Not Even Wrong

John Baez has a new issue of This Week’s Finds. He has a lot of interesting things to say about Euler characteristics and how you measure sizes in a category. Among many things I learned from Graeme Segal when he was here last semester was the idea of thinking of the Faddeev-Popov prescription in the path integral approach to gauge theory as reflecting the fact that one should think of gauge fields as a category. The category is the category whose objects are bundles with connection, and gauge transformations are the automorphisms of these objects. The general principle that when you count objects in a category you need to divide by the number of automorphisms provides a sort of motivation of the Faddeev-Popov calculation.

The US FY 2007 budget situation for math and science, which was looking very bad just recently, has taken a huge turn for the better as the House has voted to increase funding for the DOE Office of Science and the NSF. More information about this here, here, here, and here. Looks like Fermilab and RHIC will emerge from the budget process unscathed. Soon the president’s FY 2008 budget proposal will be unveiled, and we’ll see what the new Democratic majority will do about science funding.

This week’s press release announcing a “test of string theory” is from the University of Wisconsin (also here, here, and undoubtedly elsewhere). It’s no competition at all for last week’s spectacular press releases about “string theory tests”, but like the many other examples of the genre it is designed to make claims about string theory highly likely to mislead unsuspecting readers. I made some comments about this here. It’s not really that hard to come up with these “tests of string theory”, since “string theory” now has been invoked to justify studying a huge variety of different kinds of models, and is compatible with just about anything. All you have to do is find one, no matter how complicated, obscure and lacking any evidence or motivation, where you can choose the parameters so as to create effects not visible to current experiments, but perhaps visible to potential experiments, even ones many decades down the road. Without too much trouble you should be able to get a paper about this published, and at that time your university press office will surely be happy to put out a press release for you announcing that “Researcher(s) at University X have discovered a way to test string theory.” This has been going on for years, and people seem to never tire of it.

Sean Carroll seems to find it amusing that many articles on the arXiv can now be thought of as a new form of performance art. John Horgan, who got a lot of grief years ago for accusing physicists of engaging in “ironic science”, should really enjoy this.

Update: The Distler et. al. media juggernaut rolls on, informing the world that : The LHC, due to be finished by and running by the end of the year, may rule out the string theory, as well as the work by Distler and his colleagues offers something profound – a way to actually test string theory, and that if Distler’s bounds are satisfied, it would provide a weak support for string theory. The last article quotes Distler to the effect that string theory is just an “effective theory”, which I’m sure will clarify this for the public.

Update: The Shiu et. al. “test of string theory” press release has also led to lots of misleading stories. For an example check out Physicists devise test for string theory, where you’ll learn that “the University of Wisconsin theorists predict that upcoming experiments on the European Space Agency’s Planck satellite will have the sensitivity needed to prove the case for string theory.” Somehow I suspect string theorists will not give up on string theory if the Planck data doesn’t work out, and there won’t be any press releases…

Just to show that New Scientist doesn’t always get it wrong, there’s an unusually good article in this week’s issue by Davide Castelvecchi about prospects for new discoveries at the LHC. Besides the usual story, he concentrates on the question of how the data will be analyzed.

For one perspective on the problem, he gives an amusing quote from Ian Hinchliffe of Atlas who says:

People always ask me, “If you discover a new particle, how will you distinguish supersymmetry from extra dimensions?”. I’ll discover it first, I’ll think about it on the way to Stockholm, and I’ll tell you on the way back.”

Nima Arkani-Hamed optimistically claims that “The most likely scenario is that we’re going to have a ton of weird stuff to explain,’ and Castelvecchi quotes him and others as promoting a new sort of “bottom-up” data analysis. Here the idea (various implementations exist under names like VISTA and SLEUTH) is that instead of looking “top-down” for some specific signature predicted by a model (e.g. the Higgs, superpartners, etc.), one should instead broadly look at the data for statistically significant deviations from the standard model. Castelvecchi mentions various people working on this, including Bruce Knuteson of MIT. Knuteson and a collaborator have recently promoted an even more ambitious concept called BARD, designed to automate things and cut some theorists out of a job. The idea of BARD is to take discrepancies from the standard model and match them with possible new terms in the effective Lagrangian. Arkani-Hamed is dubious: “Going from the data to a beautiful theory is something a computer will never do.”

While the article focuses on the LHC, the role of such “bottom-up analyses” may soon be explored at the Tevatron, where they have a huge amount of data coming in, and have already put a lot of effort into the “top-down” approach (for the latest example, see Tommaso Dorigo’s new posting on CDF results about limits on Higgs decays to two Ws.) For the next few years all eyes will be on the LHC, but it will be the Tevatron experiments that will have a lot of data and be far along in analyzing it. Maybe lurking in this data will be the new physics everyone is hoping for, and it will be of an unexpected kind that only a broad-based “bottom-up” analysis might find. Doing so may raise tricky questions about what is statistically significant and what isn’t, and require a lot of manpower, at a time when these experiments will be losing lots of people to the LHC and elsewhere.

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.