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M- theory

  1. Mar 3, 2005 #1

    fuzzyfelt

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    Confused and just wondering if i could be pointed in the right direction to find philosophical implications of m-theory
     
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  3. Mar 3, 2005 #2
    m-theory? What is m-theory?
     
  4. Mar 3, 2005 #3

    HallsofIvy

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    According to a google search, it is apparently the 11-dimensional variety of string theory.
     
  5. Mar 3, 2005 #4

    fuzzyfelt

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    M-theory is something I was interested in back when it had correlations with post-modernism, and am now rediscovering it and trying to remember my previous knowledge of it and its implications, and trying to understand the developments that have taken place in the interim and looking to find what philosophical implications have been made of these.
    Forgive my fogginess, but roughly it deals with the idea that there are multi dimensional membranes. Some are tiny strings that through their vibrations, tension and twists create matter and forces. That our universe is a larger membrane. It requires other dimensions than the ones we are aware of to work.
    There are a couple of forums here devoted to them and anyone there I'm sure would answer this better than I could.
     
  6. Mar 3, 2005 #5

    fuzzyfelt

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    Perhaps I have used the wrong term, perhaps 'm-theory' is out-dated too. Could someone possibly direct me toward any thoughts on strings, membranes, that sort of thing.
     
  7. Mar 3, 2005 #6

    selfAdjoint

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    Up on the Strings, Branes, and LQG forum, they have a collection of links that could help you. But the best introduction if you don't have the math is Greene's wonderful book The Elegant Universe.
     
  8. Mar 3, 2005 #7

    fuzzyfelt

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    thank you selfadjoint. I shall have a good look. Do you think they are likely to have links about what philosophers make of their theories, or do you, or anyone, think there is a better way to ask the question? Or a better place to post?
     
  9. Mar 4, 2005 #8
    What is the dimension we are in now? And further more, what would the other required dimentions consist of?
     
  10. Mar 5, 2005 #9

    fuzzyfelt

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    Exactly, thanks. Are there imperitive rules and are there others yet to be determined, and in which direction are the ones yet to be determined pointing toward?
    Being new to this, I did post my first question about dimensions in their forum, but didn't see it up- posted badly or just tooo silly. It was along these lines- are dimensions nescessarily restricted to the usual 11 or 26 that is usually discussed or is this the smallest amount needed for the equations to work? That is, are other dimensions possible within the existing framework? Or are the dimensions definately fiexed and finite?
    Further, they talk of the greater dimensions only existing as bound up within, and in answer to your first question, what they all agree upon, is the 4 dimensions- spot, line, volumne and time, (visually speaking) that we percieve.
    If so, there are usual questions of within what does our universe exist...Or is our 4d universe with hidden dimensions within it, it? Why would this be the case, and how is this elegant?
    In a not very good attempt to answe your second question, the other dimensions are simply tightly wrapped up and effect us by allowing the dualities that instigate matter and forces. I would like to understand this and dualities and symmetry breaking much better. Any thoughts?
     
  11. Mar 5, 2005 #10

    selfAdjoint

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    The 10, 11, and 26 are indeed the minimum needed for the string math to work in different circumstances. Dimensions aside from these might exist, but we would surely notice if energy leaked away into them, for example. On the other hand if they were rigorously separated from the ones our physics happens in, how could we ever detect them? And if we couldn't detect them, why speculate about them?

    Surely your own life doesn't break into some fixed "spot, line, volume and time"? Rather you exist in a three dimensional space where points, lines and volumes can be defined ad lib, in any size and orientation you might choose. The time coordinate is somewhat problematical, but under the laws of relativity it too is dependent on your choice of coordinates.

    It is not nevessary for our universe to lie in a larger space, so we don't assume it is. See my response aboe on unphysical dimensions. As for compacting the extra string dimensions, Greene calls it elegant, but he is a string physicist :biggrin: . I think if physicists were given a chance to eliminate the compacted dimensions, they'd leap at it. Something like that came out a couple of years ago, called "deconstruction", the extra dimensions could be converted into parameters in the theory. There was a lot of excitement for a while, but I haven't heard anything about it lately.

    Yup, that's where the action is. It's hard to do it without the math, but with the math at least T-duality becomes almost trivial. You have a compacted dimension of radius R (a very tiny number) and certain physical equations hold there. If you plug 1/R into the equations (a very big number), and simplify algebraically, they become the right equations for large space. It happens automatically,"just like magic". So you can relate a theory that's just about a tiny corner to a theory that's about a big world.
     
  12. Mar 7, 2005 #11

    fuzzyfelt

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    thank you again, Selfadjoint. I've been reading up and come across some of your other posts and am feeling very humble about my own. Thank you for being so helpful.
    Also, I didn't mean to be rude about the aesthetics of physicists :smile:, the ideas are so appealing to me because it involves so many beautiful parts, and I think Keats was right. Just having a little appreciating them. I'll be back with more questions after I've read a little more.
     
  13. Mar 18, 2005 #12

    fuzzyfelt

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    I'm pretty sure i'm understanding things a lot more, but i haven't found a description of supersymmetry, just that it is to do with spin ... would someone help me please? And does they asnwer mean that, for example, particles and sparticles are composite opposites?
     
  14. Mar 18, 2005 #13

    selfAdjoint

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    Well you know that all the particles we know of are divided into two kinds by their spin. Those whose spin is a whole number, 0 or 1 or 2, are called bosons, and those whose spin are a whole number + 1/2, as 1/2 or 3/2, are called fermions. And it works out that bosons and fermions behave differently; bosons will cluster and can even form Bose-Einstein Condensates (BEC) where they actually share their individuality in one "big particle". Fermions on the other hand obey the Pauli exclusion principle, under which no two of them can have all the same characteristics.

    The two collections of particles seemed arbitrary, and theorists looked for a general principle that could yield them. The old mathematics of Grassmann variables showed a way. In the supersymmetric theory, every boson has a matching fermion and vice versa. The bosic photon has a fermionic photino to partner it, and the fermionic electron has a bosonic selectron. There are regular naming conventions for these extra particles.

    Supersymmetry has a number of other properties that will affect the theories you impose it on. So both the existing standard model and string theory have their supersymmetric extensions, and it has been applied to gravity too. Really it is independent of these theories; it can go on to any one of them.
     
    Last edited: Mar 18, 2005
  15. Mar 18, 2005 #14

    fuzzyfelt

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    That really helps thankyou. I shall absorb this and ask more again later.
     
  16. Mar 30, 2005 #15

    fuzzyfelt

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    Back from holidays, drove past CERN, nice part of the world, pity about all the cheese and veal, and have more questions as promised...
    About supersymmetry, I guess according to superstrings-M, is it right that there are higher levels of energy as the dimensions increase and this leads to stronger symmetry and, vice versa, lower levles of energy, smaller dimensions, weaker symmetry? What is the order of the different degrees of symmetry, is each dimension designated a degree of symmetry and if so which degree of symmetry belongs with each dimension? I like the way Selfadjoint answers my questions with intresting things rather than with equations and words like 'Jacobean matrix of the first partials of the polynomials', but any answers would be very much appreciated.
    Also, what is a soliton?
    And, in a perfect world would all uncompacted or compacted dimensions allow all lower dimensions within them? Sorry, i can't think of a better way to ask that!
     
  17. Mar 30, 2005 #16

    selfAdjoint

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    Thanks for the compliment Fi. There is not more energy in the extra dimensons, just more room to spread the energy around in. The extra dimensions do allow for greater symmetry, and this works itself into string physics via the string's world sheet, which turns out to have more symmetries than you would expect from a two dimensional surface in three dimensional space. And these extra symmetries take string physics into the hot area of new mathematics and have contributed to its continuing popularity, when according to some it is spinning its wheels and going nowhere.

    A soliton is a kind of wave that neither disperses or crests, as most real-world waves eventually do. This is because for the soliton, the dispersing forces ("Spead out, wave!") are in continuing dynamic balance with the cresting forces ("Peak up, wave!"). Obviously this is rather special physics, and it only occurs with certain types of differential equations. But such things do exist both in canals (where the first soliton was discovered in the 19th century) and in our oceans, atmospheres, electronic devices, and maybe our quantum physics.

    Sorry but I didn't quite understand your question about compaction.
     
    Last edited: Mar 30, 2005
  18. Mar 30, 2005 #17

    fuzzyfelt

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    Thankyou, sorry to trouble you with these questions, just trying to see if i am on the right track. I am feeling brave enough to deal with hamilton, lorentz, chiralities should this make it easier.
     
  19. Apr 3, 2005 #18

    fuzzyfelt

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    I can't find where i read it- i'm very lost about all of it, but maybe the word wasn't soliton- it was describing the unification of strings into m that resulted in among other things a 5 dimensional 'soliton'(?).
    I know physicists would rather do without them, but I am intrigued by the other dimensions that are required.
    I've had trouble getting the books I've ordered and not sure how dated some of the stuff i've read on the internet is- does Vafa still think there are 12 dimensions? And is there an in depth over-view of the dimensions i could read. Something that describes each dimension and what exists in them and because of which symmetry. For example, someone said that the 0branes could be time/space, is this considered far fetched, and if not does symmetry apply to them, and what type of symmetry. As they are the smallest dimension have they the least symmetry, and what sort of form does it take? And does m theory rule out the existance of a first dimension since strings are 2branes with a dimension curled in? When it says SUSY=n1 what does that mean? Or I think somethimes it says something like =4d SuSy.And then there are very odd things mentioned like the reverse side of a flat brane having supersymmetry.
    Fairly obviously i didn't do any maths at all in my final years of school. I did do a lot of art. I've been busy having babies and entertaining them and now my youngest is about to start school i'm ready to paint again, and the bits of this that I do understand have inspired me. I will paint what I feel I've learnt because what I do see is beautiful, but if this really were a very important theory, it would be important to interpret it correctly too. Or maybe that should be left to someone who did at least do year 12 maths!
     
  20. Apr 3, 2005 #19

    selfAdjoint

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    Imkagine you're in an airplane, and it's fliying straight and level. So your "up", "down", "left", "right", "ahead", and "back" are aligned pretty much with the directions those words suggest on the surface of the earth. Now let the plane bank, "ahead" and "back" are still the same but "left" now points down at an angle toward the earth, while "right" points up at the same angle to the sky, while "up" and "down" are also rotated ny the same angle from their "true" positions. Suppose the plane goes into a vertical dive, now "ahead" has switched places with "down", and so on.

    What this is all to suggest to you is that there is no first dimension and that dimensions are highly interchangable, depending on what coordinates you draw. So of the ten dimensions of superstring theory, 9 of them are space dimensions and 6 of those are compacted, but the question which 6 is meaningless, you could swap the labels of the dimensions around without changing anything. I think you really have to grasp this point, see it as a picture in your head if you think that way, before you try to think about branes.
     
  21. Apr 4, 2005 #20

    fuzzyfelt

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    I'm not sure i get exactly what you are saying. I think i get that you mean that extra dimensions simply allow extra coordinates, i don't quite get that they are interchangable depending upon point of view. I mean, it does make sense, but why then are higher dimensions spoken of as having greater symmetry? doesn't that mean that their is a difference between them and lower dimensions, even if that changes? And when you say there is no first dimension do you mean that there is no need to label any dimension as first etc., or do you mean that one cannot exist alone? Sorry to be slow here.
    Interchangeable works for me, and it doesn't matter too much if the dimensions are really just mathmatical devices, they can be portrayed as such. Aside from traditional landscapes- back as a kid in 1985 for assessment, it sounds a bit simplistic now, we were asked to do a painting based on post-modernist thought - unification (that unifying theories had met dead ends - my assumption was that this was regarding political, religous, etc. theories), fragmentation, eclecticism, infinities. My sources were artists like A.R. Penck who were exhibiting at the Venice Bienalle around that time, and found myself painting looped strings on space/time coordinates which worked really nicely except that I used black to signify infinities and black frowned upon unless it is representing something incredibly profound, which the irony of an infinity of unifying ideas it seems is not- Rothko had better uses for black. I hadn't heard of the trials of string theory at the time, but obviously I must have been influenced by sources that had, so I was working backward. Postmodernism was disenchanted with unifying theories and unlike modernism that believed in them and who's motto was form follows function, postmodernism's motto was form follows fun. Since then I did read about the t and s dualities, thought they were amazing and did do some paintings with them, but kids, moving countries and oils don't readily mix, so really trying to understand it all went onto the back burner for a more appropriate time.
    I wish i did have a greater knowledge of physics because artists are meant to reflect the thought that influences society, and progress in physics is at the forefront of that.
     
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