Not Even Wrong

Lee Smolin’s The Trouble With Physics will be out soon in the UK, available February 22 according to Amazon.uk. This month’s Physics World has a very good review of the book by Michael Riordan, under the title Stringing physics along. Before his current incarnation as an historian of science, Riordan worked as an HEP experimentalist for many years, going on to write one of my favorite books about the development of the Standard Model, The Hunting of the Quark.

The review is very well done, and I especially like his description of string theory as not a theory, but “instead a dense, weedy thicket of hypotheses and conjectures badly in need of pruning.” The one place where I really disagree with Riordan, is where, like many other people, he explains the landscape issue and characterizes the problem with string theory as “it got caught up in its own mathematical beauty.” I don’t think that that’s the problem with string theory in general, and it’s certainly not the problem with the landscape arm of string theory research, which is explicitly devoted to the idea (see for example Susskind’s book) that the universe is something of spectacular mathematical ugliness.

Riordan goes on to make the claim that the way string theory is being pursued is of danger to science in general, since its continual evasion of any possibility of confrontation with experiment is of the same nature as “intelligent design”. Riordan writes “To me, string theory and intelligent design belong in the same speculative, unproveable category.” He ends with the recommendation “The Trouble With Physics deserves a wide, careful reading by all physicists concerned about the future of our discipline.”

The write-up of Larry McLerran’s summary talk at Quark Matter 2006 has now appeared. This talk created a bit of a stir since McLerran was rather critical of the way string theorists have been overhyping the application of string theory to heavy-ion collisions.

McLerran explains in the last section of his paper the main problem, that N=4 supersymmetric Yang-Mills is a quite different theory than QCD, listing the ways in which they differ, then going on to write:

Even in lowest order strong coupling computations it is very speculative to make relationships between this theory and QCD, because of the above. It is much more difficult to relate non-leading computations to QCD… The AdS/CFT correspondence is probably best thought of as a discovery tool with limited resolving power. An example is the eta/s computation. The discovery of the bound on eta/s could be argued to be verified by an independent argument, as a consequence of the deBroglie wavelength of particles becoming of the order of mean free paths. It is a theoretical discovery but its direct applicability to heavy ion collisions remains to be shown.

McLerran goes on to make a more general and positive point about this situation:

The advocates of the AdS/CFT correspondence are shameless enthusiasts, and this is not a bad thing. Any theoretical physicist who is not, is surely in the wrong field. Such enthusiasm will hopefully be balanced by commensurate skepticism.

I think he’s got it about right: shameless enthusiasm has a legitimate place in science (as long as it’s not too shameless), but it needs to be counterbalanced by an equal degree of skeptical thinking. If shameless enthusiasts are going to hawk their wares in public, the public needs to hear an equal amount of informed skepticism.

Another shamelessly enthusiastic string theorist, Barton Zwiebach, has been giving a series of promotional lectures at CERN entitled String Theory For Pedestrians, which have been covered over at the Resonaances blog.

Zwiebach’s lectures are on-line (both transparencies and video), and included much shameless enthusiasm for the claims about AdS/CFT and heavy-ion physics that McLerran discusses. His last talk includes similar shameless enthusiasm for studying the Landscape and trying to get particle physics out of it. He describes intersecting D-brane models, making much of the fact that, after many years of effort, people finally managed to construct contrived (his language, not mine, see page 346 of his undergraduate textbook) models that reproduce the Standard Model gauge groups and choices of particle representations. Besides the highly contrived nature of these models, one problem with this is that it’s not even clear one wants to reproduce the SM particle structure. Ideally one would like to get a slightly different structure, predicting new particles that would be visible at higher energies such as will become available at the LHC. Zwiebach does admit that these contrived constructions don’t even begin to deal with supersymmetry-breaking and particle masses, leaving all particles massless.

He describes himself as not at all pessimistic about the problems created by the Landscape, with the possibility that there are vast numbers of models that agree to within experimental accuracy with everything we can measure, thus making it unclear how to predict anything, as only “somewhat disappointing”. He expects that, with input from the LHC and Cosmology, within 10 years we’ll have “fully realistic” unified string theory models of particle physics.

The video of his last talk ran out in the middle, just as he was starting to denounce my book and Lee Smolin’s, saying that he had to discuss LQG for “sociological” reasons, making clear that he thought there wasn’t a scientific reason to talk about it. I can’t tell how the talk ended; the blogger at Resonaances makes a mysterious comment about honey…

Finally, it seems that tomorrow across town at Rockefeller University, Dorian Devins will be moderating a discussion of Beyond the Facts in Sciences: Theory, Speculation, Hyperbole, Distortion. It looks like the main topic is shameless enthusiasm amongst life sciences researchers, with one of the panelists the philosopher Harry Frankfurt, author of the recent best-selling book with a title that many newspapers refused to print.

Update: Lubos brings us the news that he’s sure the video of the Zwiebach lectures was “cut off by whackos” who wanted to suppress Zwiebach’s explanation of what is wrong with LQG.

Update: CERN has put up the remaining few minutes of the Zwiebach video.

A couple weeks ago I generated a list of the theoretical physics papers that were most heavily cited during 2006, according to the SLAC database, and discussed it here. Today the people at SLAC put out their own lists for 2006, which are quite interesting to go through. Their data is quite consistent with mine, although the numbers are very slightly larger, since a small number of new citations have been added into the database over the last couple weeks, I think mainly from papers which for example appeared on the arXiv in January 2007, but carried 2006 dates (e.g. write-ups from 2006 conferences).

The main list covering all HEP papers is dominated these days by astrophysics-related papers. Out of the 50 papers on the list I count only about 15 particle theory papers, and 3 review articles. The only post-1999 hep-th paper that makes the list is the KKLT landscape paper. To make the top 50, a paper needed to get 152 citations or more.

The list I put together goes deeper, down to papers with 100 citations, but SLAC has also put out something even better: 2006 lists of 50 most-heavily cited hep-th and hep-ph papers. To make the hep-th list, a paper had to have 62 or more citations. Looking over the 20 or so post-2000 papers on this list gives a good idea of what topics have been popular in recent years: the landscape, dark energy, and various aspects of AdS/CFT, and a small number of other topics. There are also several review papers on the list. Anyone interested in understanding what topics are attracting attention in particle theory research these days should find it quite interesting to go through this list, and spend some time taking a look at and learning about any of these papers that are unfamiliar.

Discover Magazine has just announced a competition, calling on people to submit videos to them that “clearly explain perhaps the most baffling idea in the history of the world: string theory”. The challenge is called String Theory in Two Minutes or Less, and the winner gets featured in an upcoming issue of Discover. In related news, one of my correspondents suggested making my postings available as YouTube videos, but I think I’ll resist any temptation to go that route.

Michael Peskin was here at Columbia yesterday, giving the physics colloquium, which was mainly about prospects for detecting at the LHC the kind of supersymmetric WIMP that is supposed to make up dark matter. On his web-site there are slides which more or less correspond to the talk he gave. The bottom line is that he believes that over the next 5-10 years we’ll be seeing evidence for such a WIMP from all of three different sources: astronomy (GLAST), direct detection experiments, and the LHC. The claim is that the LHC should be able to detect the existence of such a particle (although it’s not easy…) and maybe even measure the mass to 10 percent.

Experimental HEP bloggers keep putting out gripping multi-part stories about what it’s like to be dealing with collider data that is not conclusive, but has anomalies that promise the possibility of something new and exciting. See the latest from John Conway and Tommaso Dorigo.

There’s a new mathematician’s blog out there, John Armstrong’s The Unapologetic Mathematician. He promises “I’m sure I can come up with a good rant once a week or so. Actually, I’ll set that as a goal.”

NPR’s last Science Friday program dealt with experimental HEP physics, featuring David Barney (CMS), Jacobo Konigsberg (CDF) and Barry Barish (ILC).

I managed to get to a few of the talks at last week’s City College workshop on non-perturbative Yang-Mills that was mentioned here recently. Unfortunately I couldn’t get up there on Friday and missed talks by Maldacena and Freidel that I would have liked to see, but did make it to some of the talks on Thursday and Saturday. It appears that progress in 3+1d remains limited, but quite a lot of work is going on with new analytical methods for dealing with 2+1d, which can be tested by comparison with extensive results from lattice gauge theory computer simulations.

Max Karoubi has a new paper on the arXiv, Twisted K-theory, old and new. It traces the origins of the subject back to nearly 40 years ago, explaining the original mathematical motivations, old and new results, and relations between them.

Over at edge.org, my friend Nathan Myhrvold has his photos and an essay about penguins. OK, besides Nathan’s background in the quantum gravity business, this has nothing to do with math or physics. But the things are damn cute…

Update: A commenter points out that I should also advertise a bit an event taking place downtown here in New York next week. I’ll be talking at the Cafe Scientifique, which will take place at 7:30 next Tuesday evening, at the Rialto Restaurant in Soho.

Too much going on, hard to keep up with all the things that seem worth mentioning. Here are some quick ones:

There was a meeting on Geometric Langlands involving mathematicians and physicists last week at the Schrodinger Institute in Vienna. David Ben-Zvi has notes for the talks.

There’s an interview with John Baez and Urs Schreiber, partly about blogging. I personally take credit for first referring to him as a “proto-blogger”, thus making him feel bad (although it was intended as a compliment…) and encouraging him to modernize:

So, I started getting a little frustrated about being called a ‘proto-blogger’. [laughter] I would joke that I felt like being introduced as like, ‘Homo erectus: Very smart for its time, with the first stone tools’. [laughter] It made me feel sort of old!

Victor Rivelles reports from the Latin American String School in Bariloche. Notes are online.

Michael Creutz has a new paper claiming that rooted fermions are not just “ugly” or “bad”, but “evil”. See here for some commentary on The Evil That is Rooting.

William Fulton is giving an excellent series of lectures here at Columbia every Friday afternoon, on the topic of Equivariant Cohomology in Algebraic Geometry. Ex-Columbia undergrad Dave Anderson, now Fulton’s student at Michigan, is writing up notes.

There’s a proposed new newsgroup “sci.physics.foundations”, which some readers here might find interesting, and which would be a better place for a lot of the discussions which people try to start here, which I then try and stop because I don’t want to moderate them. More about this here, and some discussion here.

Later this week there will be a mini-workshop at City College organized by some of the CUNY particle theorists, on the topic of Yang-Mills Theories: nonperturbative aspects. The schedule of talks is here, I’m planning on attending some of them.

Also this week, Witten is speaking at the IAS on Wednesday with the title “Operator Expansion Product of ‘t Hooft Operators”. I’d like to go down to Princeton to hear this, but have to teach here around the same time, so won’t be able to attend the talk. Maybe someone who does attend will tell us about what Witten had to say.

There’s an interesting new particle theory blog, called Resonaances, and written by someone in the CERN Theory Group (who for now is operating anonymously as “Jester”, also commenting here). It includes reports of talks at the recent Winter School on Strings, Supergravity and Gauge Theories, discussion or recent ideas about supersymmetry breaking using metastable vacua, and scary photos from the Christmas party, which included someone playing a Borat/Theorat character and Wolfgang Lerche as the string pope, intoning the following prayer:

Our Witten, which art in Princeton,
Hallowed be thy name.
Thy Nobel come,
Thy will be done,
In CERN as it is in the US.
Give us this day our daily string,
And forgive us our theory,
As we forgive those who do phenomenology.
Lead us not into experiment,
And deliver us from tests.
For thine is the arXiv,
Hep-th and math-AG,
For ever and ever,
Amen

Over at Tommaso Dorigo’s blog, he’s spreading wild rumors about a Higgs signal seen by CDF. He does acknowledge that this “signal” is not the sort of thing one should take seriously, almost certainly a statistical fluctuation. With the Tevatron getting closer to the point where it might actually see the Higgs, and the LHC sooner or later starting to produce data, I look forward to the prospect of lots of rumors being put out by bloggers of Higgs or SUSY signals. I remember many years ago that there were always new rumors of things being seen at experiments, which just about always turned out to not actually be there. In recent years the large experimental collaborations have done a better job of acting responsibly and not letting wild rumors get out. Maybe the blogging phenomenon can play a useful role in getting the irresponsible rumor game going again. Any CDF/D0 people who want to send me rumors that I can then irresponsibly help propagate are encouraged to do so.

I just got a copy of a new textbook about Lie groups and their representations, called Compact Lie Groups, by Mark Sepanski. I had been frustrated that there wasn’t a book out there of just the right level with the same perspective I’m taking during the next few weeks of my graduate course, but Sepanski looks just right. From what I’ve seen so far of it, I recommend it highly as a place to learn about things like the Peter-Weyl and Borel-Weil theorems.

Another interesting book I recently acquired is Terry Gannon’s Moonshine Beyond the Monster, which is highly readable as well as entertaining, and contains a wealth of information about affine lie algebras, “modular moonshine”, vertex operator algebras and conformal field theory, and much more.

There are two new textbooks now out about string theory and attempts to get the a unified theory of particle physics out of it, by Michael Dine, and by Katrin and Melanie Becker and John Schwarz. I haven’t had a chance to look at either very carefully, but they both seem to neglect to mention that this idea doesn’t work. The thing that most amazes me though is Dine’s choice for one of the three luminaries of the field to get a blurb from that might convince people to buy the book: Lubos Motl.

Update: John Conway, the CDF experimenter whose potential Higgs signal was mentioned here, has joined the Cosmic Variance team, and his first post is one of a series giving the details of this story.

Every year the people running SPIRES put together a list of the most heavily cited papers in their database. I’ve discussed here in the past the listings for 2003, 2004 and 2005. Up until 2003 these appeared with a discussion by Michael Peskin of many of the papers on the list and their significance, but he hasn’t done this for the past couple years. This year, instead of waiting for the SLAC people to put together the list, I decided to generate one myself. I’m not enough of an expert with SPIRES to get it to just give me the list for 2006, but it was an interesting exercise to go through the lists generated by various searches just using their “topcite 50+, topcite 100+, etc…” feature, together with restrictions on dates. I think I was able to compile a complete list of papers with 150 or more citations, and post-1990 papers with 100-150. I was just looking at papers in particle theory (hep-th, hep-ph, hep-lat), not experimental (hep-ex) papers or astrophysics (astro-ph) papers, and was not counting survey articles. I’ve put the full list on a separate web-page, Most Heavily Cited Theoretical Particle Physics Papers 2006.

There are of course lots of caveats about any conclusions drawn from counting citations, but these numbers do give some solid data about what is going on these days in particle theory research. Two topics from nearly a decade ago continue to dominate these citation counts: AdS/CFT and brane-world models. By far the most heavily cited paper is the original 1997 one by Maldacena (546 citations), and the number of such citations has actually increased significantly over the number in 2004 (451) and 2005 (436). Research into AdS/CFT heavily dominates current particle theory research, but, remarkably, this research has not led to any recent heavily-cited papers on the subject. After a flurry of activity in 1998-2000, the only 21st century paper on the topic with over 100 citations in 2006 is the 2002 paper on pp-wave backgrounds by Berenstein et. al.

Overall, the list provides a very depressing view of the first six years of 21st century theoretical particle physics, with only eight post-2000 papers getting over 100 citations. These break up neatly into 4 hep-th string theory papers and 4 hep-ph phenomenology papers. Besides the 2002 pp-wave paper (hep-th/0202021) the other three string theory papers are all about the landscape, with the KKLT paper (hep-th/0301240) getting by far the most citations (238), followed by hep-th/0105097 (Giddings, Kachru, Polchinski) with 150, and Susskind’s hep-th/0302219 (“The Anthropic landscape of string theory”) with 109.

The heavily cited phenomenology papers are mostly compilations of theoretical fits to experimental data: hep-ph/0201195 (parton distributions, 193 citations), hep-ph/0405172 (neutrino oscillations, 133 citations), hep-ph/0406184 (CKM matrix, 118) and hep-ph/0506083 (neutrino mass matrix, 103 citations).

While getting this list together, I also accumulated some other data, including lists of recent papers with citation counts in the range of 50-100, and will try and put this together and write about it sometime soon.

Some other data one might want to take a look at is the arXiv monthly count of submissions (I found out about this from a posting at physicsforums). It shows the number of HEP submissions growing until about 2002, more or less flat since then, although each of the last two years have shown slight declines.

I’ll avoid the temptation to make extensive editorial comment on the meaning of these numbers, but I find it hard to believe that anyone could claim that they reflect a healthy field. The domination of non-phenomenological particle theory research by landscape studies is especially disturbing.

Last summer the entire editorial board of the prestigious journal Topology resigned, in protest over the high prices that Elsevier was charging. It was announced today that a new journal called the Journal of Topology is being launched by many of the same people. It will be published by the London Mathematical Society, printed and distributed by Oxford University Press, and the first issue should appear in January 2008.

There’s a recent report from HEPAP evaluating how far along the field is towards reaching certain set “long-term goals” (where “long-term” here is not a very long time-scale).

The New York Times Science Times section has a new columnist, John Tierney. Tierney has been with the paper for a long time, writing columns about New York and on the Op-Ed page, typically from a consistently Libertarian perspective. He also has a blog (where he promises to “rethink conventional wisdom about science and society”) and explains his conversion to science journalism by writing that he “always wanted to be a scientist but went into journalism because its peer-review process was a great deal easier to sneak through.”

The Templeton-funded magazine Science and Spirit, dedicated to bringing science and religion together, has a new issue out. It contains an interview with Max Tegmark about the Foundational Questions Institute. There’s also an article called The World on a String about the anthropic landscape and the problems with string theory. Susskind and Wilczek are quoted saying positive things about the multiverse, Krauss and I on the other side of the question. Finally there’s a review of my book by David Minot Weld with the title Stringing Us Along. It’s pretty accurate, although it’s not true that the book describes string theory as “totally without scientific merit” (that would be the string theory anthropic landscape…). Weld appears to be the son of ex-Massachusetts governor William Weld.

The Templeton foundation has a new web-site, and has announced a moratorium on new proposals over the next few months while they change their grant-making process. The web-site gives various information about the grants they have made in the past. I hadn’t realized that they make grants in mathematics. There was one last summer for about $16,000 to W. Hugh Woodin for research in mathematical logic.

New institutes devoted to “foundations” appear to be popular, with Templeton Prize winner Paul Davies starting up one at Arizona State University to be called Beyond: Institute for Fundamental Concepts in Science. This was announced by ASU president Michael Crow, who before he left for ASU was Executive Vice Provost here at Columbia and in charge of overseeing research and various “strategic initiatives”.

In the bookstore this past weekend I saw a new glossy book from National Geographic called Theories For Everything: An Illustrated History of Science. Lots about physics, but as far as I could tell, no mention of the Standard Model, Glashow, Weinberg, QCD, etc, but a whole page about string theory. In their version of physics history, one skips from Feynman to black holes, Hawking and string theory.

The coverage of string theory in popular media these days is decidedly mixed. A couple weeks ago I attended a performance of the play “Strings” by Carole Bugge, for a review, see here. It wasn’t bad as a play, and reminded me of another similar one from a couple years back, String Fever. But I’m kind of dubious that this sort of thing actually communicates any accurate understanding of physics to anyone. The play deals with themes of adultery, loss and 9/11 with a plot based on the train ride supposedly during which Steinhardt and Turok came up with the ekpyrotic scenario (the play’s train ride is jazzed up with a woman cosmologist, who is sleeping with the two other physicists). Unfortunately the playwright’s understanding of all this seems to be based on little more than watching a British TV show on the topic. In the pamphlet distributed to the audience various popular books on string theory and physics are recommended, together with much more dubious sources, like the film “What the Bleep Do We Know?”

There does seem to be a much more skeptical take on string theory getting out into the media these days. A recent episode of Numb3rs featured Judd Hirsch telling his genius mathematician son Charlie that string theory is “bogus”, more or less the same insight into the universe as that of late sixties hippies, everything is “vibes”. String theorist Larry has been shot off into earth orbit for some reason.

As mentioned here and at Cosmic Variance, the New Yorker recently actually ran a cartoon about the string theory controversy. If that’s not an indication that something has made it into the zeitgeist, I don’t know what is. Besides the New Yorker, string theory features in Zippy the Pinhead and recent Doonesbury cartoons, as well as one from Rodrigo Alonso entitled Pulling Strings that he sent me recently.

Update: What is it with Harvard string theorists and climate change?

This week I’m getting ready for the start next week of the spring semester. I’ll be teaching the second half of our graduate course on Lie Groups and Representations, something I also did a few years ago, at which point I wrote up some notes and put them on-line. This year, since the students covered somewhat different material during the first semester, I’ll be covering some different topics, hoping to both write up some notes on the new topics, and improve the older notes. We’ll see how much of that I have time for. Throughout academia, others are also trying to figure out what they’ll be talking about during the new term, for example see Clifford Johnson’s recent posting. He’s teaching a course on string theory, something about which he seems to be a tad bit defensive. Actually his outline syllabus doesn’t really indicate what he will cover, referring to aspects of perturbative and non-perturbative string theory, gravity and quantum field theory, which pretty much includes most of modern physics. Perhaps, like some of the rest of us, he hasn’t quite yet decided what exactly to talk about…

A future course that some people might be interested in is a summer school to take place in Seattle on Lattice QCD and its Applications.

An American Physics Student in England has a review of QFT textbooks for beginners. He neglects to mention a couple of my favorites (maybe just because they are ones I learned from during my student days): Quantum Field Theory by Itzykson and Zuber, and Pierre Ramond’s Field Theory: A Modern Primer.

I saw the above link first at Dorigo Tommaso’s blog, which also contains all sorts of news about interesting results coming out of the Tevatron, including a new, more accurate value of the W-mass. See for instance here, here, here, and here. About the new W-mass measurement, there’s also a Fermilab press release, and an article in Nature. It may yet turn out that the Tevatron is the place where the Higgs is first seen.

Also in Nature is an interesting article by Frank Wilczek about recent lattice QCD results showing that QCD leads to a nucleon-nucleon potential with hard-core repulsion.

Notes from the talks at last week’s Gottingen Winterschule on Geometric Langlands are now available.

From Peter Teichner’s web-site, a new preprint by him, Hohnold and Stolz describing 8 different models for real K-theory, one of which is in terms of supersymmetric quantum mechanics. The paper is dedicated to the memory of Raoul Bott, whose periodicity theorem is a large part of this story.

From Michael Douglas’s web-site, there are slides from his recent colloquium talk here at Columbia on Supersymmetric Gauge Theory: an overview. He also has a new preprint out with Denef and Kachru entitled Physics of String Flux Compactifications. The autthors go over the arguments for the Landscape and devote significant space to discussing whether or not string theory is testable. They explain why hopes that one could use a statistical, anthropic argument to predict whether supersymmetry breaking happens at low or high scales haven’t worked out. There’s a somewhat mystifying claim that “in fact string/M-theory does predict a definite distribution of gauge theory and matter contents”, referring to various papers which don’t contain anything like a definite string/M-theory prediction of such a distribution.

As for the testability of string theory, the authors first note that while there are all sorts of exotic phenomena that one might imagine finding that are consistent with string theory, none of them are required by string theory, so:

Thus, while string theory can offer experimentalists many exciting possibilities, there is little in the way of guarantees, nor any clear way for such searches to falsify the theory.

They then go on to give what they see as four possibilities for testability:

1. “Swampland” arguments showing that string theory can’t possibly lead to a low energy effective theory that agrees with what we see. Unfortunately, there seems to be no such plausible argument, with all arguments of this kind so far only ruling out string theory as a source for very different physics than what we observe.

2. String theory must be true because there is no other possible theory of quantum gravity. They completely ignore LQG, but do admit that “one should not take this too seriously until it can be proven that alternatives do not exist”, mentioning the possibility of finiteness of N=8 supergravity.

3. Maybe the LHC will discover new physics that clearly is the result of a string theory compactification.

4. Maybe they will be able to make statistical predictions using the landscape.

These seem to me extremely weak and problematic arguments. 3 appears to be little more than wishful thinking that a miracle will happen and save the day, and all efforts over the last few years to pursue 4 seem to lead to insuperable difficulties for very fundamental reasons. In the end, the authors acknowledge this, writing “ultimately convincing evidence for string theory will have to come from observing some sort of exotic physics”, and putting their hopes in string cosmology, especially the hope of seeing networks of cosmic superstrings or signals in the CMB corresponding to non-linearities in the DBI action.

After this dismal summary of the situation and of prospects for the future, the authors decide to end with conclusions more or less directly opposite to the ones their arguments naturally lead to:

We conclude by noting that while the present situation is not very satisfactory, there is every reason to be optimistic… There are many well-motivated directions for improving the situation, and good reasons to believe that substantial progress will be made in the future.

Update: One more. There will be a public debate over the anthropic principle later this month, involving David Gross, Lenny Susskind, and others. More information here.