Posts by: Matthew Chalmers

Welcome to the arXiv galaxy

Image of the Paperscape map

Visualizing the interactive arXiv landscape. (Courtesy: Damien George, Rob Knegjens)

By Matthew Chalmers

With almost a million articles accrued over the past two decades, the arXiv preprint server has become an indispensable tool for physicists.

Now, thanks to a website called Paperscape developed by theoretical physicists Damien George at the University of Cambridge in the UK and Rob Knegjens at Nikhef in the Netherlands, its vast content can be visualized in all its glory.

The interactive graphic is based on a nifty algorithm that groups arXiv papers that cite each other together, as if they were linked by invisible springs, but forces those that don’t to repel each other. The resulting map resembles an irregularly shaped galaxy in which each “star” is a scientific paper, revealing how the various categories of research (shown in different colours) relate to each other.


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Nobel laureates react to Higgs news

62nd Lindau Nobel Laureate Meeting

Chewing the fat: (left to right) David Gross, Martinus Veltman, Carlo Rubbia and George Smoot

By Matthew Chalmers in Lindau, Germany

The organizers of this year’s 62nd Lindau Nobel Laureate Meeting couldn’t believe their luck. Having invited 27 Nobel-prize winners (average age 73.5) plus 600 young physicists to an island in Lake Constance, what should happen right in the middle of their shindig but the announcement of the biggest physics discovery in a generation. CERN’s new boson created quite a stir on the island, and it would seem that a certain Peter Higgs could soon be among the annual event’s invitees.

David Gross, who shared the 2004 prize for his work on the strong interaction, hasn’t stopped smiling, and is sure that CERN has discovered a Higgs – if not the Higgs boson as predicted by the Standard Model of particle physics. “This is a great day for me, for physics and for all of humanity,” he enthused on Wednesday after the news emerged.

Gross is particularly happy because the mass of the new particle (125 GeV) suggests that his favourite candidate for a deeper theory of physics – supersymmetry – is on the money. However, he also admitted that this particular mass value, should the particle indeed turn out to be the Higgs, would imply that the universe is in a metastable state that could decay at any moment and cause everything we know to simply disappear. The prospect prompted hearty laughter from the crowd.

Particle-physicist heavyweight Carlo Rubbia – who was responsible for the discovery of the W and Z particles at CERN in 1983, for which he picked up a Nobel prize the following year – was not getting too caught up in the elation. He wants to know why CERN’s new boson appears to be produced at a rate twice as large as would be expected. “The Standard Model should give us an exact value for this, and here there is a direct disagreement: what’s going on?” he asked. No stranger to getting major particle-physics experiments off the ground, he demanded a dedicated new collider to pin down its properties.

The third Nobel-prize-winning particle physicist at this year’s meeting was Martinus Veltman, who shared the 1999 gong for his work on the electroweak sector of the Standard Model (for which the Higgs is crucial). Veltman had not yet organized his thoughts on the discovery – indeed, he seemed somewhat subdued about the affair. “The Standard Model has now got a degree of validity that has extended way beyond what we had before the Higgs,” he said. “However, the one aspect that dominates here is that a Higgs could close the last door of the Standard Model that could lead us to a deeper theory.”

But not all Nobel laureates at the meeting were so elated. Condensed-matter physicist Robert Laughlin, who shared the 1998 prize for the discovery of a new form of quantum fluid, thinks that particle physics is in trouble, no matter what is discovered at the Large Hadron Collider. His view is that governments justified “big physics” research for defence reasons because particle physics followed nuclear physics, which had given countries the bomb. “Those motivations are less obvious today, which is good for the world but bad for the field in the long term,” he told

Meanwhile, the UK’s Harry Kroto, who shared the 1996 chemistry prize for the discovery of fullerenes, is worried about the cash and publicity consumed by big physics. “I do see that the [Higgs] discovery is wonderful, but I also see the huge amounts of money going into this field, and I wonder whether we are getting the balance right when it comes to science funding,” he told “I’m concerned, given the current funding situation, that large numbers of chemists doing fundamental work will lose out.”

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On the trail of thorium

By Matthew Chalmers

Flowers presentation
Credit: BARC

If you’re wondering who that is second from right, holding a bunch of flowers while desperately trying to smile naturally in front of a camera, right in the hub of India’s nuclear power programme, it’s me. I was in the subcontinent after being sent by Physics World magazine to write about India’s audacious “three-stage” nuclear programme that seeks to exploit the country’s vast reserves of thorium as an alternative nuclear fuel to uranium. (You can read my final article “Enter the thorium tiger” in the October issue of the magazine, which can be downloaded free of charge via this link

The bouquet, along with a large leather wallet, was presented to me as a gift from directors of the Bhabha Atomic Research Centre (BARC) near Mumbai. My fellow flower holders – all from the British High Commission in Delhi – were there to build links between UK and Indian nuclear scientists, while I was present to unearth what I could about India’s nuclear plans. The flowers came from BARC’s extensive flowerbeds, which were laid at the request of the late physicist Homi Bhabha.

BARC, near Mumbai. Credit: BARC

There’s a certain romanticism to the way Bhabha, who established India’s nuclear programme 60 years ago, is revered among Indian nuclear physicists. He not only provided a vision of energy security that thrives 44 years after his untimely death in an air crash above the Alps, but used his connections to set in place an infrastructure that ensured his vision became reality.

Initially perplexed at why other countries weren’t exploiting thorium – a fuel that has many benefits over uranium – I asked one senior BARC physicist why the UK doesn’t have a nuclear roadmap like India’s. “Ah!,” he said, waving a finger at me, “it’s because you don’t have a Bhabha!”

Indian nuclear physicists take great pride in having developed most of their technology indigenously, owing to India’s being a nuclear-armed nation outside the non-proliferation treaty (NPT). But writing my article for Physics World . was not without its challenges.

Professional hierarchy is more apparent than in, say, a UK physics laboratory, and at times the atmosphere while I was at BARC was hugely formal, particularly when the new lab director was present. Plans to meet a few students and postdocs working at BARC were soon dashed, and recording equipment in India’s heavily guarded government labs is none too popular either.

Access to India’s nuclear programme would have been difficult were it not for the diplomatic context of my visit – and even then there were issues when it came to dealing with India’s top nuclear officials.

Changing geopolitical relations, particularly since 2008, when the US and India signed an agreement that led to India being brought into the nuclear fold, have led several countries to line up to co-operate with India on civil nuclear trade and technology. The UK is one of them.

During my trip the new UK prime minister was also visiting India, along with a trade delegation. Shortly afterwards, a bunch of joint research grants between physicists in the UK and India were funded – selected from a dozen fully costed proposals drawn up in just two days in the basement of a central London hotel back in March amid a flurry of sticky notes and chirpy facilitators from the Engineering and Physical Sciences Research Council (EPSRC). It was an impressive feat to witness, although not without a few bemused faces. Most of the nine Indian and 20 UK delegates had never met nor had much idea about each other’s research interests.

The Mumbai streets. Credit: M Chalmers

One thing that most surprised me in India is how few people on the street, so to speak, seem to know anything about India’s nuclear programme. Those who did know about thorium (whom I found while sipping cold beer in Chennai’s Madras Club, having visited India’s other big nuclear lab – the Indira Gandhi Centre for Atomic Research (IGCAR) on the other side of the country to Mumbai) all thought the programme was nowhere near on track, which is not what the physicists involved will tell you. Most people I got chatting to also assumed that I was interested in their views on weapons, rather than on civil nuclear power, with one or two asserting India’s right to develop them.

There is a degree of sensitivity to civil-nuclear collaboration between India and countries that are signatories of the NPT, which includes pretty much every other country. While having lunch at BARC with the lab’s new director, he made no mention of India’s weapons research as he listed the many basic science and other non-nuclear research taking place there.

Prototype Fast Breeder Reactor. Credit: IGCAR

Yet, gazing out of the window as we enjoyed a local interpretation of fish and chips, I could see – against a background of jungle and well-tended gardens leading out to the Arabian Sea – two large ageing nuclear reactors, one of which is to be shut at the end of this year as part of India’s commitment to separate its strategic and civilian nuclear programmes (a requirement of the US–India deal). I couldn’t help thinking how apt was the phrase “the elephant in the room”, as one UK nuclear physicist described the military dimension of nuclear technology to me.

But the thing that struck me overall while touring BARC and IGCAR was the sheer amount of effort involved to harness a new nuclear fuel cycle – an effort most deem too great at this time given the availability of and experience with uranium. I left IGCAR after being hurried past a blur of laboratories each piecing together a tiny aspect of Bhabha’s plan, from advanced welding joints to material irradiation tests.

In the back seat of the car bound for Chennai airport, I tore open some gift wrap to find that I was the proud new owner of a blue velvet box containing an ornament in the form of a large gold-coloured metal leaf. Lovely.

To read more, check out “Enter the thorium tiger” in the October issue of Physics World magazine, which can be downloaded free of charge via this link.

Matthew Chalmers is a freelance science writer in Bristol, UK

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