No Joking Matter

Posted on July 8, 2013 by woit

Back now from vacation, and while I was away several people sent me links to point out that string theory promoters definitely aren’t taking a vacation. Links here with a few quick comments, followed by something about the issue of making fun of string theorists.

  • Lenny Susskind has a quite good new book out about classical mechanics (see here), but the Economist doesn’t want to talk to him about this, instead it’s the usual string theory promotional effort:

    These extra dimensions can be arranged and put together in many different patterns, in a variety of different ways. Not billions, trillions or quintillions of ways, but many more than that. The ways these dimensions are put together into these tiny little spaces determine how particles will behave, what particles will exist, what the constants of nature are—quantities like dark energy or the electric charge of an electron. In string theory all those things are features of the ways that these tiny dimensions are put together. The tiny dimensions are like the DNA of the universe.

  • Last month Cumrun Vafa was in Bangalore, explaining (see here, slides here) among other things about the significance of the web of string dualities that makes up M-theory:

    String dualities [are] in my opinion perhaps the most fundamental discovery that physicists have made in a century.

    Note that the past century includes General Relativity (barely), quantum mechanics, gauge theory, the Standard Model, as well as quite a few discoveries in other areas of physics.

  • The Strings 2013 conference included the usual public talks promoting string theory. Witten’s was String Theory and the Universe, which was pretty much unchanged (minus optimism about SUSY at the LHC) from similar talks he has been giving for nearly 20 years (since 1995 and the M-theory proposal). Linde’s was Universe or Multiverse?, about the “new scientific paradigm” of Multiverse Mania. He argues that the virtue of this is that it is “impossible to disprove”.
  • David Gross’s public talk on The Frontiers of Particle Physics had nothing to do with string theory, focusing on explaining the standard model and some of the questions it leaves unanswered. Much more interesting was his outlook talk at the conference which included the usual exhortations about string theory being alive and healthy, flourishing with many new and brilliant string theorists, but also included some material unusual in such a venue and much more challenging for his audience. His reference to connections between string theory and condensed matter physics described this as having been “overhyped by our community”. About AdS/CFT, he noted that it “does not provide a satisfactory non-perturbative quantum gravity”.

    He commented on the lack of connection between the talks and HEP physics, saying that it was “important that string theorists not retreat into quantum gravity”. About SUSY, he characterized it as “still alive, but not kicking”, and he argued that the LHC results of the past year have made more likely the “Extremely pessimistic scenario” of an SM Higgs, no SUSY, no dark matter, no indication of the next energy threshold. Since “HEP is where string theory connects to reality”, he made the point to the audience that “if this scenario materializes we are all going to suffer.”

    I’m not sure why he picked this date, but he encouraged those with post-1999 Ph.D.s to realize that it was now quite possible that those who came before them had “somehow got it wrong”. This was the first time I’ve seen an influential member of the string theory community raise this possibility and call for people to consider it seriously.

  • Sean Carroll deals here with arguments from the “Popperazi” that the string theory anthropic multiverse is pseudo-science by ignoring the serious arguments being made. He has his own definition of what science is, which looks to me to open far more questions than it answers. About string theory unification itself, the question has never been whether it’s science, but whether it’s an idea worth pursuing given the ways in which it has so far failed. The best argument for continued pursuit of the idea is of course that there aren’t obviously better ones around, but this raises its own issues.

Sabine Hossenfelder has a posting about an introduction to a Lawrence Krauss talk where the joke was made that “String theorists have to sit in the back”. The context for this was a controversy about the place of women at a discussion involving Krauss hosted by an Islamic group. Like Sabine, I don’t want to discuss here that controversy, just agree there’s a good case to be made that it’s no joking matter. I think she makes a mistake by interpreting the joke as an attack on string theorists (it’s a joke, after all, open to many interpretations), but I was struck by her perception of string theorists as an embattled minority under unfair attack, as well as the claim that it’s not all right to in any way make fun of them.

The situation these days is clearly very different than it was back in 2004 when I started this blog, partly because of the past decade of failure of string theory unification to get anywhere, partly because of the negative LHC results, partly because of the multiverse, and partly because of the public behavior of some in the string theory community in reaction to criticism. Given the high profile ongoing promotional campaign exemplified above, I don’t think we’re yet at the point where criticism of string theorists is “kicking them when they’re down”, and humor is sometimes the best way to make a point concisely. Probably the most incisive criticism of string theory ever made was made in a cartoon, and personally I’ve never understood how it is even possible to take arguments like Linde’s seriously (and am not even sure he does…), so I see a role for humor in charting the continuing story of the collapse of the heavily influential string theory unification paradigm.

Update: If you noticed more than the usual sloppiness, incompleteness and incoherence, maybe it was because this got published early, while I was in the middle of writing it.

Update: The latest on the philosophy of science from Linde (see here), who is at a workshop in Bad Honnef this week.

The multiverse is the only known explanation so in a sense it has already been tested

Is it all right to make fun of this, or should one seriously discuss the scientific merits here?

Posted in Uncategorized | 46 Comments

Hiking the Appalachian Trail

Posted on June 28, 2013 by woit

I’ll be heading North tomorrow, ultimately ending up in backwoods Maine, hiking the Appalachian Trail, then back home after a week or so. The comment section here will likely be closed for the duration.

Progress is being made on my notes on quantum mechanics and representation theory, based on the course I taught this past year. About 3/4 done with the writing at this point, the latest version is available here.

Posted in Uncategorized | 10 Comments

Strings 2013 etc.

Posted on June 25, 2013 by woit

These days one can just about attend a wide variety of summer conferences from the comfort of one’s home or office, with talks appearing online more or less immediately after they are given. This week some possibilities to consider are:

  • The big yearly string theory conference, Strings 2013, is in Seoul this week with about 279 physicists in attendance, talks are available here. As usual for recent string theory conferences, there aren’t a lot of strings to be seen. Perhaps these yearly conferences should be renamed something like “Conference on the latest topics popular among people who used to do string theory”. No sign at all of the landscape or string theory unification. For some understanding of why, see Life at the Interface of Particle Physics and String Theory, to be published by Reviews of Modern Physics, which makes pretty clear why the organizers of Strings 20XX now want to avoid this topic.
  • The 2013 Lepton Photon conference is in San Francisco this week, talks here. To mark the occasion, Gordon Watts and Jacques Distler have thrown in the towel, paying up on their bet with Tommaso Dorigo that the LHC would find SUSY or other “new physics”. Tommaso has the full story here.
  • For the more philosophically minded, the Templeton Foundation is funding a summer institute on the Philosophy of Cosmology, and you can follow the talks here. If thinking about time is your thing and you’ve missed out on the free summer amongst the redwoods, there’s still time to get in line for Templeton funds, with a few days left to apply for grants here.

Update: To round out the list, I should have included something for the mathematical physicists, this week’s Symmetries in Mathematics and Physics conference in Rio. Videos of the talks are appearing here.

Update: Jacques Distler has a posting here (or guest post here) conceding the loss of his bet with Tommaso Dorigo. Unlike some other theorists (e.g. John Ellis) who are arguing that everything’s fine, one just has to wait until 2015-6 for the higher energy LHC run, Distler is more of a realist:

…would I be willing to bet on the 2015 LHC run uncovering new BSM physics?

The answer, I think, is: not unless you were willing to give me some substantial odds (at least 5–1; if I think about it, maybe even higher).

Knowing the mass of the Higgs (∼125GeV) rules out huge swaths of BSM ideas. Seeing absolutely nothing in the 7 and 8 TeV data (not even the sort of 2-3σ deviations that, while not sufficient to claim a “discovery,” might at least serve as tantalizing hints of things to come) disfavours even more.

The probability (in my Bayesian estimation) that the LHC will discover BSM physics has gone from fairly likely (as witnessed by my previous willingness to take even-odds) to rather unlikely. N.B.: that’s not quite the same thing as saying that there’s no BSM physics at these energies; rather that, if it’s there, the LHC won’t be able to see it (at least, not without accumulating many years worth of data).

Posted in Strings 2XXX | 20 Comments

Kenneth Wilson 1936-2013

Posted on June 18, 2013 by woit

Kenneth Wilson died this past weekend, in Maine at the age of 77. Some obituaries can be found here, here, here, and here.

Wilson won the Nobel prize in 1982 for his work on critical phenomena and phase transitions, but his influence on particle theory was arguably even greater than on condensed matter physics. Unfortunately I never got a chance to meet him, but a large part of what I was learning about quantum field theory back in my days as a graduate student came either directly or indirectly from him.

Soon after the discovery of asymptotic freedom in 1973, he started work on developing lattice methods for studying gauge theories non-perturbatively with a fixed cut-off. This founded the whole field of lattice gauge theory, which remains a major and active part of HEP theory. Not many people have a whole section of the arXiv they’re responsible for. For his story of how this came about, see his 2004 The Origins of Lattice Gauge Theory.

The reason Wilson was well-placed to quickly get lattice gauge theory off the ground in 1973-4 was that he was one of very few theorists who had been thinking hard and fruitfully about the meaning of non-perturbative quantum field theory. After getting an undergraduate degree in math from Harvard in 1956, he did his thesis work under Gell-Mann at Caltech, finishing in 1961 and developing an interest in the renormalization group. From 1963 on he was focusing his research on strong interactions and the high energy behavior of quantum field theory. This was a time when QFT had fallen out of favor, with S-matrix theory considered the cutting edge. One reason others weren’t thinking about this was that the problem was very hard. It was also perhaps the deepest problem around: how do you make sense of quantum field theory? What is QFT, really, outside of the approximation method of perturbation theory?

By the early 1970s, Wilson had developed the ideas about the renormalization group and QFT that now form the foundation of how we think about non-perturbative QFTs. The first applications of this actually were to problems about critical phenomena, and it was for this work that he won the Nobel prize. With the arrival of QCD, these ideas became central to the whole field of particle theory, with much of the 1970s and early 80s devoted to investigations that relied heavily on them. If you were a graduate student then, you certainly were reading his papers.

For more from Wilson himself about his life and work, see his 1983 Nobel Prize lecture and a long interview from 2002 here, here and here.

John Preskill has a wonderful posting up about Wilson, with the title We are all Wilsonians now. He ends it by explaining Wilson’s early role in the debate about “naturalness”. Wilson was well aware of the quadratic sensitivity of elementary scalars to the cut-off and had argued that this meant that you didn’t expect to see elementary scalars at low masses. This argument was developed here by Susskind as a motivation for technicolor. Preskill doesn’t mention though that Wilson later referred to this as a “blunder”. In 2004 he had this to say:

The final blunder was a claim that scalar elementary particles were unlikely to occur in elementary particle physics at currently measurable energies unless they were associated with some kind of broken symmetry [23]. The claim was that, otherwise, their masses were likely to be far higher than could be detected. The claim was that it would be unnatural for such particles to have masses small enough to be detectable soon. But this claim makes no sense when one becomes familiar with the history of physics. There have been a number of cases where numbers arose that were unexpectedly small or large. An early example was the very large distance to the nearest star as compared to the distance to the Sun, as needed by Copernicus, because otherwise the nearest stars would have exhibited measurable parallax as the Earth moved around the Sun. Within elementary particle physics, one has unexpectedly large ratios of masses, such as the large ratio of the muon mass to the electron mass. There is also the very small value of the weak coupling constant. In the time since my paper was written, another set of unexpectedly small masses was discovered: the neutrino masses. There is also the riddle of dark energy in cosmology, with its implication of possibly an extremely small value for the cosmological constant in Einstein’s theory of general relativity.

This blunder was potentially more serious, if it caused any subsequent researchers to dismiss possibilities for very large or very small values for parameters that now must be taken seriously…

He then goes on to argue at length that the lesson of the history of science is that often what seemed like unlikely possibilities turned out to be the right ones, with the argument for unlikeliness just a reflection of the fact that people had been making assumptions that weren’t true and/or they didn’t understand the possibilities as well as they thought they did.

Wilson may be no longer with us, but his ideas certainly are, and they’re very relevant to the biggest controversies of the day.

Posted in Obituaries | 17 Comments

This Week’s Hype

Posted on June 18, 2013 by woit

In recent years universities have taken to issuing press releases when one of their particle theorists gets a paper on some speculative topic published in a journal like Physical Review Letters. Many examples of such things, often involving bogus claims to have a “test of string theory” have been covered here.

The University of Delaware has now decided to break new ground: they’ve issued a press release promoting a 1997 paper by some of their faculty that was published in Physical Review D. I gather the argument must be that it’s timely because it’s about the multiverse and anthropics.

As a bonus topic in the “This Week’s Hype” category, there’s a new paper out yesterday promoting the idea that string inflationary models have been successfully tested by the Planck data:

We argue that as a group the predictions made before Planck agree well with what has been seen…

The authors start out by addressing the obvious problem with string cosmology:

given the complexity of these models it is worth first asking why they are worth scrutinizing in detail at all. After all, if the data is perfectly consistent with much simpler models, Occam’s razor suggests we should leave it at that.

It seems that in our new anthropic multiverse-based framework that drops conventional ideas about predictions and testability, Occam’s razor has to go too.

Update: I should have mentioned that the Delaware press release links to the article discussed here.

Posted in Multiverse Mania, This Week's Hype | 5 Comments

Farewell to Reality

Posted on June 16, 2013 by woit

Jim Baggott has written a very good new book called Farewell to Reality that will soon come out here in the US. It is already out in the UK, where it is stirring up some debate, and perhaps the US will soon see something similar.

In the preface, Baggott explains that he was motivated to write the book by the experience of watching this BBC program, which featured a combination of serious science with revelations about how we’re all part of a cosmic hologram, there’s an infinity of parallel worlds, and various other examples of what he refers to as “fairy-tale” physics. In the last decade or so there have been a large number of such mass media efforts promoting highly dubious ideas about fundamental physics, and Baggott decided that in his next book he’d try and do something to counter this. I think he’s succeeded admirably: the BBC and other such organizations should atone for their sins by sending copies of the book to their viewers.

The book is divided into roughly two halves, with the first half a well-executed overview of the current state of our theories about fundamental physics, from quantum theory through the standard model and cosmology. It ends with a description of the outstanding problems left unsolved by our best theories, and a good summary of the current situation:

Several centuries of enormously successful physical science have given us a version of reality unsurpassed in the entire history of intellectual endeavour. With a very few exceptions, it explains every observation we have ever made and every experiment we have ever devised.

But the few exceptions happen to be very big ones. And there’s enough puzzle and mystery and more than enough of a sense of work in progress for us to be confident that this is not yet the final answer.

I think that’s extremely exciting…

… but there is no flashing illuminated sign saying “this way to the answer to all the puzzles”. And there is no single observation, no one experimental result, that help to point the way. We are virtually clueless.

With this background he turns to a detailed examination of the speculative ideas that have not worked out, but have dominated the field for the past 30-40 years (SUSY, GUTS, Superstring/M-theory, the multiverse). This is difficult material to do justice to, but Baggott does a good job of giving an explanation of these ideas that includes some understanding of the problems with them. He ends the book with this advice to the reader:

Next time you pick up the latest best-selling popular science book, or tune into the latest science documentary on the radio or television, keep an open mind and try to maintain a healthy scepticism… What is the nature of the evidence in support of this theory? Does the theory make predictions of quantity or number, of matter of fact and existence? Do the theory’s predictions have the capability – even in principle – of being subject to observational or experimental test?

Come to your own conclusions.

The thorniest problems that come up in this sort of discussion are essentially ones about the philosophy of science. What counts as evidence for a scientific theory? At what point does pursuit of speculative ideas that are going nowhere stop being legitimate science? One quickly realizes that naive ideas about the scientific method don’t capture how good science really works. Baggott devotes the first chapter of the book to an overview of his take on what the scientific method really is. In the end, this may be the most important issue here: will books and TV programs promoting the views of a narrow part of the scientific community that doesn’t want to admit failure end up discrediting the scientific endeavour? Some are all too willing to exploit the subtleties of good science to find a way to defend the indefensible, with the multiverse mania pointing to the all too real dangerous endpoint this can lead to.

For some reviews from the UK of the book see here, here and here.

For a BBC Radio program featuring discussion between Baggott, Jon Butterworth and others, see here. Butterworth has written more today here.

Also today in the Guardian, there’s a debate between Baggott and Mike Duff. Duff characterizes the experimental situation of string theory as follows:

Definitive experimental tests will require that the theory also incorporate and improve upon the standard models of particle physics and cosmology. An impressive body of evidence in favour of this has accumulated, but it is still work in progress.

without giving an example of any sort of conceivable such experimental test. I think Duff is being highly misleading here, since the story of the last thirty years is not one of evidence for string theory unification accumulating, but the opposite: the more we learn about string theory, the less likely it seems that it can predict anything. One can argue that string theorists just need more time (Duff points to the idea of atoms arising back in 400BC, taking more than two millennia to come to fruition), but the problem with string theory is not that progress is slow but that it is negative.

On the question of TV programs like the one that motivated Baggott to write the book, even Duff won’t defend them, but blames the situation on journalists:

As for misrepresentation in the media, there will always be sensationalists and attention-seekers in any field, but in my (admittedly biased) opinion, the worst culprits are the journalists.

This is quite amusing coming from someone who (see here) had his university put out a press release claiming that he had made the first discovery of a way to test string theory. He advertises string theory as having found application in quantum information theory, a claim that I doubt is believed by any other string theorist or quantum information theorist. No, the worst culprits here are not journalists, whose mistake is often just that of taking seriously press releases from people like Mike Duff.

Duff invokes the same criticism made back in 2006 that “Sadly, many critics of string theory, having lost their case in the court of science, try to win it in the court of popular opinion.” He’s well aware though that string theorists are losing badly in the court of science (with US physics departments now hiring virtually no string theorists). String theory unification is an idea now discredited in the scientific community, but getting propped up by TV programs and prizes from Russian billionaires. I hope when Baggott’s book comes out in the US, we’ll see a more serious discussion of the issues that it raises.

Update: Duff is unhappy about Butterworth’s mild criticism of string theory, so has responded with a comment at the Guardian site that begins

Dear John

”The concern arises if everyone makes the same wild guess, and the experiments to confirm or deny it are out of reach”.

is more-or-less what people said when theorists predicted the Higgs boson in 1964.

According to Duff, I guess, back in 1964 the situation was just like that of string theory, with the field experiencing what people were calling an unhealthy domination by the likes of Peter Higgs and others working on the Higgs mechanism. That’s a very odd take on the history, given that the work of Higgs and others was virtually ignored at the time.

Posted in Book Reviews | 84 Comments

Nature on the new Nobels

Posted on June 12, 2013 by woit

This week’s Nature has an article by Zeeya Merali about various new science mega-prizes, including Yuri Milner’s Fundamental Physics Prize. There’s also a podcast here, and a Nature editorial here.

I’m quoted in the article, saying about what you’d expect, but in general I was surprised by the extent of the negative reaction to these prizes that she found. Even $3 million winner Sasha Polyakov has concerns, saying

This new prize is an interesting experiment… Such big prizes could become very influential and they can have a positive impact, or they can be very dangerous.

Frank Wilczek has this to say:

I don’t want to run these awards down, but I find it offensive that people are trying to either borrow the prestige of the Nobel, or buy it…

Prizes are a good thing, but the question is, if your goal is to help science, are large prizes the most efficient way to do that?

Interestingly, Milner counters the criticism that his prizes have heavily gone to string theorists by noting that the award to seven LHC experimentalists this year will shift the balance on the judging panel towards experiment (since awards in the future will be chosen by past winners).

On the whole Merali doesn’t seem to have had much luck in getting the winners to reveal what they plan to do with the money. Some of the LHC winners seem to be very aware that they’ve been given a large check due to the work of others, with Tejinder Virdee of CMS planning to support science in schools in sub-Saharan Africa. I’ve heard rumors that Maxim Kontsevich is somehow using his award to help others at the IHES, but nothing else about how other theorists will use the money. They are giving public lectures, which are online, see here. After Witten’s lecture at Hunter College, the first question was about his plans for the money, but no answer was forthcoming.

The editorial chides scientists for criticizing these new prizes, saying they should “accept such gifts with gratitude and grace”. I suppose there would be a lot more of that if the prizes seemed to be helping to support science in general, not just the bank accounts of a few.

Update: At least one wealthy philanthropist has decided to give the millions for theoretical physics to an institution rather than a person. The University of Chicago has announced a $3.5 million gift from an anonymous donor, which will support a new Center for Theoretical Physics to be named after Leo Kadanoff.

Posted in Uncategorized | 14 Comments

Nature at the energy frontier

Posted on June 12, 2013 by woit

Last week a symposium on Nature at the energy frontier was held at the ETH in Zurich, funded by the Latsis foundation. Videos of many of the talks have appeared here.

As part of the symposium, David Gross gave a public talk, available here. Gross is often invited to give such talks, and I’ve either attended or taken a look at the video for quite a few of them. The first substantive posting on this blog back in 2004 was about one such talk. Back then, Gross was claiming that in 3-4 years there would be a headline in the New York Times about the discovery of supersymmetry at the LHC (he was overly optimistic about how long it would take to get the machine working properly). I wondered at the time:

What will be interesting to see will be what Gross et. al. do when this doesn’t happen. Will they drop string theory?

In all of the talks I’ve seen since that time, Gross continued to express optimism, including willingness to bet significant sums of money on a discovery of superpartners at 50/50 odds. His talk at the Latsis symposium included a remarkable change of tone, featuring an Einstein quote I hadn’t seen him use before:

The successful attempt to derive delicate laws of nature, along a purely mental path, by following a belief in the formal unity of the structure of reality, encourages continuation in this speculative direction, the dangers of which everyone vividly must keep in sight who dares follow it.

He describes Einstein as both encouraging the kind of speculative path followed by string theory and SUSY, while at the same time warning of its dangers, and noted that Einstein himself devoted the latter part of his life to a speculative path that turned out to be a dead end.

In his explanation of the standard arguments for string theory and SUSY, Gross was much more cautious than in the past, careful to explain that these arguments were based on just speculative “clues”. These clues might just be coincidences, but the main reason for not giving up on them was that we don’t really have any others.

About the LHC results, Gross described them as having now ruled out the simplest SUSY models, which could be a clue that SUSY does not exist. He said that if SUSY is not seen at the LHC, we will learn for sure that theorists have been on the wrong track for many decades. According to him, this would “change a lot of our way of thinking”, since “we have been pursuing these clues for a long time.” He didn’t discuss how ways of thinking will change, although he is well known to strenuously reject one popular idea about this (anthropics and the multiverse).

Erik Verlinde gave an odd talk with a title that promised to address these issues, String Theory and the Future of Particle Physics. He explained the history of string theory and how the original hope was that it would tell us where the SM parameters came from, something which “looks differently now”. According to him, the idea of strings moving in a compactified 10d was the “old view”, now made obsolete by branes. The “present view” is all about gauge-gravity duality, which doesn’t say anything about those SM parameters. According to him the “future view” of string theory will somehow start from some new basic principles that we don’t know yet, providing an underlying microscopic description that will explain holography, and give an “emergent” explanation of space, time, matter, etc. There was no explanation at all of what these new principles were or what the new microphysical description would be. String theory itself would just be an “effective theory”, like the Standard Model.

After this introduction, Verlinde than moved on to something that seems to have nothing at all to do with string theory, giving a long explanation of how he thinks there are some new degrees of freedom out there that have dynamics at long time scales. These should be treated by the methods of polymer dynamics, and they will explain dark matter and dark energy. He produced lots of graphs of astrophysical data, and claimed that he has an “extension” of Newtonian gravity, better than MOND, which explains the astrophysical data. At the end of the talk there were a bunch of questions about the cosmological implications of this, I couldn’t tell if Verlinde had an answer. He has been talking about this idea in public talks for a couple years now, although as far as I can tell there is no paper. Also, as far as I can tell, no one else besides him takes this seriously.

The last talk of the conference was from Nima Arkani-Hamed, giving basically the same talk I’ve written about recently here and here. I confess to not listening to the whole thing, since it was quite familiar (although I did notice he addressed the question of the possibility there wasn’t really a hierarchy problem, saying people who raised that were “frustrating”, since he had thought about it for decades, and “trust me, there’s a hierarchy problem”). In the question session, he made the same point I often end up arguing with string theory proponents about, saying (1:14) that if “you can do experiments at the string scale, wouldn’t help you at all”. The idea that you would see string excitations on a compactified space he characterizes as a misguided old idea from the 1990s. If there’s a landscape, the possibilities are so complex for Planck scale behavior that you can’t predict what experiments at that scale would see. I’m glad to see that now instead of getting into arguments like this one, I can send people to go argue with Nima.

Posted in Uncategorized | 33 Comments

Simons 75th Birthday Conference

Posted on June 3, 2013 by woit

Last week the CUNY Graduate Center hosted a conference in honor of the 75th birthday of Jim Simons. It was organized by Dennis Sullivan as a set of expository “mini-courses” on various topics related to Simons’ mathematical work. I was able to attend the morning talks, which were of a uniformly high quality, and focused on the Chern-Simons 3d QFT, as well as the “differential characters” of Cheeger and Simons. Video of most of the talks is available online here. In particular, Witten’s talk, which was a very simple physical introduction to use of the Abelian Chern-Simons term in condensed matter, is available here (followed by Deligne on Deligne-Beilinson cohomology). Talks by Robbert Dijkgraaf on Chern-Simons-Witten theory are here and here. The second Dijkgraaf talk was followed (go to 1:05) by some informal comments by Simons himself, explaining the history of how Chern-Simons came about. Mike Hopkins gave two wonderful talks, the first about differential characters in general and about his recent article with Dan Freed, the second about his work with Singer that used generalized differential cohomology.

The talks I missed were likely just as good, I’m starting to catch up on them on video now….

Posted in Uncategorized | 5 Comments

Snowmass on the Pacific

Posted on June 1, 2013 by woit

Due to popular demand from the comment section, I spent some time this afternoon taking a look at the talks now posted from the KITP Snowmass on the Pacific conference held the past few days. This is part of an ongoing project for a US HEP Community Summer Study that will culminate at a meeting in Minneapolis later this summer. The US HEP community faces serious questions about what priorities for the future should be in an environment of flat-to-declining budgets, no energy frontier projects in the US, and discouraging news from the LHC about no evidence for BSM physics.

The KITP talks cover a wide range of topics, and I haven’t had a chance to look at very many of them. For theorists, one interesting session was the Wednesday panel on Structural Issues for Theorists, which featured presentations by and discussions with the people at DOE and NSF responsible for HEP theory grants (Simona Rolli and Keith Dienes). There’s a lot of information about the situation of US theory grants there, but I was a bit struck by the impression that despite the large problems faced by HEP in the US, for theorists things look much like they always have:

  • Budgets are pretty flat. As salaries go up with inflation, and as new young people come into the system applying for grants, it’s harder and harder for people to get the grants and grant amounts they would like.
  • The split between DOE and NSF funding of often exactly the same thing doesn’t make much sense and leaves people sometimes confused.
  • There’s always a problem finding grant support for the number of students who want to do theory, leaving theorists trying to justify to their colleagues why their students should get more of the few TA positions available. The situation of funding about 180 theory Ph.D students in an environment where there are maybe 10 tenure track jobs/year in the country isn’t deemed even worthy of comment.

Some numbers from the presentations:

  • The DOE spends roughly \$25 million/year on positions at government labs, another \$25 million/year on grants to universities (the bulk going to pay grad students/postdocs/summer salary). The NSF spends \$13-14 million/year on grants to universities, another $6 million on Frontier Centers, some of which have an HEP theory component.
  • DOE funds 49 PIs at labs, 221 PIs at universities, NSF funds 186 PIs at universities.
    The DOE split by field is 128 Phenomenologists, 73 “Formal” (often “string theory”), 42 Cosmology, 27 Lattice Gauge Theory.
  • DOE funds 123 postdocs, NSF funds 50 of them. DOE funds 130 grad students in theory, NSF 50 of them.

This stable system of government funding has been crucial in determining the structure of HEP theory in the US for the past few decades, and the academic system is built around it. I keep wondering what the effect will be as new sources of money come into the system from private sources, on scales approaching that of government funding. As a somewhat extreme example that is likely a one-time thing, last year the string theorists in Princeton got \$15 million in checks from Yuri Milner, a number somewhat larger than the entire NSF $13-14 million/year budget for HEP theory.

Posted in Uncategorized | 26 Comments