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Physical reality of string theory demonstrated

by mesogen
Tags: demonstrated, physical, reality, string, theory
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mesogen
#1
Jul6-09, 10:38 AM
P: 25
http://www.eurekalert.org/pub_releas...-pro070309.php

Well, according to this article, at least.

String theory has come under fire in recent years. Promises have been made that have not been lived up to. Leiden theoretical physicists have now for the first time used string theory to describe a physical phenomenon. Their discovery has been reported in Science Express.

'This is superb. I have never experienced such euphoria.' Jan Zaanen makes no attempt to hide his enthusiasm. Together with Mihailo Cubrovic and Koenraad Schalm, he has successfully managed to shed light on a previously unexplained natural phenomeon using the mathematics of string theory.
http://www.sciencemag.org/cgi/content/abstract/1174962

Just thought I'd share.

Problem is, they didn't entirely describe high temp superconductivity.

O well.
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humanino
#2
Jul6-09, 04:09 PM
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I'm not quite sure what's new here
Fermions and the AdS/CFT correspondence: quantum phase transitions and the emergent Fermi-liquid
Maybe I misunderstand, but it seems to me that it would be quite disappointing if a fundamental theory would be confirmed by the prediction it does on the effective long range behavior of electrons in metal. Not that it is not interesting, but the hope is that it going to help with the opposite end of the spectrum, where gravity is relevant. Namely, the standard model should be able to produce the same results if we could perform the equivalent calculation. This last point, which has little to do with the relevance of string theory to describe Nature at a fundamental level (hence little to do with "demonstrating it") is quite interesting in its own.
gendou2
#3
Jul6-09, 07:08 PM
P: 235
So, string theory (more accurately AdS/CFT) explains behavior in this one case where no other theory yet has, right?
That's pretty cool, but is this really the first time such a thing has been accomplished?

In any case, this does not at all "demonstrate physical reality" of the theory!
To me, "demonstrating physical reality of a theory" means that your mathematical model is shown to be more useful or more accurate than previous models.
This paper seems to promote optimism, which is good, but has nothing to do with the completeness of string theory.

Misleading title on a science news article? That's old news. lol

humanino
#4
Jul6-09, 07:42 PM
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Physical reality of string theory demonstrated

Quote Quote by gendou2 View Post
That's pretty cool, but is this really the first time such a thing has been accomplished?
Not at all. In the realm of QCD, you will find several articles per month during the last 2 or 3 years where model calculations, often quite simple, allow new insights in the non-perturbative regime with astonishing agreement between data and those simple models, often increasing by one or two order of magnitudes, and also on much wider phase space, while respecting various analytical constraints (sum-rules, or other kinds of self-consistence, which were often believed to be quite hard and are now sometimes trivially respected). Yes, communication depends a lot on how easy it is to relate to the end result and/or the closeness of technological applications...

But it's true that the paper is fascinatingly beautiful !
gendou2
#5
Jul6-09, 07:54 PM
P: 235
Can the full text paper be viewed online for free? ;)
nnnm4
#6
Jul6-09, 09:00 PM
P: 113
Not right now sadly. Get to a University Library!
captn
#7
Jul7-09, 01:04 AM
P: 36
This may be available on the arXive---try 0904.1993 [hep-th].

Sorry, I don't know how to enter the address.


Neil
Demystifier
#8
Jul7-09, 03:16 AM
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Quote Quote by captn View Post
This may be available on the arXive---try 0904.1993 [hep-th].

Sorry, I don't know how to enter the address.
That's how:
http://lanl.arxiv.org/abs/0904.1993
It can be downloaded for free.
marcus
#9
Jul7-09, 11:03 AM
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Demystifier, thanks for the arxiv link! I will pass it on.

Coin had a cogent comment at Woit's blog:
"... One thing I’ll note is that the grandiose and wildly inaccurate claim of the headline– “Physical reality of string theory demonstrated”– does not appear to be a claim anyone with Leiden University has made. It was added by ScienceDaily (where I think this article originated?). In fact, it wasn’t even a claim made in the ScienceDaily article itself– the claim appears only in the headline, and is in no way supported by anything in the article itself (which is much more conservative in its phrasing). A consistent problem in science journalism is that someone will write a decent article and then an editor will tack on an “exciting” but wildly inaccurate headline which changes the tenor or content of the piece itself. (Actually this is a frequent problem in many other kinds of journalism as well, especially in politics– most people writing in traditional journalism have no control over their own headlines.) If you ignore the headline and just look at what Leiden University team actually did you’ll find it doesn’t have anything to do with “demonstrating the physical reality of strings” (although what they did do sounds actually pretty awesome and like a legitimately positive development for AdS/CFT as a research program)."
http://www.math.columbia.edu/~woit/w...#comment-49196

The usefulness of stringy mathematics applied to various other problems at altogether different scales has been shown already in several contexts. I think what Coin is saying is that the Leiden work does not show string validity as a fundamental description of nature, but rather shows the flexibility and agility of the mathematical resources that has grown up around string research.

In this case they applied the AdS/CFT correspondence, as part of their mathematical toolkit. The Phys.org article makes this clearer, although it has the same dubious headline about demonstrating "physical reality".
http://www.physorg.com/news166097923.html
Civilized
#10
Jul7-09, 11:05 PM
P: 164
On his blog Woit says:

The idea is to put out a press release announcing that string theory has finally lived up to its promise and shown its critics to be wrong, because of evidence it may work as an approximation method for some strongly coupled condensed matter or nuclear physics model.
I guess he doesn't know that the AdS/CFT duality is an exact correspondence, not an "approximation method." String theory consist of equations that describe relativistic quantized strings, and AdS/CFT allows us to test the validity of these equations. The only remaining question is whether quantized relativistic strings exist in nature on the scale of the Planck length, and AdS/CFT will continue to be silent on this subject, but the fact remains that the AdS/CFT duality can be and is actively being used to test the exact equations which make up string theory, it's not just a case of testing the general sort of mathematical techniques that are involved in string theory, but rather the quantized string dynamics, the predicted spectra, etc. Therefore these tests using AdS/CFT are verifying that we have found the correct description of quantized relativistic strings, and as I said the only remaining question is whether these exist in nature at the scale of the Planck length.
atyy
#11
Jul7-09, 11:19 PM
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Quote Quote by Civilized View Post
I guess he doesn't know that the AdS/CFT duality is an exact correspondence, not an "approximation method."
I thought the approximation was because the duality applied to supersymmetric versions of the theories in question, whereas the theories themselves were not supersymmetric?
marcus
#12
Jul7-09, 11:43 PM
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Quote Quote by Civilized View Post
On his blog Woit says:...
I guess he doesn't know that the AdS/CFT duality is an exact correspondence,...
You are referring to a post at N.E.W. that has not been linked-to yet in this thread or anywhere on Physicsforums.
1. if you want to take something out of context from a blog and criticize it, how about giving a link to the blog post you are quoting? Many of us here will not have read the blog post you are quoting.
2. If you think there is an error in the Woit blog you quoted, why not take it up directly there at the blog? Until some 5 minutes ago there were as yet no comments responding to that post.
It would be more "Civilized" to challenge the person openly and give him a chance to reply to the aspersions cast, than to make what may be straw man innuendo over here out of sight.

I don't believe Woit said anything about AdS/CFT being itself inexact, but you pretend he said the correspondence was an approximation (not that what it is being applied to is) and make a show of correcting the 'mistake'. I urge you to take that up directly with woit.

To correct the omission I copied the comment at Woit blog, giving him the opportunity to respond if he cares to, and thinks it worth his while. It is now the first comment to that new post:
http://www.math.columbia.edu/~woit/wordpress/?p=2172
humanino
#13
Jul8-09, 12:25 AM
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In an ideal world, Woit would be right right about the authors responsibility against the title, but it is quite possible that the title was changed without him having any control or even being noticed, and Woit is responsible for permanently feeding the sterile pseudo-debates which spoil the scientific content of even this very sub-forum. Should the authors resign from their positions ? As far as I can tell, the free paper I linked to in the arXiv is perfectly respectable in this regards. Civilized is obviously wrong about Woit, and I doubt Woit would care.
tom.stoer
#14
Jul8-09, 12:34 AM
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I am sorry to ask this question over and over again, but I still was not able to find a reference were AdS/CFT is shown to be exact. All I know are
- claims that this is the case
- arguments coming from large-N and other limits were a correspondence between certain regimes can be established

Are there articles were this missing link is discussed?
Civilized
#15
Jul8-09, 12:35 AM
P: 164
Quote Quote by atyy View Post
I thought the approximation was because the duality applied to supersymmetric versions of the theories in question, whereas the theories themselves were not supersymmetric?
OK, that would explain the use of the word "approximation" for the application of AdS/CFT to QCD, but in the same line Woit also mentions "strongly coupled condensed matter" systems, for which the duality is being applied directly to Hamiltonians we care about, as opposed to Lagrangians that are only similar to he ones we care about asin QCD/CFT.

You are referring to a post at N.E.W. that has not been linked-to yet in this thread or anywhere on Physicsforums.
I found the statement through the link in your previous post, Marcus, and furthermore it is the most recent post on the top of Woit's blog, discussing the same press release and its derivatives which are the subject of this thread. Also, you might be interested to know that you can copy a string of text and put it into Google search surrounded by quotation marks to have the search engine locate and display pages which contain only that exact string of text, and that the statistical likelihood of any one of the uncommon phrases in the Woit quote I provided being found anywere else is so low that in practice one can use this technique locate the page I was quoting.

According to Lubos Motl:


Let us return to our original questions: are these "mundane" methods relevant for unification? You should be able to guess the answer. There are two important facts you should have in mind:

(1) The holographic duality is exact, at least in principle.
(2) The equivalence is a relationship that symmetrically applies in both ways.

Because of these two reasons, it is incorrect to say that AdS/QCD and AdS/CMT are "just" approximate methods to study nuclear physics and condensed matter physics.
Source: http://motls.blogspot.com/2009/02/ar...evant-for.html

Motl is closer to being an expert on AdS/CFT than either Woit or myself, his blog is widely read by the professional string community, and he has published well-cited articles with mainstream string theorists in the recent past. Regardless of what people think about Motl, look him up on SPIRES and compare him to Woit (or yourself), and I consider myself to be in good company if I am echoing his sentiments (incidentally, I had not read his blog post untill I made my comment).

Civilized is obviously wrong about Woit, and I doubt Woit would care.
(1) Humanino is obviously wrong about Civilized, according to Lubos Motl.

(2) I am disappointed that Marcus would copy my statement to Woit's blog without my permission. Looking at his professional record I am forced to conclude that Woit is an untenured ex-mathematician who has not contributed a peer reviewed scientific publication in over 15 years, and in my opinion he has recently done a lot of harm to physics with his anti-mainstream activism. As far as I am concerned, the less attention his blog gets, the better off physics will be.
humanino
#16
Jul8-09, 12:38 AM
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Quote Quote by tom.stoer View Post
shown to be exact
No such thing is available, it's a conjecture.
atyy
#17
Jul8-09, 12:46 AM
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Quote Quote by tom.stoer View Post
I am sorry to ask this question over and over again, but I still was not able to find a reference were AdS/CFT is shown to be exact. All I know are
- claims that this is the case
- arguments coming from large-N and other limits were a correspondence between certain regimes can be established

Are there articles were this missing link is discussed?
Yes, I think so. The claim is that the correspondence is exact, but the claim is not yet proved. http://arxiv.org/abs/gr-qc/0602037
Civilized
#18
Jul8-09, 12:47 AM
P: 164
Quote Quote by humanino View Post
No such thing is available, it's a conjecture.
Of course this is true, but I would also add that mathematically speaking the existence of quantized gauge theories is itself only a conjecture, and that this would be a necessary prerequsite for a rigorous proof of the duality. In other words, the existence of QCD is "just" a conjecture. Rigorous proofs lag behind more than 30 years in high-energy physics, and they are not the right yardstick to apply.


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