Europe's most influential string theorist has an overview piece in Nature

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  • #26
josh1
Well what I was saying is that there are two aspects in the defense of string theory: "broad string theory", which includes things as AdS/QCD and Duff Brane theory, and "unique string theory", which is the D=10 quantum stuff. Some people can defend an aspect without defending the other, some people can defend both.

Now, if AdS/QCD were related to "unique string theory", I would think it vindicates, somehow, old Veneziano et family approaches but it diminishes the interpretation of strings as fundamental blocks at Planck scale. If on the contrary AdS/QCD is about "broad string theory", it does not add any bit about quantum gravity.
Who thinks this way? I believe that these remarks really represent you're own peculiar point of view and provide no real basis to doubt string theory. I certainly feel no need to defend string theory against them and continue to have no doubt that the ideas in Nicolai's work quite obviously have their origins in string theory as it is understood by most string theorists, a group to which you quite clearly do not belong.
 
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  • #27
arivero
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Who thinks this way? I believe that these remarks really represent you're own peculiar point of view and provide no real basis to doubt string theory
Could we agree that in the same way that AdS/QCD does not provide basis to doubt string theory as a fundamental theory, it does not provide basis to support string theory as a fundamental theory?
 
  • #28
josh1
Could we agree that in the same way that AdS/QCD does not provide basis to doubt string theory as a fundamental theory, it does not provide basis to support string theory as a fundamental theory?
AdS/QCD of course cannot all by itself serve as a basis to support string theory (by which I always mean the putative underlying theory that contains more than just strings) as a fundamental theory. But when viewed in the context of all the other interesting things that have come out of string theory, especially AdS/CFT, it doesn't exactly cast doubt on the idea of string theory as a fundamental theory either.

This is a convenient place to tell you that in my opinion, the real problem with research in string theory and other theories as gravitational theories is that people are not concentrating more on trying to understand the gravitational physics of the vacuum. For example, it may be that the motivation for the landscape is based on a misunderstanding of what the observed small positive cosmological constant actually means and when we do understand it the landscape, eternal inflation, the anthropic principle, and all the other ideas I personally find unpleasant will disappear. It will almost certainly provide a set of powerful selection criteria for current and future ideas.
 
  • #29
arivero
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AdS/QCD of course cannot all by itself serve as a basis to support string theory (by which I always mean the putative underlying theory that contains more than just strings) as a fundamental theory. But when viewed in the context of all the other interesting things that have come out of string theory, especially AdS/CFT, it doesn't exactly cast doubt on the idea of string theory as a fundamental theory either.
It is a question of feel, I guess. To me a final theory can (must?) have strong math links with special structures, and I acknowledge that superstrings have all these SO(8) and octonionic thingies, plus the monster group nearby, plus Leech lattices. But the links with other physical constructs, to me it is not a merit but a demerit. As a minimum, it hints that string physicists are not focused in the uniqueness goal.

Worse, this lack of focus seems to imply that string theory is just a math framework where you can find a lot of results, some related to gravity, some to elementary particles, some to other different objects. First time I heard of the argument of using strings because you automatically get gravity, I turned back because to me the surprising thing had been the opposite: to scan the space time with two-dimensional objects in a intrinsic way, and still not to find any clue of Riemannian curvature. Or to gauge supersymmetry and do not find gravity. Or to use spin two particles and not to find attractive forces. "C'mon", I though, "to find gravity with the string and superstring mathematical structure is no more surprising that to find gravity when studying pseudo-riemaniann manifolds, for an instance"

This is a convenient place to tell you that in my opinion, the real problem with research in string theory and other theories as gravitational theories is that people are not concentrating more on trying to understand the gravitational physics of the vacuum.
I could agree but for a strange reason: because the problem of the vacuum in quantum field theory is a problem that happens in the electroweak scale, so I think this is the scale which must be solved first, and gravity will come later, as a ripe fruit fells from the tree (this is actually a Spanish expression, not a reference to Newton).

A problem is that gravitational physics of the vacuum is near to fringe topics. For instance, in the guess posts of Dorigo you can find one from Rick Ryal along these lines.
 
  • #30
marcus
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By the way, a propos of that, it was a good idea of Dorigo to invite you to the rostrum at his blog.
I used to see Geoff Chew in the hall when I was in the physics building at Berkeley---he only went emeritus in 1991.
I wonder why I never heard that pun until now about S-matrix being Chewish physics, maybe because it is too terrible for anyone to have thought of in those days.
Enjoyed your guest post there and hope you get a return invitation.
 
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  • #31
arivero
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I wonder why I never heard that pun until now about S-matrix being Chewish physics,
The pun is told by David Gross, who once was told "you dont look Chewish" or something so. http://impunv.blogspot.com/ also uses the word, as in "are you a member of the Chewish religion".
 
  • #32
marcus
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Aaarghh!
(what else can I say?)
 
  • #33
arivero
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Aaarghh!
Of course string theory has nothing to with science, nor is it meant to. It is purely a religion (and like a religion ignores what experiment --- reality --- requires). Replacing science by religion is not unusual in physics. A half century ago, for example, there was much excitement about ideas extended from dispersion relations, involving smoothness of surfaces. Its center was at Berkeley and its leader was Geoffrey Chew. There was so much excitement that people at Berkeley asked each other "are you a member of the Chewish religion?". That idea had no real rationale and was wrong but was not crackpot.
This is the parragraph by R. Mirman, in the aforementioned blog. The other reference, the one of Gross, is older, told in a paper titled "Nuclear Democracy". This paper also tells that Chew method, back in Berkeley, was to run simultaneusly a a good quantity of student research, grouped around another of these "secret seminars" where seniors are discouraged. This has as result that a lot of people got involved on Chew's quest; I think that even one or two of the PF regulars.
 

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