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Do M or string theory imply a lower limit to size?

  1. Mar 27, 2015 #1
    In his 2001 Three Roads to Quantum Gravity, on its p.l66, Smolin says, "M theory, if it exists, cannot describe a world in which space is continuous and one can pack an infinite amount of information into any volume, no matter how small." As a lay person, I'm hoping to get an informed opinion as to whether that is still considered to be the invariable case, either in M theory or in any other extension of string theory that may controvert it.
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  3. Mar 27, 2015 #2


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    As far as I can tell, this is more a consequence of general quantum mechanics principles and is true in any* theory of quantum gravity, rather than being specific to String Theory.

    * at least in Loop Quantum Gravity, but I think also in Non-Commutative Geometry.

    To clarify: I'm pretty sure what I said is true of discreteness of space, but I wouldn't know how to prove it for information content.
    Last edited: Mar 27, 2015
  4. Mar 27, 2015 #3
    Yeah, I had thought it was a QM thing too, and, after one or two recent disappointments about the rigor of statements by major physicists, I'm just wanting to make sure Smolin (a leader in LQG) might not have been "unintentionally trying" to expand QM's "market share" of thesis writers, etc. If he wasn't, I was thinking there might have been developments since 2001 that could have changed the view he was presenting, which seems to have been based on units called "string bits", that I'm figuring might have been a sort of workaround toward reality, just as "limits" in calculus appear (to me) to be an approach toward infinity that never quite gets there, even if they cover more of the road than any alternative. (I didn't take calculus, and I'm DEFINITELY not trying to impugn the efforts of all you millions who did; my hat's off to you!)
  5. Mar 27, 2015 #4


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    I haven't had much of a look at it but there seems to be a whole field or at least subfield developping around information in physics - the media tag for it is "it from bit", you might want to google that. But apart from that, information is closely related to entropy and there's a lot on entropy and information in QM/QG.
  6. Mar 28, 2015 #5


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    It appears, IMO, Smolin has moved away from that view over the past few years. Ultimately, I believe the universe will submit to an explanation consistent with information theory.
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