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What are Superstrings made of?

  1. Mar 1, 2009 #1
    I know they are the smallest building blocks of matter, but whenever I watch a documentary on quantum mechanics, and they blow up the size of the string on screen, I can't help but think that there HAS to be something that can build a string. In other words, if you chop a super string, then you will eventually get another matter that is more finer.. Just like how the universe is infinitely large, there is no limit to how small matter is.. you just keep on peering upon layer and layer every time you divide matter.
  2. jcsd
  3. Mar 1, 2009 #2


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    Your assumption is based on your intuitive ideas about space, time and matter, but our intuition about these things has been proven wrong lots of times by experiments that confirm predictions made by very counterintuitive theories.
  4. Mar 1, 2009 #3
    There is an idea I hear mentioned occasionally called "string bits" which suggests that strings could themselves be described using pointlike entities that connect to each other like chainlinks. However very few people work with this idea, I don't know if it's a serious theory and I don't know anything about it. As far as I know many ideas from string theory would stop working if this were true, the string needs to be continuous and fundamental.

    To confuse you even further, many (all?) forms of string theory, including the original QCD string theory, can be thought of as "dual" models, meaning that you can interpret the theory as if the strings don't "really" exist, instead it just happens to mathematically work out that every universe made of strings is exactly equivalent to a universe made of particles and vice versa. (Of course if mathematics is telling us "you can describe this universe using strings, or you can describe it using particles, and when you do the math the behavior is identical, but most of the math is impossible unless you use the strings", then surely it would seem to be reasonable to just assume the strings are the more fundamental theory.)
  5. Mar 1, 2009 #4
    This reminds me of that poem by Augustus de Morgan
    Great fleas have little fleas upon their backs to bite'em,
    and little fleas have lesser fleas,and so ad infinitum.
  6. Mar 1, 2009 #5


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    Or, to put it another way, "it's turtles all the way down!"
  7. Mar 1, 2009 #6


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    "But it is also an example of emergent strings!"

    Gauge/gravity duality
    Gary T. Horowitz, Joseph Polchinski

    How can that be if the turtles are in "noodle soup"?

    Photons and electrons as emergent phenomena
    Michael Levin, Xiao-Gang Wen
  8. Mar 1, 2009 #7


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    This is very interesting

    This is the original paper:

    Reformulating String Theory with the $1/N$ Expansion
    Authors: Charles B. Thorn
    (Submitted on 10 May 1994)

    Abstract: We argue that string theory should have a formulation for which stability and causality are evident. Rather than regard strings as fundamental objects, we suggest they should be regarded as composite systems of more fundamental point-like objects. A tentative scheme for such a reinterpretation is described along the lines of 't Hooft's $1/N$ expansion and the light-cone parametrization of the string.

    It is cited by these papers, not many, but interesting nevertheless:

  9. Mar 2, 2009 #8


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    2018 Award

  10. Mar 2, 2009 #9


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    Either Kevlar or Carbon Fiber ;-)
  11. Mar 2, 2009 #10


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    Well, whenever I see foundational papers in string theory, you have hundreds of citations :devil:
    Last edited: Mar 2, 2009
  12. Mar 2, 2009 #11
    HAHAH! That's funny. I now think that Superstrings are simply indivisible strings.. they are the fundamental building blocks of matter.
  13. Mar 2, 2009 #12


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    I think they're made out of string cheese.
  14. Mar 2, 2009 #13


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    Set aside the string-specific part of the question; I think the easiest way to reach an intuition about a minimum scale is that, there may be a smallest observable level, in the sense that there is a level of complexity where the observer is simply unable to formulate further questions. You may not be able to distinguish the very question or measurement implied in a further division. If you can't keep track and define of the question, the relevance of ANY possible answer sort of fades.

    In this sense, the notion of smallest scale, is IMHO perhpas better conceptually thought of as a relation between observer-observed , rather than smallest scale in some unclear absolute sense.

  15. Mar 2, 2009 #14
    I hate this idea, but who knows. I'd vote for an as yet undiscovered simplicity.

    I would prefer to think that eventually we will discover some formulation from which things emerge naturally....say by chance, or by some statistically based process that favors certain darwinian results over others. I think strings are often now viewed a "fundamental entities"....bits of energy vibrational patterns...But what caused them to emerge from where ever they originated??

    The Horowitz /Polchinski mathematics is beyond my apprecation but the very idea that such ideas, such possible physical characteristics, can emerge from mathematic formulations makes it appear at least possible that things like our universe can emerge naturally...that space/time/energy/quantum fluctuations,for example, naturally arise from some more basic and ever present characteristics.
  16. Mar 2, 2009 #15
    Naty1, yes, exactly like in articles of Max Tegmark - "Physics from scratch"
  17. Mar 2, 2009 #16
    I would also point out that, you never asked "what are electrons made of?" For some reason, a fundamental pointlike object presents much less of a conceptual issue than a fundamental extended object, even for myself :)
  18. Mar 2, 2009 #17
    inre: "there is no limit to how small matter is.."

    yes, there is a limit, based on the Planck constant, which implies that there is a "Planck length" which represents the smallest possible subdivision of spacetime. i have felt that there is some correlation between planck length and the size of a "string".
  19. Mar 2, 2009 #18


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    What I meant with this is not in contradiction with what you say from my point of view. On the contrary do I see a way to combine them since I am not talking about a classical observer, I'm thinking about evolving observers and this goes well in line with your darwinian idea. It was pretty much what I'm probing in the neighbour thread : https://www.physicsforums.com/showthread.php?t=294823

    I ask the same question. I do not like the idea of fundamental continuum strings as a starting point, my comment only aimed to the general point of how can there be elementary distinguishable units (I didn't say I think it makes sense that these are strings :). The closests thing I persoanlly get strings if I try to be positive towards it, is in fact from string bits, where I picture the bits to be indistinguishable ordered states, so that when the population of bits gets high enough, the systems of states will look like a 1D continuum. I imagine that the mass of the extended object relates to the number of bits. If the bits are many enough, by the law of large numbers the string will for all practical purposes behave like an actual continuum string with a certain mass density. There are also some possible long shot ideas howto picture the string tension from this view, because the size of the string might be related to a uncertainty measure that lives in lower dimensions. It's even how I picture dynamical dimensionality, that measures defined on lower dimensions, map out an emulated higher dimension, and later on, one might argue that the measure on an alternative microstructure is more "fit", and therefor makes the higher dimensional interpretation mroe favourable although in principle they are dual. Similar do how a string traces out a membrane if you look in time. Such structures can form in the memory structure of an observer, and thus induce a map of the environment.

    This is somewhat in line with my own thinking, and I can see it tangent to string things, but it's neverthelss not string theory. Even though I don't favour strings, I do see possible ways that strings in one way or the other mightr have a place in continuum models. But they are hardly fundamental as I see it. But that's just me.

  20. Mar 2, 2009 #19
    No, with pointlike objects people have another sort ofproblems :)

  21. Mar 2, 2009 #20
    The more I read such threads the more I see that Max Tegmark is right.
    TOE should be a blah-blah-free theory. Only equations.
    Call them points, strings, branes, either, whatever.
    Just solve the equations and see how our world (and observers) emerge from them.
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