Not Even Wrong

The list of speakers for Strings 2007 is now available. Titles of talks are not available, but as far as I can tell they’re not taking up Lee Smolin on his suggestion that they have someone there to talk about developments in the LQG approach to quantum gravity that string theorists might find interesting. Also, no mathematicians on the list and fewer mathematically inclined string theorists than at Strings 2006. One experimentalist from CERN (Rolandi), presumably to talk about the LHC. Lots and lots of people who work on the landscape and various string compactification schemes, with the Stanford group well-represented.

If you’re in Princeton tomorrow there are a couple of interesting math talks. The talk by Simons at the IAS on Some Results in Differential Cohomology (with Sullivan, presumably about this) should set some kind of historical record for the highest net worth of a speaker giving a technical math talk. Ed Frenkel is giving the colloquium at the math department on Langlands Correspondence for Loop Groups; I wish I had time to go down there to hear it.

The conference in Paris on non-commutative geometry in honor of Alain Connes is continuing this week. Fabien Besnard reports on the talk by Michael Atiyah, where evidently there was some commentary on the role of mathematical beauty in physics, and warning to the young that working on the kind of idea he was discussing would be dangerous for their careers. And no, in French “Physique Retardee” does not carry the same meaning as a naive translation to English would imply…

The web-site of representation theorist Ivan Mirkovic has lots of interesting things, including notes about geometric Langland and the recent work of Witten-Kapustin-Gukov. Another interesting representation theorist web-site is that of Alistair Savage, which includes various lecture notes and an overview about quivers and geometric representation theory.

See here for the program and some lecture notes from the recent spring school at Trieste. Especially interesting are the lectures by Martin Schmaltz about Physics Beyond the Standard Model and the LHC. The Resonaances blog also has a report about a recent talk by Schmaltz at CERN. The bottom line seems to be that, contrary to what was previously thought, in many of the kinds of supersymmetric models supposed to come from string theory, you can’t run the observed scalar superpartner masses back up to the unification scale, so, even if you see such things, you won’t get information about grand unification out of them. Schmaltz gives a graphical representation of the reaction of various people to this. I’m in category A.

Tommaso Dorigo has an excellent suggestion for experimental collaborations worried about the information that their blogging members are putting out. Don’t fight them, join them! He suggests that large experiments like CDF, D0, ATLAS, CMS should be putting out a collaboration-approved blog, getting their story out to the public through this medium.

Update: I realized there is another event I should mention. This Saturday I’ll be giving a talk at a symposium at the University of Central Florida in Orlando, organized by the Society of Physics Students and the Campus Freethought Alliance. Also speaking there will be Jim Gates, who presumably will be taking a somewhat more optimistic view of string theory. I’m still trying to figure out what to talk about, current plan is to cover some of the material in my book, emphasizing the parts everyone ignores that are not about string theory…

Bloggingheads.tv now has some video up with an interesting discussion between John Horgan and George Johnson on a range of topics. One segment is entitled String theory deemed load of crap!, and discusses the controversy over string theory. Both Horgan and Johnson agree that things are not look good for a physical theory when there start being public debates on the subject. Johnson also discusses his time at the KITP and mentions this blog. He seemed to be particularly struck by the behavior of the participants at the session he ran there which involved a lot of bashing of Lee Smolin, with Mark Srednicki raising his hand when Johnson said he didn’t think anyone would call Smolin a crackpot.

Johnson also described the “echo chamber” effect of blogs like this one. I guess I better keep this going by blogging about his commentary about my blogging…

Update: Sean Carroll has a posting about this over at Cosmic Variance entitled String Theory is Losing the Public Debate. Probably best if people join the discussion over there, which so far includes John Horgan and others.

Update: If you like this sort of thing, more blog discussions about string theory here, here, and here… and here and here.

This latest news from the LHC does not sound good. One hopes it won’t affect the LHC schedule.

Update: Also discussed at the Resonaances blog from CERN.

Update: Latest (4/3/07) news here.

Shelly Glashow is traveling around, giving talks bashing his childhood hero Isaac Newton (and noting that he was “surely one of the greatest intellects the world has known”). He’ll be at NYU tomorrow talking on The Errors and Animadversions of Sir Isaac Newton. For a copy of his talk, see here, (and here for a summary in Catalan).

Tonight is the Lawrence Krauss – Brian Greene string theory debate in DC, and next week in Berkeley Krauss is debating John Terning on the subject, at an event entitled Extra Dimensions and String Theory: Physics of the Future or Pure Mathematics? The event is organized by the FQXI funded organization Multiversal Journeys.

Krauss was at the cosmology conference that Tommaso Dorigo has been reporting on, giving a dinner talk dissing anthropic reasoning and pointing out that cosmology has a “miserable future”, since everything is receding from us. His main conference talk was evidently not very optimisitic about near-term prospects for learning more about dark energy or dark matter.

For more about non-commutative geometry and number theory, David Kazhdan is giving a talk at Harvard on April 18 with the following abstract:

Discussion of Alain Connes formulation of the Andre Weil’s theorem. [ the Riemann conjecture for the functional filed case]. Alain Connes found a very interesting way to interpret the results as a computation of an asymptotic of a family of operators of finite rank.

Lieven le Bruyn has a discussion of Plato’s cave and a recent paper Modular shadows and the Levy-Mellin infinity-adic transform, by Marcolli and Manin, who motivate their title by relating Plato’s cave and holography in AdS/CFT.

Update: The Washington Post’s publication Express has an article about Lawrence Krauss and the problems of string theory, entitled Frayed String.

Update: Science has a report on the debate. Also, there’s a report (with audio) from a blogger at the Hooded Hawk blog.

Last week Princeton hosted a workshop on Physics at LHC: From Experiment to Theory. Many of the slides of the talks are available here. The talks covered a wide range of ground, from theory not obviously relevant to the LHC to reports on the status of experiments. The talk by Michael Tuts of ATLAS reports that they may be roughly 5 weeks behind schedule, with nominal schedule setting the start of beam commissioning at 450 GeV late in November. 7 TeV beams won’t be available until summer 2008, with first physics run perhaps in July, and about 10-100 pb^-1 during 2008, giving similar statistics to what the Tevatron has today for some processes. It looks like it may be the 2009 run that will most likely produce data that will go beyond the Tevatron results, although if the Higgs mass is about 150 GeV, there may be evidence in the 2008 data. Plans for a luminosity upgrade in 2015 are already proceeding.

There was also a plan for a meeting of the String Vacuum Project at the workshop, with a discussion paper available here (via their Wiki).

This week, also down in Princeton, but at the IAS, there will be a Workshop on Homological Mirror Symmetry and Applications, mainly devoted to recent work on geometric Langlands and its relation to mirror symmetry. Since I had to teach I couldn’t make it down there today, so unfortunately missed the first talks by Kapustin and Witten, as well as that of Edward Frenkel, but I’m looking forward to going down tomorrow and maybe later in the week to hear some of the talks.

Warning: There’s not much science in this posting, just mostly people behaving badly. You would be well advised to skip this one, unless you find this kind of thing entertaining…

Long ago, as a public service, I set up a posting to hold comments censored by Lubos Motl, since his preferred way of dealing with people who make comments he finds hard to answer is to delete them. It appears that now a place for inconvenient comments censored by Clifford Johnson at his blog Asymptotia is also needed. If you have a copy of a substantive comment deleted from there or want to discuss one of these, you can use the comment section here.

Since the first thing censored was one of my comments, I’ll provide a little background, then reproduce the censored material I have access to.

This exchange began with this comment from Clifford, which seemed to me to be little more than an out-of-control personal attack and rant, so my only response to it was:

Clifford,

As time goes on and the failure of string theory becomes more apparent, you are starting to rant in a manner which is converging with that of your junior colleague at Harvard. You should get a grip.

Not very long after I wrote this comment, the following comment appeared from Lubos Motl:

Dear Mr Woit,

All the best
Lubos

This was followed by a similar comment attacking Smolin for what he had written about the black hole information paradox, and Smolin responded with a short and polite answer (I don’t have copies of these).

Clifford has edited my original comment, removing “in a manner which is converging with that of your junior colleague at Harvard”, and replacing it with “…snip … – personal reference deleted -cvj”. He has also removed the comments from Lubos and the response by Smolin, replacing them with this comment. Here he claims to have deleted these comments without reading them, since, for undisclosed reasons, he has a policy of deleting all comments from Lubos. Whatever the reason for this policy, he does want to make clear to everyone that he has a high opinion of Lubos as a scientist, and for his work at the Reference Frame “widening the discussion” about physics:

Since I have a great deal of respect for his ability as a physicist, however, if he was making a physics point in his comments, perhaps he might make it on his blog and link to this discussion via trackback. I thank him for his physics contributions and widening the discussion.

I recently noticed that, around the same time I was preparing my slides for a talk about Is String Theory Testable?, Michael Douglas was doing something similar, preparing a talk on Are There Testable Predictions of String Theory? There’s a certain amount of overlap in our presentations, and people might find it interesting to compare them.

Douglas goes over much the same story I do, but reaches different conclusions. For him, string theory does “make predictions”, just lots and lots of incompatible ones, so the problem is that:

none of the ideas which have been suggested so far are guaranteed signatures of string theory. We would be happier with one prediction, which could lead to a decisive answer either way.

This is the sort of thing I would call a prediction, so I guess we agree that they don’t exist. Douglas ends by noting that the one way he can think of to get such a prediction is through a statistical argument based on counting vacua and the dynamics of eternal inflation. He doesn’t mention the argument given in my talk that this is already falsified (by the lifetime of the proton), or that such arguments inherently lead to calculations that are inherently intractable and can never be done (this argument is due to him and Denef, it is surprising that he doesn’t mention it).

Along the way, Douglas does make a couple claims about things that he thinks the statistical anthropic landscape arguments disfavor, especially varying constants and large distance modifications to gravity. Seeing these would falsify our current theory, but would not falsify string theory, since it can accomodate them, although perhaps not within Douglas’s statistical framework.

One of the more surprising responses I’ve seen to my recent claims that string theory has failed as an idea about unification because it’s inherently untestable comes from Mark Srednicki, who writes (in the context of mentioning an MSNBC interview with Brian Greene):

We see that the big issue for Brian, and for just about all scientists (though with the apparent exceptions of Lee Smolin and Peter Woit), is what is TRUE. Not what corresponds to some philosophy of what science is or is not. Lee writes that the landscape must be rejected because “it would mean the end of our field” (page 165). It should be obvious that this is not the basis that is traditionally used for accepting or rejecting a theory! Peter’s (essentially the same) argument that string theory must be rejected because (at the moment) it does not appear to be sufficiently predictive (for Peter) is also irrelevant to the question of whether or not string theory is TRUE.

If the landscape is right, we may never get anything more than circumstantial evidence that it’s right. But that’s often the case in science. We’ve been spoiled in particle physics by having extremely precise data and highly predictive and quantitative theories for the past few decades. Most of the rest of science has not been so lucky. Perhaps we will not be so lucky going forward. The only way to find out is to do more work and see where it leads.

Srednicki’s reaction to the lack of testability of string theory seems to be that testability is not what matters. What matters is what is TRUE, and it’s perfectly logically consistent for string theory to be of such a nature that we can never test it. The problem with this point of view is that science is not so much about what is true as about how one knows what is true about the world. Religious believers are also interested in what is true and think they know what this is, but science is different since it provides a means for deciding what is true. Scientific ideas about the universe are true when they make predictions that can be checked in a convincing way. Ideas that can’t be experimentally checked in some way, directly or indirectly, may or may not be true, but they’re not scientific ideas, rather something of a different nature.

The LHC is the cover story on this week’s issue of Science magazine, with three articles on the topic here, here and here.

Also in this week’s Science is an article about the “spin puzzle”, the fact that accelerator experiments with polarized particles give results for protons that are different than what one would expect from a naive quark model. The general assumption seems to be that this is a QCD effect, one that is tricky to calculate. I’ve always wondered if there is any chance that there is some sort of spin-dependent behavior of quarks different than that predicted by QCD. I don’t know of any work by people trying to come up with such models, but maybe it’s out there. I’d love to hear from some expert on this about whether the experimental results really do point to a serious possibility of something going on other than standard QCD.

A new book of interviews of scientists has recently appeared, Candid Science VI by Istvan and Magdolna Hargittai. It contains interviews with David Gross and Frank Wilczek. The authors ask both of them about their interactions with Wigner, and what they think of various other famous Hungarian scientists. Wilczek explains why he has made various moves over his career, that he was quite influenced by Peter Freund as an undergraduate, why he thinks it took so long to get the Nobel prize, and that his motivation for working on the beta-function calculation was to know if the electroweak model had the same Landau pole problem as QED.

Gross talks about his background and relation to Judaism, and also about his Nobel prize work. He remains enthusiastic about string theory, and characterizes opposition to string theory in many physics departments as due to people not wanting to learn it because it is hard work, as well as fear that if they hire string theorists, all the good graduate students will go work with them. There may be something to what he says, but I think it’s out of date, and times are changing.

I hear from David Derbes, who put together Dyson’s 1951 Lectures on Advanced Quantum Mechanics that were mentioned here earlier, that World Scientific is publishing them as a book this month. Profits will go to the New Orleans Public Library, where David grew up.

The two new Fields medalist bloggers each have fascinating blog entries on Millenium problems. Terry Tao writes a long explanation of Why Global Regularity for Navier-Stokes is Hard. He also comments about the recent New York Times piece about him and about math education issues. The comment sections of his postings have some very interesting discussions going on.

Alain Connes has a wonderful posting about Le reve mathematique, especially his mathematical dream of proving the Riemann hypothesis using non-commutative geometry. He notes that the first goal is to come up with a non-commutative geometry version of a proof for the function field case. More about this in a recent posting on the same blog by David Goss.

This seems to be the month for string theory debates, with two a couple weeks ago in the UK involving Lee Smolin, and another featuring Lawrence Krauss and Brian Greene scheduled for next week in Washington D.C. The Washington Times has an article about this.

Smolin’s book has just appeared in the UK, and there have been lots of (very positive) reviews. See here, here, here, here, and here.

Besides talks (for a report on the one at Cambridge by a skeptical American physics student in England, see here), there were two debates. One featured Smolin, Philp Candelas, Simon Saunders and Frank Close and was held at Oxford; for a report, see here. It appears to have been a respectful and reasonable public airing of a few of the issues where string theorists and some of their critics disagree.

A couple days earlier though, a debate in London between Smolin and Mike Duff (also involving philospher Nancy Cartwright) had a very different nature. According to the report from one attendee, after Smolin started things out by arguing his case:

Smolin sat down. Duff stood up. It got nasty.

The trouble with physics, Duff began, is with people like Smolin…

Duff is described as “string theorist and man for whom, one imagines, the words ‘self’ and ‘doubt’ do not often rub shoulders”, and seemed to think it was a good idea to answer criticisms of string theory with vociferous ad hominem attacks. Lubos Motl and Clifford Johnson both found Duff’s behavior an excellent example for all string theorists, inspiring Clifford to write part VII of his extended attack on me, Smolin and our two books. He admitted somewhere around part V or VI that he actually hadn’t looked at the books and had no intention of doing so, and he’s pretty steadfast in that attitude. It never ceases to surprise me that people like Clifford don’t realize that, much as they may enjoy engaging in or listening to personal attacks on me and Smolin, this just doesn’t do a lot for the credibility of their field. String theorists often complain that Smolin portrays them as arrogantly dismissing any criticism, but they should realize that behavior like Duff’s doesn’t help them at all on this issue, quite the opposite.

Duff pretty obviously has a double standard for popular books about string theory. He’s quite capable of being polite, writing a very respectful review of Susskind’s The Cosmic Landscape for Physics World. His review of Smolin’s book in Nature Physics is something very different, much more like his performance at the debate. The review begins by misquoting Smolin, based upon something that was in the proof copy of the book he had (which the author hasn’t had a chance to look at), but was different in the published version. After the review, he had been informed about this, but still seemed to think it was a good idea to use this as ammunition in his personal attack on Smolin during the debate.

One of his main points was that it is ridiculous to claim that string theory has not made any progress since the 80s. Obviously there are some areas in which there has been progress in better understanding the theory, but, as far as the central issue, that of getting any predictions out of the idea of using strings to unify physics, it’s interesting to follow the link that someone with a waggish sense of humor at Nature put at the bottom of the page of Duff’s review. It’s a story from 1986 entitled Where Now With Superstrings?, and it reports on the views of string theorists at the time, roughly one year after the early developments that caused so much enthusiasm for string theory as a unified theory. The problem of too many vacua was something people were starting to worry about, but the feeling was that:

… another problem of non-uniqueness in superstring theory, the variety (thousands) of possible four-dimensional worlds it allows, is showing some signs of resolution.

The “progress” on this more than twenty years later is that instead of “thousands”, the number has moved up to the exponent, and we’ve now got the “Landscape” of 10¹⁰⁰⁰ or so possible four-dimensional worlds. Any “signs of resolution” of this are long vanished. Just as physicists are now waiting for the LHC next year, those of 1986 were waiting for the Tevatron to start up the next year, with Weinberg claiming that the mass range to be explored by the Tevatron was “a very plausible mass for them [superpartners] to have”. The reporter wrote that:

If the Tevatron sees no superparticles, supersymmetry will lose its value in the hierarchy problem, and hence half its motivation.

So, I guess Duff is right that it’s inaccurate to say that things haven’t changed with the prospects for string theory since 1986, since the situation now is a lot worse than it was then.

If you want to listen to the debate, audio is available on-line here, with a transcript to appear shortly. For another kind of audio showing what this is all about, see this posting from Sabine Hossenfelder.

Last Friday night when I was in Rome I received e-mails in quick succession from two science journalists asking what I thought about a new mathematical result, the “mapping of E8” that was going to be announced at a press conference on Monday. Information sent to journalists was embargoed until Sunday night at 11pm, but the first journalist sent me a copy of the brief press release and told me that there was a longer one available. Reading the press release left me still baffled about what this could be about: what was the “century old problem” that this group of 18 mathematicians had solved? The obvious interpretation of “mapping of E8”, mapping it as a geometrical object, didn’t make sense since that’s a well-understood problem. The group E8 is a 248 dimensional space, but its local geometry is the same everywhere and completely understood in terms of its Lie algebra. The global topology is interesting, but also well understood.

I wrote back to both journalists that the best person I knew to comment on this and its possible relation to physics would be John Baez, and asked to see the longer press release. It wasn’t much more enlightening, but it did have a link to a web-site with details. After spending a little time reading this I understood that “mapping of E8” was a calculation of the structure of representations of the split real form of E8, and decided that I was on vacation and not about to try and quickly write a blog posting about this.

Well, here are the press releases from MIT and AIM, and David Vogan did give a public talk about this yesterday at MIT. The media blitz was quite effective, getting the story into not just the usual suspects (there’s a good version of the story by JR Minkel at Scientific American), but also achieving a wide distribution in much less usual places such as today’s New York Times, the BBC, le Monde, and many, many others. I think this may be getting about as much attention as the proofs of Fermat’s Last Theorem and the Poincare Conjecture. There are also a huge number of blog postings, and I’m very pleased with myself to note that by far the best is the one by John Baez (crucially supplemented by the first comment there, from David Ben-Zvi), so I at least sent the journalists to the right place.

For mathematical details, John’s posting and the comments there are the best place to go besides the technical papers linked to from the AIM site.

While the calculation is a computational tour de force, and the computational methods may be useful elsewhere, the level of hype in the press releases, especially about the possible relations to physics, is somewhat disturbing. The AIM page on E8 and Physics contains statements such as

…once one adopts the basic principles of string theory, it can be argued that we live in the universe we live in because it is the only one that is possible.

as well as making the highly misleading claim that the new calculation has something to do with heterotic string theory.

What initially confused me about the press release is that, with the standard interpretation of what one means by “E8”, the “E8” that appears in heterotic string theory, there is no open problem to be solved. The group is well-understood, and so is its representation theory. As a compact Lie group, the representation theory of E8 is part of the standard Cartan-Weyl highest weight theory, and was worked out long ago. To read about this, there’s an excellent book by Frank Adams about the representation theory of E8 and other exceptional Lie groups, called Lectures on Exceptional Lie Groups. It is this representation theory that appears in the heterotic string story. For more about E8, and one of the stranger things I’ve seen in a math paper, you might want to look up a 1980 paper by Frank Adams called “Finite H-spaces and Lie Groups”, in the Journal of Pure and Applied Algebra.

What the new result is about is something quite different, the “split real form” of E8. The classification of compact Lie groups proceeds by classifying their Lie algebras, giving a well-known list, with E8 the largest of the exceptional cases. In doing this, one complexifies (works over the complex numbers), studying the complex semi-simple Lie algebras, which are the Lie algebras of the complexifications of the compact Lie groups. In the simplest example, one studies SU(2) by complexifying its 3d Lie algebra (R^3 with vector product), i.e. studying the Lie algebra of SL(2,C) instead. Finite dimensional unitary representations of SU(2) correspond to holomorphic representations of SL(2,C), and the same correspondence works in general between finite dimensional unitary reps of compact Lie groups and holomorphic representations of their complexifications.

Given the complexified group, one can ask if it has other “real forms”, i.e. subgroups other than the compact one which would have the same complexification. In the case of SL(2,C), there is another real form: SL(2,R). The representation theory of SL(2,R) is a vastly more complicated subject than the case of SU(2). One reason is that the group is non-compact. Geometrical constructions of representations like the Borel-Weil construction give infinite-dimensional irreducible unitary representations. The case of SL(2,R) is difficult enough (and a central topic in number theory), but the case of representations of general real forms of semi-simple Lie groups is extremely difficult and complicated. Representations are infinite-dimensional and labeled by “Langlands parameters” instead of highest weights. This theory has been pretty well worked out over the last 30-40 years or so, with the case of E8 one where it was known how to do calculations in principle, but they had so far been computationally intractable. Dealing with this is the new advance.

What actually is calculated are things called “Kazhdan-Lusztig” polynomials; for an explanation, see John’s blog. These tell one how to build arbitrary irreducible representations out of something simpler which one does understand, certain induced representations called “standard” representations. The numbers involved here also have a beautiful geometrical and topological interpretation. This is a generalization of what happens in the compact case, where the cell decomposition of the flag variety governs how irreducibles are built out of Verma modules.

So, this is a result about the structure of the irreducible representations of one of the real forms of E8 called the “split” real form. As far as I know it has nothing to do with heterotic string theory. The only thing I can think of that physicists have worked on that might make contact with this result is the work of people like Hermann Nicolai and Peter West trying to get physics out of Kac-Moody algebras like E10 and E11. I have no idea whether they have run into the split real form of E8 subalgebras and the representation theory of these in their work. In Pisa I had the pleasure of meeting blogger Paul Cook, a student of Peter West’s who is now a postdoc in Pisa and has worked on this kind of thing. Perhaps he would know about this.

Update: I hear from Jeffrey Adams that he has put together a web-page about this, aimed at mathematicians, and designed to explain the nature and significance of this result. It’s quite clear and does a good job of this, accessible if you have a bit of background in representation theory. If not, you may at least enjoy his comment on the media attention:

This leaves the question of why this story took off in the press. For us, that is harder to understand than the Kazhdan-Lusztig-Vogan Polynomials for E8.