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What experiments could provide observable "stringy" effects.

All valid experiments are acceptable (also theoretical experiments).

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There is a basic mistake in your thought outline: A theory can never be proven. It can only be disproved by just one contrary datum. A theory is a mathematical proposition and stands or falls on its agreement with all known experimental data. Experiments continually try to validate or invalidate the current theories. –  anna v Jul 12 '12 at 7:28
Related: physics.stackexchange.com/q/9337/2451 –  Qmechanic Jul 12 '12 at 7:33
This question is a little poorly phrased. The relevant thought experiments are those that establish the holographic principle, since string theory is basically a mathematically precise realization of holography. Experimental evidence should be separated from thought experiments, because while one thinks one knows the answer to thought experiments, there are sometimes surprises. –  Ron Maimon Jul 12 '12 at 8:05
I think Argus is asking for possible experiments which would clearly show a stringy effect. If you had a particle collider operating at the GUT scale, maybe you'd see excited string states. But in my opinion the best hope for proving string theory is for people to figure out the right vacuum (e.g. right shape of the extra dimensions) and show that it predicts the particle masses and mixing angles. –  Mitchell Porter Jul 12 '12 at 10:28
I once asked myself and at SE if the LHC could hypothetically see winding modes, assuming that the extra dimensions are small enough. They would clearly be a stringy effect. –  Dilaton Jul 12 '12 at 11:07
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up vote 4 down vote accepted

I will once again state that string theory, any theory, cannot be proven right by any experiment. The experiment might validate the theory, i.e. come as a result of a prediction from the theory.

At the moment there does not exist one string theory in the manner that there exists one General Relativity theory.There are many models based on string theory, though.

Why such an interest? Because at the moment string theories are the only theories that can accommodate the Standard Model of particle physics and at the same time allow for the quantization of gravity, which has been the holy grail of theoriticians the past fifty years. That is they promise a "Theory of Everything, TOE).

What might disprove the usefulness of string theories for a TOE would be if supesymmetry were falsified at the LHC, for example. If nothing is seen other than the Higgs at the LHC, SS would seem as a nice try but bad luck. Then the usefulness of strings becomes doubtful. If SS is seen in the LHC and studied as well as the SM in the International Linear Collider to be built in the future, then strings will be good as candidates of a TOE.

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I thought SUSY does not HAVE to be broken at an energy scale reachable for the LHC and therefore even if it would not be seen up to 14TeV would not mean that ST is useless ... See for example this question –  Dilaton Jul 12 '12 at 11:14
@Dilaton It does not "have to" but it becomes very much removed from reality and will give ammunition to alternate theories. Personally I think we will find it the LHC :). After all it was first developed as a theory of nuclear physics ground states :). –  anna v Jul 12 '12 at 12:20
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since theoretical "experiments" are included, a proof that any consistent theory of quantum gravity has to be a special case of M-theory will do.

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