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What is lacking in QM that String theory wishes to fill up?

  1. Jun 28, 2007 #1

    I have heard that String Theory tries to connect QM with Einstein's world of gravitation.
    String theory adopts an entirely different approach to explain nature. Does this theory contradict with QM? For example, all matter is composed of "Strings" instead of particles/waves.
    Is there anything apart from this main reason (connecting QM and gravitation) that String theory is being given so much importance? Is QM threatened by ST in any way? Does ST have a future? I recently read in newspapers that ST was regarded as the worst theory ever proposed, as it wasted a lot of the precious time of physicists and mathematicians and has not been proved in the real world yet (as it contains far more than the normally observed four dimensions: 3D space and 1D time).

    Mr V
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  3. Jun 28, 2007 #2


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    I am very glad that you asked this question, because I have recently found out that there is a deep relation between string theory and the Bohmian interpretation:

    Anyway, irrespective of my results on the Bohmian interpretation, string theory certainly does not contradict QM. There are also "string waves" associated to a classical notion of strings. The most beautiful thing about strings is that you don't need many kinds of strings to explain many kinds of elementary particles, but one kind of string is enough.
  4. Jun 28, 2007 #3

    Read the following Site to understand extra about string theory:
    There are two ebooks that help you to know introduction of ST.

    and that is about Peter Woit (one of the dissentients of this theory).
    Mr Beh
    Last edited: Jun 28, 2007
  5. Jun 28, 2007 #4
    Do you reasearch in/study/teach string theory also? I have heard it is a extremely complicated and exhausting. Is there any article on string theory for layman's understanding? I actually want to know what they propose in this theory.

    thanks for your reply
    Mr V
  6. Jun 28, 2007 #5
    ST proposes so many dimensions. Do they really exist? And what are these dimensions related to: like space is 3D, time is considered 1D.

    Mr V
  7. Jun 28, 2007 #6
    I edited my last Post. There is the site of P.Woit and if you know extra about answer of your questions, I can help you to give the ebooks (written by this person) that show ST's problems and wrongs.

    Mr Beh
  8. Jun 28, 2007 #7


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    Not at all. Basically string theory applies the traditional methods of quantum mechanics (quantum field theory, to be more precise) to strings instead of point particles. Quantum mechanics is not modified, it's simply applied to a different type of fundamental entity.

    Superstring theory is a beautiful theory. But so far it is a mathematical theory, not a physical theory based on observations. Still, it connects so many things in a mind-boggling way (it's the first theory that treats all the particles as being excitations of only one fundamental "object", it's the first theory that *requires* the presence of gravity, it's the first theory that contains in it conditions fixing the number of spacetime dimensions, it's the first theory that requires supersymmetry for self-consistency and on and on) that it's very difficult to feel that it would have no relevance to the physical world. Now, it is quite possible that it is not the final word in the sense that it might be actually the glimpse to something deeper. But I personally think that there is a lot to gain by pursuing superstring theory. Even if it might end up not being the correct path to the understanding of the universe, I think it will keep teaching us a lot about maths and physics as well (for example, about QCD which may, in some limit, be treated as a theory of strings).

    Just my two cents
  9. Jun 28, 2007 #8
    Yeah, it is beautiful for its predictions, but ST isn't revocable because of imaginary concepts that are away from realities (for example the extra subminiature dimensions that exist) we must accept that ST is an UNSUCCESSFUL theory. Of course superstring theory also follow taht.
    Anyway, I agree with GR and believe that the predictions of it about the universe are identical with realities.

    Mr Beh
  10. Jun 28, 2007 #9
    String theory is based on the same old quantum mechanics as all other theories. There is no problem quantizing gravity per se, the only catch is that the resulting field theory is an effective theory, only valid at energies below the planck scale. What's different about string theory is that it claims to be valid at all energies.
  11. Jun 29, 2007 #10


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    One of the myths about string theory is that it is extremely complicated and difficult to understand. Nevertheless, there is an undergraduate textbook on string theory that breaks this myth:
    B. Zwiebach, A first course in string theory
    It is not for laymen (for laymen, you can read or watch "The elegant Universe"), but it is for every theoretical physicist familiar with basic quantum and classical mechanics.
  12. Jun 29, 2007 #11


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    To speak for myself and my own journey I think it's important to try to separate things.

    > I have heard it is a extremely complicated and exhausting.

    I think the fact that mathematics in itself may be abstract business is one thing. This fact has nothing to do with physics whatsoever. But mathematics on it's own is usually clean (though complex), and there are good books to read.

    IMO: The thing that you can really _loose hair_ over is when trying to understand the connection to reality. And the worst possible combination is elaborations where the author tries to smear things so that the reader is left in confusion as to what are axioms, what are physical assumptions, and what are simply mathematical consequneces and so on. As is often, once one accepts assumptions in "an axiomatic faishon" the rest of it is sometimes mathematics, which is complex on it's own. But at that point one has really skipped severel nontrivial questions..

    Try to figure out what the problem is. If the problem is that it's hard to understand mathematical reasoning, I would consult a math book, not physics books. Or if the problem is to understand what the mathematical formalism has to do with anything of interest, then the question is how to proceed, and it's harder. I'm 34 and not much hair left :frown:

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