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How reliable are Peter Woit and Lee Smolin?

  1. Jul 20, 2012 #1
    A lot of first-rate physicists praise string theory and I've read that it has quite a lot of promise. However Susskind concedes that "string theory has no shortage of critics who will tell you that it is a monstrous perversion." So I'd like to read some of these critics. The only ones that I know of who have written non-technical books are Woit and Smolin. Amanda Peet, paraphrasing, describes Lee Smolin as incapable of understanding. How reliable are these authors? I want to know before I start reading them.
     
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  3. Jul 20, 2012 #2

    jedishrfu

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  4. Jul 20, 2012 #3

    jedishrfu

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    You should also read greens books too to compare and contrast string theory

    Elegant universe

    Fabric of the cosmos

    ...
     
  5. Jul 20, 2012 #4
    I got up to about page 100 in the Fabric of the Cosmos. Green rewrites every sentence 3 times. He's way too wordy. He doesn't understand concision. I look his upbeat speaking style, his movie star looks and his enthusiasm but not his prose style.
     
  6. Jul 20, 2012 #5

    jedishrfu

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    True then perhaps michio kaku who is pretty good at explaining things and is a top notch physicist.
     
  7. Jul 20, 2012 #6
  8. Jul 20, 2012 #7

    atyy

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    Smoline's criticism should be borne in mind with his statement that "it seems that any acceptable quantum theory of gravity, whatever its ultimate formulation, is likely to reduce to a perturbative string theory in the appropriate limit." http://arxiv.org/abs/gr-qc/9508064
     
  9. Jul 21, 2012 #8

    marcus

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    Watch minutes 49-53 of this 2009 talk by Steven Weinberg.


    He says much that is kind about the string program (he's a friend/diplomat and used to do string theory himself in the 1980s) but at the same he is trying to be truthful. It's an interesting moment at the end of very interesting talk (about new physics that could emerge from LHC and the new astrophysics instruments). Thru the whole talk he did not mention superstring. And the first question was from a science journalist who asked why he didn't mention superstring and what did he think about it. So that starts at minute 49. It is a gentle and balanced elderstatesman view (or so it seems to me.)

    It was at the Science Writer's conference October 2009 in Austin Texas.

    A lot has happened since 2005, when the books you mentioned were written. They came out in 2006, I think. It's not obvious to me that they are relevant now. What you need to know is the trend in new faculty hiring in US and Canada physics departments. It tells you wordlessly what is in the minds of department chairmen and hiring committees. What lines of specialization they think are interesting or that might pay off somehow. No arguments, no rationales, no philosophizing, no animosity, no criticism of the string program, but essentially no jobs.

    I don't see that this has anything to do with the books you mentioned and I'm not sure why you would go back and read how the situation was described in 2005. Steven Weinberg's brief remarks, while not actually criticism touch all the bases (lightly) and give you all the pieces of the puzzle (if you want to fit them together.)

    I mean no disrespect to Lee Smolin and Peter Woit. Woit's blog is a valuable source of accurately reported current physics news and there is lively discussion. Smolin has done first-rate creative and fundamental work in a variety of theory areas. They are both much more than the "string critics" they are known as in the media.

    Actually as criticism I found the quotes on string by Feynman, Krauss, Laughlin, and Anderson to be more pointed, biting, memorable, and on the whole funnier. All that is somewhat dated though, and receding into the past.
     
    Last edited by a moderator: Sep 25, 2014
  10. Jul 21, 2012 #9
    thank you, for this link.


    Your sentence is a bit ambiguous. Are you saying that string theorists are not being hired any more? I find that hard to believe? That sentence could be saying something else.
     
    Last edited by a moderator: Sep 25, 2014
  11. Jul 21, 2012 #10

    marcus

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    I'll get some figures. First-time faculty hires in Particle Theory as a whole and in String as a part of that, by year, in Usa and Canada.

    The particle theory job picture for this year (Usa + Canada, first-time faculty positions) is the same as it was 8 June, over a month ago. Twelve HEP theorists have offers, of whom one is a string theorist. Faculty hiring for the fall semester could still change but now seems complete.

    Annual first time faculty hires in theoretical particle physics (Usa + Canada)
    (Up through 2010, the rates are averaged over 3 years intervals.)
    Code (Text):

    period          1999-2001   2002-2004   2005-2007   2008-2010  2011   2012
    HEP theory hires   18         24          23          13        11     12
    string hires        9          8           6           2         1      1
    The source used for the preliminary 2012 estimates: http://particle.physics.ucdavis.edu/rumor/doku.php
    Source for previous years: http://www.physics.utoronto.ca/~poppitz/Jobs94-08

    The point is that in the period 1999-2001 on average HALF the particle theory jobs went to string. Now it is more like 1/10 or 1/12. Again in 1999-2001, the average rate of string hires was about 9 per year.. In 2011 only one string theorist got hired.

    In HEP (high energy physics) theory, departments are now going more towards cosmology and non-string particle theory as relates to phenomena that experimentalists can look for. There is also condensed matter theory and atomic physics but those are separate categories.
     
    Last edited: Jul 21, 2012
  12. Jul 21, 2012 #11

    jedishrfu

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  13. Jul 21, 2012 #12
    Marcus, how about yourself? what's your job?

    Also, I listened to the Weinberg lecture. He said he gave up on super string theory in the last 90's and he's more interested in cosmology now because there is more of the excitement between experiment and theory as there was with HEP in the 60s and 70s. He also said he finds super string theory more attractive but he's working on something else to unify QM and GR. It was a good answer.
     
  14. Jul 21, 2012 #13
    weiberg is superb,

    http://arxiv.org/pdf/1109.6462v4.pdf

    ..."From the point of view adopted here, there is nothing special about
    measurement. Measurement is just a process in which the state vector of a
    system (typically microscopic) becomes entangled with the state vector of
    a relatively large system, which then undergoes a collapse to an eigenstate
    of some operators determined by the characteristics of that system. So we
    expect that the state vector of any system undergoes a similar collapse, but
    one that is much faster for large systems. But collapse to what? Without
    attempting a precise general prescription, we have in mind that these are the
    sorts of states familiar in classical physics. For instance, in a Stern-Gerlach
    experiment, they would be states in which a macroscopic detector registers
    that an atom has a definite trajectory, not a superposition of trajectories.
    In Schrodinger’s macabre thought experiment, they are states in which
    the cat is alive, or dead, but not a superposition of alive and dead. These
    states are like the “pointer states” of Zurek, but here these basis states
    are determined by the physics of the assumed collapse of the state vector,
    rather than by the decoherence produced by interaction with small external
    perturbations"...
     
  15. Jul 24, 2012 #14
    Well, they are the only non-technical critiques of String Theory that have been written, other than maybe Moffat's Reinventing Gravity: A Physicist Goes Beyond Einstein.
     
  16. Jul 24, 2012 #15
    That doesn't mean anything. Old authorities are hard to accept new ideas, even if they are quite original and ingenious. And, finally, the scientific method does not rely on authority.

    Lee Smolin, as far as I am aware, is a reliable scientist who devoted his research to a new, and uncharted area in Physics (Loop Quantum Gravity). In doing so, he follows the methods of any theoretical physicist. You must understand, however, that every step is a non-trivial endeavor. Even calculating basic things in String Theory is a hard business. And, if you want to have a prediction, you must calculate. As far as Peter Woit goes, I don't know what his expertise is.
     
  17. Jul 24, 2012 #16

    haushofer

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    But at least you can do calculations, like graviton-graviton scattering. Afaik are these calculations in e.g. Loop Quantum Gravity not possible (but I could be wrong).
     
  18. Jul 24, 2012 #17

    marcus

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    The calculation of n-point functions using the spinfoam dynamics that was worked out in 2008-2010 has been a gradual process.
    I think they are pretty much up to level 3 now: computing the 3-point amplitudes to leading order. I would not say "not possible", but it's hard. You assume so little about geometry to start with.
    Here's a sample of how this part of the program stood last year:

    http://arxiv.org/abs/1105.0566
    Euclidean three-point function in loop and perturbative gravity
    Carlo Rovelli, Mingyi Zhang
    (Submitted on 3 May 2011)
    We compute the leading order of the three-point function in loop quantum gravity, using the vertex expansion of the Euclidean version of the new spin foam dynamics, in the region of gamma<1. We find results consistent with Regge calculus in the limit gamma->0 and j->infinity. We also compute the tree-level three-point function of perturbative quantum general relativity in position space, and discuss the possibility of directly comparing the two results.
    16 pages

    One really should not say that calculation is "not possible". After all the calculations using the theory have been of enormous historical importance to LQG development. It was, for instance, calculation of the graviton 2-point function (the graviton propagator) in 2007 which brought about a completely new formulation of the dynamics (2008-2010).

    Calculation of the area and volume operator spectra, to take another example, has formed the basis for the active development we see in Loop cosmology. This has lead to more calculation and numerical simulations coming to grips with the start of expansion, with inflation, and with prediction of observable features in cosmic background radiation. Loop has a lot of engagement with real stuff that is, in fact, based on it's ability to calculate.
     
    Last edited: Jul 24, 2012
  19. Jul 24, 2012 #18

    marcus

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    Peter Woit and Lee Smolin deserve appreciation and respect for warning of, and venturing to explain the decline of the String research program that I think only began around 2003---no more than two years before their books were written. I'll post a couple of tables to show the timing.

    Number of recent string papers making the top fifty in the Spires HEP annual topcite list
    (some years omitted for brevity)
    Code (Text):

    year                2001    2003    2005    2007    2009    2010   2011  
    recent top-50 work   12       6       2       1      1       0      NA
    Here a paper is counted as recent if it appeared any time in the prior five years. Annual topcite lists gauge the currently perceived significance of recent work by how often it was cited by other researchers during the given year.

    Links to sources:
    2001 http://www.slac.stanford.edu/spires/topcites/2001/annual.shtml (twelve)
    2003 http://www.slac.stanford.edu/spires/topcites/2003/annual.shtml (six)
    2005 http://www.slac.stanford.edu/spires/topcites/2005/annual.shtml (two)
    2007 http://www.slac.stanford.edu/spires/topcites/2007/annual.shtml (one)
    2009 http://www.slac.stanford.edu/spires/topcites/2009/annual.shtml (one)
    2010 http://www.slac.stanford.edu/spires/topcites/2010/annual.shtml (zero)

    [BTW as I recall, the one recent paper that always made the top 50 during 2004-2007 was the "KKLT"
    http://arXiv.org/abs/hep-th/0301240v2
    de Sitter Vacua in String Theory
    Shamit Kachru, Renata Kallosh, Andrei Linde, Sandip P. Trivedi
    This hints at the underlying physics cause of what was going on at the time. For de Sitter read positive cosmological constant. ]

    In HEP (high energy physics) theory, departments are now going more towards cosmology and non-string particle theory as relates to phenomena that experimentalists can look for.
    I will repost the earlier jobs table for visual comparison with the record of declining citations.

    Annual first time faculty hires in theoretical particle physics (Usa + Canada)
    (Up through 2010, the rates are averaged over 3 years intervals.)
    Code (Text):

    period          1999-2001   2002-2004   2005-2007   2008-2010  2011   2012
    HEP theory hires   18         24          23          13        11     12
    string hires        9          8           6           2         1      1
    The source used for the preliminary 2012 estimates: http://particle.physics.ucdavis.edu/rumor/doku.php
    Source for previous years: http://www.physics.utoronto.ca/~poppitz/Jobs94-08

    The point is that in the period 1999-2001 on average HALF the particle theory jobs went to string. Now it is more like 1/10 or 1/12. In 1999-2001, the average rate of string hires was about 9 per year. In 2011 only one string theorist got hired.

    I don't think the now-evident decline in the program had anything to do with Woit's and Smolin's books. That would be the tail wagging the dog. But they deserve a lot of credit for having had the ability to see clearly what was going on and the courage to speak out.

    I remember there was a great derogatory clamor about a couple of "string theory critics" when criticism was not the real problem the program faced. Folks probably realized the program was in trouble (stemming largely, I think, from the 1998 positive cosmo constant discovery and the 2003 responses by KKLT and Susskind) but converted their anxiety/denial into anger focused on "critics" who were somehow by implication to blame. :biggrin:

    If you search for the underlying physics cause of the program decline it always seems to come back to the January 2003 KKLT paper that tried to accommodate the positive Lambda and came up with a seeming infinity of String solutions, followed, in Summer 2003, by Susskind's launching his "Anthropic String Landscape" campaign. This was the thread running through Steven Weinberg's 2009 brief discussion of his "disappointment" with the String program at the end of the talk I linked to earlier.
    https://www.physicsforums.com/showthread.php?p=4004614#post4004614
     
    Last edited: Jul 24, 2012
  20. Jul 28, 2012 #19
    Lee Smolin actually wish to combine string theory and LQG together, or form a novel theory that have both feature. But this is very very hard.
     
  21. Jul 30, 2012 #20
    I find it really troubling and misleading when I keep reading about Feynman being among the critics of string theory as if he's standing with Woit and Smolin. Feynman died in the 80s, when only a few of the most preliminary facts about string theory were known. There's no serious reason to listen to someone who doesn't know any of the most important facts about a subject. There are tons of people who didn't see the reason for interest in the 80's who have understood since, given all the understanding thats been gained since then.

    Feynman can be forgiven. Lots of great physicists get things wrong in their older years.
     
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