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What does the other 7-dimensions represent?

  1. Aug 22, 2004 #1
    String theory suggest that the universe exists in 11-dimensions, 3 are the co-ordinates of the space 4th is the time. What does these other 7 dimensions represent. I read an article by M. Kaku, telling that all the basic forces can be explained as the ripples in these dimensions and something like this, I couldn't fully understand this thing. I'd appreciate if you please help me in understanding this thing.

    Last edited: Aug 22, 2004
  2. jcsd
  3. Aug 22, 2004 #2
    http://www.physicspost.com/imageview.php?what=getAuthorPic&authorId=23 [Broken]

    http://www.physicspost.com/articles.php?articleId=140&page=1 [Broken]

    http://www.physicspost.com/articles.php?articleId=140&page=8 [Broken]
    Last edited by a moderator: May 1, 2017
  4. Aug 22, 2004 #3


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    Dear Chumber various people's opinions may differ on this but I will give you my personal view. I believe there is a deep significance to the extra dimensions.

    different string theorists postulate different numbers of extra dimensions. It is not always 7 extra ones.

    At least one theorist has actually dispensed with all the extra dimensions and proposed a way to do stringy speculation with just the usual 4 dims. But he is not popular.

    In any case, there is not yet one fixed official "string theory" and different versions of stringy theoretical work-in-progress have different numbers of extra dimensions.

    the deep significance of these extra dimensions may, in the end, be that the theory-builders still have a long way to go. It is even possible that they will eventually succeed in getting rid of these extra dimensions (which do not always make people happy)

    that's my view. we will see if other people have different ones :smile:
    Last edited: Aug 22, 2004
  5. Aug 22, 2004 #4


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    Dear Chumber,
    this article came out in January 2004 and it is available on line.
    No one has proved that what is attempted here (as a first try) can never be done. This paper can have flaws---I don't know whether it does or not. Whether or not it is successful, it shows an attempt to boil down to the usual 4 dimensions.

    A few months ago, when this paper came out, there was a great ruckus and outrage, as if the fox had gotten into the chicken-house. It was fun and instructive. Here is the title and abstract summary. The link is below.

    The LQG -- String: Loop Quantum Gravity Quantization of String Theory I. Flat Target Space
    Thomas Thiemann

    "We combine I. background independent Loop Quantum Gravity (LQG) quantization techniques, II. the mathematically rigorous framework of Algebraic Quantum Field Theory (AQFT) and III. the theory of integrable systems resulting in the invariant Pohlmeyer Charges in order to set up the general representation theory (superselection theory) for the closed bosonic quantum string on flat target space. While we do not solve the, expectedly, rich representation theory completely, we present a, to the best of our knowledge new, non -- trivial solution to the representation problem.

    This solution exists 1. for any target space dimension, 2. for Minkowski signature of the target space, 3. without tachyons, 4. manifestly ghost -- free (no negative norm states), 5. without fixing a worldsheet or target space gauge, 6. without (Virasoro) anomalies (zero central charge), 7. while preserving manifest target space Poincare invariance and 8. without picking up UV divergences.

    The existence of this stable solution is exciting because it raises the hope that among all the solutions to the representation problem (including fermionic degrees of freedom) we find stable, phenomenologically acceptable ones in lower dimensional target spaces, possibly without supersymmetry, that are much simpler than the solutions that arise via compactification of the standard Fock representation of the string. Moreover, these new representations could solve some of the major puzzles of string theory such as the cosmological constant problem. The solution presented in this paper exploits the flatness of the target space in several important ways. In a companion paper we treat the more complicated case of curved target spaces."


    there could easily be other papers trying ways to by-pass the extra dimensions----to obviate the need for them. I just happen to know of this one.
  6. Aug 22, 2004 #5
    I was wondering about this... I thought the main problem with string theory was that there were 5 differrent versions of string theory until Witten unified the theory into M-theory. Which was my apparently misunderstanding to be the "one" main stringt theory.

    I knew that there were other versions before with lower dim, and I assumed that there would be people still looking for these theories however I thought that there was a kind of fixed superstring theory.

    Also I assume by string theory you mean superstring theory-- are their theories still out their with out supersymetry I thought that involved nasty infities, things going faster than c, and the tachon (sorry about spelling)

    ty Marcus

    on another note School is starting soon and I look forward to returning to having constant internet and hope to learn much from you as you said I could such as about Loop Quantum Theory before I left for england ty
  7. Aug 22, 2004 #6


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    Hello Tom I hope you had a good summer. You are heartily welcome to read some LQG with me in spare moments as long as you are spending enough time on a well-rounded realworld program.

    from my point of view LQG is also not a theory, but an approach to quantum gravity that is still under development and still not fully testable.

    the Bar Mitzvah day for a theory when it can stand up and say "today I am a theory" is when it makes unequivocal predictions about the outcome of some future measurements------astro observation or lab experiment. And when it bets its life on it: either the theory or some substantial component of it will go down if the experiment turns out unfavorable.

    the reason LQG is heating up now is because it gives some indications of approaching that point. It doesnt have to do with being beautiful or divinely inspired. it has to do with the fact that without much fanfare a version of
    LQG has, curiously enough, already been falsified. Synchrotron radiation from the Crab Nebula tested and shot down Smolin's Version A of LQG and it looks like Version B will be testable within maybe 4 years.

    this is why, if you ever want to know about LQG, you should read
    "Invitation to LQG" by smolin. It has almost no formulas--you can probably understand an important 20 or 25 percent of it. It has an FAQ written for
    physicists from other fields. And most importantly it describes the
    near term experimental situation

    this paper is dynamite and it is the one of the very few papers I can imagine wanting to read with you or anyone at PF at this moment
    If you want to read it (with or without my company) I'd print it out on paper and be prepared to underline and highlight and make notes in the margins.

    Let's move this discussion to the thread Marlon started called Loop Quantum Gravity, so we dont disturb this Chumber thread.

    In Marlon's thread I put a link to Smolin's "Invitation to LQG". Dont feel obliged to respond and have fun whatever you decide to do!
  8. Aug 22, 2004 #7
    Any perspectives solidly declaring it's position, is open for further contemplation :smile:

    If one does not use compactified states as they do in string theory, what would this mean? Acceptance of the Kaluza Klein theory, allowed others to consider what this might mean in terms of what gravity was doing through unification with EM?

    The limitation of LQG is readily apparent when it comes to looking at the planck epoch? Does LQG freely admit it's limitations?

    Strings recognizes the compactfied states and supergravity. How would LQG speak to this, at such a time in the beginning of the universe?

    The rest is explained in the linked post. It seems that people still lack the vision capabilties of what brane world means? If this is considered in regards TIME, what would the issue of the graviton have to do with telling us about the nature of quantization of those gravity waves? You needed a way to see the scalable feature right from the beginning to Now. Think of the energy?
    Last edited: Aug 22, 2004
  9. Aug 23, 2004 #8
    I would like to believe the other 7 dimensions act as repositories for mass, light, gravity, life, souls/consciousness, intelligence and God in heaven...

    ...combinations thereof form entities which either have awareness and higher intellects or not
  10. Aug 23, 2004 #9


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    The other dimensions are moved through and vibrated in by the strings just like the extended dimensions. If you are made of strings then YOU are always and everywhere moving through them. You can't separate out one spacelike dimension or a group of them and say they FUNCTION different from other spacelike dimensions; the compaction is different from extension only if the topology of the compacting manifold is non-trivial, which is of course a constant interest of string theorists.
  11. Aug 23, 2004 #10


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    It seems that the 6 extra dimensions in superstrings are currently unused becasue the gauge fields comes from compactification in the bosonizable side of the heterotic string, say, in (fictitious) dimensions 11 to 26. My guess is that in 1985 they could hope to use them to implement some mechanism of symmetry breaking.
  12. Aug 23, 2004 #11
    Well, of course, then that means that strings are idempotent. But if people are born every day of every second wouldn't that mean new strings are always forming? I don't know, just theorizing.
  13. Nov 15, 2010 #12
    I admit, I am a layman, and a good deal of string theory, multiple dimensions and the math involved flummoxes me. But I try to simplify everything in a way that makes sense to me.

    I picture time as something other than a dimension. And to me the 4th dimension is a bridging direction into another area of space that we can't see or conceptualize. If there are a 5th and beyond dimensions they are just extensions of direction in that space based off of the three dimensions of space as we know it from the perspective of where the 4th bridging direction meets that space.

    The 4th dimension should be a 90 degree turn into alternate space from any and all of our existing 3 dimensions. I tend to think of the 4th dimension as a hook ladder that is adjusted in 90 degrees from x,y, and z. And any direction from the other end of the hook ladder is just x(2), y(2), z(2). lets call the distance between the two spaces t for the moment. (I realize that can get confused with time, but it can be changed later, I just like the t shape for this example). In terms of graphs you can move 4t..which is four units of alternate space from one grid(our space) to another grid(alternate space). now, you can move -4 z(2), which would be -4 in depth (or 4 spaces toward you) on the alternate space grid..but its not truly 4 toward you. And it's not backtracking into the 4t again. Its just 4 in a negative direction in the alternate universe. Think of it as following a portal that drops you off in an alternate world, and the portal disappears behind you. If you turn around and walk 4 steps back you aren't walking into the portal..you are now walking 4 steps in that world.

    The thing is, every 90 degree turn from any direction probably leads to a totally different area of alternate space or totall different existing alternate space.
  14. Dec 6, 2010 #13
    You do realize this thread is 6 years old right?
  15. Dec 6, 2010 #14
    So, now that LQG Version B was successfully tested back in 2008, and since Smolin and Co did not end up going to Sweden, it is time to move on to LQG Version C :rofl:
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