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M theory

  1. Nov 14, 2008 #1
    Hi,

    well after several readings I believe it that the theory of the cords does not give in its approximations the standard model is it by what one does not know Lagrangian M theory ?


    thanks
     
  2. jcsd
  3. Nov 19, 2008 #2
    Scientists around the world are starting to study this theory more and more. The theory would explain the big bang while at the same time proving their are infinite Parallel universes
     
  4. Nov 19, 2008 #3
    and comments like this make genuine professionals regret they ever tried to describe what they do.

    If you really had studied string theory seriously you would know what motivates M-theory. It is a web of profound dualities which have been unravelled by (among others) Witten, and which relates all the different versions of string theories. Read wikipedia seriously to begin with the minimum decent perspective at least.
     
  5. Nov 20, 2008 #4
    comment to humanino

    well humanino, showing that YOU know better is not the best quality. i'v red several m-theory articles, including wikipedia. btw, can YOU explain what is the M theory in 3 sentences, instead of telling other ppl what they know or don't know?

    all the best

    icho.
     
  6. Nov 20, 2008 #5
    Re: comment to humanino

    :rofl:


    Suppose you want to build a theory based on strings, and not point particles---then you find a set of consistency conditions when you quantize the theory correctly, including a prediction for the dimension of space-time. Once you thoroughly understand the stringy physics, you start to realize that all of the simplest theories you can write down are connected in some way---they give similar particles in the low energy spectrum when you make certain transformations. These connections give you a glimpse into some deeper theory: indeed, if you are clever, you realize that all of the string theories you can write down are derivable from some more fundamental framework. This is MTheory.
     
  7. Nov 20, 2008 #6
    BenTheMan , i appriciate the answer.
    but i need to know one thing:
    what is your conclusion about life based on the m-theory? is it all random? is it determenistic ? do we have free choice according to it ?

    thanks in advanced.
     
  8. Nov 20, 2008 #7
    You mentioned parallel Universe and Big Bang scenari, so you obviously must already know about dimensions in string theories. Putting this aside, what has BenTheMan told you that I did not already ? MTheory is the idea that the observed web of dualities is the shadow of something more profound.

    Now what are you asking ? Is MTheory quantum or not ?
     
  9. Nov 21, 2008 #8

    Demystifier

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    M-theory says nothing new about that.
     
  10. Nov 21, 2008 #9
    I know I'm new here, but I don't exact believe in the big bang...perhaps the big bounce. parallel universes...I don't know sounds too scifi.
     
  11. Nov 21, 2008 #10
    I agree. Just like the submarine or hologram are so sci-fi they can't possibly exist.

    What is "sci-fi" for you could very well be mundane for future generations. It shouldn't be a criteria for whether or not a theory is valid.
     
  12. Nov 23, 2008 #11
    Of agreement but why one does not manage to determine his Lagrangian (M theory)?
     
  13. Nov 23, 2008 #12

    Fra

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    It seems you ask: "How come" string theorists hasn't yet found the explicit form of this theory? This question seems to address the effiency of development more than anything else. Would you have expected a solution already?

    In addition to what the others said regarding the reason behind the idea of M-theory, as an imagined theory (to be found) that makes sense out of the apparently different theories around. Like another theory for the theories. I suspect that it's not yet understood what this means. This latter stuff is things that one can relate to even without string theory. And regardless of what you think of strings, I think some of these quests for the meaning of physical theory is interesting.

    Even though I don't like the original reasoning of string theory, I do think there is some hope in this extended stuff. Since M-theory isn't yet spelled out, I guess I am free to use my imagination as much as anyone else, and I could imagine that perhaps the ultimate understanding would totally do away with strings as fundamental, and then this could perhaps merge with other thinking.

    One can certainly question the physical basis and meaning of law and theory, and if we can come up with many different possible laws, what does that mean? Does it refer to different universes? or could law simply be partly in the eye of the beholder? If so, the diversity of law could have something in common with the divsersity of observers. And the selection of law might be come parallell to the problem of populating the universe.

    Smolin who is a string critic, has his own reasonings also about the meaning and evolution of physical law.

    I think it is possible that in the future ideas coming out of now competing programs. If you look beyond the specific programs I think there are elements in the dualities and stuff mentioned in the context of M-theory that makes sense, even so without string theory. To actually make THEORY part of physical interactions really does make sense IMO. Often theory is seem as something "external to our universe", but there is no way that can make sense IMO. So I think not only string theory, but also other programs sooner or later are force to question the meaning of theory, and law, and put it back in the real context. I think this is not yet understood - as to why we humans are so stupid and slow I think there no other answer than that we do the best we can.

    /Fredrik
     
  14. Nov 24, 2008 #13

    Demystifier

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    What we need here is a new Maxwell.
    Namely, even before Maxwell has explicitly written down his famous equations that unify electricity and magnetism, there was a lot of evidence that these two phenomena are related, even though explicit equations was not known in a complete and closed form. Now a similar situation is with M-theory, although, of course, it looks much more complicated than electricity and magnetism looked at the pre-Maxwellian time. So we need a new Maxwell who will really explicitly formulate M-theory as a single closed theory.
     
  15. Nov 24, 2008 #14

    Fra

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    I personally think one important difference is that in those days, the pre-maxwell diverse theories of electricity and magnetism as described by Faraday, Ampere, Gauss etc had originated from decent contact with experiment. So there different laws had a good physical basis. The diversity of law, did after all describe real phenomena. The missing part was to see their connection.

    With string theory I think it's different. The zoo of theories has emerged not from experiment, but from some mathematical creativity with a much more unclear physical basis. So I think it's far from clear what the physical relevance of these different theories of strings has?

    So what M-theory seems to be, is a speculative connection between speculations, rather than speculative connection between established physical phenomena?

    Indeed if you have a vision, that the original string ideas must be right, because of their beauty, and then when you find that there are a whole set of theories. Then the most plausible conclusion is that there has to be a connection between them. This is logical once you are there, having walked the string path. But wether the original reasoning that led there is sensible may be debated.

    IMHO at least the lesson might not be just analogy with Maxwell, it might instead suggest something else. That if we has evolve to the point of starting to model models,that may suggest something profound about the nature of law. This is the possible development I hope for.

    I think in the largest vision, this could relate to physical law, like Wilczek's vision of origin of mass as in "confined energy" relates to mass.

    Mass without fundamental mass, and law without fundamental law.

    /Fredrik
     
  16. Nov 25, 2008 #15

    Demystifier

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    Even if this is true, it is not relevant to my point. Namely, one can think about THEORIES formulated by Faraday, Ampere, Gauss, etc, even without thinking about their experimental origin. And this is exactly what Maxwell has been doing. He has concentrated only on the theories per se and then, by purely theoretical methods, concluded that it would be natural to unify these equations into new equations that carry his name. So even if string theory or M-theory has nothing to do with reality, we still need a new Maxwell who will figure it out how string theories, as pure mathematical structures, unify into a single mathematical structure called M-theory. Even those who strongly believe that M-theory is not realized in nature will much easier be able to prove it if someone first finds out what exactly this theory is. So even they should be happy to find a new Maxwell.
     
  17. Nov 25, 2008 #16

    Fra

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    This is a good point I agree. Right not M-theory just has a name and some expected properties.

    But I figure that it is easier to find people who are willing to invest their time and imagination in looking for this M-theory if there is a probably utility of it describing our world. At least from a physical point of view. Though, given that there are mathematicians who spend their lifes working out formalisms that are of high utility in a broader sense than physics, I guess there are those having enough motivation for this too.

    I would be the first to admit the profound value of a theory of theory though. And perhaps someday even the M-theory will transform into something completely different from where is started.

    I think many want the same thing, but our strategies differ drastically. I think the strategy is part of the success though, because the journey might not end, then the efficiency of the journey itself becomes critical. Perhaps one deep lesson of M-theory will be just this.

    /Fredrik
     
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