Not Even Wrong

There’s an interesting exchange today between Sean Carroll and George Johnson on bloggingheads.tv. They cover a range of topics, including the controversy over string theory and the role of blogs. Johnson describes his time last fall at the KITP, telling about drinking very expensive Scotch with Steve Shenker, and many discussions with the string theorists there who were concerned that they were getting bad publicity and didn’t know what to do about it. Some were concerned that Lubos Motl was not exactly representing them well.

Sean gives a fairly standard defense of the landscape (“maybe it really is the way the world works”), with no discussion of the main problem with the landscape, that it shows no signs of making falsifiable predictions that would make it legitimate science. Some other points of the discussion include speculation about “what if Feynman and Gell-Mann had blogs?”, and Sean’s analogy of the string/LQG debate with mainstream/”heterodox” academic economics.

Update: Sean has his own posting about this.

The public perception of string theory has definitely changed over the last few years, with the latest evidence this week’s cover story in New Scientist, which begins:

It’s the theory everyone loves to hate.

The article (available fully only to subscribers, I fear) is entitled String Theory: The Fightback, and its story line is that, because of all this criticism, after nearly 25 years of work, finally:

string theorists themselves have realised they must find ways to put their models to the test. They may still be far from being able to observe a string in a laboratory, but experiments planned for the near future – and even one currently under way – could provide tantalising evidence either for or against string theory…

Now the string community is fighting back by devising creative, if indirect, ways to look for signs of strings – from hidden dimensions to ripples in space-time and other potential signatures of a stringy universe. The time has come to put string theory to the test…

Critics should take heed. Experiments now show that string theory may be testable after all. One study at a time, string theorists seem to be homing in on models that will make specific, falsifiable predictions.

What follows is the usual misleading hype of bogus “tests” of string theory, of the sort I’ve written about extensively here. They are:

For one of my postings about this, see here. More than three years ago Polchinski and the KITP at Santa Barbara issued a press release about this trumpeting the idea that such superstrings could be observed by LIGO “over the next year or two.” The problem with this kind of “test” of string theory is that you can easily come up with string theory models that produce lots of cosmic superstrings (already falsified), no observable amount of cosmic superstrings (can’t use to test string theory), or precisely the amount of cosmic superstrings such that no hint of them would be seen until now, but there would be networks of the things lurking just below the threshold of measurability, to be discovered by the next generation of experiments (highly unlikely, pretty much pure wishful thinking). Polchinski has now stopped talking about LIGO and a year or two, and instead is promoting measurements of pulsars and five to ten years:

According to Polchinski, though, our best bet for observing gravitational waves emanating from strings is to use pulsars. A pulsar is a rapidly spinning neutron star that fires out a beam of electromagnetic radiation as it rotates, like a lighthouse. These flashing beacons act as some of the most accurate clocks in the universe, and a gravitational wave rippling between a pulsar and Earth would disturb the otherwise precise timing of the pulses arriving here. The most likely cause of such fluctuations would be black holes colliding, but waves from strings would yield a unique timing pattern that would make them stand out. “Over the next five to 10 years,” Polchinski says, “these [pulsar observations] will probe the most interesting models.”

My colleague Brian Greene is quoted about this, making the essential point about this kind of “test”:

Sure, catching sight of a cosmic string would be a boon for string theory, but is there any observation that would serve as a death knell? For many sceptics, it’s not that string theory is so hard to prove correct that puts them off, but rather that you can’t falsify it. “I’m not aware of any test that if it fails will prove string theory wrong,” says physicist Brian Greene of Columbia University in New York. “That’s a real headache. You’d like to have a situation where you have a prediction, and if it’s right the theory is right, and if it’s wrong the theory is wrong.”

The problem is that the quoted paper doesn’t actually say that. Here’s the paper’s concluding paragraph:

However, a possible discovery of tensor modes may force us to reconsider several basic assumptions of string cosmology and particle phenomenology. In particular, it may imply that the gravitino must be superheavy. Thus, investigation of gravitational waves produced during inflation may serve as a unique source of information about string theory and about the fundamental physics in general.

Given the wealth of possible string theory scenarios, I have no doubt that if an imprint of gravity waves is found in the CMB, there will be string theory models that would “predict” it. As for the idea that not seeing such gravity waves would be evidence for string theory, here’s what Glashow has to say:

Not everyone thinks these tests will be useful, however. “Not seeing something is hardly evidence for string theory,” says Nobel laureate Sheldon Glashow of Boston University, Massachusetts, an outspoken critic of string theory. He feels that such a result would mean very little. “String theorists are very wise. They can come up with a way to explain anything.” String theory is simply not testable, he says. “There are an enormous number of string theories and they describe zillions and zillions of universes, none of them observable in any way. It sounds to me like angels dancing on the head of a pin.”

“We’re still very far from being able to say, here is the exact string theory that describes QCD,” Susskind says. “But the connections that show up between nuclear physics and string theory are fascinating. Sceptics won’t consider this evidence for string theory, but nuclear physicists will use string theory and in time discover how accurately it describes these experiments.”

What Susskind is neglecting to mention here is that these are tests of whether string theory is a useful way to do calculations in an already tested theory of the strong interactions, and has nothing to do with the question of testing the idea of string theory as a unified theory of quantum gravity and particle physics.

Also in New Scientist, there’s a story about Neil Turok’s recent talk at PASCOS entitled “Is the Cold Spot in the CMB a Texture?” which links to the string theory article. Evidently there’s a patch of CMB where the temperature is anomalously low (the probability of this happening supposedly being 2 percent) and one can speculate that this may be due to a topological defect of some kind. Amusingly, the online version of the New Scientist article includes an interpolated editorial comment that someone forgot to take out before publication:

Turok presented the findings at a conference on particles Hi Anil. This threw me a bit. We say the team noticed previous work by Turok, and then before we know it Turok is the one presenting the work. When did he join them, strings and cosmology at Imperial College London last week.

I was on vacation for a while, but haven’t been posting much mostly since there’s not that much to write about. Like every summer, there are huge numbers of string theory conferences going on all over the world, but from looking at the talks that are available, the subject is about as dead as it has been for the last couple years, with essentially no new ideas. The reaction of string theorists to all the criticism that they have been getting in recent years about the lack of any connection of string theory to the real world seems to have been to rename their conferences things like String Theory and the Real World.

One other reason I haven’t been writing as much is that there are an increasingly large number of quite good math and physics blogs out there, run by other people who are doing a great job of writing about the kinds of news that I’ve often posted items about. There’s a mini-revolution going on in research-level mathematics blogging, with various Fields medalists being joined by groups of some of the best graduate students and post-docs around. Following on the heels of Berkeley’s wonderful Secret Blogging Seminar, there’s Cornell’s Everything Seminar and the Max Planck Institute in Bonn’s Vivatgasse 7 (mainly about arithmetic algebraic geometry).

Also at the Max Planck Institute, a couple weeks ago there was the yearly Arbeitstagung, a conference devoted to recent mathematics research and run in a somewhat unconventional way. The concept is to mostly not schedule talks and speakers in advance, but to instead just try and get a group of the best possible people to show up, and then to more or less democratically decide on who should speak about what, depending on who has something new to talk about. The first Arbeitstagung was organized by Friedrich Hirzebruch exactly 50 years ago, back in 1957, partly with the goal of bringing Germany back into the mainstream of mathematics research after the post-WWII period. Hirzebruch remained the organizer for many years (and was also director of Max Planck), and was there this year to give the opening lecture, on The first Arbeitstagungen in 1957, 1958 and 1962. At the first Arbeitstagung in 1957 some of the talks announced dramatic new results in mathematics, including the birth of K-theory. Grothendieck’s talk included the first definition and use of K-theory (of coherent sheaves on a projective algebraic manifold) in his proof of what is now known as the Grothendieck-Riemann-Roch theorem. Hirzebruch had worked some of this out more concretely before, and he reported on his work with Borel-Hirzebruch which links up representation theory, characteristic classes and topology in a fundamental way. Bott was not there, but had recently discovered Bott periodicity, and over the next few years Atiyah used this and the Dirac operator to reformulate Grothendieck-Riemann-Roch as a general index theorem in the context of differentiable manifolds, proving the theorem with Singer, and lecturing about it at the 1962 Arbeitagung. Hirzebruch gives an excellent description of some of this history. The talks are all available online, but I fear that there was nothing discussed this year that seems to reach the heights of what was being discovered back in those early days 50 years ago.

The latest news on the LHC schedule is: close the machine April 2008, beam commissioning starting May 2008, first beams at high energy July 2008, about exactly one year from now.

The Notices of the AMS has a wonderful set of articles this month about George Mackey, I wrote a bit about him here.

The Harvard string theory group will be minus not just Lubos Motl this coming year, but also Nima Arkani-Hamed, who will be on leave (I’m not sure where he’s going or what his plans are). I hear that the two of them had a joint goodbye party.

Starting today, Arkani-Hamed is pushing the multiverse at the String Theory and the Real World conference. For the hundredth puff-piece about how wonderful the anthropic multiverse pseudo-science is, see the article Islands in the Sea, at fqxi.org.

Bloomberg.com is carrying a review of Endless Universe, the recent Steinhardt/Turok book I wrote about here. The author of the review seems to have noticed the same thing about the book that I did:

Given the recent controversy surrounding string theory — the publication last year of Lee Smolin’s “The Trouble With Physics” and Peter Woit’s “Not Even Wrong” — it’s disturbing that Steinhardt and Turok don’t even address their dependence on it. Does their model work if string theory is wrong?

My sense is that it doesn’t, but they never even face the possibility — lending inadvertent weight to Smolin’s and Woit’s complaints that string theory is strangling physics. I hope the authors can someday publish a second edition in which they don’t treat string theory as the only game in town.

Despite its problems, string theory does now have a shop and a blog.

Update: The news is that Arkani-Hamed will be moving from Harvard to the Institute for Advanced Study.

Update: In case any one was worried that Lubos’s move back to Europe would end his entertainining rants about the stupidity of anyone expressing skepticism about string theory, don’t worry. The latest is Bloomberg: another idiotic article, which begins:

Elizabeth Lopatto is the name of the latest breathtaking idiot who was hired to write about theoretical physics for Bloomberg. I am periodically amazed that the newer journalists are always able to exceed the degree of mental breakdown of their predecessors.

and then goes on from there…

I’ve been finding recently that an increasing serious problems with blogs is that there are too many good ones with material worth reading. I’ve learned quite a lot recently from many well-informed blog postings, but the sheer number of these makes it hard to find the time for other things one should be doing.

I’ll violate my usual rule of sticking to math and physics and report that my brother Steve is joining me in the family blogging business by being involved as Publisher in a new venture that just launched this week called Xconomy. Basically it’s a blog based up in Cambridge, with offices in Kendall Square, devoted to news about what they call the “exponential economy”, that part of the economy responsible for what is perhaps too optimistically described as exponential growth in certain areas. They’re focusing on events and news relevant to new technology, especially bio-technology, businesses in the Boston area. For some interesting blog postings by their CEO Bob Buderi about what it’s like to start up this sort of business, see here and here. For a nice posting about Doc Edgerton, see here.

Back to physics and math, over at Backreaction there’s an excellent posting on the GZK cutoff and high energy cosmic ray experiments, and a report from Loops 07 sent in via Blackberry by Sabine Hossenfelder.

An American Physics Student in England tells about a recent conference on Heavy Flavour Physics, giving a very nice overview of what is going on in that field.

The latest This Week’s Finds in Mathematical Physics from John Baez is out (available here, blog entry and comments here). It’s a wonderful description of the various mathematical patterns that the standard model particles fit into. Most well known is what happens in SU(5) and SO(10) GUTs, where one can fit the fermion quantum numbers into something that can equivalently be described as the spinor representation in d=10, or the exterior algebra $\Lambda ^* (\mathbf C ^5)$. John goes on to explain various possible connections to the exceptional groups, including a recent idea from Garrett Lisi about how to use E₈ to get three generations.

The blog entry comments discuss two recent papers by Chamseddine and Connes about their non-commutative algebra approach to this question of mathematically characterizing the SM degrees of freedom. The papers are on the arXiv, entitled A Dress for SM the Beggar, and Why the Standard Model. Because of these papers and Witten’s recent one, John seems to be getting a bit more optimistic about physics, writing “I get the feeling that theoretical physics may not be quite so stagnant after all!”

All sorts of interesting stuff at the Secret Blogging Seminar, including yet more about Connes: a “review” by A. J. Tolland of the first quarter of the new book by Connes and Marcolli (available here), which A. J. claims has the title Noncommutative Geometry, Quantum Fields, Kitchen Sinks and Motives. Like the earlier fat book on non-commutative geometry by Connes, it’s an amazing document, ranging widely over physics and mathematics, covering ground from QFT to the Riemann hypothesis, at a level varying from expository sections on well-known subjects to more speculative research-level discussions. I’ve just started looking at it, may bring along a copy for summer vacation reading when I head up to a lake in New Hampshire tomorrow.

Other interesting things at the same blog include reports (here and here) from Ben Webster about talks by Sergei Gukov on categorification and gauge theory (about which he has a new expository paper here), as well as about an earlier talk by Gukov on Arithmetic Topology and Gauge Theory.

Also worth reading are posts from Ben Webster about centers of blocks of category O, various comment section discussions with David Ben-Zvi at both this blog and the n-category cafe, and a series of postings by David Speyer about quadratic reciprocity and geometric class field theory (I’m running out of energy to provide links…).

From Ben-Zvi (who could run a really great blog if he chose to…) there are notes from the recent conference at Northwestern on non-commutative geometry. These include an intriguing lecture by Beilinson, as well as lectures by Nadler and Ben-Zvi himself about their recent work which connects geometric Langlands with questions about more conventional representation theory using striking ideas about how to handle loop spaces. They have a recent paper about this, which has been very high on my list of things I wish I understood better ever since David gave an inspiring talk about this here a couple months ago.

Finally, one more thing definitely worth looking at in light of Witten’s new work: an expository and historical article by Jim Lepowsky about the story of the relation of vertex operator algebras and the monster group. He explains what is so remarkable about the specific vertex operator algebra that Witten is connecting to 3d gravity on AdS, including the ways in which it is conjecturally uniquely the “smallest” such structure in a specific sense.

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.

Experimenters at the Tevatron have released data showing the existence of a new baryon, built out of a down, strange and bottom quark, and having a mass of 5.774 +/- .019 GeV. It has been given the name “Ξ_b“. The FNAL press release is referring to this as a “triple-scoop” baryon, since it contains one quark from each of the three generations. Tommaso Dorigo has a new posting about this.

Postings on this blog tend to involve a certain amount of discussion of bad behavior by theorists, so I guess I should point out here that this story comes with some accusations of less than good behavior by experimentalists in the way this was announced. The press release is all about the announcement of this discovery by the D0 experiment, and about their paper, which was submitted to the arXiv Tuesday night. It turns out though that D0’s competition, CDF, also has had the same result for a while, and it had already been “blessed” but not officially announced. So CDF was “scooped” at the last moment for the “triple-scoop”, and I imagine there are dark accusations going around about how D0 might have found out about this and rushed out the paper and press release. Supposedly there is an informal one-week notification period that the two experiments normally observe to keep this kind of thing from happening. Anyway, looks like they’re trying to fix it up a bit: the FNAL web-site contains a “special announcement” of back-to-back seminars about this, D0 at 1pm, which will “immediately be followed” by a CDF seminar. The D0 seminar is called

First observation of a new b-baryon, Ξ_b

whereas the CDF seminar is entitled

Observation of a new b-baryon, Ξ_b

Pretty much everybody in the math community seems to be getting a blog. Many of the new bloggers are quite good research mathematicians (including even some Fields Medalists). Two very new ones are:

Secret Blogging Seminar: Named after a “Secret Russian Seminar” at Berkeley, a group blog of several ex- and current Berkeley math graduate students (Ben Webster, A.J. Tolland, Scott Morrison, Noah Snyder and David Speyer)

Math Life: The blog of UT Austin’s number theorist Fernando Rodriguez Villegas

A few things I learned from the Secret Blogging Seminar postings and following associated links:

The Microsoft Research group at UCSB working on “topological quantum computation” is now known as Station Q, and has a web-site.

Googling “Secret Russian Seminar” led to the web-site of Scott Carnahan, a student of Richard Borcherds who will be a postdoc at MIT this fall. Carnahan has some interesting sets of notes there, including notes from Borcherds’ 2004 course on QFT. Back in 2001, Borcherds had taught an earlier version of this course, and notes taken by Alex Barnard are available. According to Carnahan, Borcherds began the 2004 course with the comment:

Some of you might remember I gave a class a few years ago on the standard model. It ran into a few technical problems, the main one being the fact that I didn’t know what I was talking about. I’ve learned a thing or two since then, and I’m going to try again.

I’ve finally been making some progress in understanding some mathematics associated to BRST; if this keeps making sense I hope to get something written about it this summer. I recently noticed that the pretty much incoherent Wikipedia entry on the BRST formalism, has been joined by another incoherent one on BRST quantization. Both entries contain the warning at the top “This article or section may be confusing or unclear for some readers”, which is an understatement.

A new issue of Symmetry Magazine is out, and it contains a report on the recent string theory debate in Washington between Brian Greene and Lawrence Krauss. An editorial noted how amazing it is that this sort of thing drew 600 people willing to pay $25. There’s lots of interest out there in fundamental physics in general, and this controversy in particular.

Can’t remember where I saw this earlier today, but there’s a famous quotation I hadn’t heard before from economist John Kenneth Galbraith which seems to apply well to the current situation in string theory:

Faced with the choice between changing one’s mind and proving there is no need to do so, almost everyone gets busy on the proof.

Update: One more. Adrian Cho at Science Magazine has an article about the debate going on over how long to run the Tevatron. The chair of the P5 panel is saying that they will recommend running through 2009, but that “It would take some unusual circumstances to justify running beyond 2009.” But, if the LHC takes longer to get working correctly than planned (there’s a history of this with new accelerators), and Tommaso’s Dorigo’s rumors of sightings of a Higgs at the Tevatron ever start to firm up, it’s going to be hard to justify starting to tear the machine down…

Update: Yet one more about math blogging. Lieven le Bruyn has changed his blog from NeverEndingBooks to Moonshine Math (also known as NeverEndingBooks, v. 2). He begins with a wonderful blog posting about the j-function which explains one of my favorite remarkable facts about numbers:

$$e^{\pi\sqrt{163}}=262537412640768743.99999999999925\ldots$$

Last week both SLAC and Fermilab hosted “Users Meetings”, providing a forum to discuss the current status and future plans of the two laboratories. The SLAC agenda is here, and talks from previous years are available here, with this year’s perhaps available later.

The Fermilab meeting was also celebrating the 40th anniversary of its first Users Meeting, which was held back in 1967 at a time when Fermilab was under construction, with plans for a 200 GeV fixed-target machine underway, led by director Robert Wilson. This year’s talks are available here. The status of the Tevatron is described in Roger Dixon’s talk. Already the machine has delivered nearly 3 fb^-1 of luminosity to the two experiments there, half of this over the last year. They are projecting to have 6-7 fb^-1 by the end of FY 2009 (a bit more than two years from now). The current plan calls for operation of the Tevatron only until the end of FY 2009, and a year or so ago there was even some discussion of shutting it down before then. With the machine operating well, a healthy US HEP budget, the LHC startup now not until 2008, and some cautious optimism that that the Tevatron might be able to accumulate enough data to see the Higgs under some scenarios, it looks like no one is about to shut the Tevatron down early, rather the question will be how much extra time to give it. There seems little point to shutting it down as long as the LHC is not producing results that make it obsolete, and no one knows yet how long that is going to take. While those running Fermilab would like to know what they will be doing several years in advance so that they can plan and budget, it may be difficult to do this since no one knows what will happen with the LHC.

Fermilab is in the middle of a long-range planning exercise, with a Steering Group meeting trying to put together a plan by August 1. They have many of their materials available on-line. Some of the discussion revolves around the question of the ILC, with talks showing that in principle it would be possible to start construction of the ILC in 2012 and have it built by 2019, but few people believe that things will happen this fast. Whether building the machine makes sense will depend on what is seen at the LHC. Other scenarios are under discussion, for example see here. Other than the LHC, the main things one could conceive of building at Fermilab would be a more intense proton beam (proton driver), or accelerating muons to provide a “neutrino factory” and perhaps ultimately a muon collider.

While US HEP has a difficult task ahead to figure out what to do after the Tevatron shuts down and the energy frontier moves to CERN, at least the budget situation is looking a lot better than it was a few years ago. At the Users Meeting, there was a presentation by the DOE’s Robin Staffin showing budget figures that included a 6.8% increase planned for FY2008, after a 5.9% increase from FY2006 to FY2007. For some reason the federal government seems to have decided to put significantly more money into fundamental physics research, and HEP is benefiting from this. For more about the general situation with the Federal science research budget, see this recent talk by John Marburger, the director of Office of Science and Technology Policy.

For the budget situation in mathematics, see this report in the latest Notices of the AMS about the NSF budget numbers. After flat budget numbers for the past couple years, there was a 3.3% increase for mathematics research in FY2007, and the proposal for FY2008 has a 8.5% increase. Math is cheap compared to HEP, with the NSF spending on math (which is the bulk of federal math research funding) only about a quarter the size of the HEP budget. The AMS Notices article also computes numbers for what fraction of the NSF budget goes to different fields, noting that in FY2004 18.3% was for math, 20.9% for physics, while the FY2008 proposal goes 17.8% to math, 23.6% to physics.

Update: Also at SLAC, this week the DOE is there to review the lab. Presentations prepared for the DOE are on-line. Michael Peskin gave a presentation about the work of the theory group. He highlighted (besides hopes about the LHC) the work of SLAC’s Lance Dixon on computing perturbative QCD amplitudes, including its relation to N=4 supersymmetric Yang-Mills and to the conjectural finiteness of N=8 supergravity.

Yesterday evening there was a public debate about string theory held in Paris, between Lee Smolin and Thibault Damour. So far, accounts of the debate have appeared in Le Monde and at Fabien Besnard’s blog Mathephysique.

The Le Monde article is not very informative, but indicates that Damour defended string theory against charges that it was not testable by claiming that it predicted “possible classes of experimentally testable phenomena” at the LHC. Besnard gives a more detailed account, describing how Damour answered these charges of lack of testability with: “Lee, a subtle thinker, surely doesn’t believe himself the naive Popperian position he is defending”. He also evidently claimed that string theory was testable because it would be confirmed if a violation of the equivalence principle was found (he really should talk to Lubos, see here). Remarkably, he also claimed that observation of the kind of DSR dispersion relations that Smolin thinks LQG leads to would not be a problem for string theory, since one could also get them out of string theory (here I think he needs to talk to both Lubos and Jacques Distler).

Update: I hear that the event was recorded, and audio should be available by the end of the week at the web-site linked to above.