Latest From Langlands

Robert Langlands will be speaking at Yale in a couple weeks at a day-long Mostowfest of lectures in honor of Dan Mostow. His title is “The search for a mathematically satisfying geometric theory of automorphic forms” and he has already posted some notes for the lecture. A much longer set of reflections on the same topic was finished late last year and published in a volume in memory of Jonathan Rogawski. It’s available at the IAS Langlands site as A prologue to functoriality and reciprocity: Part 1. There’s no part 2 yet, but an earlier version of the full document is here, based on some lectures by Langlands in 2011 at the Institute, one of which is available on video here.

In all of these, Langlands is struggling with various ideas about “geometric Langlands”, meaning analogs of the Langlands program in the case of Riemann surfaces instead of number fields or function fields (functions on a curve over a finite field). One approach to this question, starting with Beilinson and Drinfeld around 25 years ago, has been extremely active and I’ve often written about this here. For the latest from this point of view, you can consult Dennis Gaitsgory’s web-site here. Langlands doesn’t find this often very abstract point of view to his taste, so has been trying various more concrete things. In particular, he’s quite interested in the connection to quantum field theory. I don’t think he’s actually found a satisfying line of attack on this problem, but it’s fascinating to see what he’s thinking about. There are all sorts of very deep questions in play here about the relationship of quantum field theory, representation theory, number theory and algebraic geometry. Langlands himself describes what he has as just “still provisional reflections on the geometric theory”, and says about his upcoming lecture:

The best I can offer in the way of a geometric theory with which I would be pleased is a sketch of the principal difficulties to be overcome. There are many. The importance for me is the very strong analytic flavour of the theory I hope to construct or see constructed.

Posted in Langlands | 2 Comments

Nobel for Englert and Higgs

Congratulations to Francois Englert and Peter Higgs, awarded the 2013 physics Nobel prize this morning. Evidently the prize announcement was delayed because they were unable to reach Higgs by phone. Surely he wasn’t unaware that today was a day he might be getting an early morning phone call…

The Higgs discovery last year was one of the great milestones of fundamental physics research and it would have been very odd for the Nobel committee Swedish Academy of Sciences to not recognize it with a prize this year. I do think though that the way they chose to do this is not ideal, for a couple reasons.

The first is that this was foremost an experimental achievement, but the experimentalists and their work remains unrecognized. The thousands of physicists and engineers of CERN, LHC and ATLAS have accomplished something amazing by working together, but this makes them somehow ineligible for the Nobel. As far as the Nobel goes they make the mistake of running their collaborations relatively democratically, without a “great man” (or “great woman”) who could stand out and be awarded a prize.

Another issue with today’s choice is that if you do want to emphasize a model of scientific research where advances come from a specific “great man” theorist, in this case they’ve left out the greatest one involved. The specific model tested at the LHC was not that of Englert and Higgs, but the one that Weinberg and Salam already got a prize for. The new prize is for the general mechanism, but this is something that was first understood by Philip Anderson a couple years before Englert and Higgs. For some details of the history, see here. The argument is often made that Anderson’s model was not relativistic, but this is a phenomenon for which relativity is not relevant, something which Anderson understood.

The Nobel prize announcement comes with a detailed discussion of the history, which discusses extensively Anderson’s work. It makes the argument that relativity was a crucial issue, and summarizes the situation with:

This was a very important step forward showing that one could indeed have massive vector particles without having a massless mode, but it did now show how the same phenomenon would work in a relativistically invariant theory. Anderson concluded by saying “We conclude then, that the Goldstone zero-mass difficulty is not a serious one, because we can probably cancel it off against an equal Yang-Mills zero-mass problem.”

Weirdly, this paragraphs contains a crucial typo. I assume they meant to write “it did not show” instead of “it did now show”.

The authors refer to what is usually called the “Higgs mechanism” as the “BEH Mechanism”, but it seems to me that if you want to insist on adding more names to the usual terminology, “Anderson-Higgs” would be better.

As far as the Nobel goes, Anderson already has one, given for other work, and maybe this is one reason he was left out this time (although getting multiple Nobel prizes is not unprecedented). Congratulations to him and the LHC experimentalists today, as well as to Englert and Higgs.

Update: Jon Butterworth has some similar comments at the Guardian, especially about the “lone genius” model for progress in science.

Update: For more from Anderson about his work on this topic, see interviews by Chandra, Coleman and Sondhi at the AIP oral history site here. One of the things I find most surprising about this history is that Brout was in close contact with Anderson during this period, but does not refer to Anderson’s 1963 paper in the original Brout-Englert paper, or in later discussions of the history (see here). Here’s Anderson’s account:

during this period I was in fairly close contact with Bob Brout. Later on, one of the co-inventors of the Higgs mechanism is Brout with Francois Englert. Bob spent several summers with us down at Bell and I know that I talked many of these things over with him. So he was definitely one of my sources for knowledge about particle physics, along with John Ward to a much, much lesser extent. Therefore, when I was recently helping edit one of the accounts of the recent Nobel Prize and noticed that they ascribed the idea, they call it Higgs, Brout, Englert, which I’d never heard, I realized that actually Brout and Englert had a fairly considerable influence on the whole development(must have gotten their ideas from me). So I had thought that it just fell into a black hole and Higgs reinvented it and everybody called it the Higgs mechanism because of that, but in fact, it is in the linear chain of what eventually led to t’ Hooft and Veltman. So I was quite happy with that.

Update: John Preskill comments “The emphasis on finding a relativistic model may be misplaced, though. Anderson understood the mechanism well.”

Update: There’s an interesting story here about the final decision process and the delay in the announcement. Evidently the way things work is that the Nobel Committee (see here for members) proposes up to three candidates. The Royal Swedish Academy of Sciences meets at 9:30 am, debates the matter, makes a decision, with the announcement of the decision scheduled for 11:45 am. Earlier today though, something unusual happened, requiring delay by at least an hour (maybe two, one source says the announcement was at 13:45 it was at 12:45). Supposedly Higgs was not reachable by phone, but that seems unlikely to have been the cause of the delay since it was known in advance that this would be the case. The press story quotes the academy’s permanent secretary as giving as reason “There were many people who had a lot to say”.

Unfortunately the rule is that deliberations are kept secret for 50 years, so I’ll be long gone before it is known what happened at this meeting today.

Update: It took two days, but the Swedes finally fixed their typo. Now Anderson “did not show how the same phenomenon would work in a relativistically invariant theory.”

Update: C. R. Hagen, the “H” in “GHK”, sent me the following commentary on the document about the prize put out by the Swedish Academy.

It is difficult to take seriously the document put forth by the Swedish Academy which purports to explain the basis for their Nobel award.

“Scientific Background on the Nobel Prize in Physics 2013

The BEH-Mechanism, Interactions with Short Range Forces and Scalar Particles”

http://www.nobelprize.org/nobel_prizes/physics/laureates/2013/advanced-physicsprize2013.pdf

Plainly and simply stated its unnamed author(s) does not understand the mechanism which they are attempting to explain to the physics and world communities. The report in dealing with the Brout-Englert paper reads “The Goldstone theorem holds in the sense that that Nambu-Goldstone mode is there but it gets absorbed into the third component of a massive vector field.”

This assessment clearly demonstrates a total lack of understanding of the mass generation and Goldstone avoidance mechanisms associated with spontaneous broken symmetry. In fact as shown by Guralnik, Hagen, and Kibble (GHK) in 1964 the missing longitudinal mode of the vector meson comes from one of the two scalar particles in the model (the other being the so-called “God Particle” recently alleged to have been found at the LHC).

There is no way to explain this incredible blunder by the Swedish Academy. In their desire to marginalize the GHK paper they have failed to understand its real contribution and have certainly failed to comprehend that the Coulomb gauge analysis of that work makes totally credible and understandable the route whereby the expected Goldstone boson is eliminated from the physical sector.

-C.R. Hagen

Posted in Uncategorized | 74 Comments

Various News

  • First a sad piece of news, via commenter Bob Jones. It seems that David Kazhdan, a well-known representation theorist, was hit by a truck Saturday morning while bicycling in Jerusalem. He’s in the hospital, with his condition described as “very serious”. I hope he manages to recover soon from this accident.
  • On a much happier note, I spent Saturday at the Simons Foundation attending a day-long program celebrating the work of Pierre Deligne. More technical talks were in the morning, with Goncharov giving a talk on this material, and Illusie discussing the mathematical significance of several letters he had received from Deligne.

    Deligne’s contributions to mathematics are immense, and go way beyond his many published works. Quite a few mathematicians have received letters like the ones Illusie discussed, laying out all sorts of new ideas. Some of these ended up getting worked out in detail by students and others, with Deligne’s name not necessarily attached. To this day, Deligne continues to send highly helpful hand-written letters about mathematics to people, although I understand that these days they arrive not by snail mail, but as a scan sent by e-mail by a secretary. These letters make up a huge resource for mathematics, perhaps someday a way will be found to archive them and make them more widely available.

    In the afternoon, Brian Conrad and Ravi Vakil gave some very good more general talks, with one theme the Weil conjectures that Deligne was responsible for finishing the proof of. The day ended with reminiscences of Deligne from Illusie, Saint-Donat, and Dennis Sullivan (since Sullivan couldn’t be there, his contribution was read off a cell-phone by Jim Simons).

    Contemplating Deligne’s remarkable career is rather awe-inspiring. For more about him, a good place to start is this page at the Simons Foundation, which includes videos of an interview of Deligne by Robert MacPherson. See also this recent piece by Illusie, which makes the point that one of Deligne’s achievements was to bring together two great but disparate currents in mathematics, the abstract algebraic geometers around Grothendieck, and the representation theorists working on what is now called the Langlands program.

  • For yet more unification of mathematics and physics, last week the Mathematical Institute at Oxford hosted a conference on Number Theory and Physics, associated with talks celebrating the Institute’s new building (see here and here). Witten’s slides are available here and here, a blog posting by Bruce Bartlett is here.

    Via Jordan Ellenberg and Mathbabe, there’s the news that Andrew Wiles took the occasion of the building opening ceremony to warn about the abuse of mathematics by the financial industry. By the way, the new building is described as housing 500 mathematicians and staff, which seems to me truly huge, quite a bit bigger than any other math institute I know of.

  • A journalist at Science magazine got not just one, but 157 open access science journals to accept a bogus completely incompetent paper. One could take this as conclusive evidence for the problem with open access journals, except that he didn’t try this also on conventional journals, and many believe that they too would publish something just as bad.
  • Brian Leiter has a discussion here of some data here about the fraction of philosophy Ph.Ds that are able to get tenure-track jobs. I had always thought that academic philosophy Ph.D.s were likely to have even worse job prospects than theoretical physicists. If you believe these numbers at all though, your job prospects as a philospher are dramatically better than similar numbers for physics theory Ph.D.s. My guess is that, at least in the US, theoretical physics Ph.D.s have very roughly a 20% chance of finding a permanent academic position, while the data here shows 60% of similar philosophy Ph.D.s with permanent positions. If you’re in a physics theory Ph.D. program, and at all interested in the philosophical side of the subject, perhaps you should immediately look into changing departments.
  • As always, multiverse-mania shows no signs of slowing down. For the latest, see articles in the new issue of Nautilus here and here.
  • Just a few short hours until the 2013 Physics Nobel announcements, with speculation raging about what the Nobel committee will do about the Higgs discovery.

Update: It’s Englert and Higgs for the Nobel. I still think that, for a prize recognizing the theorists who figured out the Anderson-Higgs mechanism, there’s a name missing in that list.

Posted in Uncategorized | 16 Comments

Beyond the God Particle

There’s a new popular book about high energy physics coming out this week, Beyond the God Particle, by Leon Lederman and Christopher Hill. The authors are unapologetic about the “God Particle” terminology, coined by Lederman back in 1993 for marketing purposes, which for better or worse is now a fixture in popular accounts of the Higgs.

The new book isn’t really a general introduction to the subject, but is focused on two pretty much unrelated subjects. The first is the actual physics of the Higgs field, with a long and detailed explanation of chirality and the way in which interaction with the Higgs field provides particle mass terms. This is great material for anyone who has been subjected to endless attempts at explaining this as the Higgs being like molasses, or a room full of people, or any number of other metaphors that don’t really explain anything. Lederman and Hill go way beyond this, with a much more extensive and serious discussion, while still staying away from using equations. For someone who wants to understand as much as possible about what “particles get mass from the Higgs” means without looking at a Yukawa term in a Lagrangian, this is the place.

The second main topic of the book is Project X, Fermilab’s proposed new high-intensity proton linac that would provide beams suitable for studying rare decays, neutrino physics, potential muon storage rings, and new sorts of fission reactors for nuclear power. This is pretty much the centerpiece of plans to try and keep US in the game of cutting edge experimental HEP physics. As far as the energy frontier goes, the situation at the LHC is explained, with the argument made that on that front, all there is to do now is to wait and see, with 2017 the date by which the authors expect to have a verdict about whether there is new physics to study at the TeV scale. Only once this is in do they see an informed decision about a new high energy machine to be possible. As far as the last 30 years of theorist’s claims about BSM physics, they’re dismissed with:

Our fellow citizens often get confused about what big science is trying to do, perhaps because of what we tell them, usually in the media. For example, all too often we hear that colliders are built “to discover extra dimensions,” to “confirm string theory,” “to discover supersymmetry.” False! Colliders are built to uncover whatever is happening in nature at the shortest distances, and not to accommodate the agendas of various sects of theorists.

Throughout the book there’s a vigorous argument that science in general and HEP in particular deserve far more financial support from the public than it is getting. On the whole I’m in agreement, but I do think the authors go over the top at a couple points. The short discussion of cosmology is HEP-triumphalist:

The great discoveries, such as the “gauge principle” shared by all forces in nature, allowed us to speculate about “grand unification” and led to the idea of “cosmic inflation” and canonized the field of cosmology. Suddenly cosmology became respectable. The leading cosmologists are all particle physicists.

The argument for the societal value of scientific research dismisses economists as “eggheads” too dense to realize that there’s a simple answer to the question “What makes economies grow”:

The answer is almost obvious, yet it took more than 200 years from Adam Smith’s The Wealth of Nations to figure it out. The answer is (drumroll): economies grow because of investment in science! Basic science, applied science, all science. All scientific research pays a handsome dividend, and the more science the better.

Given the current dysfunctional US government, funding valuable new tools like Project X will be a challenge. Lederman will be at the front of the charge to make this happen, and this book is one weapon for the fight ahead.

Posted in Book Reviews | 42 Comments

Why Are There Still So Few Women in Science?

Normally I avoid writing about the topic headlined here, not because it’s not of interest or not important, but because the usual discussions it attracts seem to me ideologically-driven, containing far more heat than light. The New York Times Magazine however has just published an excellent article on the subject, by Eileen Pollack. Pollack describes in detail her experience as a physics student at Yale, including that of having a senior thesis supervised by the great representation theorist Roger Howe. This includes her decision not to go on in the field, with this description of the perception of the Princeton graduate program:

By the start of my senior year, I was at the top of my class, with the most experience conducting research. But not a single professor asked me if I was going on to graduate school. When I mentioned shyly to Professor Zeller that my dream was to apply to Princeton and become a theoretician, he shook his head and said that if you went to Princeton, you had better put your ego in your back pocket, because those guys were so brilliant and competitive that you would get that ego crushed, which made me feel as if I weren’t brilliant or competitive enough to apply.

I think Pollack very much gets it right, including emphasizing many of the subtleties of this problem, and urge anyone interested in this to read the article. A couple comments though about two aspects of the issue she doesn’t really address.

  • There is a serious effort at an institutional level to have an impact on this problem, but it takes place mostly only at specific points where the institution can measure what is happening. In particular, in my experience academic departments do take seriously the issue at the point of the graduate school admission process, with often a careful attempt to identify promising female applicants. This isn’t at all inconsistent with Pollack’s story, which explains why she didn’t even apply to graduate school.

    At the point of hiring faculty, university administrations often provide serious incentives to departments to hire women (i.e. by providing faculty lines that can only be used for female or minority candidates). Again, this is often past the point where the problems Pollack identifies have already worked to make the number of viable female candidates small.

  • Pollack repeats the claim of a serious shortage of students in STEM fields:

    Last year, the President’s Council of Advisers on Science and Technology issued an urgent plea for substantial reform if we are to meet the demand for one million more STEM professionals than the United States is currently on track to produce in the next decade.

    something which is actually only a shortage of talented people willing to work for low wages. She opens her article with the all-too-plausible results of a Yale research study showing that

    Presented with identical summaries of the accomplishments of two imaginary applicants, professors at six major research institutions were significantly more willing to offer the man a job. If they did hire the woman, they set her salary, on average, nearly $4,000 lower than the man’s.

    This is good evidence that attitudes (women’s as well as men’s, since they were just as biased) remain a problem. But Pollack doesn’t comment on the absolute value of the salaries chosen as typical ($26,508 for a lab manager with a science bachelor’s degree), which is less than what a typical Starbucks barista makes here in New York (see here, where my location automatically gives the NYC data). Part of the story may well be women’s differential willingness not only to deal with competitive ego-crushing Princetonians, but also abusive, badly-paid working conditions for many parts of the science job market. If the pay, hours and coffee are better at Starbucks (and your co-workers are nicer…), lots of people are going to reasonably make the decision to work there instead.

Update: As anyone could have predicted, allowing anonymous comments on a topic like this soon becomes untenable. On a more positive not, Sabine Hossenfelder’s reaction to the NYT article is highly recommended.

Update: From Fabien Besnard

I’m in a special position with respect to this question, since my institution, l’école polytechnique féminine was formerly for girls only. Up to the 1980’s, the vast majority of french female engineers were formed in this “grande école”.Then, since the other grandes écoles were gradually more and more open to girls, the EPF began to be perceived not as “the engineering school for girls”, but “the engineering school for girls who can’t go anywhere else”.It reacted by opening itself to boys, while keeping its name “féminine”. Few boys came at first, but the proportion gradually rose, until a point where the EPF was not anymore perceived as a “girl only” institution. Then the boys massively came. There is a now about 60% boys among the students, a proportion which is roughly constant for the last 10 years.

The proportion of girls is still the highest in a school of engineers, and when you ask a student why she came, a very frequent answer is that it is precisely because she knew there would be many other girls. Another interesting aspect is that among the top 25% of the students, the proportion is rather inverse : 60 % of the best students are girls. The reason is that the best among the girls could have applied to one of the more selective “classe prépas” but refrained to do so for fear of being confronted to a stressful environment, with a lot of competition and… boys. Many of them seem to underestimate their chance of success in such an environment.

Lastly, in the final year of our formation (which is the fifth), the students must choose an option that will largely determine their future career. We offer a wide range of choices, from aeronautics to medical engineering and computer sciences. It is a fact that girls do not evenly distribute themselves among these different options. However, there is a fair amount of girls in each one of them.

So my experience largely confirms that the “negative feedback” effect of having too many samples of a single sex in a class acts as a magnifying glass on the small differences of taste between boys and girls, which nevertheless do exist. Also, the girls tend to underestimate their talents.

Posted in Uncategorized | 46 Comments

Particle Fever

Yesterday I got a chance to see Particle Fever, the long-awaited film about particle physics. It’s at the New York Film Festival, where there will be another showing on Wednesday, although tickets are already sold out. Oliver Peters was also there, and has a detailed review.

My own reaction to the film was kind of schizophrenic: most of it I thought was fantastically good and I really hope it finds distribution and gets widely seen. On the other hand, some of it I thought was a really bad idea. First though, the really great aspects of the film.

The main structure of the film is built around the discovery of the Higgs at the LHC, starting at a point back around 2006 or so. Theorist David Kaplan is the person most responsible for the idea of the film and getting it made, and there’s footage of him visiting the LHC while ATLAS is being installed, getting shown around by Fabiola Gianotti, who later was to become ATLAS spokesperson. This part of the film shows very well the scale of the effort represented by the LHC and its detectors, as well as giving some idea of the physical environment experimentalists work in (both the huge experimental halls and the areas around them, as well as control rooms and crummy office spaces). There’s good use of high quality graphics to give some basic insight into what is going on. Interviews with a few ATLAS physicists add a human face to the story and explain the motivation that drives people to do this kind of work.

The cameras were also there for first beam back in 2008, as well as to capture people’s reaction to the depressing news of the accident a few days later that set the whole project back by a year. There’s wonderful footage of the scene late in 2009 when first collisions finally occurred, with Beethoven’s Ode to Joy providing a very appropriate soundtrack. I especially liked the scenes of a young postdoc (Monica Dunford) carrying her laptop around, elated to show everyone plots with data from the first collisions.

The last part of the film is dominated by the July 4, 2012 discovery announcement, doing a wonderful job of showing the media frenzy as well as the joy and excitement of the entire HEP physics community at that time. All in all, if you want to get someone turned on to high energy particle physics, or just convince a young person that a career in science is an attractive idea, the CERN footage in this film should do the job better than anything I’ve seen from even the highly competent CERN press office.

Theorists provide a parallel track throughout the film, with focus on Kaplan, his advisor Savas Dimopoulos, and Nima Arkani-Hamed. All of them are highly eloquent on the topic of the significance of fundamental HEP physics research. It is made clear that the fact that the LHC is not seeing SUSY or other new particles is a big problem for theorists like these who have devoted their careers to models of new physics that was supposed to show up at the LHC. In one scene Dimopoulos and Riccardo Barbieri are discussing the matter, with Barbieri saying he has wasted 40 years working on such things, and will soon be retiring. Dimopoulos says that in his case it’s just 30 years, but insists there is still two years to go (until the full-energy LHC) before really giving up. The relation of all this to the Higgs is not made clear.

As for the really bad idea, it’s the introduction of the multiverse into the theory part of the film. Kaplan is shown claiming that the multiverse predicts a 140 GeV Higgs, based on this paper of Yasunori Nomura and Lawrence Hall (who was Arkani-Hamed’s advisor). This is at a time when there were experimental hints of a 140 GeV Higgs. After they went away, and the mass came out at 125 GeV, the “prediction” is forgotten, but a long segment still has Arkani-Hamed going on about the CC and arguing for the multiverse. Just before this segment though, Dunford the experimentalist is shown Skyping with the filmmaker, warning them “Don’t listen to theorists”. At the film showing, Kaplan and Arkani-Hamed were there and answered questions at the end. One of the first questions (not from me…) was from an audience member who asked why they had put the material about the multiverse in the film, even though it had no real link to the Higgs or the LHC experiments. Arkani-Hamed admitted that the 140 Gev prediction was tenuous, there was no “sharp” link of the multiverse to the Higgs, and that no way is now known to get predictions out of the multiverse idea or test it. Kaplan explained that the intention was to make an “experiential” film, focusing on what theorists were talking about and thinking about, without getting into really trying to fully explain the scientific issues. The problem with this is that the film comes through as promoting the Dimopoulos/Arkani-Hamed view that no SUSY means a multiverse, without showing any challenge to such an argument.

In any case, it’s a beautifully done film, on a great topic. I hope it soon gets widely distributed, although perhaps with some sort of warning tag attached.

Posted in Favorite Old Posts, Film Reviews, Multiverse Mania | 20 Comments

Why mH= 126 GeV?

This week in Madrid there’s a conference going on with the title Why mH= 126 GeV?. It brings together HEP theorists working on “Beyond Standard Model” physics, with the majority of the participants from Western Europe, especially Spain. As part of the workshop they did a survey, getting about 50 responses. Among the results:

  • For the question “Do you think that String Theory will eventually be the ultimate unified theory?”, 27% said Yes, 73% No, with the Nos breaking up into 27% just “No” and 46% “No, but it is a step in the right direction”.
  • For a question about the hierarchy problem, the three opinions that got the highest numbers were pretty much split evenly among them: “Low energy SUSY solves the problem”, “Anthropics solves the problem”, and “There is no such problem.”
  • Opinion was evenly split on whether the LHC would or would not find non-SM behavior of the Higgs, and 60-40 in favor of the LHC finding some non-SM new physics.

If you’re at all interested in what the current mood and thinking is in this part of HEP theory, you should definitely take a look at the video of this evening’s discussion section, moderated by Joe Lykken. It included extensive debate about the questions raised by the survey and what people’s answers meant. At the end there was a short interesting discussion about AdS/CFT and its relation to string theory, with Michael Douglas arguing that AdS/CFT should be thought of as an improved version of the renormalization group, with no necessary connection to string theory. String theory and SUSY only come into it by providing certain examples where you can do explicit calculations in the dual theory. By the way, I’ve heard a rumor that Douglas is going on leave from his physics job to work at the Simons hedge fund Renaissance Technologies.

Among the talks so far on-line, you might want to take a look at Alessandro Strumia’s Is Naturalness Natural, for an example of the sort of thinking that denies the dichotomy of “low energy susy or anthropics”. As the survey showed, this insistence on other alternatives has at least 1/3 support, and Joe Lykken mentioned that he was in this category.

Michael Dine’s talk on Alternative Futures for Particle Physics starts off with slides about Neil Turok’s comments on the “crisis” in the field, and shows this blog entry. He then goes on to give a string theory landscape/anthropics-based point of view on prospects for BSM physics. At the end of the talk there’s some pushback from the audience, with one questioner describing Dine’s anthropics as “a kind of sleeping pill, so you convince yourself that you are smart”, calling this “theology” not physics.

Dine describes my blog entry he showed as one that personally insults him, something that certainly wasn’t intentional. He’s not mentioned at all, but I gather he’s unhappy about my description of the material in the slides of Sally Dawson’s HEPAP presentation

Dine was chair of the committee that produced this report on The Future of U.S. Particle Theory and it’s well worth reading for a detailed overview of the current state of HEP theory research in the US, especially from the more phenomenological end. Like the slides though, I’d describe it as mostly avoiding dealing with the intellectual crisis that Neil Turok was describing. Even though Dine was the chair of the committee, there’s nothing in its report about his favored road ahead (the landscape and anthropics). I’d guess that the committee members felt that when trying to get support for HEP theory from other scientists or government funding agencies, talk of crisis-level problems with conventional wisdom was to be avoided, but even more so any mention of the string theory landscape and anthropics.

Update: For the latest on the landscape, see Michael Douglas’s talk on The string landscape and low energy supersymmetry. At the beginning of his talk he notes that “most people seem to have given up” on this, and from the talk itself it’s easy to see why. Actually, Douglas himself seems to be giving up. I’ve heard more about his move from physics to finance, which began last fall when he went on leave to work at the Rentech hedge fund. Evidently this fall he is not coming back to the Simons Center, but staying at Rentech, leaving his academic position. Rumors are that one reason he gives for leaving is that there is not much of interest going on in HEP theory these days.

Posted in Uncategorized | 41 Comments

Quick Links

  • The new issue of Nautilus has a wonderful story about Yitang Zhang, called The Twin Prime Hero, which includes a long interview with him. Zhang’s remarkable mathematical career includes several years working at a Subway in Kentucky. His sucessful work on the twin prime conjecture (see here) was done over four years, working seven days a week without almost any breaks, while teaching two classes at a time.
  • This year’s Physics Nobels will be announced October 8, Nature has a story here. For non-HEP physics, I have no ideas about likely winners. For HEP, of course the Higgs is the big news. Personally I think they should give the award to CERN + ATLAS + CMS, but that would require changing their tradition of not making this award to groups. Seems like a good time to change this. On the theory side, in some sense it is Weinberg-Salam that has been vindicated, and they already got the prize for this. If one wanted to give a prize for the general idea of the Higgs mechanism, I’ve argued that Anderson should be included (see here).
  • This weekend the IAS will host Dreams of Earth and Sky, a celebration of Freeman Dyson’s 90th birthday, see more here.
  • I’m not going to the Dyson-fest, but am looking forward to seeing the film Particle Fever this weekend at the New York Film Festival.
  • Next weekend it will be not physics, but math, as I’ll be at the Simons Foundation day-long program on October 5, Celebrating the Mathematics of Pierre Deligne. Recently I’ve been spending some time watching Deligne’s lectures from this past spring at the IHES, available in high quality video here.
  • The only mention of Bohemian Gravity! here was in a comment a while back, and I hadn’t added more, since this has gotten attention from hundreds of other sources. But of course it really is great and deserves all the attention and more, so if you’re the only reader of this blog who hasn’t checked it out, do so now.
  • Frank Wilczek has been very active on Twitter recently, and a directory of some of his recent writings is here. According to this tweet, he has plans at some point to break out of the 120 character limit.
  • Latest news from the LHC is here. Work is on schedule for January 2015 first beams at a higher energy of 13 TeV.
  • For an example showing that some basic technical questions about the Standard Model are still poorly understood and deserve a lot more attention, see Michael Creutz’s talk on Chiral Symmetries and Lattice Fermions at this recent QCD conference, as well as the preprint version here.

Update: In case you don’t get enough material from me here explaining what the problem is with the “multiverse”, Sabine Hossenfelder has more here.

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Love and Math

Edward Frenkel’s new book Love and Math is now out. It’s a must-read for those who share the interests of this blogger, so go get a copy now.

The “Love” of the title is much more about love of mathematics than love of another person, as Frenkel provides a detailed story of what it is like to fall in love with mathematics, then pursue this deeply, ending up doing mathematics at the highest level. Along the way, there are lots of different things going on in the book, all of them quite interesting.

A large part of the book is basically a memoir, recounting Frenkel’s eventful career, which began in a small city in the former Soviet Union. He explains how he fell in love with mathematics, his struggles with the grotesque anti-Semitism of the Soviet system of that time (this chapter of the story was published earlier, available here), his experiences with Gelfand and others, and how he came to the US and ended up beginning a successful academic career in the West at Harvard. I remember fairly well the upheaval in the mathematics research community of that era, as the collapse of the Soviet system brought a flood of brilliant mathematicians from Russia to the West. It’s fascinating to read Frenkel’s account of what that all looked like from the other side.

Russia at the time had a vibrant mathematical culture, but one isolated from and quite different than that of the West. Many of its most talented members had rather marginal positions in official academia, and their community was driven much more by a passion for the subject than any sort of careerism. Frenkel comes out of this background with that passion intact, and it shines throughout his book. In some other ways though, he’s more American and less Russian than just about anyone I know. Part of the Russian mathematical culture has sometimes included a certain cynicism and vision of great mathematics as an esoteric subject best closed to outsiders, with little interest in communication with the non-initiated. I confess to a personal sympathy with the cynicism part (as any reader of this blog has probably figured out) but no sympathy for obscurantism about mathematics research.

Frenkel’s sunny optimism and cheerful enthusiasm for his subject and life in general is very American, and in his writing he often gets through to melt the cynical part of this reader. What’s really wonderful though is his dedication to the cause of the opposite of obscurantism, that of doing the hard work of trying to explain mathematical insights to as wide an audience as possible. His book is packed with mathematics and physics, full of enlightening explanations of difficult topics at all different levels of mathematical sophistication.

Perhaps the most remarkable part of the book though is the way it makes a serious attempt to tackle the problem of explaining one of the deepest sets of ideas in mathematics, those which go under the name of the “Langlands program”. These ideas have fascinated me for years, and much of what I have learned about them has come from reading some of Frenkel’s great expository articles on the subject. To anyone who wants to learn more about this subject, the best advice for how to proceed is to read the overview in “Love and Math” (which you likely won’t fully understand, but which will give you a general picture and glimpses of what is really going on), and then try reading some of his more technical surveys (e.g. here, here and here).

The Langlands story is a complex one, but it starts with a very deep and beautiful idea that brings together different parts of mathematics: one way to think about number theory is to think of rational numbers as rational functions on a space, the space of primes. One then ends up seeing all sorts of parallels between the study of Riemann surfaces and number theory. Frenkel explains this in detail, including André Weil’s description of a “Rosetta stone”, a translation between aspects of number theory, aspects of Riemann surface theory, and yet a third intermediate parallel theory, that of algebraic curves over a finite field.

He goes on to explain the subject of “geometric Langlands theory”, the transposition of the Langlands program from the number theory to the Riemann surface case, creating a whole new area of mathematics, one with deep connections to quantum field theory. The book includes extensive discussion of discoveries by Witten and others linking duality in four-dimensional quantum field theory to the fundamental mysterious Langlands duality in the geometric Langlands case. Frenkel has been in the middle of these developments and is the ideal person to tell this story.

The connection between these ideas and two-dimensional quantum field theory seems to me to be a subject for which we have so far only seen the tip of an iceberg, with much more to come in the future. One part of this that I don’t think Frenkel discusses is early work by Witten (before geometric Langlands was formulated) giving explicit analogies between 2d qft and reciprocity laws in number theory. For more about this, see Witten’s 1988 Quantum field theory, Grassmanians and algebraic curves, or a more recent paper by Takhtajan. Working on writing up the material about the harmonic oscillator and representation theory from my last year’s course has gotten me interested again in the number-theoretical version of that particular story. Unfortunately I don’t know a really readable reference, hope some day to write something myself once I have a better understanding of the subject.

So, I heartily recommend this book to all with an interest in mathematics or its relation to physics. If the “Love” of the title has you hoping for a tale of romance between two people, you’re going to be disappointed, but you will find something much more unusual, a memoir of the romance of mathematics and its relation to the physical world.

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Physicists Discover Geometry Underlying Particle Physics

Today’s Slashdot tells us that Physicists Discover Geometry Underlying Particle Physics, a story that is based on an excellent article, A Jewel at the Heart of Quantum Physics, by Natalie Wolchover at the new Quanta Magazine sponsored by the Simons Foundation.

As you might suspect, the Slashdot headline is simply nonsense. What’s really going on here is some new progress on computing scattering amplitudes in a very special conformally-invariant QFT, one not known to “underly particle physics”. This is a long story, one going back to Roger Penrose’s work on twistors from the late 1960s. In recent years this has been a very active and successful field of mathematical physics research, with a large group last year putting out Scattering Amplitudes and the Positive Grassmanian, which showed how to express some amplitudes to all loops in terms of volumes of geometric objects defined as subspaces of a Grassmanian. Mathematicians who want to see some speculation about the relation of this to other areas of mathematics should take a look at section 15 of that paper.

The more recent news is that Nima Arkani-Hamed and his ex-student Jaroslav Trnka now have an improvement on that calculational method, which uses the volume of a particular such geometric object they call the “Amplituhedron”. There’s no paper yet, but you can watch recent Arkani-Hamed talks about this here or here (the last from yesterday). How this ended up with the ridiculous Slashdot headline is pretty clear, as Arkani-Hamed with his trademark enthusiasm promotes this work as a road to revolutionizing physics, getting rid of locality and unitarity as fundamental principles, finding emergent space-time, maybe emergent quantum mechanics, etc (while admitting that what has been accomplished is just step 0 of step 1 of a multi-step program). From this, one gets to the rather excessive Quanta headline about a “jewel at the heart of quantum mechanics”, ensuring that the next stage of publicity (e.g. Slashdot) will launch the hype level into outer space, escaping any relationship to reality.

For the details of what this really is, the Quanta article gives a good overview, but you need to consult the long paper and recent talks to dig out a non-hyped version of what the real recent advances are. I’m nowhere near expert enough to provide this, hope that if this turns out to be as important as claimed, surely there will soon be lots of expositions of the story from various points of view. In the meantime, best perhaps to pay attention to what Witten has to say on the topic:

The field is still developing very fast, and it is difficult to guess what will happen or what the lessons will turn out to be.

Update: Here are some slides about the Amplituhedron from Trnka (hat-tip to George Ellis).

Update: Scott Aaronson has come up with an even more dramatic advance, the discovery of the Unitarihedron, which includes the Ampltituhedron as a special case, just “a single sparkle on an infinitely greater jewel”. See his posting The Unitarihedron: The Jewel at the Heart of Quantum Computing, where he unveils this new theory.

Update: See comments here by Lance Dixon and this paper for an alternative approach to computing planar amplitudes in this theory, one not using the “amplituhedron”.


Update
: Congratulations to Kosower, Dixon and Bern for the award of the Sakurai prize for their work on amplitudes.

Update: Dixon has a guest post about this topic at Sean Carroll’s blog.

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