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Premise: the LHC is obviously mapping unseen territory in high energies, and therefore it's always possible to imagine far out results.

Excluding completely unexpected outcomes - is the LHC performing any experiment that could help with string theory or m-theory? For example:

  • direct super-strings or m-theory predictions to be tested or confuted

but also

  • measurements that would help "shape" string/m-theory into something more concretely testable or practical than the current blurry incarnation?
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Well, there's no reason to believe in supersymmetry, beyond some theoretical niceness to it, so if they see THAT at the LHC, then string theory gets a big boost, as there is no way other than supersymmetry to produce fermions in string theory.

The other thing that might be relevant to quantum gravity is that if there are large extra dimensions (as in, large compared to the Planck length, but smaller than detectable by things like the Cavendish experiment). If that is the case, then the 'fundamental' gravitational constant may be much larger than Newton's constant (they differ by a factor of the volume of the large extra dimensions), and quantum gravitational effects would be accessible at the LHC.

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    $\begingroup$ This is a good answer. I would note that while string theory does require supersymmetry (at least if it's to be a theory of the real world that includes fermions), I don't believe it requires supersymmetry to be visible at the energies of the LHC. (However there are other reasons for thinking it will show up at that scale.) So even if no supersymmetry is found, it isn't necessarily a death blow to string theory. Likewise, it is possible to have supersymmetry without string theory, so finding it wouldn't prove string theory. Certainly I agree though, it would be a big boost. $\endgroup$
    – Tim Goodman
    Commented Nov 17, 2010 at 20:58
  • $\begingroup$ Yeah, I don't think it's necessary that supersymmetry breaking happen at the LHC scale for realistic string models to work. And you can certainly have supersymmetry and no string theory, as you say. If supersymmetry is somehow ruled out, though, it's pretty much a death blow to string theory, as far as I understand. $\endgroup$
    – Zo the Relativist
    Commented Nov 17, 2010 at 21:06
  • $\begingroup$ @TimGoodman: It's not necessary that strings need supersymmetry. $\endgroup$
    – Abhimanyu Pallavi Sudhir
    Commented Aug 24, 2013 at 9:07
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    $\begingroup$ @DImension10AbhimanyuPS: Bosonic strings don't have fermions in their spectrum, at least naturally. Yes, someone may figure out a way to do this in the future, but that is tantamount to saying that someone will figure out a non-string theory way of quantizing gravity--also potentially true, but outside of the scope of the question. Every realistic existing string model of our world requires supersymmetry. And nothing in that linked question explains how to get fermions out of non-supersymmetric string theory. $\endgroup$
    – Zo the Relativist
    Commented Aug 24, 2013 at 13:27
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This article from CERN Courier is about string-theory and experimental tests of it, and about LHC. It is not really technical but it also links to various references and articles.

And for more technical info, you can browse the list of String Theory Seminar of the TH department at CERN and search for "LHC"; very interesting.

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