[pa7x1]

> I just read that string theories are all supersymmetric and attempts at formulating non supersymmetric ones pretty much failed to the point noone is interested in attempting to make them.

This is correct.

> And LHC experiments ruled out super symmetry in our universe. Does that mean quantum string theory pretty much got falsified?

This is not correct. LHC hasn't ruled out the existence of supersymmetry because it doesn't have a sufficiently high energy to do so. It's like having a ladder to look for socks in the drawers of a very tall closet. With the LHC we get to look at the first 5 drawers, we haven't seen the socks in there, we found some panties (the Higgs boson) but there are still drawers higher were perhaps there are some socks.

Nevertheless, the idea stands, we can use accelerators to test the theory and falsify it which comes to show that the theory makes predictions and is falsifiable.

[scotty79]

Ah, so LHC ruled out some supersymmetries, but not all of them?

Is there a finite number of possible supersymmetries? So that with high enough energy you can rule out all of them? Or can you just make up new ones with ever increasing energy needed to rule them out?

[pa7x1]

Supersymmetry must be broken in some way. The way it's broken is just an accident of this universe, in much the same way the radius of the orbits of our Solar System cannot be derived from first principles but they are just an accident of the evolution of our galaxy.

This means that the masses at which supersymmetric particles are found cannot be predicted from first principles, although we can constrain the range based on other observations. Like the mass of the Higgs, for example, as supersymmetric particles should interact with it and if they were too light or too massive this would have consequences that we could see.

To summarize, we cannot get from first principles the masses at which the supersymmetric particles are found exactly, as this is just an accidental feature of our universe. We do have some bounds. The LHC is not enough to discard the entire range. ncmncm is talking his ass off.

[ncmncm]

> Supersymmetry must be broken in some way. The way it's broken is just an accident of this universe

This is religion, until we have evidence, or at least a research program to obtain evidence. We don't.

High-energy physics has abdicated science, and is training up a priesthood who will reliably echo String Church doctrine. Successfully, by evidence seen here.

Fortunately we still have solid-state, fluid, low-temperature, high-Rydberg, plasma, and other physicists to take up the mantle and religiously-disinclined students. There is still plenty of physical science to do. Apostates could join in.

[scotty79]

So is there an energy level that we could use to rule out any supersymmetry?

[ncmncm]

The latter. There will never be a point when we can say we have ruled out supersymmetry. They can always say, oh, you just haven't looked hard enough yet—keep looking!

[scotty79]

So supersymmetry is unfalsifiable in practice. Is there any part of string theory that you can't just bump up to higher energies when it fails at lower energy predictions?

[ncmncm]

Not within this Solar System.