Various and Sundry

Posted on September 14, 2015 by woit

The semester here is finally underway, and I’m getting back to work on my quantum mechanics and mathematics book (latest version available here). Current plan is to have a final version by next spring, with publication by Springer late next year. This semester I’m teaching Calculus II, a subject where there’s only one thing I really dislike about pretty much all textbooks, their refusal to use Euler’s formula. Since I couldn’t find an online source I was completely happy with, I spent some of the last couple days writing up some notes for the students on Euler’s Formula and Trigonometry, which maybe someone else will find useful. In other news:

  • Nima Arkani-Hamed was here today, giving a talk on a new model he calls “NNaturalness”. The basic idea is to consider something like N copies of the Standard Model, with N a large number. Large N fixes the technical naturalness problem, with something like N=104 fixing the MSSM’s current naturalness problem, and N=1016 fixing the non-supersymmetric problem. He makes clear that he’s well aware that this is a pretty contrived thing to do, but argues that it’s interesting one can do this while evading dramatic disagreement with experiment, and coming up with potential CMB signatures soon observable (e.g. the effective number of relativistic degrees of freedom).

    He has a nice description of the naturalness problem as “in any theory where we can compute the mass of the Higgs it has a fine-tuning problem”. Probably there are people out there who think they have a way to compute the Higgs mass who would disagree with him. To me the problem is that the theories he’s talking about (GUTs, string landscape) don’t actually explain anything about the underlying physics of electroweak symmetry breaking (where does the Higgs field come from and why does it have those couplings?). Given this, it’s unclear why one should worry about the fine-tuning.

    He describes the landscape and the multiverse as “like democracy, the worst idea except for everything else”, and gives a defensive argument for why one should study alternatives like “NNaturalness”, even if they’re not as good as the multiverse (which he finds “simple and deep”). To him it’s worth thinking about alternatives to the multiverse (as a “foil”) not because the multiverse is untestable pseudo-science, but because maybe one shouldn’t just give up. So, it seems that at this point he’s not quite signing up with the intellectual suicide of multiverse mania, although he sees it as the most attractive path available.

    In other Arkani-Hamed news, the IAS has an article about his activities promoting a next generation collider here.

  • The KITP has a newsletter here, including a description by Graham Farmelo of his visit there. Oddly, no matter what he writes about, Farmelo almost always includes an unconvincing defense of string theory and/or the current activities of string theorists (for examples, see here, here, here and here). In this case he assures us that the KITP theorists are not given to “mathematical adventurism”. I think he’s right, but that’s the problem…
  • Someone pointed me recently to Olivia Caramello’s web-page on Unifying theory and her arguments with fellow category theorists. I had a youthful infatuation with category theory, but ultimately came to the conclusion that there’s a real danger in that kind of “unification” of going too far in the direction of saying less and less about more and more. Many of the ideas involved are powerful and attractive, but the remarkable thing about mathematics is that, even for the lover of grand ideas, less generality is sometimes even more so.

Update: One more. If you’re in the Bay Area next week, you might want to head up to MSRI for a series of elementary talks on the Langlands program by Edward Frenkel.

Posted in Multiverse Mania, Uncategorized | 63 Comments

This Week and Next Week’s Hype

Posted on September 3, 2015 by woit

This week’s hype comes to us from Discover Magazine, which has Is Our Universe One of Many? Here’s How We Can Find Out. Needless to say, the author doesn’t actually tell us how we can find out, just repeats the usual “maybe we’ll see bubble collisions” argument often discussed here. We’re also told that

It is important to keep in mind that the multiverse view is not actually a theory, it is rather a consequence of our current understanding of theoretical physics.

It seems that our “current understanding of theoretical physics” is the string theory landscape. If you ask what the evidence is for string theory, you’ll be given the usual circular reasoning that we don’t have evidence because of the multiverse.

For next week’s hype, there will be a promotional public talk in Paris next Tuesday entitled String Theory: results, challenges and magic. Presumably this will be much the same as the speaker’s String theory: results, magic and doubts from two years ago. The argument for string theory seems to be that it is “magic”, and somehow in the past two years the “doubts” have turned into “challenges”. The abstract describes string theory poetically as having

soured and captured the imagination of a generation of high energy physicists.

which I would say is a deep truth, if probably not one the speaker intended.

Posted in Multiverse Mania, This Week's Hype | 29 Comments

SUSY 2015

Posted on August 29, 2015 by woit

SUSY 2015, this year’s version of the big annual conference on supersymmetry, has been going on for the past week at Lake Tahoe. Joe Lykken began his summary talk by explaining how as a kid he was a big fan of the Bonanza TV show, about a ranch along the shores of Lake Tahoe. He always wanted to travel to Lake Tahoe and visit the Ponderosa ranch, was bitterly disappointed when he finally got to Lake Tahoe and found that the Ponderosa did not exist. The relevance of the story to his talk is “left as an exercise for the audience”, with a hint in the next slide, which gives the executive summary of the search for SUSY at the LHC: “We haven’t found it.” He ends the summary talk with this now well-known prediction for the SUSY 2215 conference.

In his discussion of “naturalness” (see slide 25), he makes what to me has always been an obvious point, but I haven’t seen it made ever at a conference like this:

Is the Standard Model (almost) all there is?

Maybe the naturalness argument applied to the Higgs is just wrong (well, it was apparently wrong for the vacuum energy too)

The Standard Model plus some TeV scale renormalizable additions (like dark matter) might be all there is

The Standard Model itself, or with such modest additions, is completely natural (EW scale is not a prediction)

Usual counterargument involves the putative Planck scale and unification thresholds, but this is speculative

An unsatisfying scenario, leaving many questions unanswered, but has a certain minimalist appeal

Some of the other talks included:

  • Nima Arkani-Hamed’s slides and title aren’t available, but the Twitter coverage of the conference included a picture of one of his slides. This tweet reports that he announced that he was “rather annoyed” and “sick of thinking” about naturalness. I guess if you’ve spent most of your career arguing that the LHC would “resolve the naturalness problem” (because it would move fine-tuning from the Tevatron 10% to 1% if it saw nothing), gearing up now for an argument that a 100 TeV collider is needed to “resolve the naturalness problem” (by going from 1% to .1%) would be kind of annoying… In the slide he makes the same argument as in Particle Fever: no SUSY means particle theory should commit suicide and embrace the multiverse.
  • In Gordon Kane’s talk he gave his latest string theory-based predictions for the masses of superpartners. For the last twenty years or so, his gluino mass prediction has always been the same: just a little bit higher than the current bounds. These bounds however keep moving up, so his prediction has moved from 250 GeV in 1997 to 1.5 TeV today (“Detectable soon”!). I think one very solid prediction that one could make is that Kane’s SUSY 2016 gluino mass prediction will be 2 TeV.
  • Joe Polchinski’s talk defended moduli stabilization schemes such as the KKLT one that came out of his original work with Bousso, ending with the claim that

    The KKLT construction has been thoroughly vetted, and it seems to me has survived robustly.

    The de Sitter vacua are still there, as is the landscape.

    Besides his pre-KKLT role in moduli stabilization, Polchinski is one of the most prominent exponents of the idea that particle theorists should just give up, using the KKLT moduli-stabilized string vacua as a reason for why string theory can never be tested, but we should believe it anyway. He’s been promoting this heavily since 2004, when he got Scientific American to publish this article with Raphael Bousso. My take on that article seems to have upset him greatly, and had a lot to do with the arXiv policy of not allowing trackbacks to this blog (which continues to this day).

    This blog does seem to have played an odd role in the topic of Polchinski’s talk. Back in early 2014 someone wrote to me to suggest that I might want to discuss a series of papers by Bena, Grana et al. which pointed out problems with KKLT. I responded that I didn’t think this was a good idea: while I was no expert, it seemed to me that the KKLT construction was an absurdly complex one involving poorly controlled approximations (thus hard to conclusively decide if it was “right” or “wrong”), and it had entered the realm of ideology, as a bedrock for explaining why string theory could never predict anything. What I didn’t say was that I’m a fan of arguments showing string theory can never predict anything, so why should I publicize work challenging them?

    Later in 2014, the same person wrote to me again to suggest that I change my mind, that there was a new preprint about this. I weakened and mentioned it here. A couple months later Polchinski published this, which mounts a defense of KKLT against criticisms like those of Bena, Grana, et al. I didn’t know about this, but did write a long posting about another arXiv preprint he had posted the same day, which was about “dualities” in general, and which I found quite interesting. Only after he and Bousso appeared in the comment section to criticize me about KKLT did I realize that they saw me as responsible for promoting anti-KKLT views, not realizing that I’m actually a KKLT fan. Some strange things have happened over the years at this blog, that Christmas Eve discussion was right up there.

    In any case, just to make my views clear: I’m a big fan of KKLT, glad to hear that it now has been “thoroughly vetted”. Back when I first heard about it in 2003, I thought “this is great! now that string theorists have proved to themselves that their theory isn’t predictive, they’ll move on to something else”. I’ve been surprised though about how long that is taking to happen…

Posted in Multiverse Mania, Uncategorized | 36 Comments

This Week’s Hype

Posted on August 28, 2015 by woit

Bogus media stories about how “physicists finally find a way to test string theory” have now been with us for decades, with a large number of them documented here. Recently this phenomenon seemed to finally be dying down, with such stories the province of more obscure media outlets and the press offices of not very well-known institutions. Yesterday though saw a new example of the genre, coming to us from IAS faculty and the Fermilab/SLAC publication Symmetry, which announces that Theorists from the Institute for Advanced Study have proposed a way forward in the quest to test string theory.

The source of all this is the Arkani-Hamed/Maldacena paper Cosmological Collider Physics from earlier this year. As usual with a lot of these bogus stories about “testing string theory”, the work in question actually has nothing to do with string theory. It’s about possible ways to look for particle physics effects in subtle effects in non-Gaussianities in the CMB. This is a theoretically interesting topic, but suffers from the obvious problem that, experimentally, there are no non-Gaussianities in the CMB. The limits on non-Gaussianity from Planck and other CMB experiments are quite strong.

The connection to string theory is given in the article as:

But scientists are working out ways that experiments could at least begin to test parts of string theory. One prediction that string theory makes is the existence of particles with a unique property: a spin of greater than two.

This is of course complete nonsense, since there are plenty of known particles of spin greater than two. String theory arose as an attempt to explain some of these, but it turned out that it didn’t work, the actual explanation was QCD, a quantum field theory. The author seems to have gotten this argument from the following statement in the Arkani-Hamed/Maldacena paper:

Of course, if we were to detect the contribution of a spin 4 state in the non-gaussianity, it would be a strong indication of string theory during inflation, since we suspect that a structure like string theory follows when we have weakly interacting particles with spin s greater than 2.

Knowing that there is a spin 4 state up at the inflation or Planck scale would of course be quite interesting, but I don’t see any reason to believe that effective field theory would apply to it or that this would “of course” “be a strong indication of string theory”. This argument would actually make better sense at lower energy. I suppose you could claim that lots of work being done at the LHC is “a way forward in the quest to test string theory”, since any day it could lead to evidence for a new weakly interacting spin 4 state. That would of course be pretty silly, but less silly than this article.

Combined with the bogus “test”, the article includes a large helping of the usual promotional material, ending with a section on “The value of strings”. We’re told that

Witten and others believe that such successes in other fields indicate that string theory actually underlies all other theories at some deeper level.

“All other theories”???

Update: I should make clear that my comment about the strength of the limits on non-Gaussianities was about the quality of the experimental results, and my impression that there are not near-term prospects for doing much better. Depending on what models one is talking about, such results are often not strong constraints. A correspondent suggest this source for more information about all of this.

Posted in This Week's Hype | 10 Comments

A Singularly Unfeminine Profession

Posted on August 23, 2015 by woit

Phenomenologist Mary K. Gaillard has recently published an autobiographical memoir, with the title A Singularly Unfeminine Profession, and last week’s Nature has a detailed review.

Gaillard is a very distinguished HEP phenomenologist, with a career that began in the 1960s, taking her in 1981 to a professorship at Berkeley, from which she is now retired. She has been married to two other physicists, Jean-Marc Gaillard and Bruno Zumino.

One highlight of her career is her work on charmed particles, which included an accurate prediction of the charmed quark mass (1.5 GeV, in this paper with Ben Lee, see page 905). The prediction came in a paper published in mid-1974, months before the discovery of the J/Psi in November. Unfortunately she and Lee didn’t have the courage to put the prediction in the abstract, which just said “the average mass of charmed pseudoscalar states lies below 10 GeV”.

Wikipedia also credits her (with Chanowitz and Ellis) with a prediction of the b-quark mass. Maybe I’m missing something here, but this appears to be much less justifiable, since the paper was based on an SU(5) model which is known not to work. It’s also a much vaguer prediction, and appears in the abstract in a mistaken form. In the book, Gaillard tells the story:

We were correcting the proofs for the published version of the paper in July, at around the same time I went to pick up Leon Lederman at the Geneva airport, and, through a screen near the baggage claim gate, he handed me a beautiful histogram showing clear evidence for a b-bbar spin-one bound state – named Upsilon by its discoverers – with a mass of about 10 billion electron volts, in other words, evidence for a bottom quark with a mass of about five billion electron volts. John quickly penciled in a correction to the abstract with our more precise prediction, but his handwriting was so bad the “to” was read as “60”, and our prediction came out in print as

mb/mτ=2605

implying a b-quark mass of over 5000 billion electron volts.

The upsilon discovery was announced publicly at a press conference only later, in August. I can’t help noticing that it seems that back in 1977 discussing results of an HEP experiment before the press conference wasn’t unusual. It is only more recently that one hears that to do this is to subvert the scientific process.

Among the many other things I learned from the book was the origin of John Hagelin and the Maharishi’s posters explaining that N=8 supergravity was the TOE fitting together with the Maharishi’s ideas. Hagelin was dating Gaillard’s cousin and learned about the N=8 story from Gaillard.

The latter part of her career focused first on supergravity, then in 1985 on superstring phenomenology. Thirty years later she’s sill working on much the same idea as in 1985 (see here). The book explains the idea of string theory unification using a compactification, but doesn’t reflect on the question of when or whether it might be a good idea to finally give up on this.

A major theme of the book is that of how her gender has affected her career, including more discussion of the details of her employment and job offers than would be usual in a book of this kind. It’s a complex story, with the details of it well worth paying attention to for anyone interested in the problems women encounter in science. Gaillard started out her career facing serious obstacles as a woman, but later on achieved a large degree of professional success. She has a lot to say about the attitudes and remarks she ran into from men along the way, often from ones who were close friends.

She is most critical of the CERN theory group, which she left in 1981 after being turned down for a senior staff position (at a time she had job offers from Berkeley and Femilab). To this day, as far as I can tell, CERN-TH has no women as permanent scientific staff, and only one (out of 19) female staff members. Perhaps things will change with the incoming CERN director…

Posted in Book Reviews | 12 Comments

Lepton Photon Interactions at High Energies and the Multiverse

Posted on August 22, 2015 by woit

This past week the large biennial “Lepton-Photon” (International Symposium on Lepton Photon Interactions at High Energies) conference has been taking place in Ljubljana. These have been going on since 1965, now alternating years with the ICHEP (“Rochester”) conference. It’s been quite a while since the main topic of the conference was lepton-photon interactions, these days it covers the entire field of HEP, with a format of plenary survey talks. Taking a look at the slides will give you an excellent survey of what is going on in HEP, both in experiment and theory.

One newsworthy talk was Mike Lamont’s on the current state of the LHC Run 2. The new LHC run is at 13 TeV collision energy, with 25ns bunch spacing (as opposed to 8 TeV, 50ns in Run 1). No showstopper problems so far, but increasing the luminosity (by increasing the number of bunches) has been a slow process. As a result, Lamont expects only about 3.4 inverse fb luminosity this year, down from early hopes for a number more like 10 inverse fb. The plan is for 30 inverse fb next year.

The summary talk by John Ellis featured undimmed enthusiasm for SUSY. What will be very interesting to see will be the treatment of this subject at the next Lepton-Photon conference.

One subject that was not mentioned at all in Ellis’s talk, and, as far as I could tell, not in any of the other ones either, was the multiverse. The organizers and speakers seem to all realize that there’s no scientific content to this idea worth discussing, so best to ignore it. I’m completely mystified though by the decision to have as public outreach a promotional talk about the multiverse by Alan Guth. Why anybody in HEP thinks it’s a good idea to make pseudo-science the public face of the subject just baffles me. If you want to see one reason why this kind of thing is really a bad idea and doing great damage to the public perception and understanding of the subject, take a look at this.

Away from serious scientific conferences, the multiverse continues to dominate the media’s coverage of fundamental physics. The usually sober publication The Economist features both an article and a video this week promoting multiverse pseudo-science. As usual in such pieces, no skeptical voices are to be heard. Susskind deals straightforwardly with the lack of scientific evidence problem by simply saying things that aren’t true:

This idea of a multiverse is not gratuitous speculation. No, it really comes out of both experiment or observational physics about the universe and the current theories as best we understand them.

He doesn’t explain what the experimental evidence for the multiverse is. The BICEP2 observation of primordial gravitational waves perhaps?

Posted in Experimental HEP News, Multiverse Mania | 17 Comments

Genius at Play

Posted on August 15, 2015 by woit

A month or two ago I read the new biography of John Conway, Genius at Play, by Siobhan Roberts (whose book about Coxeter I reviewed here). Since then, writing about it has been on my to-do list, but I wasn’t at all sure what to say. In today’s Wall Street Journal Jordan Ellenberg has done a better job of this than I ever could, so I have a place to start: read Jordan’s review.

Probably the first thing to say about the book is that it’s an excellent portrayal of its subject, who is an unusual and well-known figure in the math community. Roberts spent a great deal of time with Conway, traveling with him and getting to know him rather well personally, then very ably turning that experience into a quite readable and enjoyable book. It’s hard to imagine that a better biography of Conway would be possible.

In his review, Jordan crystallized precisely for me why I was having trouble writing about Conway and the book:

Will you like this book? Here’s a simple test. What’s the rule that produces the sequence 1, 11, 21, 1211, 111221, 312211 . . . ?

This is Mr. Conway’s “look-and-say” sequence, so called because each number (after the first) is what you get when you look at the previous number and say it aloud: “one one; two ones; one two, one one; one one, one two, two ones . . .”

If that makes you laugh with surprise, as it did me, you’ll like Mr. Conway, and you’ll like “Genius at Play.” If not, you might want to quit here and go read something improving about the Greek debt crisis.

I’m afraid this didn’t make me laugh with surprise; it seems that I’m immune to the charm of this sort of thing. While there was a lot of Conway’s story I found interesting and which kept me avidly reading, his mathematical interests are very different than mine. Mathematical games make up a big part of his life and career, but the only aspect of this I’ve at any time found appealing was back in high school, when I remember writing a computer program to run the game of Life. I learned from the book that this is Conway’s most famous creation, a fact he’s not entirely happy with.

I also learned that my one personal experience with Conway is widely shared: at lunch with a group here at Columbia he mostly spent the time explaining how to calculate in one’s head what day of the week any date is. Unfortunately I just didn’t enjoy the idea of spending time on this then, and still don’t.

Conway is one of the main figures responsible for an important piece of mathematics, discovering and working out the properties of some of the sporadic finite groups. This isn’t something I’ve ever known much about, and I was quite interested to learn from the book some more about the subject and the history of how it came about.

I can’t think of any other biography that I’ve read that gives such a vivid impression of its subject. In Conway’s case this is somewhat of a mixed bag. He can be a very entertaining character, but his personal flaws are also apparent, with a suicide attempt and several failed marriages testifying to some real problems. Whenever books like this appear, I think one reaction of some mathematicians (not me…) is “is this good for the public portrayal of mathematics and mathematicians?”. Conway’s mixture of genius, highly accessible mathematical discoveries often related to games, and serious issues dealing with the outside world fit rather well with a certain caricature of what mathematicians are like. In my experience with great mathematicians, very few of them other than Conway fit the caricature. While any book about him would likely reinforce the caricature, at least this one gives a very well-written and comprehensive view of its subject.

Posted in Book Reviews | 30 Comments

Short Items

Posted on August 12, 2015 by woit

A few short items:

  • The New Yorker has its own coverage here of the NSA GenCyber summer camp program for children that was discussed here.
  • The LHC is about to start doing physics again at 13 TeV, with beam intensity slowly ramping up in coming days and weeks. You can follow what’s happening here.
  • Some filmmakers are planning an IMAX film about the LHC, more information available here.
  • Online media stories with skepticism about the multiverse continue to appear. The latest one is by Shannon Hall at Nautilus, with the title Is it Time to Embrace Unverified Theories? (I think it’s a general rule that the answer to all questions in titles is No). I like one of the comments on the piece, arguing that some speculative physics is best thought of not as science or religion, but as a game.
  • It’s behind a paywall and I haven’t seen the full story, but this week’s New Scientist has a piece entitled What if .. Most of reality is hidden? A large amount of theoretical activity in recent decades has gone towards ways of figuring out how to hide new physics from any possible interaction with experiment. It seems this is another way of characterizing the problem discussed in the Nautilus article of unfalsifiable theories. Again, since it’s the title of an article, the answer should be No.
Posted in Multiverse Mania | 21 Comments

Multiverses: Science or Science Fiction?

Posted on August 3, 2015 by woit

The September issue of Astronomy magazine is now out, with a cover story on Multiverses: Science or Science Fiction? The author Bob Berman does a good job of explaining both the arguments for various Multiverses, as well as the reasons for skepticism about some of these arguments. After quoting Max Tegmark as defending multiverse theory as science since it is a prediction of an “arguably testable” theory (inflation), Berman ends the piece in a way I have to agree with:

Given the current multiverse infatuation, it may be fairest to give the last word to a prominent skeptic. Columbia University mathematical physicist Peter Woit, who maintains the popular multiverse-critical blog Not Even Wrong, pulls no punches.

“Physicists had huge success in coming up with powerful compelling fundamental theories during the 20th century,” he explains, “but the last 40 years or so have been difficult, with little progress. Unfortunately, some prominent theorists have now basically given up and decided to take an easy way out. The multiverse is invoked as an all-purpose, untestable excuse. They allow theoretical ideas like string theory that have turned out to be empty and consistent with anything to be kept alive instead of abandoned. It’s a depressing possibility that this is where physics ends up. But I still hope this is a fad that will soon die out. Finding a better, deeper understanding of the laws of physics is incredibly challenging, but it’s within our capability as humans, as long as the effort is not overwhelmed by those selling a non-answer to the problem.”

Whoa, intense. We’ve got to toss the multiverse if we care about physics!

Of course, if an infinite multiverse does exist, some other Woit is out there saying the exact opposite.

The same issue of Astronomy has a “Web Extra” entitled What happens if string theory is wrong? It mentions the 2013 poll of theorists discussed here, which had a large majority (73%) answering the question “Do you think that String Theory will eventually be the ultimate unified theory?” with a “No”, then goes on to link to a 2007 article by Sten Odenwald. Some of that article includes quotes from an interview with Lenny Susskind, which Odenwald recently included here. It will be interesting to have an update on that material in a year or so once 13 TeV LHC results on supersymmetry are in.

Bonus material: Quanta magazine has a great interactive map of “Theories of everything”.

Posted in Multiverse Mania | 59 Comments

Math and Physics Summer Camps

Posted on August 1, 2015 by woit

With the kids shipped off to NSA summer camp, now is the time for mathematicians and physicists to head off to their own summer camp experiences. Some of these have websites where the rest of us can participate a bit virtually. These include:

  • Out at Stony Brook, in mathematical physics there’s the Simons Center Workshop going on now. This features lectures at the nearby Smith Point beach.
  • Down in Princeton, the summer PiTP program for this year has just ended, with the topic New Insights Into Quantum Matter. In recent years many HEP theorists have given up on applying duality arguments to string theory unification and have gotten interested in condensed matter physics. Links on this schedule will take you to lectures that include three by Witten on Fermions and Topological Phases.
  • Utah has been the center of the algebraic geometry world for the past few weeks, with the AMS Summer Institute in Algebraic Geometry held in Salt Lake City ending today. This is one in a series of big events held every ten years and as usual was preceded by a bootcamp for graduate students. Also as usual, the NSA is helping out with the funding.

    Overlapping with this, some algebraic geometers were at camp up in the mountains nearby, at the Zermatt Resort, for the PCMI Summer Session, this year the topic was Geometry of moduli spaces and representation theory.

  • Later this month, SLAC will host the 43rd SLAC Summer Institute, with topic this year The Universe of Neutrinos.
  • For Spanish-speaking mathematicians, around the same time the place to be will be Cusco for AGRA 2015. Michael Harris has notes for his lectures and has started blogging in the appropriate language.
Posted in Uncategorized | 2 Comments