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Studying string theory

  1. Sep 17, 2005 #1
    Hey, I wanted to ask you guys a few questions about string theory. It seems like a really neat area, but is over my head. These questions are based on stuff I've gleaned from reading the "beginner" section popular websites:

    (0) Why study string theory?

    (1) Is string theory (still) an active area in physics? Have there been any major advances in the field since the "revolutions" of 1984 and 1995 (dualities)?

    (2) Is string theory at the mercy of results from the Large Hadron Collider experiment?

    (3) How hard is it to get a job as a professor in string theory?

    (4) How many string theorists are there in the U.S? World?

    Thanks for any help!
  2. jcsd
  3. Sep 18, 2005 #2
    Al very good questions. I ought to be able to answer them, since I'm starting my Masters thesis on String Theory this very year.

    0) It depends. There are different viewpoints, ranging from people fervently believing that it is the one and true road to unifying all the fundemantel forces, to people who believe that even it does not lead to realistic physics it is still a usefull tool, who's results could have alot of influence in other domains of mathematics and physics, especially as a dual description of supersymmetric field theories. I tend to fall in the later category.

    1) Incredibly active. In fact, there have been complaints (like from Smolin), that it is too dominant at the moment, and that it is difficult for a high energy theorist that is not working on ST to get hired.

    2) Not really. The theory does not as of now give any low energy predictions. A downer would be if no SUSY would be discovered, but even then the masses of the sparticles could be higher than the 14 TeV scale of the LHC, so it wouldn't be conclusive. Expect parties all round if SUSY would be discovered though.

    3) As easy as it can be in high energy theory. So not so very easy, but it's worse for other fields.

    4) A few tens of thousands would be my guess. I aspire to be one soon :biggrin:
  4. Sep 18, 2005 #3

    My hot reply is as follow

    (0) If you want waste your time... (this is not my personal opinion. It is based in people who began a PhD in string theory and after of some years abandoned the field. A woman even abandoned physics and said to me string theory is a waste of time).

    (1) Yes it is still an active area in physics. Also the study of epicicles was a active area of study in the époque...

    The number of physicists working on ST is each day more low and continue to low. No, there are not advances. In fact, this 2005 is the year of "no-go" therorems. Basically theorems that prove that string theory newer will be predictive and therefore physics. There is an increasing rumour that Witten will abandon the field this year

    (2) Many people (including Nobel laureate Laughing) believe that LHC will be the end of string theory. I wait see that before 2007!!!

    (3) It would be very hard in next years since in some few years the topic will be practically abandoned (except by radical followers). Moreover, the money is little and...

    (4) US 100-800???? Rest of civilizated world ST is not very popular. In Europe ST is not very popular.
    Last edited: Sep 18, 2005
  5. Sep 18, 2005 #4


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    your question (1) concerns research activity.
    One measure of that is number of research papers published per year. I may be able to get some information about that if you are interested.

    Another way to measure is to use citations as a measure of quality. the number of times other papers cite a given one is a rough indicator of how influential and interesting other professionals consider it. (the measure is imperfect, but it is still used by departments to rate people considered for jobs and tenure---it's good to write papers that get a lot of citations)

    so one can measure trends in citations, as an alternative to raw output, to gauge the research activity in a field

    we looked at that, as regards string, in a PF thread, check it out if you want:
  6. Sep 18, 2005 #5


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    one way to respond to your question (0) would be to list the Pros and Cons of string theory----what's good about it, making it appealing as an area of research, and what's bad, making the prospects less than rosy.

    Every year at Stanford/SLAC they have an elite summer workshop (for graduate students, postdocs, working physicists etc.) and this year a string theorist named Joe Lykken taught a course that was originally publicized as "String Theory for Dummies" (that's what the original poster on the web says) and later renamed "String Theory for Physicists".

    I don't think the content changed, just the course title.

    and to start off the course he listed and discussed STRING THEORY GOODS AND BADS

    remember he is a string theorist and was chosen to present an introductory course to string for people who already have some training in physics. his view is apt to be upbeat. but at least he mentioned some "bads"---he was not just a booster. I think he listed 7 goods and 7 bads.

    We talked about this a bit in a PF thread:

    If you read the list, in that thread, and have any questions, you might post them on that thread and maybe someone who understands Lykken's points will explain or clarify----not certain but some chance of it anyway.
  7. Sep 18, 2005 #6


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    Probably the most useful document to look at in connection with these two questions is the 2 hour Video of the June 2005 Toronto Panel discussion.

    We have a PF thread about that here:


    If you download the video so you can watch it, you can scroll to different places-----points along the timeline.

    the overall topic is the future of string theory-----spiffy title: "the next string theory revolution" but no agreement emerged about when or what that might be

    the question "why do string theory?" came up, and was responded to, primarily at two points in the video

    1:23:28 and following (question by someone with a Russian accent, I think Sergei Ketov, but could be George Minic, he says he used to have obvious confident answers as to why, now he has a harder time justifying it to himself and other physicists, so he asks what do you say? some people respond in various ways)

    1:26:20 great short speech by Andy Strominger, young Harvard faculty. forthright and courageous. my favorite part of the video. he is addressing this very issue---why should researchers do it? why should agencies fund it? what do you tell prospective students? colleagues in other branches of physics?

    the first hour of the video is a series of 7 or 8 minute presentations prepared by the panel members----it is not so interesting, I recommend skipping to the start of the second hour

    the second hour is a lively discussion where the audience participated and the panelmembers and moderator responded to questions. except for some three minutes taken up by a (....) person who should not have been there, the whole second hour is worth listening to, in my opinion.

    However if you do not have time to listen to the whole discussion, at least scroll to Andy's two minute speech
  8. Sep 18, 2005 #7


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  9. Sep 18, 2005 #8
    Can you cite a reference please, I've heard nothing of this.

    Bigplanet401: Don't let Juan's attitude toward string theory affect your own. While it may not turn out to be the "theory of everything", alot of good can come out of it, as Dimitri has already illustrated.

    I guess Juan would rather recruit you into his "canonical science" project...an even greater waste of time.
  10. Sep 19, 2005 #9
    marcus, citations is in general a good index but

    i) it is only valid for standard communities with relative weak internal bonds. It would be distorted in a small community like string theory with rigid bonds due to external 'attacks' from other communities. In that case self-citation and citation of friends is an usual practice.

    ii) LQG community is, in general, less arrogant people, and doing general surveys in quantum gravity (e.g. Smolin papers) they CITE work done by several communities: strings, loops, triangulation, Euclidean sector, etc.

    In their papers, string theorist claim that string theory is the only quantum gravity approach and do not cite relevant works of others communities outside string theory doing irrealistic the citation index to relevant papers.

    I remember the term used by certain guy (navigate a little by personal Peter Woit webpage): mafia.
  11. Sep 19, 2005 #10
    Journal of TOEs, 2005, issue 666, page "infinite - infinite"

    :rofl: :rofl:

    Cannot i state my opinion? Cannot i say to Bigplanet401 what my opinion is also maintained by lot of serious physicists including several great Nobel laureates for physics: Anderson, Laughlin, Dyson, Glashow, etc.

    Robert Laughlin makes the point that string theorists are trying to camouflage the theory’s increasingly obvious flaws by comparing the theory to

    and adds

    cannot i to say that great men like Penrose or Hawking think of string theory? Hawking has said that string theory has been oversold.

    The name "waste of time" is not my invention is based in reality of the 40 years failure of string research, and is used by many people in several forms and sinonyms. For example, Anderson uses the term "futile exercise" when refer to string theory. Great cosmologist Krauss named "complete failure", etc.

    There are two books in the topic that Bigplanet401 would read before taking a final decision

    "Not even wrong" by Peter Woit, one of more active critics of the theory for recent years. It was discussed in PF thanks to marcus. The book is recomended by Penrose, also active critic of the theory.

    If you want know a bit the history of that book (subtitled the failure of string theory) and how members of the string theory community did several atemtps for the book was NEWER published, you can see


    Other interesting book is

    Hiding in the Mirror : The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond by Lawrence M. Krauss. As said, he has recently characterized string theory like a complete failure. In fact previous attempt for explaining dark matter, inflation, etc from string theory all failed. The discrepancy in cosmology wetbeen string theory and experiment is in some models of order of 10^120!!!

    The popularized brane model of universe was totally demolished in a series of interesting papers by great specialist A. Lindé, etc. Standard string theory was brilliantly showed incomplete by decades of effort of the Brushels School, etc.

    both books are available on amazon

    Yes, this is the 40 years result of string theory "can", "could" "would" "we hope", etc.

    I said nothing about that. Read my post #3.

    But you remember to me that i also wrote about why string theory is a waste of time. Thanks :!!)


    And it would be a good thing read it (read the quotes to that people think about string theory even like string theorist Lubos Motl critize the way of string theory research of last years) before to take a final option about future career...

    Regarding your last words. It is really curious that people -who has read papers, articles, and even is revising a book- claim. Even people like S. Weinberg who has read a paper on the topic of canonical science applied to particle physics do not claim that was a "waste of time".

    People like renowned Nobel winner Ilya Prigogine was interested before his passed away and we collaborate in thermodynamics of small bodies, etc.


    Let me add the last reply received from a mathematician working in relativity theory.

    Also our recent research in history of relativity (which is not related to canonical theory of course but is an "index" of our reasearch posibilities) has been aknowledged for a number of people in sci.physics.research and in private communications. Names will appear in the final version of the document


    P.S: About Witten i am sure that i read in Woit blog but i cannot say where. If you are interested you would search there
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  12. Sep 19, 2005 #11
    anything which is not at the mercy of any experiment cannot be called physics at all.
  13. Sep 19, 2005 #12


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    In your compendium of distinguished chuckles at superstring you forgot to mention Nobelist Gerard 't Hooft. He teaches a string course at Utrecht but is skeptical of calling it a theory. Here is a quote from his popular book In Search of the Ultimate Building Blocks:

    Actually, I would not even be prepared to call string theory a “theory” rather a “model” or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe, in our case the elementary particles, and one should, at least in principle, be able to formulate the rules for calculating the properties of these particles, and how to make new predictions for them. Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair?

    quote courtesy Woit http://www.math.columbia.edu/~woit/wordpress/?p=258#comments

    Your quote from Laughlin occurred in this piece San Francisco Chronicle

    the same newspaper article has relevant quotes from Lawrence Krauss and others

    I disagree. A theoretical development still under construction may be considered part of the enterprise of physics even though it is NOT YET ready to make an unambiguous prediction.

    I would agree with you that a mature theory, to be considered science, must be potentially falsifiable in the sense that it makes some new prediction by which it can be tested. If there is no performable experiment that could refute the theory, by having the "wrong" outcome, then it's not part of what's usually thought of as science.

    String theorizing has still not given us a mature theory able to put its life on the line----to bet its life on the outcome of a possible experiment where it unambiguously predicts something not already predicted by predecessors.

    So this just means, I think, that it is not mature yet.

    To the extent that people express certainty that string has something to do with nature and eventually will provide satisfactory predictions and explanations, I think they are not being scientific. It has become a matter of faith or superstition for them.

    But not all people who work in string believe in it in this quasi-religious way. I think some of them probably just want to develop the theory further to help get it to the point of making predictions so it can be tested (along with competing alternative theories). So they work in a properly skeptical rational frame of mind.

    So why should we judge this theory-in-development to be unscientific? It may have taken a little bit too long to come to maturity and be still in the development stage----this is admittedly a problem.
  14. Sep 19, 2005 #13


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    I have a belief, it's only a belief, that something of the string theory enterprise will prove to have been the path, or one of the main maths, to the next stage, the nonperturbative unification of the three presently quantized forces with gravity. There may well be other paths involved too - triangulations, spin foams, phoenix program, whatever, but somewhere among the mathematical-physical researches in the greater string theory program will be an important key not available in other traditions.

    Studying string theory is important if only for the tools it puts in your tool kit.
  15. Sep 19, 2005 #14


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    For me, this post of selfAdjoint chimes with the two-minute statement by Strominger starting at time 1:26:20 in the Toronto video,

    and also with Strominger 8 minute presentation starting at 52:00 near the end of the first hour

    I mentioned it earlier in post #6 of this thread
    in the 8 minute talk, Strominger expressed the belief that string theory has SOMETHING, maybe only a little bit, to do with nature. I was impressed by the conservatism and modesty of what he claimed, and by the overall reasonableness. Since he was the last panel member to speak, everybody applauded. I would encourage everyone interested in the status and future prospects of string to listen to what starts at minute 52:00 of the video.
    Last edited: Sep 19, 2005
  16. Sep 19, 2005 #15
    Plus it's funny to watch how he is struggling with the microphone at the start.
  17. Sep 20, 2005 #16
    DT et al.

    Thanks for your quick replies; your posts have taken some of the indirection out of such an abstract subject. It seems that there is no clear-cut opinion, though. And after watching the latter half of the STRINGS 2005 panelists' discussion, I am more confused.

    DT responds optimisically:

    So are there more high-energy theorists who are string theorists than not?
    Have there been any major advances since 1995? J R.'s faith in the field seems less-than-fervent:

    So is the criticism here that ST is not really physics, but mathematical machinery and formalism? I would also like to know where the rumor of EW's departure came from. J R., DT claims participation on the order of 10^4, though...your estimate is lower by a factor of ten.

    Who can act as the arbiter here?


    s-A, you say:


    What is the timescale for your belief? Do you think that ST ideas now will be applicable in 1 year? 10 years? 1000 years (whimsical comment made in the video), if they have any merit at all?


    This attitude has always been a source of repose for me:

    Is this the reason for some Ph.D's leaving physics to pursue a career in business (and the dollar-signs that go with such a career?)

    And marcus, thank you for the link to STRINGS `05 video. Here is what I picked up from it:

    i. The last two revolutions were separated by about ten years. Moderator was concerned that ST was overdue for another one, but that ST papers on the "archive" were being ignored.

    ii. Moderator was "bothered" by the idea of quantum gravity being described by ANY quantum system (especially the "antidesitter, conformal field theory" correspondence -- do I have that right?)

    iii. "Young people" will lead the next Revolution.

    iv. ST is the only consistent theory of quantum gravity that exists.

    v. There was a joke about the Bush administration's willingness to fund ST...

    vi. (from a member on the panel): Told the audience to not argue the ST case, but rather explain it to people, and let them decide whether to enter the field. Called for optimism on audience's part.

    vii. An audience member who asked about a possible interface between ST and astronomy and cosmology was "canned" by the moderator.

    viii. (panel) The LHC will not address quantum gravity, but should tell scientists something about supersymmetry.

    I appreciate this very much. Thank you!
  18. Sep 20, 2005 #17


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    moderator Steve Shenker said that when an audience member asked "why do string theory?" and none of the panelists offered to reply so Steve, as moderator, had to say something and move on.

    I would advise taking it with a grain of salt. It is debatable.

    You mentioned people getting out of string----there has been a fairly steady decline in the number of stringy papers per year since 2001. People who slow down or stop doing string research dont necessarily all go to work for Wall Street. Some just move into other physics areas. I have not heard any indication that stringy math is better preparation for Wall Street than, say, statistical physics. My guess would be that it's less helpful than some lines of physics which involve more numerical modeling of complex systems.

    Here is a graphic picture of the growth areas in physics:
    The fourth chart, at the bottom, is the clearest:

    You can see green and red have caught up with blue. Blue leveled off a few years ago. Green may pass it this year.

    A fair number of people leaving string seem to go into astrophysics, including a new field called astro-particle physics, which has been growing.
    Also condensed matter physics has been growing. Both astro and condensed have a theoretical sector---problems theorists can tackle. I don't have statistics on where people go, only individual cases I have noticed. This kind of shifting is not so unusual, people who are able to move from a slow field to a hotter one sometimes do make transitions within physics.

    for a sense of what the currently attractive areas of research are in physics, look at successive years of MIKE PESKIN'S REVIEW here at the Stanford/SLAC website
    he does an annual report on "What's hot in high energy physics?"
    Note the change over the years 2001, 2002, and 2003.

    It is about time for Peskin to post his review for what was hot in 2004. He takes a while to write and post the review. I've been expecting it this month.

    If you just want raw numbers then what I find using keywords {M-theory OR brane OR AdS/CFT} is a 20 percent decline over a 4 year period from 2001 to present, of papers published per year. That is roughly 5 percent decline per year. Could actually be 20 percent decline over 3 years---6 percent annually. Part of this is just the decline in high energy versus other areas.
    Last edited: Sep 20, 2005
  19. Sep 20, 2005 #18


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    When you promise the moon, green cheese will not suffice. After a ~40 year 'renaissance', string has failed to deliver the goods. That does not mean string is the 'wrong' road: just that it might need a course correction. Perhaps Loops or CDT will get it back on track. That is the peril of doing science... sometimes you eat the steak, sometimes you get the stake.
  20. Sep 20, 2005 #19

    Also i read in some part that Feynman was also skeptic and do not believed in string theory. Is this right?
  21. Sep 20, 2005 #20
    J.R. and many many other people. In one of his last 'This Week’s Finds in Mathematical Physics' (available here in PF), John Baez’s has expressed similar view to mine ones regarding string theory.
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