HEP Physics News

Posted on July 31, 2016 by woit
  • ICHEP 2016 starts in Chicago this week. Talks about the new diphoton results are scheduled for 9am (Chicago time) Friday. There will also be talks later in the day at CERN (5pm Geneva time), scheduled as part of this summer’s TH institute. Consulting my prediction here (although I had the plenary vs. parallel wrong), I think it’s very clear that these will be negative results for the supposed 750 GeV bump. See Resonaances for discussion of the significance of this.
  • Last year I heard Nima Arkani-Hamed talk here about “Nnaturalness”. The paper is now out.
  • There’s a very interesting profile in Nautilus of Fotini Markopolou, who left theoretical physics to work on a startup in England.
  • At Quanta magazine, Natalie Wolchover has a nice article about intriguing new neutrino results. With nothing unexpected showing up at the energy frontier being explored by the LHC, in coming years it may very well be the neutrino sector, which can be explored at much lower energies, where one should look for something new.
  • Strings 2016 is starting in Beijing in a few hours. Schedule here, talk titles here.

Update: Videos of the Strings 2016 talks are becoming available here. The talks of the first day featured little string theory (except for a historical talk by John Schwarz). A major theme was 3d quantum field theory, with Witten and Costello talking about the same new ideas starting with Chern-Simons theory, and Seiberg talking about dualities in 3d qft.

Update: Slides are here. Tuesday started off with entanglement entropy and tensor networks. I confess that not only do I not see what this has to do with string theory, but have trouble seeing what it has to do with anything. The connection with quantum gravity using tensor networks seems vaguely to recall the much more well-motivated spin networks of LQG, which string theorists always denounced as not exhibiting a Lorentz invariant ground state. Now it’s the string theorists promoting this kind of network structure, noticing the same problem they used to denounce as convincing evidence their competitors had it all wrong. The world is a strange place.

Update: New Scientist has a quote from me saying the obvious thing about Nnaturalness. Blogging likely light to nonexistent for the next week, I’ll be traveling, listening to music in Nashville, as well as up in the mountains of Virginia/Tennessee,

Posted in Strings 2XXX, Uncategorized | 19 Comments

Monumental Proof to Torment Mathematicians for Years to Come

Posted on July 28, 2016 by woit

Davide Castelvecchi at Nature has talked to some of the mathematicians at the recent Kyoto workshop on Mochizuki’s proposed proof of the abc conjecture, and written up a summary under the appropriate title Monumental proof to torment mathematicians for years to come. Here’s the part that summarizes the opinions of some of the experts there:

Mochizuki is “less isolated than he was before the process got started”, says Kiran Kedlaya, a number theorist at the University of California, San Diego. Although at first Mochizuki’s papers, which stretch over more than 500 pages1–4, seemed like an impenetrable jungle of formulae, experts have slowly discerned a strategy in the proof that the papers describe, and have been able to zero in on particular passages that seem crucial, he says.

Jeffrey Lagarias, a number theorist at the University of Michigan in Ann Arbor, says that he got far enough to see that Mochizuki’s work is worth the effort. “It has some revolutionary new ideas,” he says.

Still, Kedlaya says that the more he delves into the proof, the longer he thinks it will take to reach a consensus on whether it is correct. He used to think that the issue would be resolved perhaps by 2017. “Now I’m thinking at least three years from now.”

Others are even less optimistic. “The constructions are generally clear, and many of the arguments could be followed to some extent, but the overarching strategy remains totally elusive for me,” says mathematician Vesselin Dimitrov of Yale University in New Haven, Connecticut. “Add to this the heavy, unprecedentedly indigestible notation: these papers are unlike anything that has ever appeared in the mathematical literature.”

Kedlaya’s opinion is the one likely to carry most weight in the math community, since he’s a prominent and well-respected expert in this field. Lagarias has a background in somewhat different areas, not in arithmetic algebraic geometry, and Dimitrov I believe is still a Ph.D. student (at Yale, with Goncharov as thesis advisor).

My impression based on this and from what I’ve heard elsewhere is that the Kyoto workshop was more successful than last year’s one at Oxford, perhaps largely because of Mochizuki’s direct participation. Unfortunately it seems that we’re still not at the point where others besides Mochizuki have enough understanding of his ideas to convincingly check them, with Kedlaya’s “at least three years” justifying well the title of the Nature piece.

Organizer Ivan Fesenko has a much more upbeat take here, although I wonder about the Vojta quote “now the theorem proved by someone in the audience” and whether that refers to Mochizuki’s IUT proof of the Vojta conjecture over number fields (which implies abc), or the Vojta conjecture over complex function fields (such as in Theorem 9 of the 2004 paper http://www.kurims.kyoto-u.ac.jp/preprint/file/RIMS1413.pdf), or something else. The reference to Dimitrov as discussing “applications of IUT” might be better worded as “would-be applications of IUT”.

There will be a conference at the University of Vermont in September, billed as “An introduction to concepts involved in Mochizuki’s work on the ABC conjecture, intended for non-experts.”

Update: Fesenko has updated his report on the conference (see here) to include a more accurate characterization of talks by Vojta and Dimitrov (you can see changes to that report here). Between this and the Nature quotes, there seems to be a consensus among the experts quoted (Kedlaya, Dimitrov, Vojta, Lagarias) that they still don’t understand the IUT material well enough to judge whether it will provide a proof of abc or not. Unfortunately it still seems that Mochizuki is the one person with a detailed grasp of the proof and how it works. I hope people will continue to encourage him to write this up in a way that will help these experts follow the details and see if they can come to a conclusion about the proof, in less than Kedlaya’s “at least three years”.

Update: New Scientist has a piece about this which, as in its typical physics coverage, distinguishes itself from Nature by throwing caution to the wind. It quotes Fesenko as follows:

I expect that at least 100 of the most important open problems in number theory will be solved using Mochizuki’s theory and further development.

Fesenko also claims that “At least 10 people now understand the theory in detail”, although no word who they are (besides Mochizuki) and why if they understand the theory in detail they are having such trouble explaining it to others, such as the experts quoted in the Nature article. He also claims that

the IUT papers have almost passed peer review so should be officially published in a journal in the next year or so. That will likely change the attitude of people who have previously been hostile towards Mochizuki’s work, says Fesenko. “Mathematicians are very conservative people, and they follow the traditions. When papers are published, that’s it.”

I think Fesenko here seriously misrepresents the way mathematics works. It’s not that mathematicians are very conservative and devoted to following tradition. The ethos of the field is that it’s not a proof until it’s written down (or presented in a talk or less formal discussion) in such a way that, if you have the proper background, you can read it for yourself, follow the argument, and understand why the claim is true. Unfortunately this is not yet the case, as experts have not been able to completely follow the argument.

If it is true that a Japanese journal will publish the IUT papers as is, with Mochizuki and Fesenko then demanding that the math community must accept that this is a correct argument, even though experts don’t understand it, that will create a truly unfortunate situation. Refereeing is usually conducted anonymously, shielding that process from any examination. Lagarias gives some indication of the problem:

It is likely that the IUT papers will be published in a Japanese journal, says Fesenko, as Mochizuki’s previous work has been. That may affect its reception by the wider community. “Certainly which journal they are published in will have something to do with how the math community reacts,” says Lagarias.

While refereeing of typical math papers can be rather slipshod, standards have traditionally been higher for results of great importance like this one. A good example is the Wiles proof of Fermat, which was submitted to Annals of Mathematics, after which a team of experts went to work on it. One of these experts, Nick Katz, finally identified a subtle flaw in the argument (the proof was later completed with the help of Richard Taylor). Is the refereeing by the Japanese journal being done at this level of competence, one that would identify the sort of flaw that Katz found? That’s the question people will be asking.

In some sense the refereeing process for these papers has already been problematic. A paper is supposed to be not just free of mistakes, but also written in a way that others can understand. Arguably any referee of these papers should have begun by insisting that the author rewrite them first to address the expository problems experts have identified.

Update: Fesenko is not happy with the Nature article, see his comment here.

Posted in abc Conjecture | 46 Comments

Quantum Theory and Representation Theory, the Book

Posted on July 26, 2016 by woit

For the last few years most of my time has been spent working on writing a textbook, with the current title Quantum Theory, Groups and Representations: An Introduction. The book is based on a year-long course that I’ve taught twice, based on the concept of starting out assuming little but calculus and linear algebra, and developing simultaneously basic ideas about quantum mechanics and representation theory. The first half of the course stuck to basic non-relativistic quantum mechanics, while the second introduced free quantum field theories and the relativistic case. By the end, the idea is to bring the reader to the point of having some appreciation of the main elements of the Standard Model, from a perspective emphasizing the representation theory structures that appear.

The discussion of quantum field theory I think is rather different than that of other textbooks, taking a Hamiltonian point of view, rather than the Lagrangian/path integral one in which most physicists are now trained (myself included). One basic idea was to try and work out very carefully the quantization of a finite-dimensional phase space in all its representation-theoretic glory, with the idea that free quantum field theories could then be developed as a straightforward extension to the case of taking solutions of a field equation as phase space. While this point of view on quantum field theory is fairly well-known, writing up the details turned out to be a lot more challenging than I expected.

As part of this, the book attempts to carefully distinguish mathematical objects that usually get identified by physicist’s calculational methods. In particular, phase space and its dual space are distinguished, and the role of complex numbers and complexification of real vector spaces receives a lot of attention.

At the same time, the book is based on a relatively simple philosophical take on what the fundamental structures are and how they are grounded in representation theory. From this point of view, free relativistic quantum field theories are based on starting with an identification of irreducible representations of the space-time symmetry group using the Casimir operator to get a wave-equation. This provides a single-particle theory, with the quantum field theory then appearing as its “second quantization”, which is a metaplectic (bosonic case) or spinor (fermionic case) representation. These are some of the specifics behind the grandiose point of view on how mathematics and physics are related that I described here. For some indications of further ideas needed to capture other aspects of the Standard Model, there’s this that I wrote long ago, but which now seems to me hopelessly naive, in need of a complete rethinking in light of much of what I’ve learned since then.

The manuscript is still not quite finished, and comments are extremely welcome. While several people have already been very helpful with this, few have been willing to face the latter chapters, which I fear are quite challenging and in need of advice about how to make them less so. The current state of things is that what remains to be done is

  • A bit more work on the last chapters.
  • A rereading from the start, bringing earlier chapters in line with choices that I made later, and addressing a long list of comments that a few people have given me.
  • An old list of problems (see here) needs to be edited, with more problems added.
  • I need to find someone to make professional drawings (there are some funds for this).
  • An index is needed.

Optimistically I’m hoping to have this mostly done by the end of the summer. Springer will be publishing the book (my contract with them specifies that I can make a draft version of the book freely available on my web-site), and I assume it will appear next year. To be honest, I’m getting very tired of this project, and looking forward to pursuing new ideas and thinking about something different this fall.

Posted in Quantum Theory: The Book | 13 Comments

WIMPs on Death Row

Posted on July 21, 2016 by woit

One of the main arguments given for the idea of supersymmetric extensions of the standard model has been what SUSY enthusiasts call the “WIMP Miracle” (WIMP=Weakly Interacting Massive Particle). This is the claim that such SUSY models include a stable very massive weakly interacting particle that could provide an explanation for dark matter.

According to the “WIMP Miracle”, evidence for such a particle is supposed to show up as they get produced at the LHC, and at underground detectors designed to look for ones traveling through the earth. Like all other predicted SUSY particles, no evidence for such a thing has appeared at the LHC. A sequence of more and more sensitive underground experiments has also come up empty.

One of the latest of these, LUX, announced results today, see here, press release here. These are the results from the final 20 month run of the LUX detector and they are conclusively negative: no candidate events were seen, putting four times smaller bounds on the cross-section for any such particle. New Scientist has it right I think, with a story headlined Dark matter no-show puts favoured particles on death row. Ethan Siegel has a very good article, Dark Matter May Be Completely Invisible, Concludes World’s Most Sensitive Search, which includes:

The null detection is incredible, with a fantastic slew of implications:

  1. Dark matter is most likely not made up, 100%, of the most commonly thought-of WIMP candidates.
  2. It is highly unlikely that whatever dark matter is, in light of the LUX results, will be produced at the LHC.
  3. And it is quite likely that dark matter lies outside of the standard mass range, either much lower (as with axions or sterile neutrinos) or much higher (as with WIMPzillas).

Enthusiasts are not likely to give up so easily though, with Sean Carroll tweeting that the news is only “we’re not seeing it yet, stay tuned.” Not sure what one is supposed to stay tuned to, this is pretty much a final result from LUX. There will be a next generation experiment, LZ, but that’s for after 2020. There are other competing experiments now operating, including Xenon1T, now being commissioned, which will be somewhat more sensitive. There seems to be no serious reason though to expect WIMPs to appear at somewhat lower cross-sections if they haven’t appeared yet.

With SUSY and the “WIMP miracle” now dead ideas, perhaps that will lead to focus on more promising ones. There is still a great deal that we don’t understand about neutrinos. A few days ago I saw this intriguing news about the PTOLEMY project, which I hadn’t heard about before.

Posted in Experimental HEP News | 52 Comments

Ghostbusters

Posted on July 14, 2016 by woit

Last night I went to a preview screening of the new Ghostbusters film. This isn’t a review, all I’ll say is that if you liked the first one, you’d probably like this one too.

In the first film, an early scene was set here at Columbia University, with Bill Murray an experimental psychology professor (you can watch it here). Academia doesn’t come off too well… In the new film, again an early scene is set at Columbia, but now the protagonist is a theoretical physicist played by Kristen Wiig. She first appears in a lecture hall with a huge blackboard filled with equations relevant to GUTs and supergravity. For some explanation of how that came about from Lindley Winslow, who provided this and other advice, see here.

Theoretical physics comes off better in this version of the film than experimental psychology did in the first version. Academia is still made fun of though. The chair of the Columbia physics department is portrayed as telling Wiig’s character that if she wants to get tenure she needs to do better than to have a letter from Princeton, since that department is well known to no longer be what it once was.

Update: For more about the physics background, see here. The Lindley Winslow piece doesn’t mention that Janet Conrad took over from her when she had a baby, and it was Conrad’s stuff that went into the Kristen Wiig character’s office. I’d somehow missed that the bad guy had a string theory paper:

Meanwhile, an antagonist named Rowan North got a string theory paper on Feynman ghost diagrams, which offered the opportunity for a little interdisciplinary ribbing. “Of course we made the woman a neutrino theorist and the bad guy a string theorist,” Conrad says.

String theorists really do get no respect these days…

Update: More here, including

Conrad made Wiig’s character a neutrino physicist. She decided the bad guy would probably be into string theory. There’s just something sinister about the theory’s famous lack of verifiable predictions, Winslow says.

String theorists can also be lovely people, though, Conrad says, and “I wanted to make [the bad guy] as evil as possible.” In the scientific paper she wrote for his desk, “he doesn’t acknowledge anyone. He just says ‘The author is supported by the Royal Society of Fellows,’ and that’s it.”

Also, she wrote for him “an evil letter where he’s turning someone down for tenure.”

Update: There’s a profile here of Kate McKinnon, the most entertaining of the new Ghostbusters, emphasizing her interest in physics.

Posted in Film Reviews | 14 Comments

Physics and Math News

Posted on July 11, 2016 by woit

Now back from vacation, here’s the latest on revolutionary developments in physics and mathematics:

  • On the high energy physics front, the good news is that the LHC is performing remarkably well, with already over 13 inverse fb of luminosity, far above that expected at this time, on track to end up with a lot more than the targeted 25 inverse fb for the year. The bad news however is that new reliable rumors (together with the non-observation of any sign of a “special seminar” at CERN, see here) confirm non-existence of the 750 GeV state that would have killed the Standard Model and revolutionized the field. As far as I know, the plan is still to present these results publicly the first week of August at ICHEP, it looks like this will be on August 5.

    For some interesting discussion of the statistical analysis issues that come up when trying to quantify how significant the 2015 evidence is for the supposed 750 GeV state, see the comment section of this blog entry. These subtleties it seems will be made irrelevant by the arrival of new data.

  • In mathematics there has also been an unconfirmed claim of something revolutionary, but the problem is that there’s nothing analogous to new data coming in to help decide the issue. This is the claim first made four years ago by Mochizuki to have a proof of the abc conjecture, using new methods he calls “Inter-Universal Teichmuller Theory”. The current situation is an extremely unusual one, with experts still unable to understand and evaluate the purported proof. For the best summary of the situation, see Brian Conrad’s detailed explanation from last December here.

    Not much seems to have happened since then, but one very recent development has been the appearance of a new survey of the theory. Unfortunately, my guess is that this is not likely to address the issues raised by Conrad and provide what he and other experts are looking for: precise checkable arguments. Instead the new survey is another attempt by Mochizuki to communicate his general high-level vision, often in very metaphorical terms. The last section of the survey is a remarkable attempt to position his ideas in the landscape of modern mathematics, which includes setting these ideas in opposition to those of the dominant research program (and thus of great value if they work out).

    What’s really odd here is the way that usual mechanisms for transmitting understanding have failed. Mochizuki has worked to transmit understanding of his ideas to a small number of others, but the transmission has stopped there, with understanding of the abc proof not moving from them to others. For a while the hope was that Go Yamashita would be the one to move this forward, but he has not produced a promised document, or succeeded in communicating by his talks. More recently, last year Yuichiro Hoshi produced a document that is supposed to explain crucial ideas, but it is in Japanese, so inaccessible to most experts. Why this has not been translated remains very unclear.

    Next week in Kyoto there will be another workshop trying to further understanding of the IUT theory. I hope this works out better than the last one. There’s a preparatory document here which to me seems to ignore the fundamental problem of figuring out what has gone wrong so far. In particular, its last point appears to be explicitly aimed at discouraging anyone in the audience from confronting speakers that are not successfully communicating ideas and insisting that they try to do better. It would be more fruitful to encourage this instead.

Posted in Uncategorized | 39 Comments

Short Items

Posted on June 30, 2016 by woit
  • Erica Klarreich at Quanta magazine has a wonderful profile of Peter Scholze. Scholze has been busy revolutionizing various parts of arithmetic geometry in recent years, and the article does a good job of giving some of the flavor of this. I noticed this morning that Scholze has a new preprint out, about a q-deformation of de Rham cohomology, so that may be the latest, hottest news in the subject.

    The new paper was written for the occasion of his acceptance of the 2015 Fermat Prize. Another Quanta piece makes the obvious point that we already know who one winner of the 2018 Fields Medal will be. While Scholze has been awarded a fair number of prizes already, it’s interesting that he’s not universally in favor of the prize phenomenon: see here for some discussion of his decision last year to turn down one of the 2016 Breakthrough Prizes.

  • In addition to being a great mathematician, Scholze also seems to be a fine human being. The AMS Notices this week has an interview with another such mathematician, Robert Bryant, who is now the AMS President, recently head of MSRI. Unlike Scholze, I’ve had the pleasure of getting to know Bryant a little bit, since he was a visitor one semester here at Columbia. The Notices article explains his interesting background, which is somewhat unusual for an academic mathematician. The math community is lucky to have leading figures like him combining mathematical talent and excellent personal qualities.

    I first heard about him back when I was a post-doc at Stony Brook, trying to learn more about mathematics and the math community. At some point I asked Claude LeBrun (a young geometer then, now an older one, with a conference in his honor next week in Montreal) who he thought the best young geometers were. He told me about Robert Bryant, and when I asked “why him?”, his answer was “He’s read and understood all of Cartan”. I wasn’t sure whether to take that seriously, but from the AMS interview, he was quite right about that.

  • For one last piece of mathematics news, fans of geometric Langlands may want to take a look at the new preprint by David Ben-Zvi and David Nadler on a Betti form of geometric Langlands.
  • Turning to physics, last week UCLA announced a $11 million donation to fund a Mani L. Bhaumik Institute for Theoretical Physics at UCLA. As NSF funding for theoretical physics stays flat or declines, at least in the US it is private funding like this that is becoming much more important.
  • At CERN the LHC has reached design luminosity, and is breaking records with a fast pace of new collisions. This may have something to do with the report that the LHC is also about to tear open a portal to another dimension. Not clear why people are worrying about the 750 GeV state with this going on.

Soon heading North for a week-long vacation, blogging likely slim to non-existent.

Update: For geometric Langlands fans, this and this on the arXiv from Dennis Gaitsgory tonight.

Posted in Uncategorized | 4 Comments

Some Ancient History

Posted on June 27, 2016 by woit

A couple months ago there was a session at an APS meeting with the topic Sidney Coleman Remembered. Slides are available for talks by Coleman’s student Erick Weinberg and colleague Howard Georgi. Georgi has recently posted a written version of the talk here. He also a few years ago wrote this biographical memoir about Coleman for the National Academy of Sciences.

David Derbes and collaborators [see comment section for details] are putting together a book version of Coleman’s famous lectures on quantum field theory, hope to be finished with this by the end of the summer. I’ve helped out in a very small way by sending them a scan of my notes from when I took Coleman’s course very long ago.

This will be a great resource for anyone learning QFT and, in the meantime, if you don’t have a copy of Coleman’s Erice lectures, Aspects of Symmetry, you should get one. The period of these lectures spans the late sixties and seventies, and at the time they were required reading for everyone, giving every couple years a lucid explanation of the most important new ideas in the field. The last (1979) lectures are about the 1/N expansion, and I notice that Coleman extensively credits Witten, who was a postdoc at Harvard at the time. A couple years later, Witten in some sense took over from Coleman, lecturing about supersymmetry (a topic Coleman never warmed to) at Erice in 1981.

Last Friday at CERN there was an event devoted to the 40th anniversary of supergravity. Coleman makes a couple appearances, with Sergio Ferrara claiming he was responsible for the name “gravitino” and Peter van Nieuwenhuizen quoting him as saying

I am uninterested in gravity, and superuninterested in supergravity.

One reason for this was surely the ferociously technical difficulties of constructing supergravity, with Coleman not interested in difficult calculations. Another was likely a lack of interest in topics with no known relation to experiment, which likely had to do with his comments about both gravity and supergravity. At the CERN event, Albert De Roecke’s presentation, Desperately Seeking SUSY, reviews the long story of the failure of SUSY and supergravity to make contact with experiment, including a New York Times 1993 article about the failure to find SUSY at the Tevatron. It has extensive detail about the unsuccessful searches at the LHC.

De Roeck also includes a copy of David Gross’s 1994 bet with Ken Lane that SUSY will appear at the LHC (when at least 50 inverse fb have been accumulated). Gross will likely have to pay this off next year, but another such bet just came due on June 16th, so a group of theorists should by now be buying expensive cognac for their more prescient colleagues.

Posted in Uncategorized | 24 Comments

Rumor Mongering

Posted on June 21, 2016 by woit

Since I don’t see why Resonaances should have all the fun, I guess I’ll post something here about the big upcoming news of the summer: is the 750 GeV diphoton bump still there in the 2016 LHC data? We’re very soon about to hit a major fork in the road for high energy physics: if the bump is there, the field will be revolutionized and dominated by this for years, ft it’s not, we’re back to the usual frustrating grind.

Last year’s tentative signal was based upon 3.2 inverse fb of 2015 data, and as of today the experiments have over 6 inverse fb of new 2016 data. One can guess that within ATLAS and CMS, plots have started to circulate of preliminary analyses of some sizable fraction of the new data, and some number of people now know which fork we’re headed down, a number that will grow to 6000 or so in coming weeks.

If you’re not one of those, you could try accessing this data indirectly, using a model of how the CERN administration works. According to this presentation at LHCP this past weekend

the next major update of physics results from the LHC is at the ICHEP 2016 Conference, August 2016, Chicago

and

CERN management is in regular contacts with the experiments’ Spokespersons. It is agreed that any significant (i.e. discovery-like) result (such as the 750 GeV bump becoming a signal or other) has first to be announced in a seminar at CERN.

No detailed schedule yet for ICHEP, but the first day of plenary talks there is scheduled for Monday August 8. My CERN-modeling suggests that the two forks in the road will correspond to the following two possibilities

  • A “special seminar” in Geneva mid to late July, where a “discovery-like result” will be announced jointly by the CERN DG and the two experiments.
  • A pair of seminars in Chicago on August 8 or shortly thereafter showing off bump-less plots. Much of the drama will be gone by then, since not all 6000 physicists will have kept quiet, and everyone will realize that if “discovery-like” was going to happen, it would have happened earlier.

It may become clear which fork we’re taking relatively soon, since the “special seminar” route takes some planning and will get announced in advance. If there’s no such news by mid-July I think it will be clear we’re headed down the boring fork in the road.

Unfortunately, life being what it is, that’s the most likely one anyway. To supplement this CERN-administration-modeling, you can watch the comment section at Resonaances, where rumors of no bump have already started to appear…

Update: Now, it’s an official rumor (since it’s on Twitter). I can add to this that, of the rumors I have heard, there have been no rumors that this official rumor is not an accurate rumor.

Posted in Experimental HEP News | 39 Comments

String Sociology

Posted on June 20, 2016 by woit

If you’re interested in the various sorts of internal divisions these days among people doing what gets called “string theory”, you might want to take a look at this blog entry and the discussion there with string phenomenologist Joseph Conlon.

Back in 2002 or so when I started writing my popular book, it was a lot clearer what the term “string theory” meant and who counted as a “string theorist”. If I were writing about this today, there would be a much more confusing situation to try and explain. There’s still a conventional “string theory” story about a supposed theory of everything based on quantized strings often told to the public, but it no longer corresponds much to what researchers who call themselves “string theorists” are actually doing.

To get some better picture of this, it might be a good idea to take a look at the big string theory summer conferences. The biggest is Strings XXXX, this year in Beijing, about six weeks away. No talk titles available yet, but in recent years one clear pattern has been that most of the talks have little if anything to do with the “string theory” of the textbooks (4gravitons tries to categorize things here) . These conferences have been going on for over 20 years.

Since 2002, there has been a breakaway conference, String Phenomenology 20XX, which I think Conlon characterizes accurately as follows:

one reason the String Pheno conference was founded was because people working on pheno topics weren’t getting a look-in at the Strings conference and so set up their own conference. I think the Strings conference is most accurately regarded as the Princeton view of the world (broadly, every year it reflects subjects popular at the IAS and a couple of other similar places).

Generally, the ratios vary with place. A small fraction do string pheno in the US, a significant number in Europe, almost none in India, quite a few in Korea…

This year’s version of this conference has just gotten underway in Greece, you can follow the talks here. One big topic this year is the possible 750 GeV diphoton excess. Around the time of Strings 2016 we should hear whether this is real or not. If it is, String Phenomenology 2017 will likely be completely dominated by the topic, if not, it will have vanished without a trace.

Finally, at the other end of the spectrum is String-Math 20XX, which has been going on since 2011, and this year starts next week in Paris. Quite a few first-rate mathematicians are involved this year. As with Strings 20XX, most of the talks don’t actually have anything at all to do with the theory of a quantized string, and this is more of a “QFT-Math” than “String-Math” conference at this point.

One can read the blog comments mentioned to get some idea of the arguments going on about “phenomenology” vs. “mathematics”. The “phenomenologists” argue that they are the ones doing physics and engaging with data, but don’t really point out that the models they work with have no known (i.e. not purely speculative) connection to any known physical phenomenon. They’re hopeful someday things will be different, but there’s no evidence at all of any progress in that direction.

Phenomenologists like Conlon do battle with their Strings 20XX brethren by accusing them of doing “mathematics”, not “physics”, of in essence really being just an offshoot of the String-Math 20XX crowd. There’s an implicit argument that such people don’t deserve jobs in a physics department, but should move to a math department. I can report though, that while much of the String-Math 20XX research is more than welcome in the math community, that’s not true of most of what goes on at Strings 20XX (a conference that very few mathematicians ever attend).

If you find the current situation confusing, rest assured that you’re not the only one…

Posted in Strings 2XXX | 8 Comments