Not Even Wrong

The May issue of the Notices of the AMS has memorial articles about two great mathematicians who passed away recently. The first is about Serge Lang and includes contributions from many people, including my Columbia colleague Dorian Goldfeld. When Lang died last September, I wrote a short posting here, but didn’t want to go into much detail. He was a remarkable man, with many facets, but also famously difficult. The Notices article does him justice and is well worth reading.

In the same issue, Loring Tu has the first part of a long article about Raoul Bott, who died last December. It’s a wonderful article concentrating on Bott’s mathematical career and describing in detail the setting of some of his most important work.

Today I also ran across the sad story of the death of John Brodie. Brodie was a theorist who got his Ph.D. from Princeton and worked on gauge theory and string theory. Evidently he suffered from bipolar disorder, which was a contributing factor in his death. I never met him, but had seen some of his papers. Perhaps some of the readers here knew him personally.

At the recent Solvay conference there was extensive discussion of the Landscape, and I’ve already discussed here Michael Douglas’s write-up of his talk on the subject, entitled Understanding the Landscape. Now Joe Polchinksi’s rapporteur talk on the subject has appeared; it’s entitled The Cosmological Constant and the String Landscape. Polchinski is essentially making the same argument as Susskind makes in his recent book, and his argument has pretty much the same problems that Susskind’s has, which I discussed in detail in an earlier posting. However, his article is written for physicists, not for the general public, so he is making a much more technical version of the argument. It’s probably the best version of the case for the string theory anthropic landscape available, so worth reading carefully.

Polchinski begins by explaining why the cosmological constant problem is difficult. He divides possible solutions to it into ones where the CC is fixed, and ones where it is adjustable. The problem with the idea that the CC is fixed and calculable is essentially that all the contributions to the vacuum energy that we know about give values of the CC that are far too large. These include things like fermion loops and the Higgs potential in the standard model, supersymmetry breaking in supersymmetric extensions of the SM, and Planck scale effects in theories of quantum gravity. He goes on to explain why it is difficult to try and modify the theory of gravity so that it won’t couple to these sources of vacuum energy.

There is a wide range of ideas about how to select a small CC in theories where the CC is adjustable, and Polchinski describes several of them and what problems they have. Some of these ideas naturally explain a small CC in an empty universe, but not in our matter-filled universe. Finally he ends up with the anthropic explanation: the CC is small because if it wasn’t we wouldn’t be here. He does note that:

Of course, the anthropic principle is in some sense a tautology: we must live where we can live.

this carries a footnote comparing the anthropic principle to Darwin’s theory of natural selection:

Natural selection is a tautology in much the same sense: survivors survive. But in combination with a mechanism of populating a spectrum of universes or genotypes, these ‘tautologies’ acquire great power.

Susskind makes the same sort of claim that the anthropic landscape is much like the theory of evolution, and I think this is extremely dangerous and unwise. There is a mountain of scientific evidence for the theory of evolution and none for the anthropic landscape. It is very important that this distinction be made, and trying to blur the difference between these two very different situations is not something a scientist should be doing at a time when science in general and the theory of evolution in particular is under attack by the forces of the religious right. When I was in Niger one of my travel-mates was a creationist who was generally annoyed at what he saw as the arrogant way scientists dismiss his view of the world. We discussed cosmology, and I tried to tell him a bit about inflation and what aspects of the universe it was supposed to explain. In response he asked me why he shouldn’t just go with his preferred explanation: it was all the doing of the “Big Kahuna”, as he called the deity. I tried to explain about the scientific method: your theory is supposed to make distinctive predictions that you can go out and check by making observations. I think I had some success in getting this idea across, but I don’t see any way I could have defended to him something like the anthropic landscape. It’s not legitimate science since it makes no real predictions that you can use to see if the idea is right or not. What’s at issue here is the credibility of science itself, and physicists who care about this credibility should not be claiming that an idea like the anthropic landscape has the same status as heavily tested and verified theories like that of evolution.

Polchinski goes on to repeat the analogy with evolution a bit later, and I actually don’t understand at all what point he is making here, when he argues that maybe only the anthropic principle determines the CC:

Thus we should seriously consider the possibility that there is no other selection mechanism significantly constraining the cosmological constant. Equally we should not stop searching for such a further principle, but I think one must admit that the strongest reason for expecting to find it is not a scientific argument but a psychological one (footnote): we wish fundamental theory to be as we have long assumed it would be.

and the footnote is:

Again, the Darwinian analogy is notable.

Personally I’m agnostic about whether the CC is computable from first principles or not. As a scientist, one’s job is to come up with theories and extract predictions from them to see if they are right. If you have a theory that says the CC is not computable, that’s fine, but then you have to just forget about the CC and find something that your theory does predict so you can test it. You can’t go around claiming that the fact that your theory is compatible with any value of the CC is somehow some sort of scientific success and evidence for the theory. The problem with a theory where all values of the CC are a priori equally likely is that it’s vacuous (as far as the CC is concerned). Its implications are exactly the same as throwing up your hands and saying “I have absolutely no idea what determines the CC, it could be anything”.

The fact that we are here and observe galaxies does put constraints on the CC, and Polchinski would like to make much of this. He’d like to claim that the anthropic landscape predicts that the CC is a random variable, and then, given the fact we see galaxies, it would have an expectation value about an order of magnitude higher than its observed value. He defends the theory against this mismatch by quoting Galileo’s defense that his theory might be inaccurate but was a lot better than Aristotle’s, then writes:

This order of magnitude may simply be a 1.5 sigma fluctuation, or it may reflect our current ignorance of the measure of the space of vacua

One problem with all this that Polchinski doesn’t mention at this point is that the anthropic constraint is not on the CC but on a combination of the CC and Q, the normalization of the primordial temperature fluctuations. Assuming both are random variables, the observed CC is way off what one expects. One can deal with this by just assuming that the CC is a random variable, but Q isn’t for some reason. This gets into the fundamental problem with the string theory anthropic landscape: it doesn’t just not predict the CC, it doesn’t predict anything at all. As far as one can tell, it’s consistent with just about anything. It doesn’t make any predictions, so it’s really not a legitimate scientific theory at all. One can try and claim that it really is a scientific theory, and that it does predict something: we are at some randomly chosen (according to a not yet understood measure) point in the landscape compatible with our existence. The problem with this (as Polchinski notes) is that there is a long list of properties of the world that appear to be rather special and statistically highly disfavored by any likely measure: the theta-angle is very small, proton lifetime is very long, number of generations is small, etc., etc. If one actually took the string theory anthropic landscape seriously as a theory, one would have to abandon it in face of these falsifying observations.

The crucial question for whether the anthropic landscape is science or not is whether it makes any testable predictions. Polchinski doesn’t at all address the question of whether further study of the landscape will lead to any prediction of anything, presumably because like everyone else he has no plausible idea for how this could come about. He does claim that Weinberg’s 1987 arguement makes 5 successful predictions or postdictions:

The anthropic argument is not without predictive power. We can identify a list of post- or pre-dictions, circa 1987:

5. Other constants of nature may show evidence of anthropic constraints.

Calling these successful predictions seems to me a huge stretch. 1. follows from a tautology, 2. and 3. are the same “predictions” I get by saying I have no idea what is going on here (including having no good reason to believe the CC is zero). 4. isn’t an experimental prediction at all, and 5. is so vague as to be completely meaningless.

Polchinski ends up his defense of the landscape by quoting Dirac:

One must be prepared to follow up the consequences of theory, and feel that one just has to accept the consequences no matter where they lead.

The problem with this is that Dirac undoubtedly didn’t have in mind the idea that if your theory has no experimental consequences, you should accept the idea that you can’t ever predict anything. Obviously, you should give up on your theory at that point, and this is what Polchinski and others show no signs of being willing to even consider. Back in 1998, in lectures at the SLAC Summer Institute, he wrote:

On Lance Dixon’s tentative outline for my lectures, one of the items was ‘Alternatives to String Theory.’ My first reaction was that this was silly, there are no alternatives…

and his attitude doesn’t seem to have changed since. He and others never discuss the possibility that string theory is simply a wrong idea, a possibility for which the landscape provides overwhelming evidence. This seems to be something he is unwilling to seriously consider.

There’s one peculiar reference in his paper. When he refers to the problem that the landscape can’t even predict the one thing people originally hoped it would be able to, the scale of supersymmetry breaking, he writes:

An obvious question is whether we can understand the supersymmetry-breaking scale (see [68] and references therein). Is low energy supersymmetry, or some alternative [69, 70], favored?

[69] is a reference to split supersymmetry, and [70] is a reference to a paper by Fox et. al called Supersplit Supersymmetry. The strange thing about the apparently serious reference to [70] is that the paper in question is actually an April Fool’s joke (check the date on it…). The authors were making fun of how supersymmetric phenomenology is being pursued, and specifically of the idea of split supersymmetry. In “supersplit supersymmetry”, all superpartners are pushed up to unobservability at the Planck scale, solving all the problems caused by the lack of observation of effects of supersymmetry. For any conceivable purpose, the supersplit supersymmetry model is precisely the standard model. The joke is that particle physicists have become so enamored of supersymmetry that they would happily study a supersymmetric model inherently indistinguishable from the much, much simpler standard model. Part of being unwilling to consider the idea that superstring theory might be wrong is being unwilling to consider the idea that supersymmetry might be wrong, and thus, instead of referring to the standard model, one adopts the supersplit supersymmetry model.

The funny thing about this April Fool’s joke paper is that, according to SPIRES, Polchinski’s is the sixth paper to cite it. Looking through these six papers, only one of them seems to be aware of the joke, with a footnote to the reference pointing out that the paper appeared on April Fool’s day and that the model was equivalent to the standard model. Some of the particle theory community now seems to think that the idea of a vastly more complicated model that is inherently indistinguishable from the standard model but is in some sense “supersymmetric” is a model worth taking seriously and making reference to. Yet another weird thing about this paper is that there is one trackback to it, and this trackback was generated by a comment from LambchopofGod on a Cosmic Variance posting. Presumably it’s a bug, not a feature, that any commenter on an approved blog can generate trackbacks at the arXiv, but seeing the way the arXiv handles trackbacks, who knows. In any case we’ll see at some point if trackbacks to the Polchinski paper and the Fox et. al. paper get generated from this posting. Hopefully at least a trackback to the Fox et. al. paper will appear, since many readers of that paper don’t seem to realize that

IT’S NOT SCIENCE, IT’S AN APRIL FOOL’S JOKE, PEOPLE!

This past week there has been a conference going on in Cambridge called Eurostrings 2006. It’s a bit like the annual “Strings XXXX” conferences, although about half the size and organized just by European institutions that are part of the European Superstring Theory Network, which since last year has been funded by a grant from the EU. Part of the conference consists of a celebration of Michael Green’s 60th birthday.

Most of the talks are already available online. There’s not much new being reported, but the talks include a nice review talk on topological strings by Robbert Dijkgraaf. There’s another talk on recent work on topological strings by Erik Verlinde, and a week earlier there was a conference in Munich devoted to the subject.

Nathan Berkovits talked about work in progress with Nikita Nekrasov on multi-loop amplitudes using his pure spinor formalism. This subject still seems remarkably confused, with Berkovits explaining that they have found a problem they still don’t know how to resolve: their regularization causes amplitudes with genus larger than 6 to vanish, violating unitarity. For commentary on yet another new suggested formalism for defining superstring amplitudes due to Warren Siegel and Kiyoung Lee, see this posting by Lubos Motl.

As part of the Green birthday celebration, John Schwarz gave a talk on String Theory Books. He reminisced about the writing of the two-volume book with Green and Witten (his outline refers to a “removed chapter”, and “broken vow”, what are those?). Evidently the book was written in 9 months back in 1986, a truly heroic effort given its size. Last Monday, Schwarz finally finished up a new textbook on string theory, written with Katrin and Melanie Becker and entitled “String Theory and M-theory: A Modern Introduction”. They started writing back in February 2005, planning a 350 page book to be completed by the end of September, but ended up just last week completing a 729 page book. From the table of contents it looks like GSW abbreviated and updated, containg more modern material on branes, dualities, black hole entropy, flux compactifications and gauge/string dualities. It seems rather peculiar that flux compactifications and the landscape get a whole chapter, whereas AdS/CFT is dealt with in one section of one chapter. All in all, comparing the new book to the old one, twenty years later the subject has become a lot more complicated, a lot uglier, and the prospects for using it to predict anything about the standard model have vanished.

The Schwarz talk also has a link to a video of a Berlitz commercial featuring a German radio operator misunderstanding someone radioing in a distress call that they were sinking (the German hears this as “thinking”). I can’t at all figure out what this has to do with Schwarz’s talk. Is string theory making a distress call as it is sinking, but no one understands this?

Victor Rivelles attended, and has blog entries here, here and here. He reports on a talk by my fellow Princeton student Costas Bachas about using string theory techniques to solve capillarity and wetting problems, then comments that “If LHC provides no proof to string theory string theorists will not lose their job, they can just change to applied string theory!”

Science writer John Horgan has just written a piece about the Templeton Foundation that is causing a bit of a ruckus. It first appeared in The Chronicle of Higher Education, and is also posted a the Edge web-site, where perhaps some further discussion of it will appear.

Horgan participated in a program held at Cambridge as a Templeton-Cambridge Journalism Fellow in Science and Religion, an all-expenses paid gig that came with an additional $15,000 that made it hard to turn down. He had very mixed feelings about the experience, and explains these in detail.

The financial scale on which Templeton operates is unparalleled in this area. As in Horgan’s case, the people they invite to participate in their programs are often offered a lot more money than usual for this kind of thing. The foundation has an endowment of $1.1 billion, and is funding more than 300 projects at the rate of $60 million/year, a rate they intend to double. By comparison, the total NSF budget for supporting theoretical physics is also about $60 million/year. The sheer number and diversity of organizations using Templeton money to promote bringing science and religion together is staggering. I keep finding new ones at various places around the web, and also have yet to run into any organization trying to bring religion into science that isn’t getting Templeton funding.

One new Templeton-funded project is called Foundational Questions in Physics and Cosmology, and has a very illustrious advisory board of physicists. It has just finished accepting proposals for a first round of grants to total $2 million, and has received a 172 proposals, totalling $23 million, from top institutions including Caltech, Harvard, MIT, Princeton and The Institute for Advanced Studies, Stanford, UC Berkeley, Oxford, and Cambridge. Sean Carroll (who turned down Templeton money since he disagrees with what they are trying to promote) has a posting about this, including a guest blog entry and discussion with Anthony Aguirre, who is one of the physicists running the project.

The ethical questions involved in the question of whether to accept money from a source one is not completely happy with are not at all straight-forward. One can sensibly argue that there is nothing wrong with taking money from someone whose goals one disagrees with, as long as they let you do what you want with it, and one isn’t forced to further such goals. On the other hand, publicly associating oneself with an institution to some extent lends ones credibility and prestige to the institution and inherently furthers their goals. It’s also true that money talks, and a large amount of money talks loudly. Many scientists in recent years have probably ended up doing one thing or another that they wouldn’t otherwise have bothered to get involved in because Templeton money made it rather attractive.

There seem to me to be several different things about Templeton to be wary of. One is that the foundation’s leader, Sir John Templeton, is in the process of turning over control of the organization to his son, John Jr., who has a much more politically right-wing, evangelical Christian, point of view than his father. Even if one has no problems with what the foundation has done in the past (e.g., it has not supported creationism), this doesn’t mean it won’t change what it does in the future.

I personally happen to think that bringing religion into physics is inherently a bad idea. Whatever one’s view of religion is, it is inherently a quite different thing than science, and at a time when standards of what is science and what isn’t are under attack, a blurring of the distinction between science and religion may be very dangerous. Much of what Templeton supports seems to me rather silly, but not much of a threat to anything important. For example they are funding a project in Vienna that will bring together physicists, philosophers and theologians to study the foundations of quantum physics. I don’t believe the theologians will be much help here, but they’re not likely to cause much harm. On the other hand, the large amount of Templeton funding promoting symposia devoted mostly to pseudo-science like this one on the Multiverse and String Theory is much more worrying.

Had an amazing trip, which involved several days of travel through hundreds of miles of spectacular sand dunes in four-wheel drive vehicles operated by impressive Tuareg drivers (no camels). This put me and the group I was traveling with somewhere in between Dirkou and Bilma, about at the center of the shadow seen in this picture:

At some point I may post some links to other pictures. In a day or so after I deal with a couple hundred e-mails we’ll return to your regularly scheduled programming.

Update: Fred Bruenjes was at the same eclipse camp in Niger, and has a report on the eclipse here. He also tells about traveling to the site, taking a more leisurely route than the one taken by the group I was with.

I’m leaving tomorrow night on a trip that will take me away from internet access for a week or more. During this time I won’t be posting anything, or able to manage the comment section, so I’ll be shutting off comments late tomorrow afternoon, turning them back on when I’m back on April 4th.

The trip will take me to the middle of the Sahara, in Niger, where I hope to see the total solar eclipse next Wednesday. I’d like to be able to claim that this is some sort of scientific expedition, involving perhaps testing GR by measuring the deflection of starlight during the eclipse. But that’s not the case; this is really just an excuse to go to an exotic location for a much-needed vacation. I thought for a moment about renting a satellite phone with a modem, and blogging from the desert, but decided that would seriously impinge on the important vacation aspect of this trip.

Another reason for the hiatus is that I haven’t been able to come up with an inspired idea for an April 1 posting, and this gives me an excuse for giving up on trying to do that again this year. If I get any good pictures, maybe I’ll finally get around to putting something more visually appealing here.

Bert Schroer has sent me a very long and interesting comment for posting here. I’ve put it into a separate web-page. It includes both a lot of history and many different ideas. Unfortunately I don’t have the time right now to write much about it in response, but just will make one point about the part that he explicitly addresses to me.

Schroer claims that geometric methods in QFT have so far only been useful in dealing with free fields in a fixed background gauge field or metric. This is largely, but not completely true. Most of our reasons for believing the standard model are based on perturbative quantization of gauge fields, and for this it’s true that geometrical methods are not strictly necessary. But for QCD, we need a non-perturbative quantization of the gauge fields, and here lattice QCD is the best we’ve got. It is based upon discretizing a geometrically formulated path integral, preserving as much of the gauge field geometry as possible. My own guess is that there is still a lot to be learned about non-perturbative quantization of gauge fields, based upon the geometrical formulation of the problem given by the path integral approach and I have been working on speculative ideas of how to do this (some of which even involve gerbes and algebraic geometry…). This is still work in progress, maybe I’ll someday find it really can’t work, but for now I’m quite optimistic.

There’s also a new survey paper on QFT from Fredenhagen, Rehren and Seiler. The authors discuss the current state of understanding of QFT, with some points of overlap with Schroer. Like Schroer, they also discuss string theory in detail, and are critical of the inability of the string theory research program to come up with precise statements about what the theory is supposed to be. They are however, much less forceful in their criticisms than Schroer.

Via Tommaso Dorigo of the CDF collaboration, the news that the Tevatron Electroweak Working Group has released a new analysis of combined CDF and D0 data with the most accurate result so far for the top quark mass: 172.5 +/- 2.3 Gev. Last summer this value was at 174.3 +/- 3.4 Gev (see a posting here), an improvement over the earlier value derived just using Run I data of 178.0 +/- 4.3 Gev.

The paper describing these results is available now here, and will soon be on the arXiv as hep-ex/0603039. This new result represents a determination of the top quark mass to 1.3% accuracy, and the paper claims that further Run II data should ultimately allow an accuracy of better than 1%.

For a talk about the significance of the top quark mass, see here.

The SLAC SPIRES yearly list of most frequently cited papers in 2005 is now available. I commented recently on what this was likely to show, quantifying the intellectual collapse of string theory since 1999.

There are exactly three post-1999 particle theory papers among the top 50 in the list. Two of these are about flux compactifications and have moved up significantly since last year reflecting the increasing popularity of landscape studies. At number 18 (up from 29) is the KKLT paper from early 2003, and at number 34 (up from 54) is an earlier paper from 2001 by Giddings, Kachru and Polchinski. The only non-landscape post-1999 paper to crack the top 50 is the 2002 Berenstein, Maldacena and Nastase paper on PP waves (which is part of the AdS/CFT story). It just barely makes it at number 49 (down from 32 last year).

The highest ranked post-2003 paper is the Arkani-Hamed and Dimopoulos 2004 paper on split supersymmetry. It’s at number 106, with a total of 103 citations.

There’s also a new 2005 All-time topcited list. Maldacena’s AdS/CFT paper from 1997 remains very near the top, with 3881 citations. There is nothing post-1999 on this list, which includes the top 186 papers. If recent trends continue indefinitely, it seems entirely possible that no post-1999 particle theory paper will ever make this all-time top-cited list, allowing historians of science to conclusively pinpoint the death of particle theory as having coincided fairly precisely with the end of the 20th century. This is optimistically assuming people lose interest in the landscape. It is also possible that landscape studies will come to dominate the field, with landscape papers then climbing up into the all-time topcited list. This doesn’t really change the conclusion about the death of particle theory.

The 2006 Templeton Prize of $1.4 million was awarded yesterday to cosmologist John Barrow. Barrow is the author of about 400 scientific articles and nearly 20 popular books. In recent years, one of his interests has been the possibility of time-variation of fundamental constants. At a press conference in New York yesterday, he said that new data on quasars expected within two months may provide evidence of such variation.

Science and Spirit has an article by Barrow written for the occasion and called The Unexpected Universe. It also has a report on the press conference that goes on at length about the string theory anthropic landscape and credits Barrow (and Tipler) with writing a “highly influential book for the interface between science and religion” back in 1986 entitled The Anthropic Cosmological Principle. The report includes the following gibberish:

String theorists also assume that other universes, which collectively compose a “multiverse,” exist in other dimensions outside of our observational parameters. Our own very limited experience suggests that finely tuned universes might be more likely to exist than more randomly constructed universes, at least over the long term. If this is true, then fine-tuning may be a guide that cosmologists can use to one day locate and observe an alternate universe.

Barrow himself however doesn’t seem to have much to say about the string theory landscape.

Maybe if Leonard Susskind hadn’t said unfriendly things about having no use for religion in his recent book, he could have been $1.4 million richer instead of Barrow. The New York Times headlines its story about this Math Professor Wins a Coveted Religion Award. A mathematician friend of mine is kind of outraged at this and wants to write to the Times to complain about the description of Barrow as a “math professor”.