discovery”.

An arxiv paper on the new results should be there by early morning.

It appears, Michael tells me, that the first event was detected on 27 October 2007, with a recoil energy of roughly 12 keV, and the second was seen earlier that year at roughly 15 keV. A third event lies just outside their box with recoil of 12 keV. Apparently this gives the lower bound on theWIMP mass for these recoil energies as roughly 0.5 GeV.

CDMS has a neat summary here. This is the key sentence: “We estimate that there is about a one in four chance to have seen two backgrounds events, so we can make no claim to have discovered WIMPs.”

We’ll have more on this later in our news channel so stay tuned. In the meantime,
Cosmic Variance have been doing a live blog which has lots of as-it-happens stuff to get stuck into to.