eiyaz said:
...am i correct in saying that string theory is in danger? ...
I wouldn't disagree either with what you said, or with what Haelfix said (already back in 2004) that I just quoted. But I'd put it in my own words somewhat differently.
I think there is a String
program, a well-populated and entrenched research enterprise, that is partly in some aspects in danger, but also in other respects not in danger.
I don't think there is anyone unique physical String
theory that accomplishes unification and matches known low-energy particle data. More importantly there is no one
useful theory, matching known particle physics, that theorists can actually calculate with.
So (as a non-expert, subject to correction) I would say that if there is no theory then it cannot be in danger.
However there is a well-populated busy research program, and this is PARTLY in danger of losing prestige, jobs, funding etc. It is partly in danger of being seen as NOT TERRIBLY USEFUL on the unification/basic theory front.
Now we are getting signs of "no SUSY"---there was what you mentioned but also in the past couple of months some preliminary notices from the LHC people. A quiet gradual revision of expectations, subtle change of mood. Then there was the unfavorable news about first-time faculty JOBS. We might also be seeing symptoms like an increased defensiveness, more excuses, more attacks on rival non-string QG, etc. I'm not sure about that, but it could happen.
On the other hand there is this big healthy body of stringy mathematical METHOD which can presumably be applied to a lot of other stuff besides unification. The String program can gradually change character so as to be less directly concerned with a fundamental theory of nature and more concerned with finding applications of method.
The picture is certainly not all bad!
If I were involved, what I would probably be most concerned about is the quality of incoming string PhD students. Are they as bright, independent-minded, talented as those who were entering string say 10 years ago?
My intuitive feeling is that a smart young person entering grad school now might prefer to go into cosmology (with just a dash of stringy seasoning) or into condensed matter (with perhaps some string-related method). Those who are now making a full commitment say to string phenomenology might be among the less talented or less alert. It is hard to gauge but nevertheless the kind of thing one ought to watch out for.
You brought up the topic of dangers---I guess my view would be that the interesting and possibly significant ones are dangers to the program (its academic prestige and the other things that go along with that, like ability to recruit talent etc). We just have to wait and see.
I think you are definitely right about the declining odds of SUSY (and regardless of whether logically necessary it does impact the perceived usefulness.)
==EDIT==
Haelfix, thanks for the update on your earlier POV. Always interesting. I will copy so it doesn't get covered up by this post:
Haelfix said:
I wrote that statement (in 2004!) when I was still a first or second year grad student thinking mostly as a phenomenologist. Once upon a time the whole purpose of S.T at least for people in my neck of the woods was to be able to write down low energy MSSM models and ask questions about the sort of allowed or natural objects or schemes. Nowdays the applications are much more varied and far more subtle.
I think it is pretty clear that you can have interesting phenomenology without weak scale SUSY which wasn't particularly apparent or exploited as much at the time (alternatively I just didn't know about those models) and I also think I have a greater appreciation for gauge-gravity dualities which in a sense makes the whole premise moot (it would be akin to asking whether QFT can ever be proven wrong).
There you go evolution in thought at work. The former is more a pov for a straightforward unification paradigm, the latter is a much more subtle take on what it means to be a theory of nature.
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