# Elsevier Journals – The QMUL Figure

A few weeks ago I reblogged Tim Gowers’ post about the cost of Elsevier journals. I noticed that my own institution (QMUL) had deflected his Freedom of Information request. Curious to learn more, I did some digging.

It turns out that QMUL paid a total of £545,306.93 to Elsevier for the academic year 2013/14. Interestingly this is more than other universities that joined the Russell Group recently. However it’s still much cheaper than the bill Cambridge, UCL, Imperial or Edinburgh face.

Unfortunately QMUL weren’t able to provide any further breakdown of the figures. Apparently this information isn’t available to the university, which seems like a very odd way of doing business. I think it likely that the vast majority of the cost is the subscription fee.

I should point out that QMUL and Cambridge certainly have differentiated access to Elsevier journals. For example QMUL Library does not have access to Science Direct papers before the early 1990s. Cambridge University Library has universal access to this material.

However with all the smoke and mirrors in this story, it’s impossible to turn this anecdotal evidence into an accurate account of Elsevier’s charging policy. There’s clearly a need for much greater transparency.

Below is a transcript of the email I received from the QMUL FOI Department. I owe a debt of gratitude for their help.

Dear Edward Hughes

Thank you for your email of 25th April requesting information about spend on Elsevier journals at Queen Mary University of London.

The total amount paid to Elsevier for 2013/14 was £545,306.93 (inclusive of £90,884.49 VAT). We do not hold any further break down.

If you are dissatisfied with this response, you may ask QMUL to conduct a review of this decision.  To do this, please contact the College in writing (including by fax, letter or email), describe the original request, explain your grounds for dissatisfaction, and include an address for correspondence.  You have 40 working days from receipt of this communication to submit a review request.  When the review process has been completed, if you are still dissatisfied, you may ask the Information Commissioner to intervene. Please see www.ico.org.uk for details.

Yours sincerely

Paul Smallcombe

Records & Information Compliance Manager

# Scattering Without Scale, Or The S-Matrix In N=4

My research focuses on an unrealistic theory called massless $\mathcal{N}=4$ super Yang-Mills (SYM). This sounds pretty pointless, at least at first. But actually this model shares many features with more complete accounts of reality.  So it’s not all pie in the sky.

The reason I look at  SYM is because it contains lots of symmetry. This simplifies matters a lot. Studying SYM is like going to an adventure playground – you can still have great fun climbing and jumping, but it’s a lot safer than roaming out into a nearby forest.

Famously SYM has a conformal symmetry. Roughly speaking, this means that the theory looks the same at every length scale. (Whether conformal symmetry is equivalent to scale invariance is a hot topic, in fact)! Put another way, SYM has no real notion of length. I told you it was unrealistic.

This is a bit unfortunate for me, because I’d like to use SYM to think about particle scattering. To understand the problem, you need to know what I want to calculate. The official name for this quantity is the S-matrix.

The jargon is quite straightforward. “S” just stands for scattering. The “matrix” part tells you that this quantity encodes many possible scattering outcomes. To get an S-matrix, you have to assume you scatter particles from far away. That’s certainly the case in big particle accelerators – the LHC is huge compared to a proton!

But remember I said that SYM doesn’t have a length scale. So really you can’t get an S-matrix. And without an S-matrix, you can’t say anything about particle scattering. Things aren’t looking good.

Fortunately all is not lost. You can try to define an S-matrix using the usual techniques that worked in normal theories. All the calculations go through fine, unless there are any low energy particles around. Any of these so-called soft particles will cause your S-matrix to blow up to infinity!

But hey, we should expect our S-matrix to be badly behaved. After all, we’ve chosen a theory without a sense of scale! These irritating infinities go by the name of infrared divergences. Thankfully there’s a systematic way of eliminating them.

Remember that I said our SYM theory is massless. All the particles are like photons, constantly whizzing about that the speed of light. If you were a photon, life would be very dull. That’s because you’d move so fast through space you couldn’t move through time. This means that essentially our massless particles have no way of knowing about distances.

Viewed from this perspective it’s intuitive that this lack of mass yields the conformal symmetry. We can remove the troublesome divergences by destroying the conformal symmetry. We do this in a controlled way by giving some particles a small mass.

Technically our theory is now called Coulomb branch SYM. Who’s Coulomb, I hear you cry? He’s the bloke who developed electrostatics 250 years ago. And why’s he cropped up now? Because when we dispense with conformal symmetry, we’re left with some symmetries that match those of electromagnetism.

In Coulomb branch SYM it’s perfectly fine to define an S-matrix! You get sensible answers from all your calculations. Now imagine we try to recover our original theory by decreasing all masses to zero. Looking closely at the S-matrix, we see it split into two pieces – finite and infinite. Just ignore the infinite bit, and you’ve managed to extract useful scattering data for the original conformal theory!

You might think I’m a bit blasé in throwing away these divergences. But this is actually well-motivated physically. The reason is that such infinities cancel in any measurable quantity. You could say that they only appear in the first place because you’re doing the wrong sum!

This perspective has been formalized for the realistic theories as the KLN theorem. It may even be possible to get a rigorous version for our beloved massless $\mathcal{N}=4$ SYM.

So next time somebody tells you that you can’t do scattering in a conformal theory, you can explain why they’re wrong! Okay, I grant you, that’s an unlikely pub conversation. But stranger things have happened.

And if you’re planning to grab a pint soon, make it a scientific one!

# Elsevier journals — some facts

Excellent article uncovering the problems of journal subscription.

I’ll try chatting to the relevant people here at QMUL and see whether I can dig deeper into the legal implications threatened by Elsevier. Will let you know what I find.

Originally posted on Gowers's Weblog:

A little over two years ago, the Cost of Knowledge boycott of Elsevier journals began. Initially, it seemed to be highly successful, with the number of signatories rapidly reaching 10,000 and including some very high-profile researchers, and Elsevier making a number of concessions, such as dropping support for the Research Works Act and making papers over four years old from several mathematics journals freely available online. It has also contributed to an increased awareness of the issues related to high journal prices and the locking up of articles behind paywalls.

However, it is possible to take a more pessimistic view. There were rumblings from the editorial boards of some Elsevier journals, but in the end, while a few individual members of those boards resigned, no board took the more radical step of resigning en masse and setting up with a different publisher under a new name (as some journals have…

View original 10,726 more words

# The Amplituhedron – Now In Poster Form!

Recently there’s been a lot of excitement about the amplituhedron. This wacky new object might just revolutionize our understanding of particle scattering. To help you get your head round it, here’s a poster I made for an outreach competition.

Click for the full size JPEG file. If you want a hard copy to impress your friends at home, just drop me a comment! I’ve got a few spares, which I’ll happily put in the mail.

By the way, check out The Naked Scientists podcasts – great info and entertainment for the daily commute!

# The Quick Way To Become A Physicist

So you want to become a physicist, right? Problem is you don’t know much physics. Maybe you did some in high school. You might even have read a few physics blogs. But despite your enthusiasm, the road to the research frontier looks perilously long!

But I reckon it can be hiked in less than a year, just by dedicating a few hours of your weekend.

Thanks to the sterling work of Leonard Susskind, anybody can now learn enough physics to dive straight into research. In a series of video courses he explains the theoretical minimum you need to dive into modern research. There’s even an accompanying set of popular science books.

So challenge yourself to cover each of his core courses in a month. If you watch a lecture every Saturday and Sunday you’d manage it, more or less! Supplement your viewing with some problem questions and you’ll be well on the way to a firm foundation in the laws of nature.

Be warned – physics isn’t always easy to learn. Things can get tough, particularly when you’re studying on your own. But with the power of the internet, help is never far away. I suggest you hang out at Physics StackExchange. Asking and answering questions is the lifeblood of research culture, so don’t be shy!

Once you’ve burned through the core courses it’s time to step up a gear. Take a look at Susskind’s advanced courses. Although these are harder, there also infinitely more exciting! Plus, you can just pick and choose the ones you want to. Few research physicists start out with a encyclopaedic knowledge of every area.

If you keep up your twice a week lecture strategy, you’ll be equipped with the theoretical minimum within 9 months. Novice to expert in less time than it takes to train for a marathon! Sounds pretty good to me.

There’s one final step – read real life papers. This is pretty scary at first, so I usually start by browsing the introduction and conclusion. Once you’ve done this a few times you can take a deep breath and dive in properly. Remember to have a pen and paper handy – you’ll only learn by actively working out what’s going on!

Where to start? I think you could do worse than tackling the top 40 most cited papers of all time. Okay, this list is biased towards high-energy theory. But between you and me, that’s the coolest part of physics anyway!

Three months of reading real papers won’t give you enough time to get through all 40! But even if you just browse two or three, you’ll still be intellectually fraternising with the greatest academics of our generation. Your journey from layman to physicist will be complete.

So get inspired and give this project a go! I’ll be fascinated to hear from anybody who tries out some new physics, whether it’s for 24 hours or a whole year. I firmly believe that science should be available to everyone. Now more than ever before that opportunity is open to you!

# Double Whammy – New Evidence for Inflation and Gravitational Waves

Today the latest results from the BICEP2 telescope in Antarctica are out. And boy, are they exciting! They provide stark evidence for two widely believed theoretical predictions, namely inflation and gravitational waves. The authors are already being tipped for a Nobel prize.

So what’s the science behind this magnificent discovery? It’s easiest to start with the name of the telescope. BICEP stands for “Background Imaging of Cosmic Extragalactic Polarization”. That means looking for signals from the Big Bang. Cool, huh?

After the Big Bang  the universe was a hot dense soup of particles. Eventually (380,000 years later) things were cool enough for the universe to become transparent. Particles could bind together to form hydrogen atoms, emitting light in the process. Nowadays we see this ancient light as microwave radiation covering space.

This cosmic microwave background (CMB) has a particularly puzzling feature. It’s much more uniform than we should expect from a generic Big Bang explosion. Intuitively most explosions don’t generate exactly symmetrical outcomes!

What’s needed is some mechanism to smooth out the differences between different parts of space. Here’s where the idea of inflation comes in. A fraction of a second after the Big Bang we think that the universe blew up at an astonishing rate. This happened so fast that there was no time for inconsistencies to creep in. The result – a uniform cosmos.

It’s certainly an appealing explanation, but the problem is that there’s been little direct evidence. Until now, that is. Cosmologists on the BICEP project were looking for a particular signature from inflation, and it seems like they’ve found it!

To understand their method we need to know something about light. A wave of light can oscillate in different directions perpendicular to its path. A light wave coming into your eyes from your screen will oscillate somewhat up-down and somewhat left-right. These two options are known as polarizations of light.

It turns out that you can measure exactly how light in the CMB is polarized. This is useful because inflation produces a particular polarization pattern called a B mode. It’s taken decades to locate this smoking gun, but now the BICEP team have done it.

Hang on, couldn’t these B modes come about some other way? Probably not. The B mode pattern we observe seems to arise from the interaction of light with gravitational waves. And to get enough of these we need inflation. Or perhaps this effect is an observational fluke? According to the paper, we’re 99.999999% sure it isn’t.

It’s worth pointing out that this result is a double whammy. It confirms theories of inflation and gravity. Nobody has yet detected a gravitational wave, despite the fact they’re theoretically an easy consequence of Einstein’s general relativity. This latest development is further indirect evidence of their existence.

# Anomaly Cancellation

Back in the early 80s, nobody was much interested in string theory. Some wrote it off as inconsistent nonsense. How wrong they were! With a stroke of genius Michael Green and John Schwarz confounded the critics. But how was it done?

First off we’ll need to understand the problem. Our best theory of nature at small scales is provided by the Standard Model. This describes forces as fields, possessing certain symmetries. In particular the mathematical description endows the force fields with an extra redundant symmetry.

The concept of adding redundancy appears absurd at first glance. But it actually makes it much easier to write down the theory. Plus you can eliminate the redundancy later to simplify your calculations. This principle is known as adding gauge symmetry.

When we write down theories, it’s easiest to start at large scales and then probe down to smaller ones. As we look at smaller things, quantum effects come into play. That means we have to make our force fields quantum.

As we move into the quantum domain, it’s important that we don’t lose the gauge symmetry. Remember that the gauge symmetry was just a mathematical tool, not a physical effect. If our procedure of “going quantum” destroyed this symmetry, the fields would have more freedom than they should. Our theory would cease to describe reality as we see it.

Thankfully this problem doesn’t occur in the Standard Model. But what of string theory? Well, it turns out (miraculously) that strings do reproduce the whole array of possible force fields, with appropriate gauge symmetries. But when you look closely at the small scale behaviour, bad things happen.

More precisely, the fields described by propagating quantum strings seem to lose their gauge symmetry! Suddenly things aren’t looking so miraculous. In fact, the string theory has got too much freedom to describe the real world. We call this issue a gauge anomaly.

So what’s the get out clause? Thankfully for string theorists, it turned out that the naive calculation misses some terms. These terms are exactly right to cancel out those that kill the symmetry. In other words, when you include all the information correctly the anomaly cancels!

The essence of the calculation is captured in the image below.

Any potential gauge anomaly would come from the interaction of $6$ particles. For concreteness we’ll focus on open strings in Type I string theory. The anomalous contribution would be given by a $1$-loop effect. Visually that corresponds to an open string worldsheet with an annulus.

We’d like to sum up the contributions from all (conformally) inequivalent diagrams. Roughly speaking, this is a sum over the radius $r$ of the annulus. It turns out that the terms from $r\neq 0$ exactly cancel the term at $r = 0$. That’s what the pretty picture above is all about.

But why wasn’t that spotted immediately? For a start, the mathematics behind my pictures is fairly intricate. In fact, things are only manageable if you look at the $r=0$ term correctly. Rather than viewing it as a $1$-loop diagram, you can equivalently see it as a tree level contribution.

Shrinking down the annulus to $r=0$ makes it look like a point. The information contained in the loop can be viewed as inserting a closed string state at this point. (If you join two ends of an open string, they make a closed one)! The relevant closed string state is usually labelled $B_{\mu\nu}$.

Historically, it was this “tree level” contribution that was accidentally ignored. As far as I’m aware, Green and Schwarz spotted the cancellation after adding the appropriate $B_{\mu\nu}$ term as a lucky guess. Only later did this full story emerge.

My thanks to Sam Playle for an informative discussion on these matters.

## Musings Mathematical and Otherwise

Gowers's Weblog

Mathematics related discussions

4 gravitons

The trials and tribulations of four gravitons and a postdoc

Eventually Almost Everywhere

A blog about probability by Dominic Yeo