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Physics on film

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December 2009 Archives

By Matin Durrani

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 e-mailed 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 the WIMP 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 has been doing a live blog, which has lots of as-it-happens stuff to get stuck into to.

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

By Matin Durrani

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 conference at 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”.

The conference ends today.

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Agency men: Drayson and Scolese (Courtesy: RAL)

By Hamish Johnston

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?

Taking an author’s ‘literary fingerprint’

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Billy S A king of infinite space

By James Dacey

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.

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Any WIMPs in here?

By Michael Banks

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 CDMS team 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 such Nature 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 told physicsworld.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”.

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ATLAS collisions

By Hamish Johnston

According to several physics bloggers (and backed up by the above image) physicists at the ATLAS experiment have managed to collide 1.18 TeV bunches of protons to achieve the highest energy yet — 2.36 TeV.

This makes the Large Hardron Collider the most energetic particle collider, beating the Tevatron’s previous record of 1.96 TeV.

The LHC became the world’s most energetic accelerator ten days ago, when proton pulses were first boosted up to 1.18 TeV.

There hasn’t been an official statement from CERN about this — we’ll keep you updated.

By Hamish Johnston

Over the past few years the supply of Mo-99 — which is used to make the medical isotope Tc-99m — has been threatened by two unscheduled shutdowns of the ageing NRU reactor in Chalk River, Canada.

Normally NRU supplies North America with Tc-99m and accounts for a significant chunk of world production, so any prolonged shutdown is bad news.

That’s why the Canadian government convened the Expert Review Panel On Medical Isotope Production earlier this year to identify the most viable options for future isotope production.

The panel has just submitted its report and you can read all 135 pages of it here.

The main recommendation is the replacement of NRU with another multi-purpose research reactor that would supply isotopes as well as fulfilling other scientific functions. However, revenues from isotope production would only offset about 10-15% of the cost of such a reactor — so other research activities would have to justify the bulk of the price tag.

The panel also recommends that Tc-99m production in a cyclotron accelerator, be investigated. Although this would involve a significant amount of research and development, the infrastructure is already in place in several places in Canada.

Could we see the rebirth of the University of Manitoba cyclotron?

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Future winners may have to do with less

By Michael Banks

You could say physicists have much to be gloomy about these days with the Science and Technology Facilities Council in the UK cutting funding for projects to patch up its budget and scientists in Japan bracing themselves for deep cuts to the country’s science budget next year.

And now future winners of the Nobel prizes could end up feeling short changed if the Nobel Foundation, which manages the finances of the prizes, cuts the amount of money it dishes out every year.

The Foundation announced at the weekend that it might cut the $1.5m it hands out for each of the six prizes awarded each year. The reason, it says, is the credit crunch and the impending recession, which has led to losses in the foundation’s assets.

Indeed, when the credit crunch struck in 2008 the foundation’s assets lost nearly one-fifth and since then has only slightly recovered. “We have sailed the storm, but have taken on some water,” said Michael Sohlman, executive director of the Nobel Foundation, at a press conference.

So as this year’s Nobel prize winners — including US president Barack Obama who won the Nobel Peace Prize — attend the awards ceremony in Stockholm on Thursday, future winners may have to do with less.

Is this the world’s smallest snowman?

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“I’m riding in the midnight blue”

By James Dacey

Sizing up at just one fifth the width of a human hair, this must be a very strong contender for the smallest snowman in the world.

His body has been formed by welding together two tin microparticles (10 µm in diameter), which are usually used in the calibration of electron microscopes. A focused ion beam was deployed to etch out his eyes and mouth and a tiny fleck of platinum forms the nose.

The little fella’s creator is researcher David Cox who works at the National Physical Laboratory (NPL) in London. He was taking time out from his usual job of fabricating devices for the Quantum Detection Group. “I guess I was just born to make stuff,” Cox writes on his homepage.

There is a video on the NPL homepage showing just how Cox sculpted his miniture friend.

By Margaret Harris

These are exciting times for laser fusion. In the next couple of years, the US National Ignition Facility (NIF) should reach “ignition” — the point at which a fusion device starts to kick out more energy than it takes in. But what happens after that? After all, releasing the energy of the stars is one thing: releasing it in a form that could actually turn on some lights is another.

One project that aims to bridge this gap is called the European High Power Laser Energy Research Project — HiPER for short — and it’s the subject of Physics World’s latest video feature. In the first video, HiPER director Mike Dunne describes how the project will work, and outlines some of the technological hurdles that need to be overcome to transform laser fusion into a practical power source.

When he’s not co-ordinating the efforts of researchers at HiPER’s 26 member institutions, Dunne is also head of the UK’s Central Laser Facility (CLF) in Oxfordshire. The CLF is home to a number of lasers — including Vulcan, one of the highest-intensity lasers in the world — that provide possible templates for the high-power, high-repetition-rate system that HiPER will need. For a view of what it’s like to work on these giant lasers, tune in to our interview with fusion scientist (and Vulcan laser user) Kate Lancaster, as she talks about the basic physics research taking place there.

The Bohr-Einstein Debates, With Puppets from Chad Orzel on Vimeo.

By Hamish Johnston

A few months ago physics blogger (and Physics World contributor) Chad Orzel promised his readers that if they stumped up at least $2000 for a charitable appeal, he would put on a puppet show about the famous debate over the interpretation of quantum mechanics between Niels Bohr and Albert Einstein.

He raised over four grand…so raise the curtain and enjoy…

The action opens at the 1929 Solvay conference with Einstein (played by a bichon stuffed toy) expressing his concerns with quantum theory in an appalling German accent — ‘if vee detect zee electrons vun at a time…’

Bohr — a black Labrador retriever — responds and the debate is underway.

The supporting cast includes Paul Ehrenfest as a hedgehog and Paul Dirac as a “disinterested” elephant.

Oh, and Orzel’s dog (a real dog) plays the role of a sceptical audience.

The show is a delight — but I’m left wondering how Orzel got through it without contracting a serious case of the giggles! I suspect many takes were involved.

Why the canine obsession? Orzel has just published a book called How to Teach Physics to your Dog.

And you can read Orzel’s Physics World article on measuring the electron’s electric dipole moment here.

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By Hamish Johnston

Alexander Unzicker wants you to place a bet on the Higgs boson — or more precisely whether it will be discovered at the LHC.

He has set up a site called www.bet-on-the-higgs.com, where he explains how you can bet on the discovery of the Higgs at intrade.com — which is a ‘prediction market’ based in Ireland.

If you are tempted to place a bet, please make sure that doing so is legal where you live.

Here in Dirac House I can’t even look at intrade’s Higgs pages — they are ‘forbidden’ — but Unzicker has posted a screen shot of his intrade account, which I have reproduced below.

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Buy low, sell high

Sorry about the fuzziness, but if you squint you can see that he is wagering on the ‘Observation of the Higgs Boson Particle’.

What’s not clear from the screen shot is whether Unzicker — who teaches maths and physics in Munich — is betting for or against the discovery…you’ll have to check his website to find out.

By Hamish Johnston

“The governments of the world have made a substantial investment in fusion research; the time has come to begin to capitalize on this.” This is the battle-cry of Stephen O Dean, president of the research and education foundation Fusion Power Associates.

Writing in our latest supplement Fusion challenges and solutions, Dean argues that now is the time for the fusion community to pull together to make fusion power a reality.

You can download a PDF of the 16-page supplement here and read the following articles:

JET set to break own fusion record
The completion of a €60m upgrade means the Joint European Torus can better mimic the technology needed for ITER, as Andy Extance reports.

Laser fusion shifts into HiPER drive
As an alternative to using magnets, laser-driven fusion power, is coming to the fore. Margaret Harris describes the current state of play.

Building career prospects in fusion
Greg Tallents and Howard Wilson showcase two new UK postgraduate training programmes educating the fusion scientists of the future.

Fusion supercomputer starts up
The High Performance Computer for Fusion, with a peak performance of 100 teraflops per second, could help get the best out of ITER’s plasmas, as Sibylle Günter explains.

FPA president predicts bright future
Stephen O Dean discusses his vision for fusion power, and how the research and education foundation Fusion Power Associates can help.

Putting a value on fundamental research

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Blue-sky thinkers Lord Drayson (centre) promotes the economic-impact of science

By James Dacey

It is very well-documented that the World Wide Web emerged as an incredibly successful “by-product” of the blue-skies research carried out at CERN. But should all scientists be required to justify their funding by the “impact” of their work on the rest of society?

A new proposal by the UK government would mean that every application for a research grant will require the researchers to detail the direct benefits of their work on the economy, public policy, and a number of other realms.

At a public event in London last night Lord Drayson, the UK Science Minister, was met with a number of concerns from UK researchers who have taken issue with the new scheme.

“We need to change the way we do science in this country. It is perfectly reasonable to expect scientists to do more to demonstrate the importance of what they do,” Drayson told the audience.

“Science should be accountable where science is funded by the tax-payer.

“[The new scheme] is asking people within their grant applications to think about the impact they give and to describe it,”

Perhaps offended by the tone of Drayson’s comments, several people argued that researchers already do this sort of thing as an intrinsic part of their work. One member of the audience dismissed the new scheme as nothing more than “box-ticking” by the Government.

A major sticking point is whether researchers should be assessing the impact of the work that they have already done or the impact of the research they hope to carry out, as this is apparently unclear under the new proposals.

“It would be lovely if we did have a crystal ball which could predict the future applications of our research, but the reality is that most research simply does not work this way as many benefits result from serendipity,” said Colin Stuart an astronomer working at The Royal Observatory in Greenwich, who was also on the panel.

Blue Skies ahead? The prospects for UK science, was hosted by the Wellcome Collection in central London and the event was chaired by Brian Cox, the CERN physicist and presenter of a number of popular science programmes in the UK. You can watch a recording of the debate online.

Earlier yesterday evening, Cox tackled Drayson on the issue of science and economic-impact as part of a new BBC radio series The Infinite Monkey Cage, which you can listen to here.

If you want to have your say regarding the proposed reform then the consultation will run until 16 December. Whatever comes out of this, however, I’m sure many UK physicists will still be left wondering how the Government will put a price on some of the true blue-sky research such as the search for the Higgs.

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Higgs Boson Will UK money continue to fund the search for him/her indefinitely?

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Figure 1 of the first of many papers

By Hamish Johnston

What surely must be the first paper reporting proton-proton collisions in the Large Hadron Collider (LHC) has appeared on the arXiv preprint server.

It’s by the ALICE collaboration — over two pages of authors from 113 institutes — and describes collisions in the ALICE detector that occured last week.

Aamodt et al describes 284 collisions that occured when both beams were at 450 GeV.

The events were used to determine something called the ‘pseudorapidity density’ of charged particles in the detector.

And what exactly is pseudorapidity? As far as I can tell, it’s a rather complicated way of expressing the angle between the momentum of a particle in the detector and the momentum of the beam.

The paper says this about these early results:

“They demonstrate that the LHC and its experiments have finally entered the phase of physics exploitation, within days of starting up the accelerator complex in November 2009.”