Yesterday Sean Carroll and I appeared on the BBC Radio 4 program The Material World, in a segment on String theory – knot good enough?, about the controversy over string theory. The segment started with a piece from the play Humble Boy by Charlotte Jones, in which the main character is working on string theory. I don’t think anything either of us said was particularly controversial or would be in any way surprising to a regular reader of either of our blogs. The same program had a segment on the multiverse three weeks ago.

Some more titles of talks at next week’s Strings 07 have appeared. Witten’s talk is entitled “Three-Dimensional Gravity Revisited” and presumably will be about the new ideas described here. So, at least one talk there will be about a non-string theory approach to quantum gravity more along the lines of the LQG program. The schedule doesn’t seem to include any discussion session like the one at Strings 05 where the audience voted against the anthropic landscape.

A competing conference to Strings 07, Loops 07 will be taking place at the same time next week, but in Mexico, not Madrid. It’s much smaller, with less than a third as many participants. There will be one plenary talk on string theory, Moshe Roszali speaking on “Background Independence in String Theory”.

As the hunt for the Higgs is heating up at Fermilab, and CERN has officially announced the delay of LHC startup until next May, there’s a group of filmmakers who may be well-positioned if something exciting is found at the Tevatron. For the last few years 137 Films has been making a film to be called The Atom Smashers, following scientists working at FNAL. Filmmaker Clayton Brown is keeping a blog about this.

Yet another bogus “possible [experimental] signature for string theory”. Even Lubos doesn’t seem to believe this one, so I’ll just quote his argument:

*My personal guess based on our work on the weak gravity conjecture is that the black hole bound is also satisfied in string theory for localized macroscopic objects, up to small corrections. This belief of mine is supported by the observation that Gimon & Hořava don’t have any explicit solution for their “superspinar”.*

Christina Sormani tells me she has created a Wikipedia article on the proof of the Poincare conjecture, see here. For the latest on Perelman, see here.

‘String Theory – knot good enough?

‘Radio 4 Drama’s science season continues on Saturday with Charlotte Jones’ play Humble Boy. In it, a young physicist turns to String Theory in an attempt to unite the irreconcilable in his life. But is he doomed to failure?’

Sounds fairly realistic … will have to listen in tomorrow.

hehehe

http://xkcd.com/c171.html

So, at least one talk there will be about a non-string theory approach to quantum gravity more along the lines of the LQG program.???

Aaron,

If Witten is talking about the same thing I heard him talk about, it’s an approach to quantum gravity that involves non-perturbative quantization of the 3d version of Ashtekar variables, no strings anywhere to be seen.

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I think it’s unseemly to speculate on what other people are working on, so I probably should just be quiet. I’ll just say that it’s silly to frame this as a LQG vs. string thing. Witten invented the Chern-Simons quatization of 2+1D gravity way back when.

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For the latest on Perelman, see here.Well, I know next to nothing of the russian language, but tried one of those online translators, and giving some discounts to the usually terrible literal translations and other funny effects, I did not like what I read. Ridiculous.

Tried Babelfish. They are making fun of him for riding the subway in sneakers rather than driving a Lamborghini in Guccis, after he turned down a million dollar reward?

How profound.

Babelfish translation

Aaron,

The LQG comparison may be silly (but only very slightly so…), but I think it’s remarkable that for the second year in a row Witten’s talk at Strings XXXX will not be about string theory. And, I strongly suspect his talk will be by far the one with the most interesting new ideas.

Peter,

Your Perelman link — how would you feel if people followed you with cell phone cameras and posted it to the web?

Kris,

I don’t think it would bother me, if it was a rare event. A lot of it would certainly get annoying. Perelman may feel quite differently, I have no idea. I couldn’t read the Russian comments, and if they’re stupid and disrespectful, that’s a shame.

in English via google language tools

Can someone who actually knows russian translate this?

Here is my try at translation of the Perelman “news”.

Almost forgot. Recently I met Perelman in St. Petersburg subway. Yes, that same crazy scientist who proved the Poincare conjecture. They wanted to give him Fields medal and 1 million bucks, but he told everybody to fuck off.He boarded at subway station Kupchino and left at Victory Park. During that time I discreetly took pictures of him on my cell phone. The picture quality is bad, but that’s all I have.

He looked like an accomplished tramp; he also had a huge fingernail on his little finger that he used to constantly probe in his mouth. Terrible. Nobody recognized him except myself, that was somewhat strange. However, my surprise disappeared when I tried to tell about this encounter to my acquaintances: less than one out of five heard anything about Perelman. Although he was shown on TV many times.How’z’bout we wait for the talk and then see what’s in it?

Here is a translation of a note about Perelman:

I almost forgot! A few days ago I met Perelman in St. Petersburg’s metro. Yes, that crazy scientist who proved Poincare conjecture. They wanted to give him a Fields medal and 1,000,000$, but he said — go fuck yourself. So Perelman got in on “Kupchino ” station and he got off on “Park of Victory” and all the time when he was in the car I was recording him on my phone. Quality is poor, but it is what it is.

He looks like a homeless. He has a very long nail on his pinky, and he pecked in his mouth with this nail. Awful. Apart from me, nobody recognised him which was sort of odd. Yet I am not surprized anymore — when I described the story to my friends, at most one out of five ever heard about Perelman. Although there were many programs about him on TV.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Overall, the author uses quite illiterate Russian, and I am not surprised that it is hard to translate mechanistically. The following comments are totally useless, and many are indeed stupid and stinky, so after reading such comments one may want to take a shower.

Aaron,

Well, I heard him give a talk with pretty much the same title a few weeks ago here in New York. During the talk he brought up the question of LQG, noting that in 3d you could covariantly express gravity in terms of a gauge theory, that the way this was done in 4d (LQG) was non-covariant. I’m not sure I really understand this point, maybe he will elaborate at Strings or in a paper.

In the question session afterwards someone asked him about whether what he was doing could be embedded in string theory. His only answer was to note that recent arguments claiming to show that you can’t decouple supergravity completely from string theory in a limit failed in 3d, implying that even if you embedded what he was doing in string theory, it could be completely decoupled from the string theory. There was nothing at all about string theory in his talk. Perhaps he has come up with an important connection to string theory in the last few weeks, perhaps there is some less important connection to string theory which he’ll mention in Madrid but didn’t mention in New York. But, as far as one could tell from his talk here, the important new idea he has about 3d gravity doesn’t have anything to do with string theory.

Not even having the benefit of the translation yesterday, I thought that these pictures and the picture taker — not Perelman himself — were a bit creepy.

I wonder who decides the list of invited speakers. There are some pretty odd choices there — some people whose recent papers have hardly been cited, and others whose talks are clearly going to be re-runs of talks given many times before……the only novel-looking talks are those of Verde and Vafa.

Er … Pavel, what was wrong with Eugene’s translation?

To tell the truth, I am a bit disappointed with Perelman. I was hoping that he would be wearing a T-shirt with “F*** the IMU” on it.

«Er … Pavel, what was wrong with Eugene’s translation?»

I think Pavel meant that the article’s author used “illiterate Russian” not Pavel and thats why machine translations of it suck even more than usual. (seems clear to me)

Regarding the 1 in 5 ratio who knew of Perelman, I bet all of them know who Paris Hilton is. She achieved so much after all…

Eugene is a Russian speaker!

gunpowder,

I presume the speakers are chosen by the “International Advisory Committee”

http://gesalerico.ft.uam.es/strings07/020_organization07_contents/021_international_ac.htm

Have you considered that the very small number of talks that sound like they’ll have novel ideas might be due to something other than the advisory committee not doing the best possible job of coming up with speakers?

Well, the paper is out, and it’s about finding dual CFTs for 3D gravitational systems. So, I suppose it depends on whether you call AdS/CFT string theory or not.

The Pavel Krapivsky and Eugene Stefanovich translations are correct… with Eugene capturing just a little more correctly (for examples Eugene gives the translation “bucks”, which is what the author wrote, whereas Pavel gives “$”, normally understood as dollars, which is not what was written.

However, both I think did not capture the true flavor of the obscenity, because while there are a variety of ways to say “**** you” in Russian, the one chosen was one of the strongest…so strong in fact that some Russians will not utter it and will prefer a euphemistic, watered down form. It is also doubtful that a machine translation would get the obscenity, because нахуй correctly written should be two words, на хуй…which I will not translate here for reasons of decorum.

What is NOT correct is the statement that Perelman appears often on Russian TV. I get 16 channels of Russian and Ukrainian TV, and have yet to see Perelman on the news.

Aaron,

Invoking the letters AdS/CFT doesn’t make it string theory. This isn’t string/gauge duality since there are no strings on the AdS side.

People have looked a lot at exactly this AdS_3/CFT_2 correspondence, trying to relate string theory on AdS_3 to 2d CFT. This gets very complicated and ugly from what I can tell. What Witten has done is throw out the strings on the AdS side, making things much simpler, and it seems, much more interesting.

Strangely, most string theorists don’t feel the need to live in such pigeonholes.

On page 37, Witten does mention the possibility of embedding this into a string theory.

“Have you considered that the very small number of talks that sound like they’ll have novel ideas might be due to something other than the advisory committee not doing the best possible job of coming up with speakers?”

I really wouldn’t presume to judge that. What I do know is that, if I were on that committee, I would find some diplomatic way of telling the invitees, in the strongest possible terms, that we don’t want to see the nth re-hash of a talk claiming that eternal inflation is absolutely guaranteed to work, that 3-dimensional gravity is really cool despite the abundant evidence that it is utterly unlike 4-d gravity, etc etc etc.

sorry Peter: I stopped after reading the 1st sentence of the abstract, because it looks one more paper that studies irrelevant physics in order to find interesting mathematics.

Is this recent theoretical trend healthy for physics? Please search “FIND A WITTEN AND TOPCITE 500+” on SPIRES: how many of these 46 super-papers should an experimentalist read? And what about other theorists that do Witten-style research without being Witten?

There was a New Yorker article about Perelman, Yau & others pursuing the Poincare Conjecture proof:

http://www.newyorker.com/archive/2006/08/28/060828fa_fact2?currentPage=10

http://www.newyorker.com/archive/2006/08/28/060828fa_fact2?currentPage=11

!!

He quit his job as a mathematician, because of his discovery..because his notoriety would force him to deal with the unethical idiots.

You now understand Perelman’s MIND (totaly Ideality, VS Reality=Corruption), which accounts for his isolation. The latter is perceived as eccentricity, the extreme language FU!.

This reminds me of the quote:

“An unreasonable man tries to Change the World, a reasonable man adapts to it..we need more unreasonable men”

— Revolution VS Evolution

“Captain Pike has an illusion, and you have reality. May you find your way as pleasant.””

— “The Menagerie”/Star Trek, Talosians final message to Capt. Kirk

Perelman changed the world of mathematics, & has “retired” into a world of mathmatical-ideality (“illusion”..mathematics is said to be imaginary by a famous mathematician)

ST is an “illusion” (all math, no connection with real-world experiment), & after 20 years needs to be “retired”. The Star Trek quote refers to 2 paths: Reality & Illusion. “Not Even Wrong” is accentuating that the Illusion is going no where.

I am confused about what Witten tries to do. Wasn’t CS theory for general group G solved 20 years ago, with all correlators being framed knot invariants which can be readily computed from G. Why not just put G = SO(2,1) and be done with?

In my understanding, the difference between a spin connection and a SO(2,1) gauge connection is that you have a vielbein which can be used to write down the Einstein-Hilbert action,. But the CS action does not depend on the vielbein, so I don’t see what special about spin connections in this case.

Anyway, it is striking that there are two unphysical assumptions: D = 3 and a negative cc. Witten suggests in section 1.2 that a world with positive cc (like the one we may be living in) is always at best metastable, which is pretty close to the anthropic worldview.

M,

I agree the Witten paper has no direct physical relevance, and there’s no reason experimentalists should be reading it. But it’s a fundamental new idea about gauge theory, gravity and mathematics, and as such it may some day lead to something directly physically relevant. I think a lot of Witten’s best work should be thought of as analogous to some of the best work of experimentalists developing new detector technologies and acceleration techniques. There’s no reason a theorist should be reading the papers of people who are making advances on using lasers to accelerate particles, and this work is not of any immediate use in HEP, but it is very important that someone is doing this kind of thing, and it is the sort of thing that may lead to important breakthroughs in the future.

Thomas,

CS theory is just not well understood at all for cases like this of non-compact space and groups. One of the interesting things about Witten’s work is that I think it shows how little we understand about what many people think of as simple gauge theory QFTS which are completely understood.

Aaron,

I was making no comment at all about string theorists, I was making comments about string theory. You seem a tad defensive…

I won’t be surprised a few years from now when string theorists are working on 4d gauge theory approaches to quantum gravity using Ashtekar variable, insisting what they are doing should be called “string theory”. I think Nati Seiberg made the comment to a reporter a couple years ago that whatever theorists had some success with in the future, they would call it “string theory”.

Classical Einstein gravity may be formulated as a theory of SO(n,m)- and/or ISO(n-m)-connections. This basic fact underlies the approach of LQG just as well as many developments in the study of supergravity, which is usually best understood as a gauge theory for the super Poincare Lie algebra.

The crucial point of LQG is 2-fold

1) conceive the space of all these gauge connections as a space of holonomy functors

2) pass from the space of ordinary (smooth) connections to the larger one of “generalized connections” (essentially dropping smoothness and continuity of the holonomy).

It is mainly the second point here which makes LQG different from other approaches of quantizing gravity. I don’t think that Witten is talking about quantizing Chern-Simons using “generalized connections”.

But I do very much agree that it is good that attention is being paid to understanding gravity as a theory of gauge connections. Of smooth connections, in particular. One look at the LQG program anew, without passing to generalized connections.

One should look at […]

I was making no comment at all about string theorists, I was making comments about string theory.I just think it’s amusing that anything you think is interesting you define to not be string theory. I think most of the rest of world would consider AdS/CFT as part of the circle of ideas generally called “string theory”.

You seem a tad defensive…Are you really going to play the “defensive” game? It doesn’t put you in very good company.

There is nothing wrong with Eugene’s translation, I just submitted mine before I saw his. LDM rightly says that it is hard to “capture the true flavor of the obscenity”.

Aaron,

Most of the world considers AdS/CFT to be “string theory” because the AdS side of the correspondence is a string theory. I seem to be repeating myself, but it’s a simple fact that in Witten’s paper the AdS side of the correspondence is NOT a string theory. Claiming that what Witten is doing in this paper is “string theory” is simply dishonest.

And I think that’s all there is to say on the subject.

Peter said:

Claiming that what Witten is doing in this paper is “string theory” is simply dishonest.Urs said:

One look at the LQG program anew, without passing to generalized connections.One convenient way to do that—combining a fresh look with an illustrative comparison—is to follow Laurent Freidel’s recent online seminar talk of 15 May.

Matter coupling to 3d quantum gravity and effective field theoryThe link to the series of online LQG seminars is at

http://relativity.phys.lsu.edu/ilqgs/

The direct link to the PDF of Laurent’s slides is

[url]http://relativity.phys.lsu.edu/ilqgs/freidel050807.pdf[/url]

The direct link to the MP3 audio of his talk is

[url]http://relativity.phys.lsu.edu/ilqgs/freidel051507.mp3[/url]

A key point which Laurent makes at the outset is that because matter is present the system has infinitely many degrees of freedom and that he is intentionally restricting himself to using analytical tools which apply to the 4D case (with matter) as well. He explicitly excludes AdS/CFT.

In the work described in the talk, the authors get Feynman diagrams of matter out of spinfoams (the “paths” of spacetime geometry evolving in a path-integral picture).

Since both talks are recent and concern 3D gravity, they make an interesting side-by-side comparison and allow the fresh look that Urs mentioned.

Perelman is a very intriguing character. I liked the quote from joe about needing more “unreasonable men” to change the world.

LDM: I have been studying a bit of the Russian language, but strangely enough I could not find the insulting expression in my russian textbook ;-), thanks! However, from your post I should be very careful about that insult as you imply that it is very strong…

Why is theoretical physics harder than mathematical physics? Witten gives a good explanation on p. 10:

😉

Peter, I do not understand your analogy: nobody would worry that people who develop lasers might have lost contact with the reality. On the contrary, the physical relevance of a certain kind of theoretical work looks questionable, even taking into account that sometimes progress comes from unexpected directions. I wonder what Newton would have achieved by studying topological supergravity in lower dimensions.

What I meant is that it is still an open (though possibly also still intractable) problem to find the quantized configuration space of

smoothconnections in the case of either Yang-Mills theory or of Einstein gravity, or of any other non-trivial nonabelian gauge theory.I am talking about the analog of the “LOST theorem

href=”http://de.arxiv.org/abs/gr-qc/0504147

or the analogous result be Ch. Fleischhack

http://arxiv.org/abs/math-ph/0407006

by CH. Fleischhack — but for

smoothconnections.In fact, this has been done in the case of abelian (but possibly higher) connections by Freed, Moore and Segal. They find a couple of very interesting — and very subtle — quantum effects. Precisely

thiskind of analysis ought to be done for Yang-Mills and/or Einstein gravity in Palatini form.Clearly nonbody can do it right now. But that’s the interesting problem to solved. I would appreciate if people started looking into this problem more seriously. Freed-Moore-Segal demonstrate that there is gold to be found here…

Not sure if it has been mentionned on this blog already but there has been a quantum gravity school in Poland last march organized by John Barrett and Hermann Nicolai covering some string theory, some LQG, and some stuff related to noncommutative geometry and to quantum groups. Some of the lectures notes are online, all the talks being available as mp3s http://www.fuw.edu.pl/~kostecki/school.html

M:

The history of the laser is the opposite. Some very great physicists did think it was crazy. When Townes met Niels Bohr in Denmark and explained to him the idea behind the maser, he said “but that is not possible”. Townes never could convince him.

Von Neumann had the same reaction (but later changed his mind).

Noted Columbia theorist Llewlen Thomas said flatly it could not work, and stopped talking to Townes. All this is recounted by Townes in chapter 5 of his book “How the laser happened”.

So in some sense, the laser analogy is not too bad, but contrary to Peter’s opinion, the theorists can learn a lot from experimentalists, as the laser history shows.

If I cared to refute Peter’s analogy, I would prefer to cite an observation of Ulam’s in regard to Von Neumann:

“Von Neumann was the master of, but also a little bit the slave to, his own technique. When he saw that something could be done, he let himself be carried away on tangents. My own feeling is that some of his work on classes of operators or on quasi-periodic functions, for example, is very interesting technically, but to my taste not terribly important; he could not resist doing it because of his facility.” – Adventures of a Mathematician, pg. 78.

Witten results are technically interesting to mathematicians, but to my taste, not terribly important for real physics.

M,

Another way of saying my analogy is that every scientific field is limited in what it can do by the limits of its tools. What Witten is doing is trying to come up with new understanding of the basic tools of fundamental physics, QFTs. Personally I think a deeper understanding of the relation of math and QFT may lead to new tools that might ultimately allow the solution of fundamental problems in HEP. Sure, this hope is very speculative and maybe wrong, but I think it’s as promising a speculative idea as any others out there at the moment.

It’s hard to tell where new ideas like Witten’s will lead, maybe nowhere. But at least he’s coming up with new ones, not endlessly working on the same tired ones that don’t work like most people.

LDM, I didn’t know this history, but I insist that inventing the laser might have been successful physics or unsuccessful physics. In any case, physics.

Peter, in some speculations I see the effort to come back with results (e.g. today the arXiv:0706.3688 paper by Chamseddine and Connes), while a too large fraction of hep-th now looks disconnected from reality.

Anyhow, let’s wait 30 more years to see if we will better understand physics by studying things like gravity in 2+1 dimensions, the SM landscape in 2+1 dimensions, etc.