Suspicious Dualities

These days some of the strongest criticisms of what is going on in string theory are coming from Lubos Motl’s weblog. His latest post asks what would have happened if currently fashionable ideas about string theory had appeared in the sixties before the standard model. They would have led to claims that many things about particle physics were inherently unpredictable, or dependent on the details of the earliest moments of the big bang. But when the standard model appeared in 1973, it made a wide range of detailed predictions of this type.

He also makes some remarkable statements about string dualities:

“Virtually all conjectured non-supersymmetric dualities (except a few exceptions in the topological context) are suspicious, and even those that are true may be true only because we define one of the sides to be dual to the other – while other equally consistent definitions may exist, too.”

and claims that in the mid-90s Tom Banks described how research on string dualities was being done as follows:

“If you can’t show that a conjectured duality is wrong in 5 minutes, it must be correct.”

Funny, I’d always suspected that was what they were doing, but I’d never have dared to suggest it. And by the way, I’m wondering if Jacques Distler has given up on string theory. It’s been several months since he’s written anything about strings, and a month since he’s written anything at all.

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22 Responses to Suspicious Dualities

  1. Torbjorn Larsson says:

    Sure. But Lubos says “Although string theorists are obviously capable to study any of these things, …”
    which I criticize; as hubris if you like.

  2. Anonymous says:

    I kow that Lubos did not have this in mind, is is awfukky lowbrow

    Harsh, but just.

  3. Torbjorn Larsson says:

    I don’t believe I did that! awfu*ll*y of course, my fingers slipped.

  4. Torbjorn Larsson says:

    “We need to define what string theory is *not*…”

    I kow that Lubos did not have this in mind, is is awfukky lowbrow :-), but there is a constraint of sorts right here, in his model of theories:

    “… construct a bound state of these electrons called the feminist …”

    There is no obvious one-to-one correspondence between different brain constructions and states (ie male and female) to feminist actions.

    So we should really know to stop here. (Apart from that nerve interactions are through ions, transmitter substances, reinforced/inhibited couplings and growth/death, so electrons should not describe them.)

  5. Peter Woit says:

    I’ve been moving to a new apartment today, so have been away from e-mail and just recently came into the office. I’ve deleted some of the more egregiously off-topic posts just now, so if you’re wondering what that discussion is about, to some extent it’s about posts that are no longer there.

    M has it right about why I don’t just let anyone post anything they want to. To put it in more personal terms: I want this weblog and its comment section to be something that I’d actually like to read. In the past when I’ve let people post whatever they want, the comment section has degenerated into something I found not worth reading. When this happens, I assume that many other sensible people will decide the comment section here is worthless, and stop reading it or writing in to it. I’m not going to let that happen.

  6. Kostya says:

    Dear Peter,
    Why do you let crackpots to post on your blog?
    I guess it’s amusing to read their comments but it gets kind of annoying at the end of the day.
    Lubos, please don’t waste you time answering to their stupid comments.

  7. M says:

    From Quantoken:

    Not only Peter will delete any thing about alternative ideas, he will also delete arguments against those alternative ideas he deletes just as well. He is against string theory. But basically he is only interested in arguments either for or against string theory, and for or against LQG, and nothing else.

    I have not noticed Peter selectively deleting comments just because they weren’t about string theory or LQG. I have seen him repeatedly request that people keep their comments related to the topic at hand. People who post comments that push their own particular flavor of a “theory” that supposedly explains all kinds of wonderful things that standard theory does not are usually not adhering to Peter’s guidelines, and thankfully he is not overly shy about removing such comments.

    If you want to see how free-for-all physics discussion forums operate, visit any of the unmoderated Usenet physics groups, like sci.physics.relativity for example. A relatively small number of people actually try to hold intelligent discussions, but the great majority of the traffic consists of discussions of nonsensical alternative “theories,” insults, and off-topic items. In an unmoderated public forum, it just doesn’t seem to happen that intelligent discussion of carefully thought out alternative ideas will take place over any length of time. Turkeys flock together, and the turkeys will be attracted to a forum where “alternative theories” can be discussed like fruit flies are attracted to a piece of overly ripe fruit (especially if they think serious scientists might read their stuff).

    I really hope Peter continues to hold standards for keeping comments on-topic. It is really nice to have a few forums where people can discuss serious physics without the clutter of unsubstantiated (or poorly supported) claims posing as an alternative theory. It think Peter already errs on the side of keeping comments that are at best marginal, although some people whose comments were deleted would probably disagree. Perhaps he will occasionally have a topic where discussions of far out ideas will be on-topic, and then there would be no need to suppress even the nonsense.

    Finally, I think that anyone who carefully thinks through an alternative idea and plays by the rules that all serious physicists play by — and that means making quantitative predictions, having predictions that agree with known empirical results, and not making unsubstantiated wild claims — can expect a respectful hearing by at least some people. Peter has said more than once that occasional references to personal web pages that discuss alternative ideas are fine; he just doesn’t want to have people filling the comment section with that kind of stuff. For those who want to stimulate a more vigorous discussion of their ideas, take it to the unmoderated physics groups on Usenet and it will probably generate some traffic there.

  8. Lubo Motl says:

    Quantoken, your comments are irrelevant because you know nothing about the subtle questions that are discussed.

    It’s just trivially true that the 1/2 BPS sector of type IIB string theory on AdS5 x S5 is equivalent to Quantum Hall System.

    A natural question is whether this can be extended to similar systems used in condensed matter, and it is a technical question that can’t be ultimately answered by your passionate guesswork.

  9. Lubo Motl says:

    “Fascist and antif*ist” – have not you wondered that this is an oxymoron?

  10. Quantoken says:

    Lubos meantioned that he had done some research relating “Fractional Quantum Hall Effect and string theory”

    It is absolutely ridiculous for a string theoretist to even waste one second thinking about the connection between the two subjects. There are as unrelated as trying to use Euler’s law to try to forecast the weather. They belong to completely different domains. The FQHE is problem of manybody of quantum theory in condensed matter physics, and problem that has been well studied and well understood, and does not need any external explanations. There is no physical fractional charge whatsoever.


  11. Anonymous says:

    Fascist and antifeminist

    “The crudest approximations will be enough for this calculation because the physical object under investigation is pretty simple”

  12. Lubos Motl says:

    Well, I can’t deny that our two blogs have a significant overlap in the readership, but one may still argue that my blog is being read by many serious people, and even many of those who read both of these blogs have very different reasons why they read one as opposed to the other.

    My comment comparing the situation of theoretical particle/string physics to biodiversity climate science was not predominantly about the anthropic principle although I mentioned some anthropic examples. Let me say more examples what I had in mind – something related to my recent research that seems increasingly less attractive:

    Fractional Quantum Hall Effect and string theory.

    Non-singlet states in various matrix models.

    Calogero models and string theory.

    And so forth. One may propose many dualities between string theory and these conventional theories and constructions and their generalizations. But do we really believe that these connections are deep? Is there a reason why string theory should be helpful or illuminate either of these things? It has illuminated Calabi-Yau manifolds, for example, but it does not mean that the success can be extended anywhere.

    As far as I know, string theory has not given new insights about the FQHE and my bet is that it won’t give any in the near future.

    I personally doubt that string theory is deeply connected with all these (and other) things, and even the speculative idea that it *is* connected is not attractive to me in any deep way. String theory should be a theory of everything, but not everything in this sense. I would find it more rational and satisfactory if string theory showed that some of these otherwise nice things – like the Calogero model – can’t have any relation with the most fundamental laws. We need to define what string theory is *not*, and undoubtedly some of the things that string theory is not have been proposed as examples what string theory *is*.

    Of course, any idea can be embedded in string theory, including feminist social theory. Take a Calabi-Yau space, heterotic strings, compactify, discover electrons, construct a bound state of these electrons called the feminist, let it evolve, and decode the brain hologram. The crudest approximations will be enough for this calculation because the physical object under investigation is pretty simple, and what you will get is feminist social theory.

    But in this example, the theory is not connected to the characteristic stringy phenomena. Although string theorists are obviously capable to study any of these things, I doubt whether we should pretend that it is a part of string theory.

  13. Anonymous says:

    Lubos’ posts in this blog are legendary ones.

    Many of us know to him and his fascist style.

  14. Anonymous says:

    “what your low-brow blog and its low-brow readers enjoy”

    “- (Lubos). You and you readers are stupid.”

    Hmm, it appears to be true then that, no matter how
    smart you are, how righteous your cause is or how
    strong your arguements are, in the end it’ll come
    down to namecalling!

  15. Arun says:

    I postulate a (Peter blog) (Lubos blog) duality and can confirm it in 5 minutes 🙂

  16. Juan R. says:

    – (Lubos). You and you readers are stupid.

    – (Peter). Thanks for the clarifications.


  17. Anonymous says:

    From the perspective of time, all discoveries seem trivial. The “duality revolution” was certainly a big step. However, one can ask what is the true physical origin of various dualities and why they work so beautifully for superstrings while not much can be done without supersymmetry. In my opinion, dualities have no dynamical content. All what they represent are very strong constraints imposed by supersymmetry, and they hold only in BPS (and almost-BPS) sectors. Same thing about AdS/CFT: when two structures have the same symmetry, you will certainly find some matching observables.
    In non-supersymmetric theories, BPS-like configurations — instantons play some minor role
    but the important dynamical effects like confinement have a different origin.
    If you agree, then here is no point in talking about non-supersymmetric dualities. We are stuck with very difficult dynamical problems, like in QCD. I am curious what others think about it…

  18. Mike Ros says:

    I have the impression that a sizeable fraction of Peter’s readers are also Lubos’ readers

    I anticipate that it works both ways; I always read both.

  19. Torbjorn Larsson says:

    It is worse; Lubos included himself. May I suggest Vicodins? 😉

  20. Just another low-brow reader says:

    From Lubos:

    … or about simple-minded destruction of string theory which is what your low-brow blog and its low-brow readers enjoy.

    As one of Peter’s blog readers, this would make me low-brow. But I also read Lubos’ blog, so I guess that makes me one of his low-brow readers too. In fact, I have the impression that a sizeable fraction of Peter’s readers are also Lubos’ readers, so does this mean that Lubos’ blog is therefore infested by low-brow readers? Such a deep, difficult question almost makes my head hurt.

    Lubos can be so endearing sometimes…

  21. Peter says:

    Hi Lubos,

    Thanks for the clarifications. I thought from the context of my post and yours it was clear that your gedanken experiment referred to the whole anthropic principle line of thinking.

    I don’t want to discourage people from thinking about anything, but I do want to discourage them from thinking about one particular thing (string/M-theory based unification in 10/11 dimensions) since, despite twenty years of effort, it has failed completely and has now led a sizable part of the community off into pseudo-science. It would be good for physics if people thought more about other things than this, just about any other things…

  22. Lubo Motl says:

    Dear Peter,

    what you have not understood is that the rule “if you can’t rule it out in 5 minutes, it’s true” has really worked in all the important cases during the duality revolution, and in some cases it also worked afterwards.

    Non-supersymmetric dualities have never been a part of the basic established structure of string theory. For example, type 0A is, in some sense, dual to M-theory on a Scherk-Schwarz circle. Except that such a statement is physically unverifiable because in order to connect the two limits, one has to go through spacetime that is completely unstable.

    A more modern example is the description of non-SUSY configurations obtained by adding things such as anti D3-branes to supersymmetric AdS spaces; it’s questionable whether these configurations may be seen in the dual boundary CFT.

    My gedanken experiment about the 1970s was not about putting the whole string theory as we know it to the test – or about simple-minded destruction of string theory which is what your low-brow blog and its low-brow readers enjoy. It was about checking ideas how to go beyond the current state of affairs. Unfortunately, you’re extraordinarily capable to distort statements and facts in such a way that you want to discourage as many people as possible from thinking about anything.

    All the best

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