Falsifiable predicted consequences of SuperSymmetry?

[JustinLevy]

What are some falsifiable predicted consequences of SuperSymmetry?
Clearly, if super particles are found, people can rejoice in this new fundamental knowledge of nature. But if it turns out to be a incorrect alley that some theorists journeyed down, do we at least have a way to prove this to ourselves?

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And while this is an extension to the main question: in a more general context, given that symmetries can be spontaneously broken, how can we rule out any symmetries?

For example, the standard model lagrangian is parity invarient, yes? but due to spontaneous symmetry breaking, the empty vacuum itself (the 'ground state') violates parity invarience, and this can and has been seen in experiments via weak decay measurements, no? So how can we rule out symmetries? What symmetries have been ruled out conclusively ... or so far does it seem possible (albeit unlikely) that nature is fundementally "maximally symmetric", having every symmetry we can come up with?

 

[JustinLevy]

Surely someone here must know a falsifiable prediction of super-symmetry? No?

Or maybe someone knows enough to point me towards some reference material that could lead me to the answer? For I haven't been able to find anything yet.

 

[humanino]

You need to specify a supersymmetric model. The so-called minimal extension of the standard model definitely makes predictions, whose tests have already been simulated for feasibility at LHC. I think that counts as falsifiable. Basic keyword would be MSSM.

 

[JustinLevy]

So if I am understanding, your answer to my question "So how can we rule out symmetries?" is that we can't.


I find this amazing. There are some "theory of theories", that rule out theories that combine certain elements without any regard to the details. I was hoping there were such theories that allow us to say for certain, something like: we don't have U(4) symmetry because it would be self-conflicting to match with such and such.

For example, if a molecule has a certain symmetry, and then this symmetry relaxes to a new one (the symmetry is broken), one can still predict relations between the number of vibrational modes in each representation of the new symmetry group using facts about the original symmetry.

It sounds like for all we know, the universe has every symmetry possible, they are just all spontaneously broken. This is kind of disheartenning that we can't rule anything out.


So if, as you suggest, we can only falsify models which incorporate a symmetry instead of the symmetry itself, of all the current models is there something in common? Such as, 'all predict new particles below XXX in order to match current data'? A weaker criteria of "this would be enough to make theorists abondon this symmetry", would be pretty close to my original hopes of a symmetry being "falsifiable" itself.

 

[humanino]

So if I am understanding, your answer to my question "So how can we rule out symmetries?" is that we can't.

There is one reason you can't "rule out supersymmetry". The idea of supersymmetry is already fruitful in condensed matter and nuclear physics. The question is "is supersymmetry realized at a fundamental level ?". To answer this question, you need to specify a supersymmetric model. The MSSM is such a specific model. It makes falsifiable predictions, and thus it can be rules out.

 

[JustinLevy]

Thank you for your responses.

Just to make it clear, in case it is not, I was not suggesting that supersymmetric models are not falsifiable. You seemed to have focussed instead on that, which was not my question.

But I guess we've said all there is to say about that.


So if we can't rule out symmetries that may merely be spontaneously broken, are there any "theory of theories" that let's us rule out the reverse? -- that any of the symmetries we see now are merely "effective" symmetries (only exist at low energies)?

 

[Haelfix]

Well taken from the point of view of the higher energy theory, you still have to satisfy various constraints. For instance representation theory constraints. So eg your gauge group can't be something like a sporadic group. There are further constraints even amongst the Lie groups (eg you want a chiral theory with 3 generations for instance).

Its conceivable that you know, the gauge group could be something like SU(X) where X is some ridiculously large number (X is constrained, it can't be anything in the world, but it could in principle be a big integer). But then that might wreak havok with various quantum gravity proposals, not to mention its very hard to make a working model.

As far as spacetime symmetries are concerned. Well, again you can have some really big groups (say the superconformal group) that spontaneously breaks down to something like the super Poincare and that's ok and won't violate various theorems (like the Haag-Lopuszanski theorem) but it still must contain the poincare group (or the graded poincare group) as a subgroup so it can't be anything in the world.