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Ian Swanson and other talks

Because the behavior of Linux and Mozilla is mostly unpredictable, I will try to write shorter articles.

Ian Swanson from Caltech has been visiting us. He has told us a lot of interesting stuff, and was also giving a special seminar yesterday (Friday) at 3:00 pm.

He used PowerPoint with a lot of sophisticated equations, tables, and some animations. His topic was String integrability and the AdS/CFT correspondence.

Let's describe Ian's talk and the current status of the post-BMN business. Because I am writing this for the second time, let me be shorter:

  • the industry of the pp-wave limit has transmuted into the spin chains and integrable systems
  • Ian Swanson et al. (which includes John Schwarz, but also Jonathan Heckman who is now at Harvard) studied the physics of strings beyond the pp-wave - which means that AdS5 x S5 is described as the pp-wave deformed by some 1/R^2 corrections
  • the gauge theory side of the calculation more or less reduces to the spin chains and other tools of integrable systems
  • the string theoretical side is described by the Green-Schwarz string that, at least classically, becomes the supercoset SU(2,2|4) / ( SO(5) x SO(4,1) ), if I remember well - and as long as you forget about stringy loops, the ghosts (like Berkovits' pure spinors) are not necessary
  • the integrable structure on both sides agree, even though it is not manifest
  • most of the calculations are done at the leading order of the 1/N expansion (or the J^2/N expansion), and the stringy loop corrections are more or less open questions
  • the results are still expanded in lambda'=lambda/J^2, and in 1/J
  • the gauge theory (spin chains) agrees with the string (supercoset) at the one-loop and the two-loop level
  • there is a discrepancy at the three-loop level, and Ian says that it is believed that the problem is a subtlety neglected by the spin chain models
  • many states are combined into various multiplets, and there is indirect evidence of the existence of an infinite number of conserved charges that make up the integrable structure

Symplectic field theory

Before Ian's talk, we also saw another talk in the Science Center C (Shing-Tung Yau invited us), namely a talk by the mathematician Helmut Hofer from NYU. It was about symplectic field theory, and already the meaning of the term is not quite clear.
  • instead of a manifold, Hofer was discussing a concept of a polyfold
  • it seems that the dimension of the polyfold may jump from point to point
  • this technology should be powerful for infinite-dimensional systems, and it should give a unified framework to study Gromov-Witten theory, Morse theory, and many other theories like that
  • nevertheless one may draw finite-dimensional examples. Hofer's example is a heart connected with Jupiter by three tubes, while Jupiter is surrounded with red Saturn's rings :-)
  • this mathematical machinery should explain how Riemann surfaces bubble off - all such phenomena have a local flavor in his formalism
  • in the second part of his lecture, Hofer discussed applications, and Sergei Gukov told us a couple of words about this second part, too
  • the first 30 minutes were spent with deriving the equations analogous to cubic string field theory, namely QF+F*F=0
  • then he discussed how to construct Riemann surfaces from pieces - namely from Riemann surfaces with holes p and antiholes q - where he formally defines the commutator of [p,q] to be hbar, whatever it exactly means - this commutator is probably the source of the word "symplectic"
  • it's not clear what's the relation between the different things he was discussing
Let me mention that if my description of this mathematical talk makes no sense to me, it may be my fault, but it is not guaranteed that it's my fault. ;-)

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reader NL said...

Speaking as an experimentalist whose talks have always been in PowerPoint or some non-M$ equivalent, is it unusual that Ian used PowerPoint?

reader Lumo said...

Dear Nathan,

it's becoming more usual - my estimate is that 1/3 of the talks are computer-based these days, and one half of the computer-based talks rely on PowerPoint - the other one-half being mostly Linux programs visualizaing directly TeX, PS, or PDF.

I was told that the percentage of computer talks is still negligible in maths, and it is huge in the commercial sector.


reader Arun said...

Here is a criticism of the "Powerpoint" way of thinking. don't think physics is in any danger of falling into the trap discussed above, whatever form of slide technology that physicists uses. However, in my opinion, and in my experience, such as it is, managers prefer not to deal in complexity, and Powerpoint is used as a tool to hide that.

reader Lumo said...

Come on, Arun. I can't believe that you're serious.

Sure that one of the points of PowerPoint is to make complex things look comprehensible - the point of the powerpoint presentations is to explain something, and convey the essential points.

I think it's a very important goal - and it's important for managers and scientists alike. What to do with your statement that the managers don't like complexity? You may be surprised how complex things do they often have to solve.

But otherwise, of course that they dislike complexity, and they prefer things to become simpler and more efficient. So do I. You don't??? If someone *enjoys* if things are complex and confusing, then it's hard to resist the temptation to kick the person's buttocks, especially if (s)he is a bureaucrat that will make *your* life complex. ;-)

Of course that one of the goals of theoretical physics is to make the important about the word convertible to convincing slogans following bullets in a PowerPoint file. How could it be otherwise?

If some group of people does not use computerized presentations etc., it just means that this group is technologically delayed.

Blaming the Columbia disaster on PowerPoint is silly.

PowerPoint is a clear progress for presentations. It does not solve everything, but it solves a lot.

reader Lumo said...

And one more thing. Ian Swanson's PowerPoint file could have been typed directly in TeX, with some simple projecting software, or something else - he heavily uses the full, displayed mode of TexPoint, that I discussed a month ago on this blog. (Well, he said that he often pastes the TeX source from his papers.) ;-)

I just can't see anything reasonable in these comments "against PowerPoint" etc. - they just look to me as pronouncements of left-wing morons who want to fight against America, capitalism, Microsoft - and everything else that works - and this fight is so important for them that it even affects their opinion about how presentations should be done. Sad.

If someone thinks that his or her output is better without PowerPoint, he does not have to use it. Most people don't use it. But the results of managers etc. simply DO show that PowerPoint is useful in the commercial sector, and it is increasingly useful in science, too.

reader NL said...


TexPoint is indeed great stuff. Until recently I had just assembled simple graphs in simple TeX files but now, combining PowerPoint and TexPoint, the slide quality is through the roof.

The complaints about PowerPoint aren't ludicrous- the default PowerPoint mentality, if accepted by both presenter and presentees, only encourages bureaucratic idiot-speak and excessive simplification. I've never seen this as a problem where stuff of importance was concerned, though- only in speeches made to low-level funding apparatchiks and whatnot.

reader Lumo said...

Hey Nathan,

well, there's always a question of the right measure. Some categories of people simply *can't* think in more complex ways - and the only thing that PowerPoint reveals is that these things, as they think about them, *are* quite simple.

My feeling still is that 80% of talks are immersed in unimportant and boring intermediate results, and the point is usually obscure. Well, the reason most likely *is* that there is no important point in the talk - no PowerPoint, if you will.

You know, there are two very different questions: one of them is whether a scientist is thinking in the right way, and takes all necessary details into account when he derives a result. The second question is how he presents the results to others.

If someone uses illegitimately simplified reasoning, then it's of course wrong. But deriving a result is something else than presenting it. Presentations simply must be trying to convey a maximal number of useful information in the given time, regardless of the format - and PowerPoint just happens to be a useful tool.

If you saw Ian's PowerPoint file, you would be impressed how detailed it is.

On the other hand, my PowerPoint slides for the classes are much less detailed, but of course they only serve as framework to make everyone sure what is being discussed using the blackboard.


reader Lumo said...

Because Arun gave us a link to the article based on opinions of the guy named Tufte, let me also link an article "Five experts dispute Tufte on PowerPoint":

reader Arun said...

Lubos: I'm not blaming the technology as such. Powerpoint is simply a tool. But there are poor habits of thought that it seems to encourage (or lets people get away with).

If you can make an effective whiteboard presentation, you can probably make an even more effective Powerpoint one, I'm not denying that.

I have much more to say, especially in response to the URL you provided. Maybe I'll do it on my blog later. The world, in bulk, is more like "Dilbert" and less like a good physics department.

reader Arun said...

You might find this interesting: it is on Powerpoint and includes a reference to Feynman: is a image, but I'm not sure I should link it in as such in blog comments.)

reader Lumo said...

It's been explained in the criticisms of Tufte I linked above - which you obviously have not read yet - that the problem was that the engineers thought that the point was unimportant, which is why it was just one slogan in the PowerPoint file. If they thought it was more important, there would have been more material about it. At any rate, PowerPoint is not guilty, it's just a tool that can be used by wise people and less wise people.

reader Arun said...

Sorry, in addition to the above you need: - this one begins talking about Feynman

and this one continues to blaming the Columbia accident on the Powerpoint style of cognition, here is what the accident investigation board itself said:

As information gets passed up an organization hierarchy, from people who do analysis to mid-level managers to high-level leadership, key explanations and supporting information is filtered out. In this context, it is easy to understand how a senior manager might read this Powerpoint slide and not realize it addresses a life-threatening situation.

At many points during its investigation, the Board was surprised to receive similar presentation slides from NASA officials in the place of technical reports. The Board views the endemic use of Powerpoint briefing slides instead of technical papers as an illustration of the problematic methods of technical communication at NASA.

reader Lumo said...

Well, there are thousands of issues related to space shuttles that have been life-threatening. It was not the first space shuttle that disappeared.

I don't believe that replacing PowerPoint with reading technical papers on the seminars that most people don't understand would have saved the space shuttle.

For an engineer or a scientist, it is extremely important that he or she still imagines very specific technical things and calculations behind the words - science is NOT just a game with the words, as some non-scientists (and crackpots) imagine it. Every word or sentence hides something very explicit behind it. But on the other hand, it does not mean that we should not use the words.

reader Lumo said...

Incidentally, Arun, some of your comments about Feynman partially indicate that you're a bit confused.

Do you distinguish Challenger and Columbia? Challenger burned in 1986. PowerPoint 1.0 was presented by Apple in 1987, and Columbia was much later. Do you realize that?

Feynman's investigations of Challenger have nothing to do with PowerPoint - I could also argue that Challenger collapsed because they were NOT using PowerPoint - if I were not ashamed to present the arguments analogous to yours in their quality. ;-)

reader NL said...


I think I can actually claim responsibility for introducing Ian to TexPoint...

reader Lumo said...

You taught him TeXpoint well! ;-) I suppose that it was more important when he learned TeX itself. :-)