Talk:String theory

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• Archive01: prior to January 2006

String hypothesis?

Given all of the noise being generated about evolution being "only a theory" and the responses to this that "a theory in science is as close to fact as you get," should not "String Theory," when used in Physics (as opposed to pure mathematics), be properly called "String Hypothesis" or "String Hypotheses?" Physics certainly has not verified strings in nature to anything close to the extent that biology has verified evolution. --DvTHex 04:24, 21 January 2006 (UTC)

In short, no. People call it string theory, so that's what Wikipedia should call it. The point is that the word "theory" doesn't make any judgment about the validity of a given idea. –Joke 15:02, 21 January 2006 (UTC)

Yeah, I cringe sometimes when I see people defending evolution simply on the basis of the word "theory" that is commonly used for it. In actual scientific usage (as far as I can tell), the heirarchy of "hypothesis" < "theory" < "law" that many learn in junior high simply doesn't get used. "Theory" seems to be used in practice to refer to any reasonably developed self-consistent model, whether it's been thoroughly tested or not. (Meanwhile, nothing's been newly called a "law" in over a hundred years, and "hypothesis" is usually only used to refer to ideas in a preliminary or less-developed state.) Of course, evolution is one of the best tested theories in all of science, but it's those tests that seal the deal, not the name "theory" that we happen to apply to it.

Having said all that, I think I have seen the term "string hypothesis" before. But in my mind, that would refer only to the underlying concept itself; the vast body of results and structure based on the hypothesis can only be called "string theory", whether it turns out to describe nature or not.--Steuard 17:58, 21 January 2006 (UTC)

"South Pole Neutrino Detector Could Yield Evidences of String Theory"

Here is a news report that might have some information worthy of this atricle. —The preceding unsigned comment was added by 24.42.118.244 (talk • contribs) 16:14, 28 January 2006 (UTC)

Anon comment

I don't think the string has so much dimensions but capabilities. The string would need to built of a super partical that operates in all dimensions. A Dimension is a concept. strings are built of super particals. the universe is a Haze of identical particals. how can I explain. . . like cells in the body. All cells are basically the same but choose to take on different functions to support a fully functioning body. All particals in the universe are ultimately the same they take turns in managing energy and motion in different dimensions. Thats why strings vibrate in so many ways. Its like a shimmer across the strings surface as each superpartical rotates work. like an octopus skin changing color.

Is that correct??. . the partical would be immensily complex yet not complex at all. it has no begining or end it is a cirlce. . a 10 11 26 or whatever dimensioned circle. the number of capabilities depend on the number of dimensions.

How many different properties of the universe are need in order to have the universe sustain itsself. Is it actually sustaining its own operation. . How long in relation to what exists beyond the universe is a second. What exactly is the universe?? Why does it move in way it does. What makes a string??? Find out what makes a string and you have found the first piece of the puzzle. What is a super partical how are they woven into a string. —The preceding unsigned comment was added by 194.237.142.11 (talk • contribs) 16:07, 2 February 2006 (UTC)

Not to beat down the new guy, but this talk page really needs a statement to the effect: Please only make comments relevant to improving the string theory article. Please refrain from rambling on about your personal philosophy of what you think string theory may or may not be. See Wikipedia:Talk page guidelines. -- Fropuff 16:53, 2 February 2006 (UTC)

What you have described have nothing to do with string theory. Dan Gluck 19:14, 14 September 2006 (UTC)

Weird anonymous deletions

Some IP has been deleting things from the tallk page. Cf. this edit and these edits. I didn't check back further. The IPs check out as in Ontario, Canada. Probably nothing to worry about, but worth keeping an eye out for. –Joke 22:52, 13 March 2006 (UTC)

String theory is indeed testable and falsifiable and verifiable

To say that string theory is not testable is incorrect. String theory can be tested by picking up an ball and observing it leave your hand and hit the ground. This is called gravity. String theory predicts gravity. Gravity has been a confirmed prediction of string theory. I will soon remove all statements from the article that claims that string theory is not falsifiable, because it is not true.Atraxani 04:36, 19 March 2006 (UTC)

I assume by the absense of any responses that all of you agree with me.Atraxani 00:18, 20 March 2006 (UTC)

What an odd claim. A "test" of string theory must by definition distinguish between it and other theories purporting to explain the same physics. Your "drop a ball" test fails to distinguish between string theory, general relativity, Newtonian gravity, or even "fixed -9.8m/s^2 radial acceleration". Also note that gravity is a "postdiction" of string theory: truly convincing tests would involve predictions of previously unobserved phenomena. (Mind you, even just getting the known particle spectrum right would probably be plenty for me.)--Steuard 18:22, 20 March 2006 (UTC)

String "theory" is not a complete theory but rather a collection of interesting theoretical ideas. There are many many different string models and none of them (as yet) make contact with the Standard Model. The big problem (as I as an experimental physicist see it) is that there is still SO much freedom in string theories that pretty well anything we discover at the LHC won't be able to kill it. As for Atraxani's comment, since string theory can't begin to answer the question "How many different types of higgs particles are there?", (or rather, as it CAN answer it with any number experimentalists eventually detect) the theory in this respect is not testable. When someone makes a string theory that connects to the Standard Model I will be very impressed. Until then the use of the word "theory" in String Theory is just wrong.141.151.89.144 02:17, 3 July 2006 (UTC)

The two tests I know of is discover supersymmetry and detect the graviton. Neither one would actually test all of string theory. I do not think all of string theory is testable. Read the interviews on http://www.pbs.org/wgbh/nova/elegant/ . What experiment or observation will tell us that strings are the building blocks of matter? Timothy Clemans 02:49, 20 March 2006 (UTC)

Bad Sentence in History Section

The 7th paragraph starts with "Roughly between 1984 and 1986, physicists. . ." The last sentence of this paragraph has errors. Originally, I isolated a couple, but it is better to replace it than to try and fix it.

For a very long time it was completley forgotten about but recently it has been brought back and is one of the most worked

on theories because if it can be proven it can explain the origin of the universe and everything else.

could be replaced by

Since shortly after this time to until very recently, this theory has been almost completely disregarded. It now has

significant effort and research being invested into it, as it has potential to give insight into the origins of matter.

To say "and everything else," is a terrible thing to have in any essay or definition. If there is a long list of items correted, then a brief list of those items would be applicable, otherwise it is ambiguous dogma.

deleting a formula

The formula explaining why there are 26 dimensions is meaningless without explaining what the simbols (such as \rho) stand for. Since there is a reference cited anyway, I am deleting the formula. Shokopuma 20:08, 1 May 2006 (UTC)

Falsifiable vs. predictive

String theory as a whole has not yet made falsifiable predictions that would allow it to be experimentally tested . . .

Since string theory may not be tested in the foreseeable future, some scientists have asked if it even deserves to be called a scientific theory: it is not yet falsifiable in the sense of Popper.

yeah back in the days one would have laughted at such nonesense. Not falsifiable meant unscientific, but of course string theorists rewrite history and physics all together and no it means scientific. Just take the comment right beneath me: "If tomorrow gravity stopped working, string theory would be falsified." I wish i would recognize salient sarcasm but i don`t.Slicky 10:32, 15 July 2006 (UTC)

These statements are incorrect, as User:Atraxani seems to have tried to have point out above. String theory is conceivably falsifiable. If tomorrow gravity stopped working, string theory would be falsified.

The reason it's criticized (whether or not the critics explicitly recognize this) is because it does not yet make predictions—that is, it says nothing about things that we don't know yet but will probably know soon. It has little if any predictive power; it has only descriptive power. The descriptive power it has is sufficient to make it falsifiable, but only in such a way that if it's falsified, more accepted theories of physics will also have to be falsified. Correct or incorrect? —Simetrical (talk • contribs) 23:48, 1 June 2006 (UTC)

The point is that it doesn't say anything new which is falsifiable. In fact, it is not even clear if it says anything at all, because even gravity doesn't exist in some versions of it. Anyway, when people say it is not yet falsifiable, they mean that the theory have so many variations, part of which have no been solved yet, so one cannot perform an experiment which falsify this theory, assuming that it does not flasify the physics we already know. Shokopuma 20:24, 4 June 2006 (UTC)

How is that a valid assumption? That means it predicts nothing new, not that nothing conceivable could prove it false. Accepted physical theories are falsifiable, they're just unlikely to be falsified except in certain already-identified corner cases. Same goes for string theory. Prediction is a fine criterion, but it's not the same thing as "falsifiable in the sense of Popper", which is only applicable if it's impossible to conceive of any event that would falsify the theory. —Simetrical (talk • contribs) 23:08, 5 June 2006 (UTC)

Simetrical, I don't think you're correctly understanding "falsifiable in the sense of Popper." In order for a theory to be falsifiable in this sense, the theories distinctive predictions must be falsifiable. In other words, the theory must make some new predictions, and those predictions must be falsifiable.

Popper introduced falsifiability as a way of determining what is or is not a scientific theory. In fact, he made this the defining characteristic of a scientific theory. If he meant simply, "There must be some way to prove the theory false," then this criterion would be worthless for determining what is or isn't science. By that definition, "God exists and general relativity is right" would be a scientific theory, because it could be falsified in the same way as general relativity. But in reality that example is not a scientific theory, because the only new prediction it makes (i.e., the only prediction it makes that isn't already made by general relativity) is that God exists, and that prediction isn't falsifiable.

In other words, string theory is falsifiable in the colloquial sense, but as of yet is unfalsifiable in the Popperian sense. Popperian falsifiability refers specifically to the falsifiability of the distinctive predictions of the theory. --Tim314 17:32, 14 July 2006 (UTC)

Has anyone read Bohm and his theory of Thought Processes impeding our understanding of things? Could it be possible that the falsifiable criteria for String Theory is the thing which stops us from really facing up to its implications? Maybe its lack of predictability is the whole point and its the tests that we impose upon it which are causing us to not properly understand it? ThePeg 17.30 11.06.06

Some physicists indeed think that the fact that string theory has so many solutions allows for the Anthropic principle to be the way to choose between these solutions. In this sense, having many solutions - which makes the theory almost non falsifiable - may mean that the Anthropic principle is improtant. However, if the theory is almost non falsifiable, how can we know whether it is correct or not? Dan Gluck 19:58, 14 September 2006 (UTC)

---

Quick question regarding Quarks

So, Quarks are made up strings, right? Is there an intermediate/yet-to-be-discovered sub-sub-atomic particle which is between quarks and strings? Am I looking at this the wrong way? Thanks!

--72.90.177.220 02:54, 8 June 2006 (UTC)

Yes, it is possible that quarks are composties of some sub-quark particles. However, if we assume quarks (and electrons, etc) are point-like (rather than composite) on distances scales much, much shorter than we can test directly (and if we also assume the three coupling constants of the Standard Model are unified at a certain "Grand Unified", very short distance scale) then we can rather amazingly explain the values of those constants that we observe. If instead, quarks were composites, this argument would break down, and it would instead be a bizzare coincidence that these predictions match what is observed. So probably not.—The preceding unsigned comment was added by 24.7.93.102 (talk • contribs) .

I just want to add that the simplest option, which is usually assumed, is that quarks are approximately pointlike up to very high energies (i.e. very small length scales), and if you go to higher energies (smaller length scales) then you reveal that they are in fact strings. i.e. quarks are not made up of strings, they ARE strings (or some other extended objects in string theory). Dan Gluck 19:58, 14 September 2006 (UTC)

Questionable sentence in "History"

Vis-à-vis bosonic string theory, the article says the following:

Most importantly, the theory has a fundamental instability, believed to result in the decay of space-time itself.

I'm not a specialist, so I can only guess that this refers to the existence of a tachyon in the bosonic string spectrum and the fact that D-branes in bosonic string theory are unstable. . . but Dirichlet branes are not spacetime. Did something get garbled or oversimplified here? Anville 20:00, 8 June 2006 (UTC)

The bosonic string has two tachyons: the open string tachyon, whose condensation (according to Sen's conjecture)creates D-branes and thus lower the number of spacetime dimensions in which the open string "lives"; its further condensation lowers even more this number, as 24-branes become 23-branes, then 22-branes, and so on until there are no open string any more. Another is the bosonic string tachyon, and this it is unknown how this one decays, but some believe its decay is related to lowering the number of dimensions in which the closed string lives, which is just the number of dimensions of spacetime (remember that spacetime coordinates are just degrees of freedom of the bosonic string). Dan Gluck 18:40, 11 June 2006 (UTC)

Table corrected

Someone deleted my previous corrections to the table in the "basic properties" section, I wrote them once again. The tachyon in bosonic string is an instability, as in any field theory. the nature of this instability is discussed in the previous section. In type II string theory there are no open strings only perturbatively. However it is well known that these theories do include open strings, attached to D-branes. For references, see Polchinsky's book ("string theory"), volume 2, chapter 13. Dan Gluck 18:53, 11 June 2006 (UTC)

string theory = B.S.

it is so B.S., it's not even wrong. see http://www.nwfdailynews.com/articleArchive/jun2006/notevenwrong.php

Or at least, that's Peter Woit's take on the issue, and Lee Smolin's seems similar (both of them have recently written books on the subject). But keep in mind that rather a lot of physicists (inside and outside of string theory itself) still see string theory as continuing to show promise, and disagree strongly with some of Woit and Smolin's conclusions. If nothing else, work originally on string theory has led to a number of useful developments in related (and testable!) areas of physics, to say nothing of the large amounts of mathematical progress that it has inspired. It's important to take string theory's critics seriously, but don't dismiss the whole program without carefully considering the scientific arguments on both sides.--Steuard 14:46, 24 June 2006 (UTC)

Yeah but it is the percentage that counts, you should have gotten by now a decent picture about what kind of people comprises the global theoretical-physics-community. And unless you constantly lie to yourself you will notice there is no way that more than 50% of them are pro-string. So why doesn`t the article represent that, or have you already reached a point in your life where no other truth but string theory is acceptable.Slicky 11:15, 15 July 2006 (UTC)

Perhaps the arguments you personally make criticizing string theory are self-consistent, but what you're saying here certainly seems at odds with the complaints of most of the string theory critics that I have heard from. Where you claim that the majority of theoretical physicists are anti-string, most string critics seem to complain to the contrary that alternative views are "shut out" of the scientific discourse because string theorists somehow push all of the grad students and funding in their own direction. I don't believe either claim: I think that the majority of theoretical physicists are at least open to the idea of string theory, but that they do so on its own merits rather than because they fear for their jobs if they say otherwise. I do think that including critics' concerns about the theory in the article is a good idea, but it won't make your case look very good if your complaints are mutually exclusive.--Steuard 21:55, 16 July 2006 (UTC)

The dissenting view expressed by such credentialed mathematicians and scientists as Woit and Smolin needs to have a voice within this article, not just in the list of "references". --Christofurio 18:30, 24 June 2006 (UTC)

I was shocked to see that this article has no Criticism section. most people I talk to believe string theory is 100% total B.S.

I don't think we can exactly write "most people the anonymous editor has spoken to think string theory is 100% total B.S." But, seriously, I have tried to expand on the criticisms in my recent edits (it does, in fact, have a criticisms section called, aptly enough, "problems"), and overall they make up a greater fraction of the article. Perhaps someone who reads Woit's book can add something. –Joke 03:39, 28 June 2006 (UTC)

Well, the more you look into string theory the more you will see how political it really is. These are for the most part a pack of religious fanaticists who wanna bring religious views into mainstream physics (that is very harsh and overexaggerated) but just look deeper into the issue and you will notice a direct connection between the supporter`s religious views and their favoring of string theory. This has nothing todo with string theory itself - rather that its premise has been made somewhat religious for the populace and now most pro-stringists show almost cult like behavior. Just make one critical comment in this article and count the minutes till it gets reverted by some stringist who fears he won`t be able to make ends meet if the golden castle is gonna crumble down, that is if the general population looses interest in living in 10^1000000 infalsifiable dimensions. I`d say quality over quantity.Slicky

"Pope Benedict XVI also appointed Witten as a member of the Pontifical Academy of Sciences (2006)." Not surprised on my part. I stand to the fact that you are either a scientist at heart or a cult member/leader. —The preceding unsigned comment was added by Slicky (talk • contribs) .

Witten had many contributions which are useful outside string theory as well, such as in a general context of quantum gravity, in QCD and in mathematics, so I think he deserves some respect even if you think string theory is BS. Dan Gluck 20:02, 14 September 2006 (UTC)

recent edits

I tried to shorten this article up and clarify it. This involved moving the section on cosmic strings to the cosmic string page – the debunking of CSL-1 has somewhat damped interest in this topic – and moving the "aspects of quantum field theory section" to its own page, Relationship between string theory and quantum field theory, because I have a hard time seeing how this fit into the main thread of the page (and, quite frankly, I don't agree that many of the topics mentioned are more natural in string theory, and I think it would be hard to find a significant number of string theorists who argue that they are). This page still has problems with the uneven technical level and chatty phrasing. –Joke 03:36, 28 June 2006 (UTC)

I removed two incorrect statements in the "Problems" section. 1) It said that d-branes have no quantum description. Just not true. They have a perturbative quantum description in the DBI/Super Yang Mills Theory. They have non-perturbative quantum desciptions by various dualities, and as realizations as solitons living on other branes. ADS/CFT gives complete, non-perturbative, quantum desc. of all of Type IIB (in ADS), including all of its brane objects.

2) It said the Landscape contradicts the old idea that string theory has no adjustable parameters. Again, just not true. The idea has always been that string theory has no adjustable parameters *as a theory*, but many adjustable parameters describing its solutions, including its vacua. For example, the coupling constant of string theory is understood not as some external parameter (as in most quantum field theories) but as the value of the dilaton, a dynamical field in the theory. The Landscape actually represents a dramatic reduction in these parameters: rather than an infinite continuum, these parameters can take on only finitely many values in the Landscape. But these parameters are still just describing which solution/vacuum of string theory one is living in. – a PhD,7/15/06

1 – I agree about dualities. As for perturbative description in DBI/SYM, it was my understanding that this doesn't work, per the 1989 paper of de Wit, Lüscher and Nicolai "The supermembrane is unstable." I wasn't aware that these problems had gone away.

2 – I agree, it doesn't contradict it and I never suggested it did. But, if you remember, in the mid '90s it was popular to suggest, particularly in popular lectures, that there were only five versions of string theory and that once we found out which one we lived in, the problem was substantially solved modulo choosing a Calabi-yau. Then things got a little simpler with dualities and somewhat more complex with M-theory. With the advent of the discretuum, people have stopped talking this way and in retrospect it has come to seem naïve. Nonetheless, I don't object to removing this sentence. –Joke 16:53, 16 July 2006 (UTC)

1) If I recall, the instability you mention was in a specific quantization of a 2-brane, related to matrix theory. I think that instability is now understood to reflect the fact that this description is non-perturbative, describing not just one brane, but any possible mulit-brane configuration. See review of Matrix theory by Washington Taylor. But as for DBI/SYM, this isn't contraversial as a perturbative, quantum description of fluctuations of branes. (Holography has a great deal to do with the fact that this perturbative description is actually much, much better than you'd think).

2) The landscape is still basically the question of choosing that Calabi-Yau. We relax the Calabi-Yau conditions, turning on fluxes wrapping the various cycles. (These hadn't been studied until recently because it is hard to solve). The fluxes back-react, so they aren't CY anymore. But the landscape is just basically the set of these solutions, charactarized by the (quantized!) fluxes wrapping the cycles.

Hope this is helpful.– a PhD,7/16/06

"Evidence of string theory?" section

I removed this text:

Many researchers at Northeastern University and the University of California say that scientists might soon have evidence for extra dimensions and other exotic predictions of string theory. Early results from a neutrino detector at the South Pole, called AMANDA, show that ghostlike particles from space could serve as probes to a world beyond our familiar three dimensions and one dimension of time.

This is not a solid test of string theory. It is the result of a fanciful press release. Apparently it is quite popular these days to claim that your experiment can test string theory. –Joke 18:13, 12 July 2006 (UTC)

False history

The history of the string theory is false and based on rumors. The finding of the strong force wasent by a accident ina 200 year old book. thats all a lie and theoretical physicers are sad/pissed because of that rumor. I suggest we change it to be accurate or move that part to a rumor section im going to quote his own words.

By Gabriele Veneziano

i acationaly see writing in books that this model was invented by chance or was found in a math book. makes me feel pretty bad

Do not add rumors, and histories to history parts wich is supposed to hbe true.

--zelos 12:34, 15 July 2006 (UTC)

Provide a reference for this statement. I'm not saying you're wrong; I'm just saying you're going to have to supply a suitable source citation before making the change to the article. --Christopher Thomas 19:12, 15 July 2006 (UTC)

Hi Chris, Looking at the diff, zelos is right. The deleted sentence sounds like some over-eager, breathless assertion lifted from some pop-sci article. I, too, have been able to use 200-year old formulas I found in a book to explain all sorts of things. So does everyone. Its just a goofy sentence. What little I remember about Veneziano relations from grad school is that they were difficult and opaque. In general, quantum mechanics and quantum field theory is littered with special functions. The sentence should go. linas 20:59, 15 July 2006 (UTC)

The deleted sentence sounded like nothing of the sort. Here it is,

In 1968, theoretical physicist Gabriele Veneziano was trying to understand the strong nuclear force when he made a startling discovery. Veneziano found that a 200-year-old formula created by Swiss mathematician Leonhard Euler (the Euler beta function) matched the data better than current theory on the strong force. Veneziano applied the Euler beta function to the strong force, but no one could explain why it fit so well.

while the "formula created by" could be rephrased, this is the interpretation you find in the Elegant Universe and all sorts of other popular books. It is also the correct one. Even Green, Schwartz and Witten says "However, a way of doing this was found by Veneziano in 1968. Veneziano simply postulated a formula for the scattering amplitude, namely [the Euler Beta function]." (pp. 5–6). The text that is there now is incorrect because it asserts that Veneziano had a model, which he did not. The quote from Zelos above is (i) ungrammatical (ii) unsourced and (iii) does not contradict the version that was originally in the aricle. –Joke 16:20, 16 July 2006 (UTC)

We seem to be using different definitions of the word "model", as I'd understood that "scattering amplitudes approximately follow the Euler beta function" _is_ one (albeit a simple and black-box model). --Christopher Thomas 17:27, 16 July 2006 (UTC)

Modified to attempt to address your objections. I strongly object to the tone of the original text, which you largely restored. It reads like an adventure story, not an encyclopedia article. --Christopher Thomas 17:36, 16 July 2006 (UTC)

The real point is that it was strictly a phenomenological proposal. He just postulated the beta function because it fit the data well, not because there was any physical motivation for using this particular function other than that it had the right pole structure, nor because there was a model that would produce this particular amplitude. –Joke 16:29, 16 July 2006 (UTC)

I'll replace it with the much more neutrally phrased version from Gabriele Veneziano, but if this is material from textbooks, I'm reluctant to drop mention of it without suitable citations/justifications. --Christopher Thomas 21:40, 15 July 2006 (UTC)

You shouldn't demand a reference to remove an unsourced statement! Rather, you should provide one that justifies keeping it. -- SCZenz 01:11, 16 July 2006 (UTC)

User:Zelos made strong statements about the validity of the passage in question and quoted statements allegedly by Prof. Veneziano as justification for removing the passage. Darn right I want references for that quote, not hearsay. As for the passage itself, here are more hits than you can shake a stick at discussing the Veneziano amplitude and the Euler beta function. The sensationalistic tone of the passage has already been changed. What specific complaints do you have about this version of the relevant section? --Christopher Thomas 04:36, 16 July 2006 (UTC)

PBS NOVA, the elegant universe, there they talk to him and he says that statement. And i think its not right taking the honor of discovering it after hard work by claiming it came from a old book zelos 05:31, 16 July 2006 (UTC)

So, tempted by the Borgesian pleasure of leafing through a cherished textbook's pages, I looked up the Veneziano amplitude in Zwiebach's A First Course in String Theory. The in-depth discussion can be found in chapter 22, starting on page 513. Equation 22.109, which gives the Veneziano amplitude itself, reads as follows:

$A(p_{1},p_{2},p_{3},p_{4})=g_{0}^{2}\int _{0}^{1}d\lambda \,\lambda ^{2\alpha '(p_{1}\cdot p_{2})}(1-\lambda )^{2\alpha '(p_{2}\cdot p_{3})},$

where the p_i denote the momenta of the four interacting particles, $\alpha '$ is the slope parameter, g₀ is the open string coupling and $\lambda$ is a coordinate of a world-sheet puncture (arbitrary but confined to the interval between 0 and 1). That's quite a mouthful, but the reader can easily compare it to the expression found at beta function,

$\mathrm {\mathrm {B} } (x,y)=\int _{0}^{1}t^{x-1}(1-t)^{y-1}\,dt.\!$

Neglect the constant out in front and replace $\lambda$ with t, and the resemblance becomes clear. (On the following pages, Zwiebach rewrites the Veneziano amplitude in terms of gamma functions to investigate its poles, of which it has an infinite number.) The statement in the current version of the article is accurate, if not the most illuminating thing I've ever read; the confusion here is fundamentally misguided. After all, we use integral calculus all over the place, and that is hundreds of years old — thousands, if you count Archimedes. The old sentence was about as silly as saying that Veneziano used "algebraic techniques which date back to al-Khwarizmi" — just the sort of silly breathlessness one gets from n-times-digested pop science. The new phrasing is verifiable, more concise and even a little educational, if you already know a bit of math.

Let me amplify: it does no dishonor to Veneziano to say that he used old mathematical tools to do something new and interesting. Does it dishonor you to say, correctly, that the words you speak have existed in your language for hundreds of years, and had ancestors in other languages before that? Anville 15:32, 16 July 2006 (UTC)

ahh .. well, then, perhaps we should note that Veneziano's work makes liberal and abundant use of the 1000-year-old concept of exponentiation, which has been layered on top of 20,000-year-old addition, which itself was invented by some unknown person whose identity is lost in the shrouded mists of time, and so cannot be properly credited for leading to the important concept of "addition", which is so commonly used in string theory, the practioners of which learned thier math skills by reading a book that they got from the library. Which we should mention. linas 00:14, 18 July 2006 (UTC)

Editing the Overview

Added some stuff and: Corrected some flase statements: - that the length of a string is a planck length.

Deleted the statement in the remark that "Some string theorists think that this phenomenon prevents the singularities of classical general relativity from forming.". There are many thoughts about how this may happen and this remark is not the place to mention them, nor to mention only one of them.

Deleted the remark that "much progress has been made in the direction" and the ref in the sentence: " It is not yet known whether string theory will be able to describe a universe with the precise collection of forces and particles that is observed, nor how much freedom to choose those details that the theory will allow, but much progress has been made in this direction.[3]" because this is not yet a well accepted view or work. It may appear somewhere in the article, not in the overview. — Preceding unsigned comment added by Dan Gluck (talk • contribs) Dan Gluck 19:47, 18 July 2006 (UTC)

Brief Question

Although I have not read the entire article, I have one question. Are superstrings replacing quarks, or are they simply the sub-constituents of quarks? Also, does it state in this article that the precise energy content of a superstring is proportional to its (representative) particles' mass? (Given that the frequency of the open [non-graviton] superstring represents the particle type, and energy amplitude is proportional to the particle mass. Of course the energy properties of the superstring depend on its location on the Calibi-Yau shape, manifold if you like) Is this true? --Dark Observer

"Are superstrings replacing quarks, or are they simply the sub-constituents of quarks?"

I believe the latter of your statement is correct. 67.68.54.24 16:09, 10 September 2006 (UTC)

It would be fair to say that strings are replacing quarks, in the sense that if you take a quark (or an electron) and zoom-in, you are probably expected to see that it is actually a string (or some other extended object of string theory).

The energy of the string is equal to the energy of the particle, and it receives contributions from both the string velocity and the string oscillations, just like the energy of the particle receives contributions from both its velocity (kinetic energy) and its rest mass. Therefore the string oscillations are responsible to the rest mass (the energy of the string oscillations = the rest mass of the particle). Remember the string and the particle are just two different ways to look at the same thing (the particle is the convinient way to use for low energies / large length scales, and the string should be used for high energies / small length scales). Dan Gluck 19:08, 14 September 2006 (UTC)

Can't edit Footnotes Section

Hello, When I try to edit the "Footnotes" or "References and further reading" I don't get the text displayed in the article webpage, but instead get this:

===Footnotes=== <references />

All I'd like to do is correct the spelling of "charateristics" to "characteristics" in footnote 3. Maybe I'm just experiencing a little bug. Can somebody else have a try? Thanks, Daniel.

I've made your change, thanks for pointing it out. This is the new Wikipedia reference system. You have to edit the section that contains the footnoted text – "extra dimensions" in this case – to edit the text of the footnote. –Joke 22:41, 25 August 2006 (UTC)

Edits made on 11th September

I reverted a series of edits made by 198.240.130.75, being uncertain as to their veracity and usefulness. If there are any experts in String Theory around, maybe they can exmaine these edits more closely and decide what to do. Yandman 14:59, 11 September 2006 (UTC)

I'm no expert on string theory, but I know a lot about how physicists talk about things. This appears to have been written by someone quite knowledgable; so it's very likely to be true. However, the tone and choice of emphasis may reflect a particular (skeptical) viewpoint; then again, the article may largely have reflected the optimism of string theorists before this (most popular writing on string theory does), so this may bring balance. Obviously a willingness by the anonymous editor to make comments and discuss the changes would be helpful. -- SCZenz 16:02, 11 September 2006 (UTC)

I am something of an expert on string theory, and I can't find too much to complain about in these edits. (I see that the anonymous user has reinstated them.) The aren't inaccurate, certainly, and while their POV is at least a little bit "skeptical" it isn't violently so: by and large, they highlight some important disclaimers about the theory. My main concern is just making sure that they fit with the style and level of the rest of the article (I'll want to look at that paragraph on background dependence more carefully).--Steuard 17:55, 11 September 2006 (UTC)

I am a professional string theorist (post-doc at UCLA) and I have to say that there are incorrect statements in the second to last paragraph of the section "Problems and Controversy". The statement that supersymmetry is required to get rid of tachyons and produce fermions is false, although a common misperception. For example, see pages 58-59 of volume 2 of Polchinski's textbook(this is already in the references). You will find a description of a heterotic string construction that has no spacetime supersymmetry, but also is free of tachyons and has fermions in the spacetime spectrum. The confusion might arise because supersymmetry is required to exist on the string worldsheet. But this is just a part of the mathematical construction and does not lead to an observable supersymmetry in proper spacetime.

Even were the claim that string theory needs supersymmetry true, the statements made about supersymmetry are pretty dubious. It is a nice pithy statement that supersymmetry is the square root of spatial translations, but the reality is slightly more subtle(the author should learn about local supersymmetry or "supergravity"). It is fair to say that time-dependent spaces aren't supersymmetric, but the statement about black holes is not quite related to that. Supersymmetry is defined as a certain mathematical condition (the existence of globally defined Killing spinors) and the black holes in question do satisfy this property. One might put in the statement that "string theory has only successfully described supersymmetric black holes and that such objects are, as of now, merely suggestive mathematical abstractions". But any criticism along these lines should be a sharp, and correct statement.

If one really wants to intertwine the viability of string theory with supersymmetry, one has to be fair. The best way to put it is that "string theory doesn't require supersymmetry but strongly suggests it". If no supersymetry is found in nature(say at the Large Hadron Collider at CERN), then this puts a serious damper on string thoery but does not logically kill it. Conversely, the discovery of supersymmetry will not prove string theory but will give it a big boost.

I'm not taking it upon myself, but my suggestion for edit is to delete (or perhaps rewrite) from that paragraph everything from "On a more technical level," onwards. The earlier part of the paragraph and the next paragraph are fine. --Joshua Davis 11 September 2006

I very much agree with Joshua's comments. –Joke 01:51, 12 September 2006 (UTC)

I generally agree with Joshua's comments, but remember that when people say there is only 1 string theory, they refer to the supersymmetric models linked by several dualities. It will be probably true to say that if there is no supersymmetry then this version of string theory is dead. The non-supersymmetric versions are expected to recieve very large corrections, and these may render them unstable, and I think this is why they are usually being ignored. In any case, even if supersymmetry is not detected in the next accelerator (or the one next to it), it can still be that it simply exists in higher energies, so supersymmetry as such may never be proven not to exist (of course it creates other problems but this has nothing to do with the current discussion). I think 198.240.130.75's comment about gravity/gauge duality is not precise since there is much evidence for this duality (at least in certain limits). Dan Gluck 11:44, 14 September 2006 (UTC)

Just a question.

A black hole singularity is an infinitesimally small, two dimensional ring that spins at the speed of light and its surface wiggles with quantum foam. Wouldn’t this pretty much describe a closed string as well? Especially since closed strings describe fermions and the shorter the wavelength at which they oscillate, the greater the mass of the particle of matter they represent. Wouldn’t this prove that strings do exist?

A black hole's singularity is 0-dimensional, and its event horizon is 2-dimensional. Strings are 1-dimensional. So there certainly isn't a direct analogy. Brian Greene does discuss the relationship between strings and black holes in one of the later chapters of The Elegant Universe, though. (A caveat for my own piece of mind: Mr. Greene is a little bit overenthusiastic about the prospects for proving/solving string theory in the near future. Regardless of what impression you're left with if you do read his book, nobody has a clue if string theory is real, and there are no clear prospects for resolving the matter anytime soon.)

In the future, please ask science questions at Wikipedia:Reference desk/Science. Article talk pages are for discussing changes to the articles only. -- SCZenz 16:10, 12 September 2006 (UTC)

Made some corrections

String theory is a model, or a mathematical model, not a conceptual model.

It is unkown whether string theory is mathematically sound. In fact string theory is not fully defined non-perturbatively, so it cannot be mathematically sound, it is not even mathematically defined. Moreover, even algebra isn't "mathematically sound" in the sense that one cannot prove that it does not lead to a contradiction (Goedel's theorems).

String theory has not been experimentally tested at all, hence I deleted "with repeatable results".

Deleted a completely unrelated / false part in the end of "T-duality" sebsection. Dan Gluck 10:23, 14 September 2006 (UTC)

Another change: it is not exactly true that string theory needs 11 dimensions. It certainly needs 10 dimensions, and a 10-dimensional type IIA theory can also be seen as 11-dimensional. The 11 dimensional supergravity approximation is good if the coupling of the 10-dimensional type IIA theory is large, so in a sense the theory is 11-dimensional only if the 10-dimensional type IIA description has a large coupling. For other cases, the 10-dimensional description is good even at large coupling (in type IIB, for example). It is true that it is thought that the underlying theory is "M-theory" which is defined (when it is known how to define it) in 11d. In all, the question whether there are 10 or 11 dimensions is a matter of definition or taste. Regarding 4 dimensions, it is not unique to humans that we percieve only 4 dimensions. It is also a physical experimental result, at least for energies lower than 1 TeV (i.e. for energies probed so far). Dan Gluck 10:27, 14 September 2006 (UTC)

Number of Dimensions

This article states a number of times that string theory requires the dimension of spacetime to be 10 or 11. However, this is not strictly true. The actual condition is a bit technical; the (super-)Weyl anomaly on the string worldsheet must vanish. For the bosonic string, this is most easily done for 26 flat spacetime dimensions; for the superstring the simplest result is ten flat spacetime dimensions. But there are other possibilities. The most commonly studied are probably the two-dimensional strings, or more generally non-critical strings. There are others however. For a reference that I'm not making this up, you can see Polchinski vol. 1, section 9.9. Incidentitly, the two-dimensional string theories are generally more well-defined than their higher-dimensional cousins, since they sometimes have non-perturbative definitions in the form of matrix quantum mechanics.

I'm not advocating that we go into all of this in this article(although I've been thinking about starting a technical article on d=2 strings). However, I think that the statements that string theory must have a certain dimensionality should be scaled back. Maybe we should use phrases like "The string theories most often studied have ten dimensions" or "The string theories which are considered most phenomenologically viable are in ten dimensions" or more precisely, "the string theories known to have supersymmetric vacua are defined in ten dimensions". These have the benefit of being correct without having to introduce a bunch of new material. On the other hand, this material might be of interest and worth introducing, perhaps in a seperate article. Joshua Davis

Well, this is a bit controversial (not what you're saying, but how we should interpret it). I recall that User:Lumidek wrote a nice little thing about this on his blog, [1]. While I agree with the spirit of what you are saying, I think your formulations are a bit cumbersome and would cause the lay reader to miss the point – perhaps we could put a comment in a footnote? –Joke 00:17, 15 September 2006 (UTC)

I agree that we don't want to draw a lot of attention to this. I just get irked by factually incorrect statements, even if they do rather accurately reflect the spirit of what one wants to communicate. The fact is that d=10 is basically thought of as the best way to go in order to connect with reality, so I don't want to confuse that fact. Maybe try something like "String theory strongly suggests that spacetime has ten dimensions", then maybe a footnote with a link to non-critical string theory.

That sounds good to me. –Joke 00:38, 15 September 2006 (UTC)

So I went ahead and changed the opening paragraph a little to reflect the point about how ten dimensions isn't strictly needed but yet basically what's called. Also added a link to non-critical string in the footnote. –Josh

OK Jushua it seems fine (in fact I have already pointed that out in footnote no. 4, though I agree it's not easy to get there). However be careful about these things. You may also say that it is not correct that string theory "predicts" gravity, since there are versions without gravity. In fact for almost every statement you can make, there is some version of string theory for which it is not correct. I think it is usually enough to write "in string theory..." even though the statement is correct only for the superstring theory which is usually studied, and put the reservations in notes or footnotes, for those who will read it all to the end. Dan Gluck 13:14, 16 September 2006 (UTC)

Model or Framework?

I want to raise an objection regarding the statement "String is a model". I would prefer "String is a (conceptual, mathematical) framework" instead. My reasoning is that models are directly testable; they say "this physical quantity should be this". A framework is the set of mathematical tools and physical concepts with which one constructs models. That is, a framework is not really testable, rather a model constructed in a given framework is testable. So I could propose the framework "quantum field theory", but you can't test it; there are no specific predictions. To test it, I need to posit a particular model that obeys the rules of QFT; say quantum electrodynamics. Then I can calculate a cross-section, go to lab, and check it. If I hadn't specified the Lagrangian of QED then I wouldn't be able to calculate anything specific.

In this vein, I would say perturbative string theory, as it currently stands, is a framework. I can specify a particular model, say Type IIB string theory in 10 flat spacetime dimensions. This model is falsifiable; I don't even really have to do an experiment to see that we do not live in ten flat dimensions. But I can make another model, where I compactify 6 dimensions on a Calabi-Yau. This has too much supersymmetry in the effective d=4 description so its false. Now I look at another model, with Ramond-Ramond fluxes in the Calabi-Yau; that's starting look more like our universe but maybe has the wrong gauge group. So I work up another model. This doesn't seem very different than what historically occurred in the construction of the Standard Model of particle physics.

I will be the first to point out that string theory is more subtle than this. Many of the models in this sense are related by various dualities. And there is a conceptual aspect that these models are thought to be different states in a more grandiose model like M-theory. I don't know the answer but there is a similar ambiguity in quantum field theory. Even in QFT one has to specify boundary conditions to the path integral. It might be that one has to specify the background spacetime solution in which strings interact.

I think this is a fair viewpoint to try to include in the article in some way. I think it more accurately captures the state of string theory as a science and puts the criticisms of it in better perspective. Joshua Davis 21:33, 23 September 2006 (UTC)

At the very least, it is certainly more a collection of related models than a single model, isn't it? -- SCZenz 22:45, 23 September 2006 (UTC)

Yes, that may be a good starting point for describing it. But I would suggest going a little further. For example, the two-dimensional string theories have no clear relation with the web of dualities which relate the ten-dimensional superstring models. But those constructions fall within the framework of string theory. Joshua Davis 19:02, 24 September 2006 (UTC)

I think I basically agree with most of your comments. However, there is obviously some subtlety. I think one could argue that what you are calling models within a framework are really solutions of a particular model (or theory).

For example, consider GR. Obviously, most solutions of GR do not come close to describing our universe. I think one would usually call GR a model for (or theory of) classical gravity. But would you call GR a framework, and each individual solution a falsifiable model?

At some level, the examples in string theory you give above are not too different from the GR example, because they are basically different solutions of a set of effective field equations for allowable backgrounds. (Obviously, there is more to it than this, but just thought I'd put forward that perspective, too.) All the best--Jpod2 12:00, 25 September 2006 (UTC)

GA Re-Review and In-line citations

Note: This article has a small number of in-line citations for an article of its size and currently would not pass criteria 2b.
Members of the Wikipedia:WikiProject Good articles are in the process of doing a re-review of current Good Article listings to ensure compliance with the standards of the Good Article Criteria. (Discussion of the changes and re-review can be found here). A significant change to the GA criteria is the mandatory use of some sort of in-line citation (In accordance to WP:CITE) to be used in order for an article to pass the verification and reference criteria. It is recommended that the article's editors take a look at the inclusion of in-line citations as well as how the article stacks up against the rest of the Good Article criteria. GA reviewers will give you at least a week's time from the date of this notice to work on the in-line citations before doing a full re-review and deciding if the article still merits being considered a Good Article or would need to be de-listed. If you have any questions, please don't hesitate to contact us on the Good Article project talk page or you may contact me personally. On behalf of the Good Articles Project, I want to thank you for all the time and effort that you have put into working on this article and improving the overall quality of the Wikipedia project. Agne 00:54, 26 September 2006 (UTC)