Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Witten remains a strong string theory believer

  1. Sep 2, 2009 #1
  2. jcsd
  3. Sep 3, 2009 #2

    RUTA

    User Avatar
    Science Advisor

    Witten won a Fields Medal (Nobel Prize of math) and I understand his IQ is estimated at over 200. Clearly, he's a genius. But, Witten's accomplishments and brilliance don't convince me that string theory is physics. Here's what P.W. Anderson (Physics Nobel) had to say about it:

    “Is string theory a futile exercise as physics, as I believe it to be? It is an interesting mathematical specialty and has produced and will produce mathematics useful in other contexts, but it seems no more vital as mathematics than other areas of very abstract or specialized math, and doesn’t on that basis justify the incredible amount of effort expended on it. My belief is based on the fact that string theory is the first science in hundreds of years to be pursued in pre-Baconian fashion, without any adequate experimental guidance. It proposes that Nature is the way we would like it to be rather than the way we see it to be; and it is improbable that Nature thinks the same way we do. The sad thing is that, as several young would-be theorists have explained to me, it is so highly developed that it is a full-time job just to keep up with it. That means that other avenues are not being explored by the bright, imaginative young people, and that alternative career paths are blocked.”

    Philip W. Anderson in “God (or Not), Physics and, of Course, Love: Scientists Take a Leap,” The New York Times, Tues, 4 Jan 05, p D3.
     
  4. Sep 3, 2009 #3
    How fair!

    Vladimir Kalitvianski.
     
  5. Sep 3, 2009 #4
    The FORBES article is excellent.

    RUTA posts:
    Others have labored in obscurity until their theories were recognized...like early string theorists...It still is worthwhile to pick work that interests YOU....not what necessarily interests others....
     
  6. Sep 3, 2009 #5

    RUTA

    User Avatar
    Science Advisor

    That's nice if you have the funding! Most young researchers must follow the money.
     
  7. Sep 4, 2009 #6
    How true! I have become an old researcher without a decent possibility to extensively develop my nice solutions.:frown:
     
    Last edited: Sep 4, 2009
  8. Sep 4, 2009 #7

    atyy

    User Avatar
    Science Advisor

    Doesn't this sound like an argument against not just string theory, but all quantum gravity and much beyond the standard model research? If supersymmetry is somehow excused, then string theory will escape too, since supersymmetry is a prediction of string theory.

    I also find Anderson's argument surprising from his emergence or "more is different" viewpoint, since gravity is emergent in string theory. I suppose the reason he wouldn't like string theory is that string theory claims to be non-emergent, although within it, gravity is emergent. I think Wheeler liked "no tower of turtles", perhaps Anderson likes "tower of turtles" - a view I personally find aestheticaly appealing. If string theory turns out to be right, we can take comfort in the fact that strings themselves are emergent within eg. AdS/CFT and presumably M-theory.
     
  9. Sep 5, 2009 #8
    If that's how things are in theoretical physics now, then what the advantage of staying in the academia? I know quite a few people who continue science after their PhD and they're not that cynical.
     
  10. Sep 5, 2009 #9
    Very true, and also true in almost any endeavor.

    Even business owners and exhaulted "captain's of industry" must follow their customers money. The trick is to make the compromises that suit you.
     
  11. Sep 5, 2009 #10
    How does its emergent gravity avoid the Weinberg-Witten theorem?
     
  12. Sep 5, 2009 #11

    atyy

    User Avatar
    Science Advisor

    Emergent gravity must have something else emerge with gravity. In string theory, space also emerges. In many condensed matter models, Lorentz invariance emerges.
     
  13. Sep 5, 2009 #12

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Atyy, keep in mind the context of Philip Anderson's remark. It was at the end of 2004 when the string community seemed dominated by Susskind's anthropic point of view. The idea was to give up on the quest for a predictive testable theory of nature---assume things are loosely constrained by the fact that we are here, physics is accidental like the fact that there happen to be 9 planets, or "environmental", just pick a beautiful theory that compats with past experimental results.

    Strings 2005 at Toronto was organized by people who accepted the Susskind line. But at one point discussion moderator Steve Shanker called for a show of hands vote of the whole meeting and about 3/4 of the rank and file rejected the accidental or "environmental" or anthropic approach. They wanted to continue trying to explain why things have to be this way. The leaders had gone anthropic but the rank and file refused to follow. Shanker was on mike and said "holy sh*t!" when he saw the show of hands.

    By 2008 the leadership had swung the other way. The organizers of Strings 2008 did not invite any "String Landscape" speakers. Nobody talked about the 10^500 vacua. Susskind was not even there.

    Anderson's remark was made at the height of a serious struggle to preserve the foundations of traditional science. When he implied that people (like Weinberg momentarily, like Wilczek briefly) who had compromised with the Landscape talk were "abandoning a 400 year old Baconian tradition" he was nailing the coonskin to the wall. It was time to take a stand and he was doing that.

    What happened was Edge magazine (not a scholarly source!!) encouraged a bunch of creative scientists from many fields to answer the question What do you believe but can't prove? In other words the editor John Brockman challenged them to risk baring their hunches, dared them to make statements which they could NOT support as scientists, that they would not otherwise make in public. On newyears Jan 2005 several score answers were published by Edge. They were very interesting. Two princeton guys, Philip Anderson and Paul Steinhardt, came our fiercely against String Landscape, against giving up the fundamental science quest and saying it's just an accident which vacuum state. They came out against the prevailing views of the string leadership, which characterized string at that time. But did not characterize it later, like in 2008.

    So I think that Philip Anderson's statement---his answer to the Edge Newyears 2005 Question, must be understood in that context. It has nothing to do with other approaches to quantum gravity. Because the leadership of the nonstring QG community had not for a moment suggested that it would be OK to have a theory that was not falsifiable. In that community they had not gone anthropic. They still held to the doctrine that a scientific theory must be empirically testable and not stand by beauty alone. They were not threatening to redefine the science enterprise. So Anderson was not talking to them. He was laying dire Anathema on whatever of the top string people were straying down Susskind's path. I think it helped save the situation.

    Steinhardt used more words and made this plainer. There was less chance of misunderstanding the message (as you seem to have done with Anderson.)

    I think now the Landscape biz is doornails that these guys would feel no urge to fulminate in exactly this way.

    The key sentence is: "It proposes that Nature is the way we would like it to be rather than the way we see it to be." Well it was the leadership in 2004 who were proposing to go party with nontestable theories, if they looked attractive. It was the leadership, not an intrinsic property of the string formalism to be "proposing" this. Anthropery was not intrinsic to the formalism, it was a philosophical "out". Anthropery was merely Susskind's bright idea to save the program---something he thought up when he heard about the KKLT paper's 10^500 vacua. It was a philosophical dodge he took in 2003, and which gained ground for a year or two.
     
    Last edited: Sep 5, 2009
  14. Sep 5, 2009 #13

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Steinhardt's response to the 2005 Edge question is much clearer, he uses more words and avoids the risk of being misunderstood. He has the same things on his mind as Philip Anderson:

    http://www.edge.org/q2005/q05_print.html#steinhardt

    ==quote==
    I believe that our universe is not accidental, but I cannot prove it.

    Historically, most physicists have shared this point-of-view. For centuries, most of us have believed that the universe is governed by a simple set of physical laws that are the same everywhere and that these laws derive from a simple unified theory.

    However, in the last few years, an increasing number of my most respected colleagues have become enamored with the anthropic principle—the idea that there is an enormous multiplicity of universes with widely different physical properties and the properties of our particular observable universe arise from pure accident. The only special feature of our universe is that its properties are compatible with the evolution of intelligent life. The change in attitude is motivated, in part, by the failure to date to find a unified theory that predicts our universe as the unique possibility. According to some recent calculations, the current best hope for a unified theory—superstring theory—allows an exponentially large number of different universes, most of which look nothing like our own. String theorists have turned to the anthropic principle for salvation.

    Frankly, I view this as an act of desperation. I don't have much patience for the anthropic principle. I think the concept is, at heart, non-scientific. A proper scientific theory is based on testable assumptions and is judged by its predictive power. The anthropic principle makes an enormous number of assumptions—regarding the existence of multiple universes, a random creation process, probability distributions that determine the likelihood of different features, etc.—none of which are testable because they entail hypothetical regions of spacetime that are forever beyond the reach of observation. As for predictions, there are very few, if any. In the case of string theory, the principle is invoked only to explain known observations, not to predict new ones. (In other versions of the anthropic principle where predictions are made, the predictions have proven to be wrong. Some physicists cite the recent evidence for a cosmological constant as having anticipated by anthropic argument; however, the observed value does not agree with the anthropically predicted value.)

    I find the desperation especially unwarranted since I see no evidence that our universe arose by a random process. Quite the contrary, recent observations and experiments suggest that our universe is extremely simple. The distribution of matter and energy is remarkably uniform. The hierarchy of complex structures ranging from galaxy clusters to subnuclear particles can all be described in terms of a few dozen elementary constituents and less than a handful of forces, all related by simple symmetries. A simple universe demands a simple explanation. Why do we need to postulate an infinite number of universes with all sorts of different properties just to explain our one?

    Of course, my colleagues and I are anxious for further reductionism. But I view the current failure of string theory to find a unique universe simply as a sign that our understanding of string theory is still immature (or perhaps that string theory is wrong). Decades from now, I hope that physicists will be pursuing once again their dreams of a truly scientific "final theory" and will look back at the current anthropic craze as millennial madness.
    ==endquote==

    In other words, it's not bad to be immature or wrong. Lots of great people have worked on theories that remained unfinished or turned out wrong. What's bad, in his view, is to go Anthropic in desperation and try to relax the standards of scientific endeavor, just to save a pet project.
     
    Last edited: Sep 5, 2009
  15. Sep 5, 2009 #14

    atyy

    User Avatar
    Science Advisor

    Ah that's too bad, I thought I was going to have a sharp disagreement with Anderson - at the same time I will leave open that we do have a sharp disagreement, since I'm not sure he would like me to understand that his opposition is to the anthropic principle, and not to string theory - I believe Witten also dislikes anthropic stuff. I have to admit that my first gut feeling is horror at the anthropic principle, but some aspects of it are intriguing to me as a neurobiologist - because if the anthropic principle became scientific, that would mean we would have a theory of the physics of intelligence :smile: and maybe even of consciousness :tongue2:

    The other thing I like about it is it is a discussion of a quote of Einstein's that I like "The most incomprehensible thing about the world is that it is at all comprehensible."
     
  16. Sep 5, 2009 #15

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    You have to grant that Einstein expected rational explanation. His curiosity would have been unsatisfied if someone had merely declared it was a lucky accident that we happen to live in one of the universes which our intelligence can grasp.

    There are possible evolutionary selection mechanisms that one can explore. If, as Alan Guth suggested, "the universe was created by some guy in his garage"----or, as Andrei Linde imagined, it was created by a couple of graduate students, then selection for reproductive success favors comprehensibility. If conscious agents sometimes accelerate or enhance reproduction, there might be a straightforward Darwinian reason that universes typically follow simple mathematical laws. That is just one possible Darwinian explanation for Einstein's mystery---a form of the "efficacy of mathematics" mystery.

    And mathematics itself clearly evolves, as long as mathematicians are critical of each other's inventions and discoveries, and as long as they keep trying to mutate the structure by adding new concepts and methods it will evolve. As long as people keep trying to apply math to understand nature, math will be shaped by this process so as to be better at making nature comprehensible. We don't know what "mathematics" ultimately is. It is just a bunch of rules and symbols that continue to evolve for doing physics etc. The useful linguistic inventions survive and reproduce.

    (As long as we require predictive understanding and discard what is merely myth, this kind of conceptua/linguistic evolution will continue. It is community and tradition driven. Which is why Anderson is right to cherish the Baconian ethic.)
     
    Last edited: Sep 5, 2009
  17. Sep 5, 2009 #16

    atyy

    User Avatar
    Science Advisor

    The Darwinism I'm liking best at the moment is Zurek's. It seems to address some problems with his older decoherence approach.
     
  18. Sep 5, 2009 #17

    marcus

    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    You read more widely than I do. What does Zurek say?
     
  19. Sep 5, 2009 #18

    atyy

    User Avatar
    Science Advisor

    I'm still trying to understand it, so just my quick impression. Anyway, it's actually just about the emergence of the classical from the quantum, not any of these strange Susskind/Guth/Linde fantasies. The old decoherence approach had the problem that it used the Born rule implicitly in tracing over environmental degrees of freedom, so it still kind of had wave function collapse. Now he says that by adding (i) the universe has subsystems and (ii) measurements can only be made on states that leave multiple fragments in the environment, we can "justify our con dence in quantum mechanics as ultimate theory that needs no modi cations to account for the emergence of the classical."

    I'm sure I'm garbling it, so here are the references.

    http://arxiv.org/abs/0707.2832
    http://arxiv.org/abs/0903.5082
     
  20. Sep 5, 2009 #19

    Fra

    User Avatar

    There has in some papers when people comments on other papers about evolution and antrophics been a confusing between more proper evolution, darwin style, and the antropic rescue of a situation where something has gone beserk and inflated a gigantic landspace in where we are apparently lost.

    I suspect from a brain/biology point of view this would be an important distinction. A proper evolutionary model would IMO rationally inflate the hypothesis space on demand, as not to flood/drown the testing in a gigantic space (landscape). This would be fatal behaviour for say a brain!

    If we try to find similarities between the antrophics on string theory and other (IMO) more clever ideas, this is as I see it a key distinction.

    One that Smolin tried to make as well in the reasoning motivating this CNS.

    /Fredrik
     
  21. Sep 6, 2009 #20

    RUTA

    User Avatar
    Science Advisor

    Do you have a more recent quote from Anderson to support this?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Witten remains a strong string theory believer
  1. String theory (Replies: 8)

Loading...