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:Whoever added that tag should have posted something. Tagging and running is not good form. However, after taking a look, I suppose it has something to do with so many sections carrying no citations, several others only carrying one, and usage of the present sources in such a sparse manner (there are only 52 inline citations for a very large article). I even found an unsourced explanation in reference #15. <span style="font-size:0.75em; color:white; background-color:black; border-radius: 4px;"> —[[User:Sowlos|<span style="font-weight: bold; color:white;">Sowlos</span>]] </span> 10:36, 26 July 2013 (UTC)
== The "Criticisms" section ==
I think this section can be improved. In the current version, three specific criticisms are mentioned, but the first ("High energy") just says unification theories are hard to test because of the high energies. That seems like a very generic fact, not a specific criticism of string theory. As the article says "It is widely believed that <i>any</i> theory of quantum gravity would require extremely high energies to probe directly, higher by orders of magnitude than those that current experiments can attain". Since this is widely believed to apply to <i>any</i> theory of quantum gravity, is it really appropriate to list it as a criticism of string theory? Notice that the article already has a Section on "Testability and experimental predictions" that mentions the same thing, so it's redundant. I suggest moving the words in the existing "High Energy" paragraph of the "Criticisms" section up to the "Testability" section. It would be okay to refer to this again, in passing, in the criticism section, but make it clear that it's not specific to string theory.
Having done that, I think the remaining Criticisms section could be beefed up with some more of the actual criticisms that have been raised specifically about string theory, such as those discussed in Penrose's book (e.g., degrees of functional freedom, questions about actual finiteness), and also criticisms of the "multiverse" aspects.
In addition, I think this might be the appropriate place to at least mention some of the methodological and sociological concerns that critics have raised regarding string theory. For example, the criticisms claiming over-hyped pronouncements in the popular media, concerns about too much focus on one particular (and highly speculative) avenue of research, lack of any clear principles or understanding of what string theory actually <i>is</i> according to its own proponents, excessive reliance on formal mathematical and aesthetic criteria rather than being guided by experiment, indeed being more about mathematics than physics, etc.
Also, I think the current section on "Number of solutions" could be clarified. It refers to "lack of uniqueness of predictions due to the large number of solutions", but this seems like an obtuse way of describing the actual criticism, which is (rightly or wrongly) that string theory (in its present state) makes no testable predictions at all. This seems like a more direct and clear way of expressing the criticism, rather than saying "critics charge that string theory has a large number of solutions, so its predictions lack uniqueness". (If I predict that either the American league or the National league team will win the world series, would that be best described by saying my prediction lacks uniqueness, or by saying I haven't really made a prediction at all?)[[User:Longerboats5|Longerboats5]] ([[User talk:Longerboats5|talk]]) 15:14, 13 August 2013 (UTC)
:Let me begin by saying that I agree with much of what you say. I agree that the point about high energies is not a criticism of string theory per se, and I think it's fine to move most of this discussion to the section on "Testability and experimental predictions". I also think it should be mentioned in passing in the "Criticisms" section. I agree that the section should probably discuss the sociological concerns that critics have raised. Since these criticisms are more subjective, the best way to do this would be to include quotes from prominent critics.
:On the other hand, I disagree with what you're saying about some of the technical points that Penrose has raised in his book. I would argue that some of his points are not completely accurate, and I think that discussing these points in the article would give them undue weight. For example, the point about the discrepancy in degrees of freedom in the AdS/CFT duality is a very idiosyncratic view expressed in Penrose's book. As far as I know, there is no other critic who has questioned the correctness of the duality in this way. On the other hand, there are literally tens of thousands of articles which study various aspects of AdS/CFT and find that it works exactly as expected. In many cases, we have a detailed understanding of exactly how the degrees of freedom in string theory map to degrees of freedom in the boundary conformal field theory.
:As the article says, the real problem with string theory is that it has a very large number of solutions. Given a particular compactification of the theory, it's possible to come up with predictive models, and indeed, there are models with large extra dimensions that have been ruled out by the LHC. The problem is that there are many different compactifications of string theory that lead to realistic models of low-energy physics, and therefore it's probably not possible to uniquely predict coupling constants and particle masses from string theory.
:One does sometimes hear the claim that "anything goes" in string theory, but this is not quite true, and I'm afraid that treating it as a legitimate criticism would compromise the technical accuracy of the article. There are definitely some observable phenomena that are not predictions of string theory. For example, if the Fermi satellite discovers violations of Lorentz invariance near the Planck scale, then string theory would not be a viable fundamental theory. Similarly, if we ever discover that the fundamental constants are time-dependent, then string theory could not be right.
:So to summarize, there are ways in which the "Criticisms" section could be improved. String theory models are in general very difficult to test, and the article should reflect this fact. But I think it's difficult to include all of these criticisms without compromising accuracy as some of these criticisms are known by the experts to be invalid. [[User:Polytope24|Polytope24]] ([[User talk:Polytope24|talk]]) 22:00, 13 August 2013 (UTC)
:: I agree that the article should avoid giving undue weight to technical criticisms that have been stated by just one individual (e.g., Penrose's degrees of freedom arguments). The focus should be criticisms that have been voiced in multiple sources. On the other hand, I'm not sure the article needs to necessarily exclude criticisms of string theory solely based on the fact that string theorists (even in "tens of thousands of papers"!) believe the criticisms are invalid. Indeed one of the meta-criticisms is the alleged group-think mentality, whereby a whole community is mistaken about something, so I'd be wary of using the "all string theorists know this criticism is invalid" criterion to decide - even if we were trying to decide, which of course we aren't. We're not here to pass judgement on the validity of the criticisms, merely to report them, in a balanced way, <i>if</i> they meet the notability and verifiability criteria. It's tricky, because there are notable, reputable, and verifiable sources (e.g., Penrose) that have voiced criticisms, and yet we may decide not to mention them to avoid giving undue weight to ideas that the experts know to be invalid. I suppose an alternative would be to mention those criticisms and then include caveats explaining that string theorists do not regard them as valid criticisms - but that might get tedious. Having said that, I guess it's okay to omit criticisms that are unique to any single individual, so I'd agree to not mentioning (for example) the degrees-of-freedom arguments - unless someone finds additional sources for it.
:: I think lack of falsifiability is a criticism that has been voiced by many people, including string theorists themselves. For example, the section could include some quotes from Weinberg, such as <i>"Since the 1980s string theory has not come up with a prediction of anything new that we could then verify in the laboratory in a way that could convince us that string theory is right"</i>, or <i>"The critics are right. We have no single prediction of string theory that is verified by observation. Even worse, we don’t know how to use string theory to make predictions. Even worse than that, we don’t really know what string theory is."</i> Many people, even many prominent string theorists, have made similar comments, so I think it would be okay for the Criticisms section of this article to convey a stronger sense of this criticism. Right now the article gives the impression that the theory is criticized for making <i>too many</i> predictions, whereas I think the general sense of the criticism is that no one has identified any firm prediction of string theory. Maybe it's semantics, like my baseball analogy, between too many predictions = no prediction. I understand your desire not to give the impression that "anything goes" in string theory. There's obviously some structure to each of the possible solutions of each possible development of string theory (so to speak), but I think the criticism is that there is enough flexibility so that it can't really make any firm prediction. We could cite Rovelli's comments on this:
::: <i>"The main shortcoming of string theory is definitely its failure, so far, to produce any concretely verifiable physical prediction. To be sure, string theory has provided numerous “predictions”, like short scale modifications of the gravitational force, black holes at CERN, dielectron resonances, or the existence of supersymmetric particles at low energy, but so far all these “predictions” have been falsified by observation. The theory has survived these failed predictions, because they were not solid predictions, but only hints of possibilities, effects compatible with the theory, but not necessary consequences of the theory. The real problem is that the theory does not appear, so far, to have any verifiable necessary consequence at accessible scales... If there is an accurate string description of the real world, then there are probably so many of them to make the discovery of the right one virtually impossible and in any case devoid of predictive power."</i>
:: To me, this kind of wording better conveys the sense of the criticism than the current wording in the article about "too many solution", which makes it sound like an over-abundance of goodness.
:: By the way, I would be wary of citing things like Lorentz invariance or gravity as falsifiable "predictions" of string theory. I know people sometimes say things like that, but I don't think those statements are taken by many people to represent the kind of predictions that Weinberg (for example) says are lacking.[[User:Longerboats5|Longerboats5]] ([[User talk:Longerboats5|talk]]) 04:34, 15 August 2013 (UTC)
:::That describes many of string theory's shortcomings as as scientific theory succinctly and would make for a very good quote in the criticism section, however if we collect a few reputable sources essentially saying the same thing (which is not hard), we can put it in our own words.<span style="font-size:0.75em; padding:1px; border:1px solid black; border-radius: 3px;"><span style="background:black; color:white;"> —</span>[[User:Sowlos|<span style="background:black; color:white;">Sowlos </span>]]</span> 07:49, 15 August 2013 (UTC)
== "Theory" vs. "research framework" ==
I'm going to go ahead and change the first sentence to say that string theory is a "physical theory" rather than a "research framework". If anyone disagrees with this description, I'd be happy to discuss it here.
My worry is that using the term "research framework" will give the impression that there are many different types of string theory. This is a very common misunderstanding. When physicists talk about "string theory" they're talking about a ''unique'' mathematical structure that cannot be modified without spoiling its consistency. There are, of course, many different models constructed from string theory, but these are all just solutions of the same ten-dimensional theory. The existence of these solutions does not make it a framework rather than a theory. You could argue, I suppose, that the existence of string theory is still conjectural in the sense that we don't have a non-perturbative formulation of the theory, but this does not mean that string theory is merely a research framework.
[[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 22:32, 10 May 2013 (UTC)
:It goes way back to this edit [[http://en.wikipedia.org/w/index.php?title=String_theory&diff=437889230&oldid=437836457]. There is an ambiguity with the word "theory". String 'theory' is ''not'' a theory in the sense of a 'group of hypotheses that have been supported with repeated testing'. So we agreed to replace 'theory' with 'mathematical framework' and eventually 'research framework'. [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 17:17, 11 May 2013 (UTC)
::Can't there be untested theories? Under your definition, most of the quantum field theories that physicists study are not really theories... [[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 20:37, 13 May 2013 (UTC)
:::[[scientific theory]] - "A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of knowledge that has been repeatedly confirmed through observation and experiment." String theory just isn't a theory in that sense of the word. [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 00:55, 14 May 2013 (UTC)
::::Okay, so string theory is not a theory in that sense. Neither is [[supersymmetric gauge theory]], [[supergravity theory]], [[Chern-Simons theory]], [[Seiberg-Witten theory]], [[Liouville field theory]], [[noncommutative quantum field theory]], or any number of other things that physicists call "theories". [[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 06:08, 14 May 2013 (UTC)
::::: [[Quantum field theory]] says it is "a theoretical framework", it doesn't say it is a theory and most of your links don't say they are theories. Anyway it is best not to be ambiguous, and "theory" in a science article would seem to mean [[scientific theory]] [[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 07:14, 14 May 2013 (UTC)
:::::: It is appropriate to say that quantum field theory is a "theoretical framework" because the term "quantum field theory" does not refer to a specific theory for describing nature. Rather, it is a huge class of theories obtained by quantizing classical field theories. The resulting theories include all the ones I listed above, as well as more phenomenologically interesting ones like ordinary Yang-Mills theory.
:::::: The difference between quantum field theory and string theory is that while there are lots of different quantum field theories, there's only one unique mathematical structure called string theory. This is an important point that should be emphasized in the article.
:::::: The definition in the [[scientific theory]] article is obviously trying to distinguish between the notion of theory used in science and the colloquial notion of theory. That's fine, but it doesn't capture all the different ways in which the term "theory" is used in science. As I've been saying, it's very common in mathematical physics to use the term "theory" for a particular collection of mathematical data (a state space, an algebra of observables, etc.) even if such a "theory" is not a realistic model of physics. This is absolutely standard and, I think, completely appropriate for an article on string theory. [[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 08:29, 14 May 2013 (UTC)
I can corroborate what 208.46.240.4 is saying regarding the use of the term "theory" in science. As a child I was taught that the term "theory" in science was reserved for well-tested and established sets of ideas, but as a professional scientist I can say with certainty that that is not at all how the term is used among actual scientists. (And considering that the title of the article - and the universally accepted name for the subject - is "string theory", it's a bit silly to argue that it is not a theory.)
However, I do not entirely agree that string theory is as unique as 208.46.240.4 says it is. While the five SUSY string theories are probably all related to each other by dualities, that's not exactly the same thing as saying that they are the same theory, nor is it well-understood how bosonic string theory is connected to them. Then there are theories like the little string theory on NS5 branes, non-critical string theories, confining gauge theories and whatever it is that is holographically dual to them, etc.
So I do think there's an important point that "research framework" may have helped get across, namely that we don't really know what kind of string theory describes the world, if any, and that much of the research in the field is not focused on that question specifically, but rather on understanding the mathematical breadth and structure of the theory.
Let me add that I think 208.46.240.4's edits to this article have been excellent across the board, and have significantly improved it. Thanks very much! <small>'''<span style="color:Olive">Waleswatcher</span>''' [[User_talk:Waleswatcher#top|''(<span style="color:green">talk</span>)'']]</small> 19:51, 14 May 2013 (UTC)
:Thanks for the comments and praise! You're right that there are different kinds of string theory if you count bosonic string theory, noncritical string theories, etc. I am open to suggestions on how we could include these topics in the article.
:I also strongly agree with what you're saying about string theory research. Much of the current research focuses on the mathematical structure of the theory and the relationships between different mathematically interesting QFTs. In my recent edits, I've been trying to change the emphasis of the article to focus on these topics. [[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 22:23, 14 May 2013 (UTC)
::Are we ok with going back to "research framework"? Waleswatcher agreed that it helped and as he says there are 5 string theories[[User:Bhny|Bhny]] ([[User talk:Bhny|talk]]) 04:26, 29 May 2013 (UTC)
:::Okay, I changed it back to framework, but I'm still not completely comfortable with this phrase. I think the article needs more work to emphasize the uniqueness properties of string theory. There's a lot of confusion about this point. For example, Bhny writes that "there are 5 string theories", but this completely misses the point that Waleswatcher was making. These five string theories are all supposed to be "equivalent" in some sense so that there's really only one string theory. If you're going to talk about multiple string theories, you're talking about things like bosonic and noncritical string theories, which are not viable theories of particle physics. [[Special:Contributions/208.46.240.4|208.46.240.4]] ([[User talk:208.46.240.4|talk]]) 17:05, 31 May 2013 (UTC)
:I'm going to vote that string theory is a theory. I'm fairly sure physicists in general define 'theory' as 'a mathematically consistent model of something happening', regardless of whether or not it makes any attempt to be accurate to the real world. Pretty much, anything with a lagrangian is a theory, by a physicist's definition. Whether or not string theory really describes all real-world particles completely, and whether or not it makes any testable predictions, is not the issue. And if you insist on testable predictions, keep in mind that string theory does make many testable predictions - they're simply not feasible with current technology. Much like nobody was going to make a higgs boson back when Higgs first talked about it. [[User:KagakuKyouju|KagakuKyouju]] ([[User talk:KagakuKyouju|talk]]) 07:26, 18 November 2013 (UTC)
== Three spatial dimensions implied (in inflation)? ==
See my question in: [[Talk:Inflationary epoch#Three spatial dimensions implied|Talk:Inflationary epoch]]. I'm not sure string theory in considered contradictory to inflation. I think not. Short answer: Yes or no? Please answer my question I point to there, or at least not duplicate. If more appriopriate here (lengthy discussion likely) then point people to here if appropriate. [[User:Comp.arch|comp.arch]] ([[User talk:Comp.arch|talk]]) 14:52, 24 March 2014 (UTC)
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