Latest From the LHC

Posted on September 11, 2009 by woit

Things seems to have been going well at the LHC recently, with the current schedule expecting injection of beams in a little more than two months from now, on Thursday November 19. After that, the plan is for a week and a half of beam commissioning at 450 GeV, and 450 GeV collisions at the beginning of December. The machine will then be ramped up to first 1 TeV, then 3.5 TeV, with 3.5 TeV collisions on December 14.

Soon after that (December 17), the machine will go into a technical stop period for the holidays, starting back up January 7. From then on, the plan is for a month of more commissioning work and pilot physics. The first regular physics run at 3.5 TeV will last about 3 months, with expected luminosity of 54 pb-1. Then in May, the energy will be increased to somewhere in the range of 4-5 TeV, with a run beginning in June at that energy lasting until mid-October, with expected luminosity of 274 pb-1. The machine will then be reconfigured for a one-month run with heavy ions, and then go into a long shutdown at the end of November.

Anyway, that’s the latest plan, reality may turn out differently. For up to the minute information on how things are going, you can follow along here. The last sector to be ready is now supposed to be sector 67, which is in cooldown, the magnets currently around 200K.

See here for a recent Science Magazine story on the subject from Adrian Cho.

Posted in Experimental HEP News | 9 Comments

Mathematicians: An Outer View of the Inner World

Posted on September 7, 2009 by woit

A friend recently loaned me a wonderful book, the recently published Mathematicians: An Outer View of the Inner World, which consists mainly of photographs of mathematicians by Mariana Cook, paired with a page of comments from the mathematician being photographed. For more of the photos, see Mariana Cook’s web-site. The comments typically deal with the story of what led the person into mathematics, or a summary of their career, or some general thoughts on mathematics and the pleasures of studying it.

Many of these mini-essays are well-worth reading. The Viscount Deligne describes working with Grothendieck and contrasts this to some of his later experience:

When I was in Paris as a student, I would go to Grothendieck’s seminar at IHES and Jean-Pierre Serre’s seminar at the Collège de France. To understand what was being done in each seminar would fill my week. I learned a lot doing so. Grothendieck asked me to write up some of the seminars and gave me his notes. He was extremely generous with his ideas. One could not be lazy or he would reject you. But if you were really interested and doing things he liked, then he helped you a lot. I enjoyed the atmosphere around him very much. He had the main ideas and the aim was to prove theories and understand a sector of mathematics. We did not care much about priority because Grothendieck had the ideas we were working on and priority would have meant nothing. I later met other areas of mathematics where people were worried about doing something first and were hiding what they were doing form one another. I didn’t like it. There are all kinds of mathematicians, even competitive ones.

Michele Vergne has an intriguing comment about the “quantization commutes with reduction” question, which is a fundamental issue for how symmetries work in quantum physics. When you have a gauge symmetry, do you get the same thing if you first eliminate the gauge variables (go to the symplectic reduction) and then quantize, or if you quantize and then take the gauge-invariant subspace? This turns out to be a remarkably interesting mathematical question. Perhaps the best way to think about its physical significance is to take it as a criterion for any viable notion of exactly what “quantization” is, and how it is supposed to interact with the notion of symmetry.

Today I can see a dim light on a problem that has been on my mind for a long time. This is the assertion: quantization commutes with reduction. It was a beautiful conjecture of Guillemin-Sternberg, which was clearly true, but revealed itself hard to prove in general. I was able to prove an easy case. A much more difficult case was then proved by another mathematician ten years ago, using surgery. For me, this method via cuts is ugly. I would have liked to prove this conjecture with my own methods. Long after the full proof was found, I kept reorganizing my own arguments in all possible ways. If I repeated them over and over, the difficulties were bound to disappear. But they did not. These ceaseless failed attempts left a scar. I do still hope to discover where exactly the difficulty was, and today I feel I know the small hole where the difficulty was hiding. I think it can be grasped easily. Then, maybe, I will be able to formulate and prove the theorem in a much more general way. True, for thiat I need someone else’s idea, but just recently, I used a brilliant idea of one of my students to explain a very similar phenomenon. I believe it can also be used to understand this case. Anyway, I will try. Tomorrow.

Posted in Book Reviews | 10 Comments

String Theory Skeptic

Posted on September 2, 2009 by woit

The latest Forbes magazine has an article entitled String Theory Skeptic, which gives me a lot more credit for the problems of string theory than I deserve.

The article as I just saw it online appears to have a minor editing problem, with the quote

It’s common in physics for people to have incredibly ambitious ideas that don’t pan out but lead to rich mathematical ideas that end up being very useful.

which is attributed to Peskin in the middle of the article, appearing a second time at the end, right after a quote from me. In any case, even if Peskin is the one who said it, not me, it’s something I very much agree with, and perhaps a good summary of the string theory situation.

Update: I gather that the Peskin quote is the “knockout quote” of the piece, set off and summarizing things, with the online formatting what makes it appear to be in the body, at the end.

Posted in Uncategorized | 48 Comments

ICM 2010

Posted on August 27, 2009 by woit

The International Congress of Mathematicians is held every four years, and the next iteration, ICM 2010, will be held about a year from now, in Hyderabad, India. These are huge conferences, planned well in advance, with 1465 mathematicians already pre-registered.

The list of speakers gives a good indication of what the mathematical establishment views as the most important research activity of the past four years, and this list is now available here. There are a large number of parallel sessions, and a limited number (20) of plenary talks.

The winners of the Fields medal are announced at the ICM, at the same time as the composition of the committee that made the choice (the chair of the committee, Laszlo Lovasz, is known). One way to help guess who will win a Fields medal is to take a look at those on the speakers list who are under forty. I’m not privy to any inside information, but many people think Ngo is a shoo-in for his work on the fundamental lemma (he’s a plenary speaker), and there’s some speculation about Jacob Lurie (who is a parallel session speaker).

This year there’s a new prize to be awarded at the ICM, the Chern Medal, for “an individual whose accomplishments warrant the highest level of recognition for outstanding achievements in the field of mathematics.” This one, unlike the Fields, comes with a significant amount of money ($250,000, and another $250,000 for the medalists favorite mathematical organization).

Posted in Uncategorized | 35 Comments

Percontations

Posted on August 24, 2009 by woit

The Templeton Foundation has recently been sponsoring a series of Bloggingheads diavlogs, under the name Percontations. This week’s episode is Fiddling With the Knobs of the Universe, and it has cosmologist Anthony Aguirre and string theorist Clifford Johnson doing their best to hype string theory and the landscape. Critics are dismissed as people who believe obviously wrong things like “if it’s statistical it’s not science”.

Johnson argues that string theory landscape research is just like any other kind of science, capable of making testable statistical predictions, predictions based on generic properties of the theory (e.g. T-duality), and predictions of some parameters based upon fixing others by observation. He neglects to mention that decades of work by people trying to do such things have shown that there are very solid reasons why they don’t work. Not only have no predictions come out of this, but the reasons why have become clear.

While hyping the landscape, he acknowledges that string theory has had a problem with hype in the past. “We all bought into it to some extent” that string theory was going to give the Standard Model, and it was bad that this was promoted in the press as a polished, definitive story of how the world works. He claims to be happy that this has been backed away from in the last several years (although he never seems to have been happy about the existence of string theory critics who have raised the issue of the problems publicly).

In a recent posting, Johnson partially resolves a mystery I’d always wondered about, that of why he left Cosmic Variance. He explains that one reason was that Cosmic Variance was taking “the obnoxious route of calling someone an idiot or stupid for their religious beliefs at the outset.” Bloggingheads has recently featured Sean Carroll and Mark Trodden of Cosmic Variance also discussing cosmology and the multiverse (see here and here), but these episodes were not sponsored by Templeton.

Posted in Multiverse Mania | 35 Comments

Various and Sundry

Posted on August 20, 2009 by woit

Back from a final short summer vacation, with no further travel plans for the indefinite future. Some things I’ve recently come across that might be of interest:

  • Tommaso Dorigo has posted his contribution to a session on “Blogs, big physics and breaking news” held at last month’s World Conference of Science Journalists in London. There’s a recording of the session available here. Besides Tommaso, one speaker was Matthew Chalmers, who talked a bit about the “String Wars”, including the role of blogs in it. The last speaker was CERN’s James Gillies who discussed CERN’s efforts to do a better job of putting out information about progress on the LHC project, under some pressure from the phenomenon of others disseminating such information if they don’t…. They’ve done a much better job of this recently, putting out informative press releases almost immediately after major decisions are taken. I’m glad to hear that he finds the role of blogs to have been a positive one.

    For a recent LHC update, see these slides from a talk at the Lepton-Photon Symposium. On page 35 there’s a copy of the latest detailed schedule that I’ve seen, which one can compare to the continuing updates on progress here.

  • Also at Lepton-Photon, here’s a talk by Shamit Kachru about using AdS/CFT to build technicolor-type models of electroweak symmetry breaking that involve strongly coupled gauge theories. He and his wife Eva Silverstein will be leaving Stanford and joining the KITP in Santa Barbara this fall, see the press release here.

    For lots more about the KITP, its programs and its finances, see this presentation by David Gross to the NSF.

  • I see there’s an interesting sounding workshop at the Fields Institute this fall, but it scares me to see that it is described as a celebration of Allen Knutson’s 40th birthday. I seem to have gotten old very quickly, with conferences now devoted not only to people younger than me, but to people much younger than me that I recall meeting when they were just starting graduate school…
  • My nomination for the all-time highest quality discussion ever held in a blog comment section goes to the comments on this posting at Secret Blogging Seminar, where several of the best (relatively)-young algebraic geometers in the business discuss the foundations of the subject and how it should be taught.
  • There’s a long and well-informed article here on the multiverse, bringing together the “What the Bleep” crowd, mainstream physicists, theologians, and the logo of the Stanford Institute for Theoretical Physics (the one Kachru and Silverstein are escaping from).
  • For a selection of the latest in cutting-edge applications of new internet technology related to physics, there’s Gordon Watts with his Deeptalk, the nLab site of the n-category cafe, and the Twitter feed of Cosmic Variance.
    • Posted in Uncategorized | 9 Comments

    This Week’s Hype

    Posted on August 12, 2009 by woit

    From Softpedia this week, the news is of a Universal Theory of the Universe in the Works. According to the article,

    The theory of quantum mechanics was devised around 1920, and explains all this, but without accounting for gravity. Therefore, uniting the two ideas has since been an effort taken on by a large number of physicists. Now, an international group believes it is closer than ever to finally managing a breakthrough.

    Professors A.A. Coley, from the Dalhousie University, in Halifax, G.W. Gibbons at the University of Cambridge, in the UK, and C.N. Pope at the Texas A&M University, in the United States, led by young mathematician Sigbjørn Hervik, at the University of Stavanger, in Norway, believe that string theory is the best option physics has at bringing the two together.

    It’s hard to tell what this is based on, but the only paper I see with those authors is this one, which doesn’t really have much of anything to do with string theory.

    The source of the Softpedia article is one from Science Daily entitled A Grand Idea About the Universal Universe that tells us that:

    A mathematician in Norway and international fellow scientists have now conceived a grand idea about the universal universe. They have developed a method that may provide answers to universal problems and characterize and describe the universe….

    “The problem is that quantum mechanics does not include gravity and the theory of relativity does not include quantum mechanics”, Hervik says.

    Many attempts have been made to find a unifying theory of both. String theory is the best candidate so far, according to Hervik.

    Ultimately this all goes back to yet another university press release, this one about Hervik’s Universe.

    Posted in This Week's Hype | 15 Comments

    25 Years On…

    Posted on August 6, 2009 by woit

    Five years ago the 20th anniversary of the “First Superstring Revolution” was being celebrated, and I wrote some postings about this history (see here, here and here). This month is the quarter-century anniversary, and I haven’t seen any evidence of anyone celebrating.

    25 years later, it’s pretty clear that the anomaly cancellation discovered by Green and Schwarz doesn’t actually provide at all the kind of explanation of some aspects of the standard model that people got excited about back then. 1984 also saw the beginning of endlessly repeated and overhyped hand-waving arguments that string theory is needed to cure the perturbative ills of quantum gravity. It turns out that these arguments don’t actually work either. The latest issue of Science has an article about recent discoveries showing that N=8 supergravity amplitudes are much better behaved than expected. Zvi Bern compares the widespread belief that string theory is needed to deal with perturbative divergences to the belief that ulcers are caused by spicy food. While you could make a plausible hand-waving argument for this, it turns out that the real culprit is a bacterium, not enchiladas. According to the article:

    The work doesn’t disprove string theory, but it has string theorists backpedaling a bit in their criticism of quantum field theory. “At certain points, our understanding has been incomplete, and we may have said things that weren’t right,” says John Schwarz of the California Institute of Technology in Pasadena. “That being said, the fact is that we still need string theory.”

    Forced to concede that a quarter-century’s worth of argument about perturbative amplitudes was wrong, Schwarz tries to shift ground by claiming that the QFT problems are non-perturbative. That may very well be, but until one actually has a viable non-perturbative version of string theory, it will be hard to argue that string theory is the only way to go.

    A new review article about quantum gravity describes how things are 25 years after the revolution, with many if not most string theorists having given up hope that string theory has anything to say about unification:

    A personal anecdote might best convey the current state of affairs. Early in the spring 2007 semester my University of Florida colleague, Charles Thorn, began a seminar by announcing his belief that:

    String theory is just a technique for summing the leading terms in the 1/N expansion of QCD.

    After years of hearing more ambitious assessments this was so shocking that I checked to be sure I had understood correctly. Charles confirmed that I had; in his current view, the effort to regard superstrings as a fundamental theory of everything was a blind alley. Later that year I related Charles’ pronouncement to string theory colleagues on three continents and solicited their own opinions. About half of them agreed with him, more often the younger people.

    Update: One more, from Martha Stewart, Some Pearls of Wisdom on String Theory.

    Posted in Uncategorized | 29 Comments

    Various Items

    Posted on August 6, 2009 by woit
  • CERN just issued a press release announcing the decision about the energy for the initial LHC run: 3.5 TeV/beam.

    The procedure for the 2009 start-up will be to inject and capture beams in each direction, take collision data for a few shifts at the injection energy, and then commission the ramp to higher energy. The first high-energy data should be collected a few weeks after the first beam of 2009 is injected. The LHC will run at 3.5 TeV per beam until a significant data sample has been collected and the operations team has gained experience in running the machine. Thereafter, with the benefit of that experience, the energy will be taken towards 5 TeV per beam. At the end of 2010, the LHC will be run with lead ions for the first time. After that, the LHC will shut down and work will begin on moving the machine towards 7 TeV per beam.

  • The Lost University will be running two courses on physics, starting September 22. The more advanced one will be taught by Jeremy Davies, based on Lynne McTaggart’s book The Field:The Quest for the Secret Force of the Universe

    This book cites scientific experiments that examine the Zero Point Field, which is believed by some to be a universal energy source that connects everything.

    The other physics course will be taught by Sean Carroll, Clifford Johnson and Nick Warner. It’s entitled Introductory Physics of Time Travel and will be the prerequisite for a later course on “Advanced Physics of Time Travel”. One of the texts will be Sean Carroll’s forthcoming book.

    More about this from Clifford Johnson here.

  • The Anacapa Society, an organization aimed at promoting theoretical physics research at undergraduate institutions, has taken up permanent residence at Amherst, more here.
  • Tommaso Dorigo is trying to stir up trouble again, this time by pointing out the intriguing fact that, looking at events with just electron-positron pairs, both D0 and CDF have seen more than expected at an invariant mass around 720 GeV. Not that this is statistically significant or anything…
  • Talks from the recent FQXI conference in the Azores are available here.
  • Talks from the on-going Newton Institute workshop on Non-Abelian Fundamental Groups in Arithmetic Geometry are available here. Commentary from Jordan Ellenberg about Deligne’s talk is here. Jordan notes that:

    When I was first giving public lectures, someone gave me the hoary advice that I should quell nervousness by imagining the members of the audience in their underwear. Strange to think that, in this new broadband world, most of them actually are.

    • Posted in Uncategorized | 3 Comments

    Back

    Posted on August 5, 2009 by woit

    I’ve spent most of the last month traveling, first to Latvia and Russia, then to China, finally to Seattle. Back now, looking forward to staying in one time zone and not seeing the interior of a plane for a while.

    In China I visited Shanghai, Suzhou, Hangzhou, Yellow Mountain, Hong Kong and Macao, all of which was an amazing experience (thanks to John Baez for, among other things, urging me to search out the few remaining sections of old Shanghai). The weather unfortunately was less than ideal, with record heat in Shanghai, rain at Yellow Mountain, and clouds the day of the eclipse. Still, it was a lot of fun to be in People’s Square and see the city go dark for 6 minutes. Here’s one view from about that moment:

    After getting back to New York from China, I turned around and went out to Seattle to attend my friend Nathan Myhrvold’s surprise 50th birthday party. This was held at the new lab of his company, Intellectual Ventures, and among the organizers were Bill Gates and Lowell Wood. In attendance were many of the luminaries of the technology and culinary worlds, with Wylie Dufresne of New York’s WD-50 one of several chefs who came in to attend the party and serve amazing food to the guests. Not the sort of party I normally attend…

    Regular blogging will resume imminently. Things seem to have been rather quiet the past couple weeks anyway. The news of delays at the LHC reported here earlier has been getting more media attention. There’s a very good article about the LHC problems by Adrian Cho at Science here, and the New York Times ran a front-page story yesterday. For some reason, the Times decided that it was important to quote what prominent theorists have to say about this, including:

    “I’ve waited 15 years,” said Nima Arkani-Hamed, a leading particle theorist at the Institute for Advanced Study in Princeton. “I want it to get up running. We can’t tolerate another disaster. It has to run smoothly from now.”

    Gordon Watts has some comments about this here (including pointing out that “running smoothly from now” is probably not in the cards), and there’s also a good posting at Resonaances.

    My understanding is that the LMC (LHC Machine Committee) was meeting today to go over all that is known about the splices problem and discuss the question of what the highest energy is at which the machine can safely run in its current state. A smaller group of people, in consultation with the experiments and the director, will then have to decide either to run at that energy, or accept further delays for repairs to allow running at a higher energy. It’s not known how long that decision will take, but presumably it will come soon. If no further repairs are to be made, the current schedule has the machine ready for injection of a beam in mid-November.

    Update: It’s 3.5 TeV/beam.

    Posted in Experimental HEP News, Uncategorized | 12 Comments