# When to study string theory

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1. Dec 18, 2014

### physicsfirzen

Hello Everyone,
I want to know if it's a good time to study string theory from the basics? Or is it wiser to wait till next year, after the 2015 LHC run, if indeed we find any evidence for it?

I have done a course in mathematical physics, classical and quantum field theory, electrodynamics and a bit of chaos theory. Any other topics or prerequisite that i may need?

Thanks

2. Dec 18, 2014

### ShayanJ

Hello
String theory is far from being a testable theory. In fact it seems more probable that they disprove it in LHC than giving an evidence for it. Because, for example, if supersymmetry is ruled out(which is a very big if), string theory will be out of physics(but still very respectable in mathematics). But if they find evidence for supersymmetry, it just means string theory can continue its life as a ghost(but a ghost very much like a really good theory) in physics till a miracle happens and its proved, or its disproved.
So I can only tell, if you like it, go and learn it and don't let anything stop you. But if you don't like it, just leave it alone!
But if you're kind of guy who wants to know currently working things and doesn't want to struggle with things to get them working, string theory is not for you and you should go for other things. But actually we still have much things to fix even in things that are currently working and so its just less "not-working" than string theory and not totally working. So it just boils down to this sentence:
If you love string theory, go and learn it and serve your beloved one. Otherwise, just remain outside and observe how it goes on.

3. Dec 18, 2014

### ChrisVer

Well, if you want to work into String theory then you don't have to care about the experiments in LHC and so on, because string theory is not a testable theory right now. It won't be disproven even if there won't be any signal of SUSY in LHC. Why? Because SUSY is not going to be disproven either... it will lose or come very close to losing its ability to solve the hierarchy problem, and that's all. Strings can send SuSy scale at any value.
So even if you won't find SUSY at TeV scale, string theorists won't care that much... they will say it's in the $10^{15}GeV$ (the number is randomly taken). And so on..
Maybe some phenomenological string theories, that were trying to reach the MSSM, will fail...

If you like it, and have what it needs [from mathematical point of view], go for it...
From mathematics, because I don't know what means mathematical physics for you, I'd say topology and differential geometry, group theory...
From "physics" you won't need much...

4. Dec 18, 2014

Probably after QFT I and ideally II. Three of my friends took our Polchinski based course this semester. They were taking QFT I but had taken it before. Everyone in the class thought it was really difficult, a lot of conformal field theory.

5. Dec 18, 2014

### Haelfix

If you have taken quantum field theory and have done well in it, you can learn string theory. It's going to be difficult no matter what level of background you have, simply b/c it requires rather esoteric knowledge from several places in theoretical physics. You have to have mastered GR, QFT, and ideally have a working understanding of semiclassical gravity and conformal field theory. The texts typically start from a rather unfamiliar setting as well, since they typically use the Schwinger proper time formalism which is usually supplemental material in a qft course.

Most of the texts will review this material, but as usual it helps immensely if you have seen it before.

6. Dec 18, 2014

### physicsfirzen

Thank you all for the suggestions!