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Unprovable <=> no application

  1. Mar 29, 2007 #1
    Hi,

    latetly I've been reasoning a bit about the string theory (or M-theory).
    The scientists are very interested in showing the correctness of
    the theory, but to what purpose I question myself?
    How will the theory be used?
    How will the theory be applied?
    There must be some application for it.
    Let us say there exist an application for the M-theory -and by application I mean something usefull, or rather valueble to explore.
    Now that application would be the one to use to prove the correctness of the theory.

    But as the scientists now state there is no way of proving the theory, it also implies that there is no application for it. Hence we reached a contradiction!

    Can somebody help me out here. Am I just doing a silly reasoning, or
    am I missing some part of the puzzle, or is it so that the thinkable applications are quite meaningless for us to make usage of?

    Regards
    /Reklam
     
  2. jcsd
  3. Mar 29, 2007 #2

    marcus

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    Reklam, what you say is basically right
    to be applicable and to be testable are parallel ideas

    to be testable a theory must predict the outcome of a do-able future experiment
    something where we don't know the answer, and that the other theory we have does not predict

    it must say "if you do this and this, set up the experiment this way, then you will observe X as the result"
    and the theory bets its life on this prediction---if you do the experiment and you get Y instead, then the theory is killed.

    this is very similar to being applicable: the theory of microwave or of semiconductors allows to build microwave or semiconductor devices. It says "if you make a tube or a crystal this and this way, then it will do X for you. so one gets technology in the SAME WAY AS ONE GETS FALSIFIABLE PREDICTIONS.

    If a theory is not falsifiable, that means that it is very flexible and can adapt to any possible outcome of any future experiment (where other theory doesn't tell us what to expect).
    If it can live with any conceivable result of any experiment then it cannot be tested, it does not predict, and it is not useful in applications.

    Because of the KKLT paper of January 2003 many people started to suspect that string thinking was not falsifiable, not predictive in this sense.
    We are living through the fall-out of that January 2003 paper---and actually there were earlier signs and earlier papers but this one brought it to a head.
    the image opened up by the KKLT paper is of a vast LANDSCAPE of different possibilities.

    this paper in case anyone wants it and has not got a link is here. You just click on PDF and you get a copy
    http://arxiv.org/abs/hep-th/0301240

    the authors names are Kachru, Kallosh, Linde, and Trivedi, which is why it is known as the KKLT paper.

    I don't think any of us has a good idea of how this business that started with the KKLT and Leonard Susskind's Landscape paper in 2003 will end.
    It is probably not very interesting to discuss about the troubles of string theory.

    But what I like in your post is what you say about ANY GENERAL THEORY (which does not have to be string but can be anything.)
    You suggest that a theory must be testable, by predicting something previous theory doesnt, and if it does not pass the test then it is falsified and proven to be wrong.
    that is what testability means and it is very close to the idea of having useful applicability---not quite the same idea but similar.
     
    Last edited: Mar 29, 2007
  4. Mar 29, 2007 #3
    Okay marcus, this guy is all yours. :rofl:
     
  5. Mar 29, 2007 #4
    That's exactly the area I'm doing my PhD on. The shear vastness of possible vacua from super potentials, uplifting terms, Kahler potentials etc makes me sometimes wonder how the heck progress can be made. Some kind of general theorem needs to be proved about allowable and disallowable contributions to such systems because it's like looking for a needle in a near infinitely large haystack at the moment. :cry: Finding viable minima is hard enough and short of obscene fine tuning, inflationary considerations usually exclude them in short order.

    KKLT use D term uplifting which explicitly breaks supersymmetry, but things like gaugino condensates and alpha' corrections to the Kahler potential allow for similar methods without the use of D terms (see Westphal hep-th/0611332 for example) which just opens up even more possibilities. :yuck:

    Not exactly a shining confidence in my thesis topic is it?!
     
  6. Mar 29, 2007 #5

    marcus

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    a thesis can demonstrate guts, poise, ability to complete work, ability to focus one's life and to be a worthy member of the community, and that you understand the format----either positive or negative results are OK---a thesis doesnt have to demonstrate earthshake results. It demonstrates something about you that is as important as the results.

    No matter how yucky you find it. if you are already into it then hopefully you will just grit teeth and go for finish-line. wish you very very much luck and success on this.
     
  7. Mar 29, 2007 #6
    You are mixing supersymmetry breaking and moduli stabilization in a confusing way. The large number of vacua of the landscape does not come from the different possible ways to break supersymmetry (which I don`t think you can count in any systematic way), but rather from the large number of ways one can stabilize the moduli.

    Can you be more specific about your thesis?

    Why would you work on something you don`t believe in?
     
    Last edited by a moderator: Mar 29, 2007
  8. Mar 29, 2007 #7

    marcus

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    Josh the last time you were in school tht I know of was as a senior in the undergrad physics program at U Toronto and that was, say 2004-2005, if I remember.

    I don't think your question sounds like you've been where he's at.

    One might choose to do a PhD thesis in string for many reasons, including the availability of an advisor, or past history of what you've studied.

    In science people often don't BELIEVE in the theories they study anyway. Part of the work that needs to be done is studying a theory to see if you can find some way to test and falsify it.

    For many PhD students, who have gotten themselves into string, it could be agonizing just slogging ahead to get finished---and it is quite possible that many of them have by now lost any hope that what they are working on might describe nature. Don't ever undermine someone's resolve who is in that place, is my thought: give them every encouragement you can to get finished with it. There will be other chances and other fields down the road.
     
  9. Mar 29, 2007 #8
    I wasn`t trying to undermine his resolve and I`m pretty sure that there`s nothing I could say that would.
     
  10. Mar 29, 2007 #9
    Have you considered loop quantum gravity :)
     
  11. Mar 30, 2007 #10

    marcus

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    that's a vague ill-posed question, since most people seem unclear or inconsistent about what they mean by loop quantum gravity. Let me put the question in a more operational way:

    AlphaNumeric, i think you are in the UK at one of the universities there. I'm curious to know IF YOU HAVE HEARD ANYTHING about the QGQG-1 school that is in progress now that is funded by the ESF (european science foundation) and is mostly for EU participating country PhD students and postdocs. Here is a website.
    http://www.fuw.edu.pl/~kostecki/school.html
    The First Quantum Geometry and Quantum Gravity School

    There are 93 participants and quite a lot are from Britain. The school is in English language but the location is in Poland.
    I'm curious to know if string PhD students in UK heard anything about it--I'm sort of wondering about the size of your "universe", what your information horizons are like.

    If you read the program and the outline of various series of lectures it will give an idea of things that LQG community works on these days. the idea is to introduce the participants (prospective PhD students etc) to the current research and stuff LQG people work on---research problems and so forth.

    Did you hear this was happening? Do you know anyone who attended?

    Two people who post here at this forum (francesca and f-h) are there, so we heard about the QGQG school well ahead of time. But you and your friends might not have.
     
    Last edited: Mar 30, 2007
  12. Mar 30, 2007 #11
    Thanks :)
    Perhaps I didn't explain myself properly, I know the vacua are generated by different moduli stablisation methods (gaugino condensates, corrections to Kahler potential etc), but depending on certain properties of the local stable minima (like [tex]D_{\Phi}W = 0[/tex] etc), susy in various moduli can be broken by the value of the F terms there or by adding in D terms to uplift from AdS to dS/Minkowski.
    I'm only about 3 months into doing anything even close to research based so I'm still at the formative stage, but it's presently in the area of finding stablised vacua in either IIB or Heterotic string models which have gaugino condensates or string loop corrections to them. Then seeing if it's possible to induce an inflaton in the system to describe inflation and hopefully get a cosmologically viable system (ie produce power spectrums similar to those of Quevado et al in their racetrack models). January and Febuary was mostly spent just reproducing others results to get comfortable with the material and it's only been the last month or so where I've tried new stuff, no matter how trivial an extension of someone else's work it might be.
    Perhaps my last post sounded a little dispondent. I feel that the current approach to cosmological systems via string theory is extremely promising but at present it's severly hindered by a lack of general approaches. Viable systems are found one at a time, by hand or some extremely slow algorithm, and short of fine tuning to parts per trillion they don't give good phenomenology. If a general result was developed like "Only terms of the form ..... are allowed in a superpotential" then it would greatly improve the outlook. At present it's quite hit and miss. I can find vacua pretty quickly but few are even close to viable. There's certainly the impression of the area creeping towards something good though so while there are days where I bang my head into the table a lot, others are quite interesting and stimulating.

    As one of the lecturers in my department said, you spend your entire undergrad 'career' learning the lifes acheivment of a genius every week. It slows down considerably when it's your turn to produce something.
    Don't worry, I don't feel undermined :smile: I can see how my post might have seemed a little dejected about my topic, I suppose it's one of those cases where voice inflextion would be important.

    I have a fair amount of confidence that some form of string theory or a work induced by it will contribute something to our understanding of the universe in a practical way even if the theory as a whole as it is now doesn't live to see 2020. Even if not verifiable by the exclusion of other theories, the fact that it seems string theory can give a good cosmological description via compact dimensions is interesting in itself.
    I've looked at it in an extremely superficial and qualative way and it seems very interesting but the problem is that it's not very mainstream and noone in my department does it, only 2 or 3 even do string models. It's interesting but even compared to string theory, pretty inaccessible.
    I'm in the UK yeah, but I've not heard about that. I get emails all the time about various conferences in the UK and across Europe but haven't had anything about that I think.
    The majority of the emails I get about conferences are to do with lattice QCD (:yuck: ) since that's what many of the lecturers in my department do, but there's a number on strings and string phenomenology too. My supervisor is organising a conference in Germany in the summer on the material related to KKLT which I might be going to if I continue on the course of research I'm doing at the moment.
     
  13. Mar 30, 2007 #12

    marcus

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    for people who want to know what it's like in England now
    http://www.dur.ac.uk/john.lucey/webcam.html
    here is a webcam trained on one of UK most beautiful buildings ( Durham cathedral)

    right now the weather looks quite grey and miserable by my California standards. even tho it's 3:30 in the afternoon
    ===========

    AlphaNumeric, speaking of conferences this summer in Germany, the big international one is SUSY 07, in Karlsruhe at the end of july. (Im not telling you anything! :-) but other people might like to know about it.)

    There is something very good about this years SUSY which is that for a week or so before the conference starts they have a FREE SCHOOL for grad students.
    And Frank Wilczek is one of the lecturers at the school. Pretty cool.
    The idea is you go to the school and they lecture on the basics to get you up to speed to enjoy the conference.

    =============
    Look at the lineup at this school
    http://www.susy07.uni-karlsruhe.de/

    ===quote===
    Before SUSY07 there will be introductory lectures for those who have not been working on all aspects of the exciting physics expected from the LHC and cosmology from
    July 23 - July 25, 2007.

    The lectures will cover:
    * Basics of Supersymmetry - D.I. Kazakov (Dubna)
    * Basics of Higgs Physics - S. Heinemeyer (Santander)
    * Basics of Physics at the LHC - H.A. Baer (Tallahassee)
    * Basics of Direct Dark Matter Searches - J. Jochum (Tübingen)
    * Basics of Indirect Dark Matter Searches - W. de Boer (Karlsruhe)
    * Basics of Cosmology - E.W. Kolb (Fermilab)
    * From Symmetry to Supersymmetry - J. Wess (Munich)
    * Expectations of a final theory - F. Wilczek (MIT)

    Participation is free
    ==endquote==

    I'm glad they phrased it "exciting physics expected from the LHC and *cosmology*"
     
    Last edited: Mar 30, 2007
  14. Mar 30, 2007 #13
    Well, this certainly shows it`s not a communication problem.

    That explains it.

    See you in stockholm.

    It didn`t. That was just marcus being marcus.
     
  15. Mar 30, 2007 #14
    Thanks marcus, for the balenced answer.

    /Reklam
     
  16. Mar 30, 2007 #15
    I don't quite follow. You mean what I've said is a little on the naive/simple side or just nonsense thinly vailed by big words? Or am I missing something? (it is 2am and I'm not firing on all cylinders today). Also, did I miss something with Stockholm too?
     
  17. Mar 31, 2007 #16

    marcus

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    nice balanced statement.
    your point about cosmology: it looks like cosmology is in the forefront as a touchstone (this applies to non-string QG reseach as well) in a lot of people's minds.

    I got the impression your current PhD research has to do with cosmology also---the impression I got was of KKLT "phenomenology"---of your digging in amongst the vast array of vacua to find some testable consequences and the test was maybe related to astronomical observation.

    Am I mistaken? I havent reviewed your post and may be misremembering

    Oh, I looked back and saw that I was mistaken---your research is indirectly connected with cosmology but not as direct phenomenologically as i
    remembered:
    Well anyway, I'm curious. What is the conference you mentioned that relates to what you are trying to do? You spoke of a conference this summer in Germany that you might go to if you were still working on this KKLT-related problem. Is there to be a summer workshop specifically focused on all these vacua?
     
    Last edited: Mar 31, 2007
  18. Apr 1, 2007 #17
    It's certainly about digging around for possible vacua and then considering their inflationary implications, but it's currently learning more towards finding a justifiable and more systematic way of finding/creating the vacua rather than the fantastically boring "Trial and error" method sometimes employed to get anything more than the most basic of systems. There's two papers on using algebraic geometry for it I'm currently reading/working through (1 and 2) which might allow for much better searches or ways to exclude large chunks of possible configerations in short order. Shame I goofed off in my lecture course on Rings :yuck:
    The one my supervisor talked about was this : http://www.hep.phys.soton.ac.uk/cosmofun/objectives.html

    Not specifically about vacua, but Quevado is (hopefully) going to be a speaker there and he's done work in this area and a number of other people are listed as doing SUSY inflation or cosmological talks. It may be the case that because my supervisor is organising it, I get to tag along and hopefully learn something. It does seem a little more 'applied' than what I've been doing.

    There was a conference in Trieste last week on vacua that my supervisor went to. She said it was good, but the place is the middle of nowhere and the person she wanted to talk to (Westphal) was unfortunately ill!
     
  19. Apr 1, 2007 #18

    marcus

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    thanks,
    I'm impressed by de Carlos statement of research objectives
    (like finding particle theory basis for inflation and dark energy)
    also impressed by the person. seems to be very nice/genuine but also
    have strong optimism and leadership qualities. lucky to be working with that one (just a superficial outsider first impression)
    have fun:smile:

    ==========
    maybe I should volunteer information, to reciprocate more, though not sure it could be of interest or use to you. Not unlike you,
    nonstring qg people (e.g. some of those teaching at the QGQG-1 school) seek a quantum geometry basis for inflation and dark energy,
    and at the same time a qg basis for particle theory. If you would ever like me to PM a list of recent (since 2005)
    papers forming a qg counterpart to these string research interests please ask.
     
    Last edited: Apr 1, 2007
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