Talk:String theory/Archive 2

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)

There are no strong leads other than string theory. String theory is acknowledged by many top physicists, such as the praised Witten. Where do we go, if not string theory? There is a small minority that opposes the theory and these are either the pessimists or people who have a theory of their own that is better.Sr13 08:44, 26 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 examine 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 world sheet. 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 theory 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 receive 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)

Please don't knock on Brian Greene, I have read his book back to front, and it has personally turned me onto hypothetical physics, and I'm none for the worse.

That's great, I'm not saying science education is a bad thing, and it's always nice to have people interested in particle physics. I did, after all, recommend his book for the above question. At the same time, as someone with some familiarity of the experimental tests we will do in the near future in particle physics, I couldn't recommend his work without the caveat that his work oversimplifies things in favor of making strings seem testable. If an educated critique of some aspects of his work is "knocking him," and you think it's bad just because you enjoyed the book, I really don't know what I can tell you. If after reading The Elegant Universe you agree with Greene and are uncomfortable with different views, then I think you may be "for the worse" after all. -- SCZenz 17:39, 14 October 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" subsection. 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 perceive 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. Incidentally, 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 separate 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)

Just wanted to let you guys know that I've been trying to spruce up the non-critical string article. Any help would be appreciated. Joshua Davis 03:08, 28 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)

Does anyone else have any sort of response to this? I agree there aren't a lot of citations but most statements in this article can be verified in one or two canonical references like Polchinski's book. It doesn't seem to make a lot of sense to refer to the same reference over and over again in the text. Or maybe I'm missing the point of the complaint. Joshua Davis 06:22, 26 September 2006 (UTC)

While a diversification of sources are idle (for cross referencing and so), you can utilize the same source for multiple citations through the article. WP:CITE links to some good info on that. Agne 08:23, 26 September 2006 (UTC)

There is also the problem that by using only a very limited number of sources, the sources may be missing something that would be needed for an article to be completely broad on a topic, and people just using those sources might never realize it. Homestarmy 18:23, 26 September 2006 (UTC)

There is more discussion of this at Wikipedia talk:WikiProject Physics. The people at GA did not bother to get the opinion of science editors when they came up with this idea. Nor did they bother to decide on what number of inline references was too few to qualify. --ScienceApologist 20:42, 26 September 2006 (UTC)

I have made a request regarding this issue here. --ScienceApologist 21:01, 26 September 2006 (UTC)

Question

I am an engineering student at Iowa State University, and I am doing a project for my technical writing class involving Wikipedia. I chose to write an article on the string theory, and when i posted my article it was incorporated into this one. My hope in writing the article was to provide a more "general" description of the string theory. I was hoping to add a section this article that presents the string theory to those who are not familiar with physics and the topic. Would this be a worth-while thing to add? As a new Wikipedia user, any suggestions would be appreciated! Thanks. Mkroh 01:10, 28 September 2006 (UTC)

I looked at the article that you made called The Need For Strings. It is still saved in the history if you'd like to see it, but I see that another user replaced it with a redirect to string theory. I agree with this user that it is not necessary to have such an article; most of those very points are made in the string theory article. You are welcome to help edit this article, but you shouldn't just put up a redundant one.

Now that you bring it up, this article looks like it could perhaps use more motivation for why physicists would propose something like string theory. Maybe a few more words about the quest for unification of forces and the problem of quantum gravity would help. There is probably a place on WP where this is discussed thoroughly, but maybe we need to link to it in a more transparent way. Joshua Davis 02:35, 28 September 2006 (UTC)

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Removed an entry in "See also" section

I removed a bullet titled 'Dance of Shiva' in the "See also" section. Don't understand why this is relevant to string theory.KrishSundaresan 21:37, 29 September 2006 (UTC)KrishSundaresan

Added Section

I added a section titled "Motivation." I intend to add to it and continue to edit it, but I just wanted to start it and see what kind of feedback I would get from those more experienced with this article than myself, or see what others would have to add. Mkroh 22:38, 6 October 2006 (UTC)

Archive Box

I've formated the Archive Box into something easier to access opposed to an unformated link.Wikidudeman 22:42, 30 September 2006 (UTC)

The neutrality of this article is disputed.

Just adding this section title won't help us much. What are you disputing? Awolf002 17:27, 14 October 2006 (UTC) Obviousness;look at this page and the entry.First sentence of entry is misleading, as to distinctions between mathematical and physics theories, and ignores recent discoveries that indicate spin factors of particles are being proven.This is an elementary particle(3D) not a zero dimensional theoretical mathematical model or the point particle, and yet the string is taken beyond such limitations in this sentence and granted 3D status.Bias.This is not to argue string concepts, rather the way they are presented in a favorable light out of context, and ignoring multiple other approaches to a unified theory.The comparisons are the starting foundation of the article.

Added Sentence

Added the following sentence to the introduction: The goal is to be able to describe the four forces (strong, gravitational, electromagnetic, and weak) with the same set of equations. Mkroh 00:18, 18 October 2006 (UTC)

Information on extra dimensions?

Is there any information on things that have been proposed as dimensions 5 through 10? I wondered if the five senses could be considered part of those missing dimensions. Does that make any sense? Titan4mmb 03:41, 22 October 2006 (UTC)

Sorry, but your idea does not make sense. Extra dimensions are planck-scale (of the order of 10^-35m) and curled up into Calabi-Yau spaces, so they have nothing to do with your dimensionless senses. The theory is not mystics. Kurochka 10:33, 22 October 2006 (UTC)

A speculation on the 10 dimensions

I think this new section should be removed. As the title already indicates, and the text clearly shows: This violates WP:NOR. Does anybody have any attribution of this text to a WP:RS? Awolf002 14:47, 5 November 2006 (UTC)

Agreed. Joshua Davis 19:46, 5 November 2006 (UTC)

References and Popper

I agree with the GA review committee that this article could use more inline references. It's handy when you come across a bold statement, and your immediate question is, "says who?" For instance, the idea that anthropic explanations are not considered scientific in the Popperian sense. First of all, this passage should explain what "the Popperian sense" is, in a few words, and then give a citation to support that claim. The notion that a few general sources support any unreferenced statements is rather dangerous, as anyone can add any claims to the article at any time. It's also inconvenient to check those claims. For example, if there are several books referenced, one might need to read through the entirety of all of them to find the source for a claim, which may or may not even be supported by any of the references. Connecting statements with specific sources and if applicable, specific page or chapter numbers would be of immense help to fact-checkers and students. -- Beland 01:31, 10 November 2006 (UTC)

I hardly think you need a citation when you say as in the final paragraph that the explanation is unscientific in the Popperian sense. Perhaps a rephrasing to say that it is difficult to consider the explanation as scientific in a Properian sense as that it a statement pointing out the currently unfalsifiable nature of the universes as vacua. It could also represent a biased statement but are we forgoing all interpration and common sense as well.??? --66.194.118.10 22:10, 14 January 2007 (UTC)DAYork

We should be forgoing original research, which an absence of citations tends to indicate. The claim that string theory is unfalsifiable is disputed among physicists and philosophers of science, and thus isn't NPOV. Certainly if string theory predicts electromagnetism, then it is falsifiable, since it would be false if there were no electromagnetism. And that's just one of many predictions (logical entailments) of string theory. -- Jibal 06:57, 6 March 2007 (UTC)

FWIW, the "unscientific in the Popperian sense" you're referring to is I think more appropriately "unscientific in the Positivistic sense", a school of thought Popper was often thought to belong to because he wrote about it so much, but was mainly opposed to. 76.178.143.51 (talk) 06:28, 29 February 2008 (UTC)

Verifiability

I think the phrase in the text, "No version of string theory has yet made an experimentally verifiable prediction that differs from those made by other theories." is misleading. An anonymous editor recently tried to remedy this by pointing out that there are, in fact, falsified string theories, but his/her edit was reversed. I think that this editor made a good point; if one looks at a particular string theory, one can often see why it is not true(for instance, heterotic SO(32) in d=10 Minkowski space). So any given background is falsifiable in this sense. But I have another point; it is simply not true that string theory is indistinguishable from field theory in principle. String scattering amplitudes generically have amuch different behavior than field theories at energies above the Planck scale(see e.g. Polchinski's book). This, of course, has not been able to be tested yet(or maybe ever) but is a prediction which differs from field theory. Also, superstring theory predicts ten spacetime dimensions; this is also not predicted by other theories. So I think we should change "verifiable" to "verified" in the text I quoted. I'll make this change if I don't get any objections. Joshua Davis 04:38, 20 November 2006 (UTC)

String theory has been tested and found wrong since it requires some weird number of dimensions while it is known that physics would be impossible in any dimension but 3+1. See Our Almost Impossible Universe: Why the laws of nature make the existence of humans extraordinarily unlikely, R. Mirman, for the proof. Someone keeps removing this, trying to hide the failure of string theory, preventing others from learning of that. What can be done? It shows contempt for other people. R. Mirman 19:16, 9 February 2007 (UTC)

Wikipedia has a policy of not allowing people to present original research in the encyclopedia. Please see WP:OR for more details. --Dante Alighieri | Talk 23:56, 9 February 2007 (UTC)

by 216.9.143.161 (talk)

Hi. First, please sign your comments, by adding "~~~~" in the end of it. Even though you don't have a user name, you're still asked to do that. Second, I agree with your remarks about string theory, and it's not OR, see for example Polchinski's text book regarding the dimensions problem, and this highly cited article by Lennie Susskind regarding the landscape and the anthropic principle. Finally, i don't know this "Our Almost Impossible Universe..." book, but since string theory is a wide academic branch, a strong argument against it should come from some widely known or highly cited critical review in order to be notable, and notability is also a criterion of appearing in Wikipedia. While Woit's book is certainly notable, the other one is not. By the way I haven't read either :-) but I've read about Woit's book plus many remarks by him and a summary by him. Woit's book certainly doesn't say that string theory has been falsified because we live in only 3 dimensions. His main argument is that string theory is NOT falsifiable, and that's the problem with it according to him. Dan Gluck 11:07, 9 August 2007 (UTC)

"want to"?

From "Basic Properties": "Like springs, the strings want to contract to minimize their potential energy" Talk about anthropomorphism! "tend to"? "will, if unconstrained,"? "tend towards a state of minimal potential energy by contracting"? --Hugh7 09:31, 13 December 2006 (UTC)

Done Dan Gluck 20:22, 9 April 2007 (UTC)

Huh?

"Studies of string theory have revealed that it must never be known by Pete and also predicts not just strings, but also higher-dimensional objects..."

Who/what the heck is pete?

A bit of minor vandalism. In that case, it was removed two minutes after it was placed, but it would seem you saw the vandalized version. --TeaDrinker 05:23, 28 December 2006 (UTC)

Introduction...

I don't quite follow where it begins "String theory is like a big tree, being purple and like a kitty Cat with a ball of yarn, and everyone knows there is nothing cuter..." - could someone enlighten me? Is it saying that string theory is ridiculous, or demonstrating all the possibilities of multiple worlds, or what? If so, it is badly worded... Just my contribution. Parky 23:23, 5 January 2007 (UTC)

This was just vandalism which has been corrected Dan Gluck 20:24, 9 April 2007 (UTC)

Can someone post something on this website that explains string theory in a way so that you don't have to be a quantum mechanic to understand?

go to simple.wikipedia.org, that has a good description for us non-quantum mechanics —Preceding unsigned comment added by 76.124.50.59 (talk) 01:25, 18 March 2009 (UTC)

Analogy with Guitar Strings

I am certainly no expert on string theory, but i play guitar and suspect that a guitar string can only really produce different notes by shortening the string, not by vibrating at different frequencies (wouldnt that just make it softer or louder??). Is the analogy between a guitar string and the particle-string accurate, made on the third line of the first section?24.235.120.106 18:29, 8 January 2007 (UTC)James

By lengthening and shortening the guitar string you are in fact making it vibrate at frequencies. Intensity in determined by the amplitude of that wave, not the frequency. Therefore the analogy used is still valid, it is just slightly misleading if you are unfamiliar with either sting-instrument theory, or wave terminology.

The "different" notes are harmonics. On a real-world guitar I don't think that there's any way to strum a guitar so that you play a harmonic without playing the fundamental note, but in principle the guitar string can vibrate at any of its harmonics, not just the fundamental. Geoffrey.landis 19:45, 18 January 2007 (UTC)

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By stretching the string aren't you increasing the frequency?

To James: audio frequency determines pitch (and rapid frequency changes make complex sounds).

To Geoffrey: each note on a guitar is composed of a series of harmonics, one of which is dominant (the lowest); but it is possible on a guitar to isolate specific harmonics by plucking the string muted in particular places along the string (muting directly above the fifth half-step, or fret, produces a harmonic note two octaves above the base note; muting at the seventh half-step produces a harmonic note one octave and seven half-steps above the base note; the twelfth half-step produces a harmonic note one octave above the base note; there are quite a lot of other harmonics that can be isolated in this manner along the string).User:Eyelidlessness

I think that the whole reason why this topic was created was to answer the question: does the frequency of a superstring determine the type of particle (as defined by that particles rest-mass and spin-charge) and the amplitude of the string defines the scalar magnitude of the particles vector (speed)?

Actually, both the frequency and the amplitude determine the particle type.PhysPhD 17:37, 25 April 2007 (UTC)

Eclipse

I deleted this line: "(Of course, the existence of such a simple test of general relativity rested on the historical accident that the moon and the sun have the same angular size as seen from Earth, allowing total solar eclipses to occur.)"

Primarily, it is incorrect. The feature of an eclipse required for the testing of the bending of light is that the moon's angular diameter be GREATER THAN or equal to the angular diameter of the sun. It's not required that the moon and sun have the same apparent angular diameter, only that the sky get dark enough when the sun is up that the stars can be observed. Second, since we can do this measurement with radio telescopes even without a total eclipse, the "historical accident" only affected the timing, allowing the confirmation of GR to be done without waiting for radio telescopes to be developed.

This could be clarified by adding explanations, but why should it be? The point has nothing to do with string theory. The article has a link to the solar eclipse page, to allow those interested in it to find that proper information. Geoffrey.landis 19:41, 18 January 2007 (UTC)

String Theory vs. Superstring Theory

I think it is important to differentiate between standard String Theory and Superstring Theory. I added "This phrase is often used as shorthand for Superstring Theory," but most of the article is discussing Superstring Theory so perhaps the content related to Superstring Theory should be moved to the Superstring article.—The preceding unsigned comment was added by 70.63.79.219 (talk • contribs) 13:54, 28 January 2007.

I thought they were the same thing.Wikidudeman ^(talk) 04:06, 5 February 2007 (UTC)

No, that is not needed. There is currently almost no research on the bosonic string theory, since it is not consistent (it is unstable). Moreover, it is now thought to be related to superstring. So there is no such subject as "bosonic string theory" separately from "superstring theory", and the latter is known as simply "string theory". Dan Gluck 20:43, 9 April 2007 (UTC)

Directly Testable Alternative to String Theory

After reading an article in Scientific American's website on The Geometer of Particle Physics which refers to the work of mathematician Alain Connes [2] on noncommutative geometry and renormalization, it appears that a directly testable method is available as an alternative to String Theory. The article referenced is at [3]. When the Large Hadron Collider boots this year it will give Connes data to to extend his work to smaller scales.

The point of making this comment is that testable alternative to Sting Theory should at least be presented under an Alternatives to String Theory section, and particularly, Connes work should be referenced and his webpage at Wikipedia elaborated on in light of this promising body of work. --4.156.144.246 18:46, 6 February 2007 (UTC) --4.156.144.246 18:48, 6 February 2007 (UTC)

This should appear in quantum gravity article, since it is not related to string theory. The current article should only have a link to that one. Dan Gluck 21:33, 9 April 2007 (UTC)

Overview not up to standard

The overview doesn't cite sources very well, and there are far too many rhetorical questions asked. --24cell 07:48, 7 February 2007 (UTC)

Clarification

I need some clarification here. In the last part of the intro., it says,

Studies of string theory have revealed that it predicts not just strings, but also higher-dimensional objects (branes).

Doesn't string theory assume the existence of objects called strings rather than predict them ? Same for branes ? Could someone knowledgeable about these matters clarify this ? Thanks. MP (talk) 16:34, 7 February 2007 (UTC)

Scientific theories make or entail claims about the world -- such claims are predictions, not assumptions. Suppose that I have a frog theory that posits that there is a frog at the bottom of every well, even those we aren't able to descend. A prediction of this theory is that one will hear croaking coming out of any well. Eventually, if we develop the technology to descend down to the bottom of every well, the theory predicts that we will actually find frogs at the bottom of each of them. At no point is the existence of frogs an assumption of the theory. -- Jibal 07:20, 6 March 2007 (UTC)

Branes are a prediction of string theory, not an assumption. They arise in many ways. 1) If we postulate (assume) strings that have ends, a mathematical transformation called T-duality brings about an equivalent theory with dynamical branes in it. 2) Some string theories have excitations that are a bit like electromagnetism, called Ramond-Ramond fields, which need to be sourced by extended objects, the branes. There are many, many other ways that branes pop-up.PhysPhD 02:39, 29 March 2007 (UTC)

Thanks for that

"String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects called strings, rather than the zero-dimensional point particles that form the basis for the Standard Model of particle physics."

What? —The preceding unsigned comment was added by 84.66.228.157 (talk • contribs) on 04:35, 30 March 2007.

In the standard model, the particles are points. In string theory, they are little lines. Dan Gluck 21:34, 9 April 2007 (UTC)

Quantum strings ?

Is a 'quantum string' the same as a 'string' (a string in the sense of string theory) ? I think they are the same, but I need some experts to verify this. The article mentions quantum strings, but I don't think it's made clear that these are the same (if they actually are) ? I await clarification. MP (talk) 17:23, 7 February 2007 (UTC)

One can study classical (ie, non-quantum) string theory, and this is generally done as you're learning string theory. It's (currently) more of a pedagogical tool and toy model, so almost always when people refer to string theory they are referring to the quantum version. If you want to emphasize aspects of the string that are quantum or non-quantum, you prepend quantum or classical. That is, the fact that a given string vibrates at a given set of frequencies (harmonics) is a classical property (witness a guitar string), but the fact that a string vibrates only at certain amplitudes is a quantum property. I should note that many classical properties are inherited by the quantum string -- so a quantum string has both quantized frequencies and quantized amplitudes. 69.143.82.37 17:07, 7 March 2007 (UTC)

String theory stub

I'd like to create a string theory stub. My proposal can be viewed here. MP (talk) 20:11, 8 February 2007 (UTC)

The string theory stub has now been created. You can find it here: Template:String-theory-stub. MP (talk) 20:48, 12 February 2007 (UTC)

New article on String duality ?

The subsection on duality is very long. How about we create a new article called String duality to include the bulk of the material in the present subsection and include a main article link to this proposed new article ? Comments appreciated. MP (talk) 19:49, 9 February 2007 (UTC)

I think that would be appropriate given the size and importance of the material. -- Fropuff 19:57, 9 February 2007 (UTC)

Done. I have 'created' string duality in the sense that I just copy and pasted the present article's material there and have not removed the material from here. I am not confident of removing the material here and rehashing it into a more concise form, as I don't know enough about the topic. I'll leave that for more knowledgeable editors to deal with. MP (talk) 20:21, 9 February 2007 (UTC)

Too much repetitive info. ?

Is there too much repetition in the article, for example, in the intro. and the overview ? MP (talk) 19:00, 10 February 2007 (UTC)

Mirman

Removing information is vandalism R. Mirman 16:16, 11 February 2007 (UTC)

You are mistaken, on this matter and others; removing information is not WP:Vandalism. -- Jibal 07:27, 6 March 2007 (UTC)

You've been informed about WP:OR. If you do not begin to comply with Wikipedia process and community standards, you will end up blocked. --Dante Alighieri | Talk 20:09, 11 February 2007 (UTC)

Do not remove correct material! Or is the material required to be wrong? The material proving that space must have dimension 3+1 added to the article is not original research. It has appeared in papers and in two books, going back more than two decades. References are given in the added material, and these have further references. Look at the books instead of jumping to the conclusion that they are original. It shows contempt for others to force them to believe in material that is known wrong, and waste their time doing work that cannot lead anywhere. What right do you have to do that to them? It also undermines the credibility of Wikipedia if it carries only material known to be wrong. Why is the material continually removed? This is highly improper. R. Mirman 13:40, 11 February 2007 (UTC) (moving comment that was placed INSIDE the template at the head of the page for some reason --Dante Alighieri | Talk 15:50, 12 February 2007 (UTC))

Your book (I see it's sold on Amazon) is self-published at vanity press publisher iUniverse. I am unable to find any reviews of your book in Physics journals, nor any papers that you've submitted to peer-reviewed journals. The mere fact that your ideas have been printed is not sufficient... ANYONE can publish ANYTHING. If you can provide references that show your articles have been peer-reviewed or supply reviews of your book(s) by reputable academics, then (AND ONLY THEN) they can be used as sources for the article. --Dante Alighieri | Talk 17:23, 12 February 2007 (UTC)

Given your stance on peer-reviewing[4], I shall assume that you do not plan on offering any journal articles. However, at that same link there are 3 reviews from (presumably) your peers who don't seem much impressed by your post. --Dante Alighieri | Talk 17:31, 12 February 2007 (UTC)

Asians?

What does the first line have to do with anything, is that just vandalism?

I'm unsure what it is that you saw, as there is nothing in the first line about Asians... nor has there been at any time in the recent history. --Dante Alighieri | Talk 23:48, 12 February 2007 (UTC)

The last version of the 'asian info' in the first line is here. MP (talk) 16:13, 13 February 2007 (UTC)

I stand corrected. I didn't see that diff when I was looking before. Sorry. :) And yes, that was "just" vandalism. --Dante Alighieri | Talk 22:40, 13 February 2007 (UTC)

Where are 'the same set of equations' ?

The end of the first paragraph mentions the 'same set of equations'. Perhaps the link could be sharpened (which is presently very vague for the topic in question) to the actual equations that supposedly unify the 4 forces. Admittedly, this is asking for a lot, but someone out there must know what these equations are. Experts, we need your help !!! MP (talk) 19:34, 17 February 2007 (UTC)

You ARE asking for a lot. Had anybody known what these equations are, he would have gotten a Nobel prize. All that exists currently is either unfinished propositions or equations which consists of much more parameters put by hand than those needed to be predicted. It is possible to put a link to unfinished propositions which give for example gravity and supersymmetric gauge thoery which can be hopefully broken to the standard model, but I'm afraid that putting such a link will encourage people to think that there is a solution to the problem. If anyone is interested, he should better go to the related links in the body of the article.Dan Gluck 19:07, 9 April 2007 (UTC)

The sentence in question has been changed (not sure when and by whom) to include the word 'may' instead of 'appears to be able to'. I am happy with this. MP (talk) 15:56, 11 April 2007 (UTC)

Supersymmetry and String Theory

The article states:

Investigating how a string theory may include fermions in its spectrum led to the invention of supersymmetry, a mathematical relation between bosons and fermions.

Supersymmetry was invented/discovered by Wess and Zumino in context unrelated to string theory. See the article on Supersymmetry for further references. 69.143.82.37 17:17, 7 March 2007 (UTC)

Removed dead link

I have just removed this dead link from the article: Has string theory tied up better ideas in physics?, Northwest Florida Daily News, 6/23/2006. If someone can find the correct link (if it still exists in some form, then it's still here in the talk page. MP (talk) 20:13, 7 March 2007 (UTC)

Predicted extra dimensions

I don't think the section on extra dimensions is correct, and, at a minimum, there certainly there isn't a citation around the relevant passages.

There are:

One intriguing feature of string theory is that it predicts the possible number of dimensions in the universe. . . .

Unlike general relativity, string theory allows one to compute the number of spacetime dimensions from first principles.

I don't think that's right at all. Extra dimensions are assumptions of string theory, and the number of dimensions were selected to conform the theory to the observed behavior of particles. That isn't a "prediction," and the number of dimensions is not being "computed" from "first principles," dimensions are being added to make the theory work with experimental results.

And isn't there still some question about whether the ten-dimensional theories are really eleven dimensional ones?208.226.153.24 18:11, 5 April 2007 (UTC)

You are totally wrong. Superstring theory is based on a two-dimensional quantum supergravity with weyl invariance in 2 dimensions - this is the theory on the worldsheet. The weyl invariance is gauged, and is anomalous unless the number of space-time dimensions is 10 (in a Lorentz-invariant theory).In strong coupling, a certain version of string theory (called type IIA) is better expressed at low energies in terms of a 11-dimensional theory coined M-theory. All this is explained in the article.Dan Gluck 18:42, 9 April 2007 (UTC)

Respectfully, it seems to me that you've entirely missed the point, and that in fact you are in error. The claim in the article is that the number of dimensions is "predicted" and that the number of dimensions is "computed" from principles. But that isn't what you're description says. Your description says that you picked a set of dimensions in order to make the math work out, and in fact you're not even sure about what number of dimensions you've picked. That isn't a "prediction" its an "assumption" of the theor(ies). Respectfully again, this isn't a disagreement about physics, its a disagreement about the English language. 207.237.10.120 03:51, 10 April 2007 (UTC)

The most accurate statement would be, that superstring theory is consistent only in 10 dimensions (if we ignore for a moment the non-critical string). Therefore it is not correct to say that this number is selected "to conform the theory to the observed behaviour of particle". The term usually used is "predicts", because if one takes the fundamental assumptions of string theory then this number can actually be computed, but I added a clarifying sentence in order to make this more accurate. Dan Gluck 19:19, 12 April 2007 (UTC)

Last Edit

I changed a paragraph the introduction to reflect the ongoing debate on the predictability of string theory.

I created in the introduction a paragraph about string theory as a possible theory for the strong interactions (thorough gauge-gravity duality), because although the math is identical, it is a theory of totally different phenomena than quantum gravity.

There was a link in the introduction about AdS-CFT RHIC-related stuff. This was a non-scientific media report, and the link was in the wrong context - suggesting that success in predicting stuff at RHIC is related to string theory as a theory of quantum gravity. I changed the link to few links to the related scientific papers and placed it in a paragraph of a correct context - the new paragraph in the introduction about gauge-gravity duality.

In the "problems and controversy" section, I added a paragraph about the "string wars" - the 2 new books by Woit and Smolin and the discussion that followed. I incorporated into this paragraph the quote by Smolin which has previously been put out of any context, and added the infamous "only game in town" answer for balance - perhaps both quotes should be omitted? —The preceding unsigned comment was added by Dan Gluck (talk • contribs) 18:52, 9 April 2007 (UTC).

"There are different versions of string theory, depending on factors such as what type of string is being used (open or closed)" I deleted this since no theory of purely open strings or purely closed string is thought to be consistent. The former is surely not unitary because closed strings appear in loops, and the latter is probably impossible because one must probably incorporate D-branes as non-perturbative effects, showing up at the loop expanion for high genus (see Polchinski chapter 9). Dan Gluck 19:48, 9 April 2007 (UTC)

Problems with String Theory

String theory is an interesting way of combining quantum mechanics and Einsteinian relativity. However string theory, in my opinion, hasn't given any major predictions about the universe and the way it functions. Does string theory actually tell us anything about the universe that we didn't already know? Wikiisawesome 11:41, 11 April 2007 (UTC)

No. At least not yet, and in many people's opinion not in the foreseeable future. I tried to reflect it in the last edit.Dan Gluck 19:21, 12 April 2007 (UTC)

The article should better reflect that there are still many fundamental problems with the string theory and its successors (M-theory etc.). I mention just three problems which a good Theory of Everything (TOE) should solve:

1. A good TOE should be able to formulate its own principles and fundamental equations. Moreover, these principles and equations should clarify and simplify our picture of the physical world and allow some testable predictions. As far as I know, nothing like that is still available for the string theory (M-theory), in contrast to its rather long development and far-reaching claims.

2. A good TOE should allow calculations of all interaction constants and particle parameters from its fundamental principles. It was actually one of the original Einstein's goals - to give some purely geometrical or mathematical origin to fundamental physical constants (see e.g.: J. D. Barrow: The Constants of Nature. J. Cape, London, 2002, esp. Ch. 3.). No variant of string theory is able to calculate these parameters from some first principles.

3. If the TOE is formulated in some space of higher dimension (11, etc.), as expected, there should be also a unique and justified principle of compactification - e.g., a principle how to project the structures from the 11-dim world to our tangible 4-dim world. In its contemporary status, (super)string theory is very fuzzy and ambiguous concerning the compactification.

Many physicists of unquestioned competence think that the very word "theory" is rather premature in connection with the (super)string model of physics. Einstein himself probably would not be very happy with its present form and claims. --ArepoEn 08:36, 18 July 2007 (UTC)

These are all good points which I think are addressed to some extent in the text, particularly in "Problems and Controversy". Feel free to clarify the article yourself, though, if you feel it is necessary. --Joshua Davis 17:30, 18 July 2007 (UTC)

Point 2 would be nice, but we can't insist upon it. The distance from the earth to the sun might have been thought of as such a parameter, but of course it's value is a function of the complicated history of the universe, not just the theory governing its dynamics. Similarly, the charge of the electron may turn out to be incalculable from first principles, due instead to the complicated dynamics of a modular field that happened to settle down to a particular value in the visible universe.PhysPhD 18:26, 18 July 2007 (UTC)

String theory can be a theory but yet not a Theory of Everything. One option to which PhysPhD implies is that additional ingredients such as the anthropic principle should also be considered. Another option, for example, discussed recently by David Gross, is that string theory is a framework, like quantum field theory: due to its huge number of solutions, it cannot predict things such as the number of non-compact dimensions (your no. 3) or coupling constants (your no. 2), but given a solution (our place in the anthropic landscape), we can in principle calculate. This is similar to quantum field theory because quantum field theory per se does not predict which fields there are and what are the gauge groups or coupling constants, but given these it gives us tools to calculate, and furthermore it imposes constraints on the fields and possible couplings (for example gauge anomalies must cancel, CPT invariance must hold, etc.). Just to remind you, quantum field theory is the cornerstone of modern particle physics and has been checked experimentally to great accuracy. The big problem with string theory remains contact with experiment (your no. 1). I hope the article is clear enough about it. Personally I don't believe this problem will be overcome in our lifetime (or at all), but there's no consensus regarding that point. Dan Gluck 19:36, 18 July 2007 (UTC)

You are assuming that, basically, if it was true, we would know it right away because the problems would sort themselves out? This makes little to no sense at all! The fact that we are this far scientifically is astounding. Although you do raise good points about whether we should've known the answers right away, the fact remains; algebra does not solve itself, rocket science does not solve itself... altogether, no problem solves itself. Why should something deemed so unachievable not be difficult to uncover? What gives humankind the right to uncover it in the first place? Conclusion: if you are going to say that string theory should be easy to understand, think about it for a minute and you'll realize that string theory is uncovering one of the greatest finds since discovering that the earth is not flat. It's a breakthrough and will take time to prove. Musicnotz (talk) 17:32, 29 July 2008 (UTC)

Background Independence

From the Problems section: "Philosophically, string theory cannot be truly fundamental in its present formulation because it is background-dependent: each string theory is built on a fixed spacetime background." This is opinion, not a neutral fact. My opinion differs: Background independence is an aesthetic criterion. Possibly nature is background independent, but it's possible nature does not treat all backgrounds the same, preferring AdS, say. Either way, the "cannot" assertion needs to be modified. I'll give it a shot. PhysPhD 03:38, 13 April 2007 (UTC)

I agree Dan Gluck 06:13, 15 April 2007 (UTC)

Actually I like better the current version. I think most DO see background independence as a requirement, because general relativity is background independent. I don't really know anyone who doesn't think like that, except for PhysPhD, so I've added the "citation needed" tag. Dan Gluck 07:01, 15 September 2007 (UTC)

interesting at what background do strings vibrate, what's their makeup, and where do they float in? —Preceding unsigned comment added by 82.217.143.153 (talk)

It is usually thought that they can vibrate in any background which is a solution to the equation of motion, however most works are on a flat Minkowski space (R^9,1), or on AdS₅ × S⁵ (see AdS/CFT correspondence). There is no answer to the question "what they are made of", since everything is made from them - they are the fundamental stuff of the universe. They float in space which is empty other than having strings moving in it (and possibly D-branes or NS-branes), but if they have edges then these must be attached to D-branes. They may also be emitted or absorbed by D-branes or NS-branes. Dan Gluck 07:01, 15 September 2007 (UTC)

Technical Page?

Is it worth creating a second page with a more technical intro to string theory, more like a lot of math pages that aren't affraid of including equations? If people think this is a good idea, someone who knows how could create the page and I could start filling it in...PhysPhD 04:27, 13 April 2007 (UTC)

There's a couple ways of approaching it. One could try to keep this article as accessible as possible putting the technical details into more specific articles like superstring theory, bosonic string theory, type II string theory, etc. The other alternative (and a seemingly acceptable common practice) would be to put the nontechnical overview at Introduction to string theory and keep the technical information here. See for example: introduction to general relativity and introduction to quantum mechanics. -- Fropuff 05:21, 13 April 2007 (UTC)

I prefer the first alternative, but though I can do it in principle, it's a lot of work... Dan Gluck 18:38, 13 April 2007 (UTC)

Integrated Functionality???

I deleted the section on "integrated functionality" again. Nothing in that section has anything to do with string theory. What is described in that section can either happen in standard quantum field theory, or is just incorrect. It reads like the author's source is a science fiction tv episode. PhysPhD 18:20, 17 April 2007 (UTC)

I've taken a look at it, and it does indeed seem to be gibberish as-stated. It's possible that it's a mangled presentation of something correct. If that's the case, though, it's best to present an explanation here, with references, rather than reinserting the passage in question into the article. --Christopher Thomas 18:39, 17 April 2007 (UTC)

After examining this, Integrated Functionality is not nonsense, it has been part of this article for a long period of time already. Also, it is completely correct. Although, it would be better to expand it, the section has described Integrated functionality quite well in essence. It is not going to be in any TV episode unless the TV episode is only for scientists specializing in string theory. —The preceding unsigned comment was added by Arthur.kam (talk • contribs) on 13:25, 19 April 2007.

Then please provide suitable references that mention it and give a non-mangled description of it. --Christopher Thomas 19:18, 19 April 2007 (UTC)

I don't mean to sound haughty, but I am a "scientist specializing in string theory", and even though this may have been here a long time, it doesn't mean it's right. It is common knowledge in physics that various processes can turn one kind of particle into another. This much is true, but it just has nothing to do with string theory. Worse, the whole paragraph is full of mumbo-jumbo, to the point that it could have been written as intentional vandalism. "The energy consumed by this process is inversely proportional to the energy produced by the cancellation of matter and antimatter." This sentence has no discernible scrap of truth, whatsoever.PhysPhD 21:26, 19 April 2007 (UTC)

Yes, that section was joke or a test or whatever. Testimony of bad quality control. --Pjacobi 21:35, 19 April 2007 (UTC)

I've found the insertion point. It was added on 14 December 2006 by 219.78.47.142 (talk • contribs • WHOIS). Vandalism was added immediately after by a different IP. When that vandalism was reverted, this passage wasn't, and subsequent vandalism reversions only went back to the last edit by a non-IP user. --Christopher Thomas 21:49, 19 April 2007 (UTC)

Some restraint in adding preprints

New, interesting, preprints are popping up every day on arXiv and are discussed on the relevant blogs. But this here aims at being an encyclopedic article, doucumenting established knowledge. So can we pls wait adding new stuff until it has evolved to a review article written by a respected author, or something similar? --Pjacobi 12:16, 21 April 2007 (UTC)

What is the context of your remark? Dan Gluck 11:05, 22 April 2007 (UTC)

http://en.wikipedia.org/w/index.php?title=String_theory&diff=prev&oldid=124587390 and most other arXiv-Link-insertions. --Pjacobi 15:35, 23 April 2007 (UTC)

Website about String Theory and the 10 Dimensions.

Hey everyone. If you like being confused by this stuff, go to

www.tenthdimension.com

and watch the video, "Imagining the Ten Dimensions" under the "Navigation" bar.

It's really cool and kinda confusing, but cool and fun to watch. —The preceding unsigned comment was added by Tidman5 (talk • contribs) 17:46, 24 April 2007 (UTC).

This video is totally unscientific nonsense (at least from 5 dimensions and up) and has nothing to do with string theory Dan Gluck 19:42, 30 April 2007 (UTC)

Agreed; this video is more philosophical and is, in fact, jargon. It makes little to no sense as it is only about trying to explain the unexplainable, and, while entertaining, is unscientific. It has absolutely nothing to do with string theory. Musicnotz (talk) 17:26, 29 July 2008 (UTC)

Princeton physicists connect string theory with established physics

This seems like major news which should be reported within the article:

...Princeton researchers have found new mathematical evidence that some of string theory's predictions mesh closely with those of a well-respected body of physics called "gauge theory," which has been demonstrated to underlie the interactions among quarks and gluons, the vanishingly small objects that combine to form protons, neutrons and other, more exotic subatomic particles. The discovery, say the physicists, could open up a host of uses for string theory in attacking practical physics problems....

...The team's paper appears in the March 30 issue of the scientific journal Physical Review Letters. Klebanov's co-authors include graduate student Marcus Benna and postdoctoral fellows Sergio Benvenuti and Antonello Scardicchio.

...In the 1970s, physicists posited that when gauge theory loses its power to describe particle behavior as quarks bond together, string theory might be able to step in and handle the job. What string theorists needed was some indication that both theories were headed in the same direction. The lucky break came in 1997 and early 1998 when a precise relation between the two was conjectured in the work of Princeton physicists Alexander Polyakov, Steven Gubser and Klebanov, as well as the Institute for Advanced Study's Juan Maldacena and Edward Witten....

...String theory, for all its mathematical beauty, once again seemed too difficult to test -- until Niklas Beisert, an assistant professor of physics at Princeton, published a paper in late October of last year containing an equation that turned out to be a crucial piece of the puzzle. "Beisert and his collaborators made an inspired guess based on sophisticated notions of gauge theory behaviour," said Curtis Callan, the James S. McDonnell Distinguished University Professor of Physics at Princeton. "Their equation allowed Igor and his colleagues to work out the 'transition' between the two regimes. They demonstrated that it exactly matched string theory's predictions at the strong interaction limit....

See these websites [5]

[6]

RK

NO, NO, NO. This is yet another confirmation of the AdS/CFT correspondence, the best known example of the gauge-gravity duality conjecture. Unfortunately the reporter didn't understand what's going on. Dan Gluck 13:43, 24 May 2007 (UTC)

Uhhhh... Wow.

how can string theory be proven? I've never actally seen it work...

Do you mean mathematically, or to test it in nature? Mathematically it can only be show to be consistent, either by its own or also with quantum field theory and gravity. This is thought to be correct, but a real proof will probably not be seen in the near future. The Testability of the theory is a big problem, which is addressed in the article. Dan Gluck 13:45, 24 May 2007 (UTC)

Testing String Theory

I just - somewhat bluntly - reverted an edit that painted a very rosy picture of the prospects of experimental verification of string theory, claiming the optimism to better reflect the "expert" consensus. The consensus among basically every other string theorist I know (including one of the people behind the work at Princeton alluded to above) is that it is very unlikely we would have confirmation of s.t. as a theory of gravity any time soon. There are some scenarios where it could amazingly appear at the LHC, but this is just what people talk about to get grant money. People who believe in string theory (such as myself) just don't expect to see it there. The problem is that the Planck scale, where quantum gravitational effects are believed to become significant, is like 15 orders of magnitude higher than the energies produced at cern. Some phenomenological theories (eg ADD) would move the scale way down, but most think it would take a stroke of blind luck if these theories are realized. Assuming the Planck scale is where most people think it is, no theory of quantum gravity (not string theory, not Smolin's loop quantum gravity...) is going to be tested at the LHC.PhysPhD 06:13, 27 May 2007 (UTC)

Removed an apparently incorrect quotation

This sentence contains an alleged direct quote that appears in a publisher's blurb as if it is a paraphrase (that is, not in quotes):

• "String theory —the hot topic in physics for the past 20 years—is a dead-end," says Smolin, one of the founders of Canada's Perimeter Institute of Theoretical Physics and himself a lapsed string theorist [7].

A quote from Smolin may be good here, but unless the above can be verified as his actual words, someone needs to find another one. I've removed the sentence.

I removed the "only game in town" quotation (which I originally put as a counterbalance to Smolin's quotation), for the same reason, as well as for the sake of preserving neutrality. Dan Gluck 08:49, 7 June 2007 (UTC)

Removed quote

This quote was removed from the article:

"String theory —the hot topic in physics for the past 20 years—is a dead-end," says Smolin, one of the founders of Canada's Perimeter Institute of Theoretical Physics and himself a lapsed string theorist [8].

A quick Google search will reveal that this is from the Publishers Weekly review of The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next by the named author. I have no particular opinion about whether the quote, properly cited, should return to the article.

CRGreathouse (t | c) 12:28, 7 June 2007 (UTC)

What is the meaning of the remark?

The following invisible remark has been added to gauge-gravity duality section: <!-- This section is linked from [[String theory]] --> What is the meaning of this? Dan Gluck 17:28, 26 June 2007 (UTC)

link to pseudoscientific explanation deleted

I have deleted a link to an animation taken from the pseudoscientific "the tenth dimension" book and website, which has nothing to do with string theory's interpretation of this concept. Dan Gluck 14:29, 4 July 2007 (UTC)

Preface

I added a Preface right before the Overview section...

I think it's important for the readers to know that an article could be endless if it highlighted all the possibilities that string theory says could happen, and that the information presented is going to highlight one of the many "versions" of String Theory.

Feel free to edit the preface, but after hearing many documentaries on it (many of which conflicted with each other) it's good to know that the information you read isn't always the ONLY way string theory could work. --Huper Phuff ^talk 21:45, 12 July 2007 (UTC)

Edit: I noticed there is a part in the intro that talks about the different versions of String Theory, so the Preface might be up for debate...I say it's still necessary... --Huper Phuff ^talk 21:45, 12 July 2007 (UTC)

The article covers these issues, so there's no need for this awkward disclaimer.PhysPhD 22:56, 12 July 2007 (UTC)

There is something which SHOULD be added, and I think the overview is the place: That's explaning that string theory can be approached either by using worldsheet tools or by using supergravity tools, and that the two approaches are complementary. The article puts emphasize mainly on the first approach (partly I'm the one to blame for that). I intend to edit the overview in that spirit. Dan Gluck 06:41, 13 July 2007 (UTC)

Removed Line

There was a sentence that I have deleted which stated that String Theory was at this point, a mere philosophy since it has not made any falsifiable prediction. This is an extreme POV since String Theory is not just some random philosophical speculation but a mathematically consisitent model that has compelling features to be considered as a contender for the Theory of Everything —Preceding unsigned comment added by 220.227.207.36 (talk)

I agree. Certainly it is not a philosophy since it has a mathematical structure. At most one may say it's mathematics rather than physics, but that's a matter of POV as well. Dan Gluck 14:00, 24 July 2007 (UTC)

The reason it is stated as a philosophy, "religion", belief or w/e...is because the field of science is about studying the physicaly world and making theories that fit this "idea" of the world that can be proved through experiments and/or testing. Since string theory, as of yet, cannot be proved it has a very careful placement. If you can never prove something, then it merely becomes a personal belief, however there are ideas on how string theory can be proved so it does have some scientific application (also because it can be proved mathematically). That why it is appropriately named string THEORY. For example: if you say the universe is infinite, because string theory predicts it...there's no way of proving that the universe is inifinite so it merely a personal belief. --Huper Phuff ^talk 21:07, 29 July 2007 (UTC)

Hi Huperphuff. I totally agree with you. However the term "philosophy" is not accurate, because a philosophy has no coherent mathematical structure. Furthermore, string theory has a huge contribution to mathematics. However, it cannot be considered as mathematics, since it lacks the rigour needed for that. It is sometimes called "methametical physics", though in my point of view it should more properly be called "physical mathematics" or, more properly, "non-rigourous mathematical structure". Anyway, it is a matter of POV how to call it, and there is certainly no concensus that it should be called "philosophy", just as there is no concensus that it will never make contact with experiment, so your sentence violates WP:POV, just as would be a sentence calling it "non-rigourous mathematical structure", which I believe it is. Dan Gluck 18:26, 30 July 2007 (UTC)

String Theory is a tightly constrained theory?

I noticed that a previous edit in which I said string theory was not a tightly constrained theory was removed without editorial comment in discussion. I'll assume for the moment that it was done in good faith. But I would like to know what the reason for that removal was.

My understanding of string theory shows that it has not even been proven to be a finite theory. Rather it was assumed to be finite until Dr Smollin showed that it was never proven. Furthermore, until Witten introduced the idea of a membrane it was really 5 different theories. But even though the membrane idea is only a "concievable" link between the five theories it is not in anyway proven or even well defined.

So unless someone can explain how this isn't an important issue and that it doesn't belong in the category of an "unconstrained" theory I will put my previous comment back in. Does anyone want to refute this? I think it may be just as important an issue as string theory not making any predictions that can be validated at conceivable energy levels. For instance, if you just adjust the parameters, which you can do because its so loosely defined, you can make it match whatever you want - albeit with negative sideeffect that don't actually show up in observed reality. —Preceding unsigned comment added by 75.7.37.102 (talk)

Please define "constrained", and what it has to do with finiteness. That seems like an unrelated issue. String theory does very little to constrain the low energy physics, as it appears to have many solutions, each corresponding to different effective theories at the energies we probe. But while its solutions are plentiful, it is a highly constrained theory. At the level of the space-time action, M-theory is unique, with no adjustable parameters, just many solutions.PhysPhD 05:46, 31 July 2007 (UTC)

"Unconstrained" , in this context just means that string theory doesn't appear to have any underlying truth it absolutely adheres too. Rather, it is many different theories but one can't predict in advance which part of the total should apply to what natural phenomena, accept after the fact. If you apply one particular part of the broad idea to the wrong physical reality you get artificial artifacts that don't appear in nature. A "real" theory has an underlying direction about what the mathematics applies to. It understands what part of nature it applies to in advance and doesn't try to make a patchwork quilt ater the fact to make it match nature.

Being "finite" is even more important. That just means the mathematical expressions you are using represent energy that is constant and conserved. Physics is about transformation of energy in different forms but in which the particular system one's equations represent that energy level does not "blow up". This is very basic to a theory being constrained or not. Transformation of energies into particles and vice-versa can occur but energy should never be unaccounted for.

—Preceding unsigned comment added by 75.7.37.102 (talk)

I am not going to be able to address this vague and shifting notion of "constrained". By the way, energy is not conserved in even classical general relativity, but it is conserved in divergent relativistic field theories, and nothing like what you describe occurs in any theory. Theories requiring a regulator are everywhere in physics, some tested to 10 decimal places.PhysPhD 15:16, 31 July 2007 (UTC)

The assertion you are making about string theory is what requires the burden of proof. It is self evident from my description that "any" theory in science must be constrained in some way - that it must know what it applies to in advance in order to make predictions. This isn't rocket science. It is defenders of string theory that have the burden of proof. What is yours, other than saying I'm being vague. These overarching principles are "general" principles that are well understood, recognized, and respected. This is completely different from your notion of "vague".

—Preceding unsigned comment added by 75.7.37.102 (talk)

Hi. First, please sign your post on the talk pages, even though you don't have a username. You can do it by writing ~~~~ at the end of your post. Second, the burden of proof lies on you, you must bring reliable sources which claim that string theory is not constraint and that your definition of "constraint" is widely used, otherwise it's original research for which Wikipedia is not the place. Finally, I think both me and PhysPhD agree that string theory has many many solutions which have nothing to do with our universe, which is your major claim, and the rest of the argument seems to me semantics. The reason why I deleted the paragraph was not because I disagreed with it, though in retrospect the use of "constraint" was ambiguous and therefore inappropriate. The reason was simply to make the introduction shorter in order to comply with Wikipedia:Lead section. I think that the statement that it has a huge number of solutions is enough. Dan Gluck 20:08, 31 July 2007 (UTC)

A sensible quantum gravity?

The introduction said "a sensible quantum theory of gravity emerge". "Sensible" is not well defined and I changed it to "consistent". However, it is not known - though there are signs in favour - that string theory is consistent (certainly it is not obvious that it is "sensible"). Therefore I wrote "a consistent quantum theory of gravity seem to emerge". Perhaps it should better be "a quantum theory of gravity, hopefully consistent, emerges" ? Dan Gluck 20:17, 31 July 2007 (UTC)

Dan, it's very difficult for me to understand how you can think string theory is consistent. It isn't. It seems to be a theory in which certain patterns emerge under certain conditions, that correctly mathematically model certain aspects of physics. But there is no real understanding how it models certain parts and why it brings in erroneous artifacts at the same time. Its like a dream sequence where certain aspects of life show themselves and other bizarre aspects emerge at the same time.

It seems to me you've decided string theory is a good theory and just aren't applying the rigorous questioning unproven theories deserve.75.7.37.102 04:19, 1 August 2007 (UTC)

Dear 75.7.37.102 :-), consistent means mathematically consistent, so that it does not contradict itself. It has nothing to do with whether it agrees with reality.

It is not true that string theory predicts at the same time things that are similar to reality and things which are not. String theory has many solutions, and every solution is a different prediction - some think about it as string theory predicting many different universes, in one of which we live. Some solutions ("univereses") are very different from reality (= our universe), while others are more similar. Hopefully, one of these solutions is exactly like reality (i.e., one of these universes is ours). However it is extremely difficult to verify that because there is a huge number of solutions. The main problem is that there is a huge number of such "universes", and string theory doesn't tell us in which of them we live, so it's not really helpful, hence the alleged problems of lacking a predictive power and not being falsifiable. If you ask for my personal opinion, actually I agree with this criticism. However this is unrelated to consistency. Dan Gluck 07:43, 1 August 2007 (UTC)

Does string theory predict the number of space-time dimensions?

I just undid an edit that went way too far in weakening this claim about string theory. I think the edit was correctly motivated by the existence of non-critical string theories with different dimensionalities. However, its claim that only "exactly flat" solutions have constrained dimension is incorrect. For example, in the standard 5 superstring theories, all metrics that obey Einstein's equations and have perturbative curvature would be constrained to be 10-dimensional, right? In all cases that I know, string theory succeeds at the highly non-trivial task of constraining the dimension of space-time according to the local field content of the (space-time) theory.PhysPhD 20:04, 21 September 2007 (UTC)

I put back the edit and just found the talk page; let me address the points you raise. The original version really went way too far in claiming string theory predicts the dimension. First, the statement made in my edit is that ``exactly flat spacetime solutions exist only in the so-called ``critical dimension" ", not that ``only "exactly flat" solutions have constrained dimension". The latter would indeed be incorrect, but the former is precise. As the article later discusses, the requirement to model realistic physics is to have four large dimensions, with the others -- however many there are -- being unobservable. This is consistent with a much wider variety of total dimensionalities. One way to see this is that currently known methods for stabilizing moduli and tuning the cosmological constant to a small value to provide four large dimensions use a fine-tuned near-cancellation between large contributions to the potential energy, which go well beyond weakly curved solutions to the classical Einstein's equations.

Even at the classical level, Einstein's equations are emergent at large distance scales; string theory generalizes these to the conditions for worldsheet conformal invariance. The dimension is generalized to the ``effective central charge", governing how fast the Hagedorn density of states grows -- roughly speaking it governs how many directions there are into which the string can wiggle. I wanted to retain the spirit of the section in noting that string theory does constrain the dimensionality relative to other physical quantities, in the sense that it correlates total dimensionality with the tree-level potential energy (see Polchinski's book for the precise expression proportional to D-26 or D-10 for the bosonic or superstring respectively). Note also that critical and noncritical corners of string theory are connected by dynamical transitions, so it is not consistent to claim that ``critical string theory" exists independently and predicts the number of dimensions a priori. Moreover, noncritical corners have a much wider variety of solutions than the linear dilation solution the article had mentioned in a footnote (just as in critical corners of string theory, for which as you say there is a wide variety of solutions to Einstein's equations going beyond flat space).

I'm sure the wording could be improved, but I hope people can keep the claims accurate in future edits of this point. There is no known prediction of the total effective central charge, or of the total number of large weakly curved dimensions, in string theory. There may later develop an understanding of a dynamical mechanism for preferring particular backgrounds of string theory. Low-energy supersymmetry, if observed, would point to late-time solutions in the critical dimension. But all this is yet to be determined. Please not also that my edit is more conservative, and so seems to me should be the default until someone really does derive the dimensionality from string theory independently of anything else. Moreover, the physics of the more generic backgrounds of string theory exhibits interesting phenomena, and may play an important role. —Preceding unsigned comment added by 76.205.212.31 (talk)

(First, 76.205.212.31 please try to conform to the format/signing conventions, including the four-tilde signature. Thanks.) To reiterate what I said above, the problem with your edit is that it takes away the completely valid success of string theories in relating matter content to dimensionality. For a given local field content, consistency predicts the dimensionality. It is great to emphasize that there is a lot of (beautiful) complexity to this story, such as Simeon's dimensional transitions. And yes, the linear dilaton is just a non-critical case that we happen to be able to solve, not the whole picture. But we owe it to string theory to emphasize this very non-trivial relationship between field-content and dimensionality.PhysPhD 20:57, 22 September 2007 (UTC)

The revised version does mean to emphasize that string theory fixes the dimension in terms of the tree-level potential energy; this is precisely the corrected version of the relation you mention. I'm quite sure we agree that we owe it to both physics and to the readers of wikipedia to be careful and accurate, and if you edit in such a way as to further emphasize the consistency criterion relating dimension to potential energy, (i.e. retaining the correction noted above in the new version) I'm all in favor. Regarding the question of complexity vs simplicity: there are very simple insights and results in this area. The situation is somewhat analogous to a previous era in string theory when the connection to 11d sugra was missed (by people aside from those working on it, who had the right intuition). The 11d limit is simpler in some ways, more complicated in others, but it is important to be aware of it. There had been pseudo-theorems about predictions of upper bounds on the rank of gauge groups in string theory -- these claims were completely washed away by the string duality results. Similarly here, the claim that string theory predicts 10 dimensions is wrong, but there is a corrected version we are discussing, and I agree with you this should be emphasized. 76.205.212.31 22:07, 22 September 2007 (UTC)

I prefer the new version, which is more accurate than the statement that sting theory predicts the number of dimensions (or anything :-) ).Dan Gluck 10:20, 24 September 2007 (UTC)

guitar string analogy

Why did you delete the nice analogy "just as a guitar string can produce different notes"? I returned it. Dan Gluck 09:03, 24 September 2007 (UTC)

I really appreciate the guitar analogy as well, it really tied the theory into my head (no pun intended though funny after realizing). As a non-math person (sorry i'm a silly visual artist with wide interests) it is important for the article to try to reach a little bit beyond the math. Something i would personally like to see on it, would be a link to maybe fundamentals of math for physics (probably beyond the scope, but just as a reference point from this article to one). thanks, keep up the good work on weeding out the nonsensible arguements for those of us not as well informed on the technical aspects of this subject. Joe iguana 00:28, 12 November 2007 (UTC)

String theory is special in that its mathematics is virtually all modern mathematics, excluding much of discrete mathematics. So you're asking for too much, However, for the most basic concepts, you may look at vibrating string, then standing wave and wave. For more, you should just go to the relevant physical field and read - classical mechanics, electromagnetism, quantum mechanics, special relativity, general relativity... that's already a very long list. It took me 12 years to learn all this. Good luck. Dan Gluck 18:36, 12 November 2007 (UTC)

Added diagram

I've ported a diagram presenting the level of strings in comparison to other entities (molecules, subatomic particles) from the French Wikipedia. The caption has been directly translated from French. —Preceding unsigned comment added by 203.28.13.57 (talk) 03:08, 20 November 2007 (UTC)

VERIFICATION, FALSIFICATION, PHILSOPHY OF SCIENCE AND STRING THEORY

Early in the article is the following:

For a scientific theory to be valid it must be verified empirically, i.e. through experiment or observation. Few avenues for such contact with experiment have been claimed.[1] With the construction of the Large Hadron Collider in CERN some scientists hope to produce relevant data, though it is widely believed that any theory of quantum gravity would require much higher energies to probe directly. Moreover, string theory as it is currently understood has a huge number of equally possible solutions.[2] Thus it has been claimed by some scientists that string theory may not be falsifiable and may have no predictive power.[3][4][5][6]

First of all, verification (as mentioned near the top) and falsifiability (mentioned near the bottom) are not the same thing; although the passage above does not state that the two are the same, the implication is strong. Verification has long been recognized (at least since the time of philosopher David Hume who wrote on the subject) to be logically impossible as a result of the so-called "logical problem of induction". Any verification of a universal statement (as most scientific theories aim to make universal statements) relying on a finite number of observations (this process in the field of logic is referred to as induction) runs into this problem (it is logically fallacious to make universal statements based on a finite number of observations). If all scientific theories must be verified then we would have no scientific theories, as all would fall to the problem of induction.

It was due to this gaping hole in most scientists' understanding of and statements about their own practice that the philosopher Karl Popper proposed his theory of falsificationism in the 1930s and later, as Popper realized that science must be saved from itself in way; if science indeed operated by induction then it could not logically claim any higher level of knowledge than any other arbitrary set of statements that merely were consistent with observations. In any case, induction was illogical, and scientists had to be saved from any taint of illogical reasoning. Popper and his works were hugely influential (especially among scientists themselves when they became increasingly acquainted with his work and his glorification of science and scientists) and falsificationism to this day remains about the extent of what most scientists are familiar with with respect to philosophy of science.

Although compelling, Popper's falsificationism runs into one very large problem when one examines scientific practice; scientists often do not actually behave this way. This has been called the "is-ought" problem. Popper's description of science as a process by which scientists make statements and vigorously attempt by experiment to falsify them is a compelling myth. While it maintains science as logical, and to an extent serves to distinguish it categorically from other fields of human endeavour (or statement making), later philosophers of science have shown that while Popper might well have compellingly shown what scientists "ought" to do, he has failed to show that falsification "is" what scientists actually do. Indeed many authors have shown over the years that scientists will hold on to theories in spite of their logical status as "unfalsifiable" (it can be argued that evolution, insofar as it makes NO predictions about what creatures will look like in the future, is unfalsifiable), and that they often in their work make no effort to falsify their theories, and that often scientists actually DO use induction and verificationism in the course of their work, or rely on statistical arguments which by their very nature are not universal in nature and would count as unscientific in the Popperian philosophy. It has also been argued that scientific facts are whatever the group of people accepted as "scientists" say. All of these approaches have been considered in the history and philosophy of science.

The collision (sorry ... couldn't resist the pun) of two major theories-the standard model, and string theory-that is about to occur at the LHC should be very instructive to the community that studies history and philosophy of science. What will people see? How will they interpret the results? Who will (and who will not!) get access to this very special piece of equipment? How will the argument unfold from there?

Nevertheless, I propose that these types of philosophical arguments about string theory (verification, falsifiability) should be dropped (or at least separated), as they really have no bearing on the theory itself (they are simply non NPOV bickering between the camps), and to lead off the article about string theory with these philosophical arguments is inappropriate, misleading, and shows bias. My experience is that scientists will often trot out "Ockham's Razor" or "verifiability" or the "scientific method" or indeed Karl Popper when it is convenient and they wish to attack a view they don't believe in (those who are clinging to the Standard Model in this case in the face of string theory). It could be equally argued that clinging to the belief in the somewhat arbitrary ancillary hypothesis of the Higgs Field and the Higgs Boson is unscientific, since, as Karl Popper says, the addition of ancillary hypotheses to a theory in order to protect it from falsification is unscientific. Philosophy of science is its own subject, and should be written about as such. Major conflicts in theories are often the most interesting places to be (I think it was the philosopher of science Imre Lakatos that said you can always tell which scientists have the most in common ... they are the ones that are arguing the most between themselves!), but these articles in Wikipedia are supposed to define and explain the topic, NOT the conflict between views.

In any case, as an encyclopedic type resource, I think Wikipedia contributors should refrain from making these kinds of judgmental edits that do not serve to make clear WHAT the theory is. UNLESS one is actually writing an article about the debate itself between opposing views (in the case of String Theory vs. The Standard Model this would be a very interesting article indeed), one should refrain from engaging in debate WITHIN an article that is simply supposed to discuss a view, or theory, or whatever. The debate is and should be kept a separate topic until overall consensus is reached. For now there is no consensus, and a resource such as Wikipedia should serve as an encyclopedic resource to help people understand, not as a forum for bickering between people with conflicting views on a rather esoteric subject that is nevertheless of great importance to our understanding of the world. Keep the articles helpful to people who just want the "WHAT IS THAT?" explanation.

J.A.Ireland, BA (IHPST) (talk) 22:53, 18 January 2008 (UTC)

Uh, I'm sorry. Could you summarize that novel you just wrote, lol?--Princess Janay (talk) 15:49, 28 February 2008 (UTC)

Maybe I missed this when I read the above paragraphs, but what qualifies String theory as a scientific theory? Is it a testable model? I am talking about at this moment in time, as the article says it is an incomplete theory. If it is incomplete, does it make sense to call it a theory? Is it not really a hypotheses? 86.41.100.223 (talk) 13:17, 29 February 2008 (UTC)

String theory is a mathematical theory hypothesized to have relevance to a scientific understanding of nature.PhysPhD (talk) 18:29, 29 February 2008 (UTC)

In fact, the problems with falsificationism are even greater than what you've stated. As Quine points out, you can never really falsify a scientific theory in isolation--only against a background of other beliefs and theories about the world. Thus, Quine endorses "holism"--the view that we can never falsify any particular belief but can only detect a problem in our whole network of beliefs, such that we still have the option of which belief or theory to revise. In philosophy, there's still a great deal of dispute on most of these points, but Quine's views are probably better accepted than Popper's.

This article is hardly the only place where ignorant views on the philosophy of science are put forward... But I'd certainly second the suggestion that we delete such ignorance in an article about string theory. --anon

Kaluza-Klein

In fact, Kaluza and Klein's early work demonstrated that general relativity with five large dimensions and one small dimension actually predicts the existence of electromagnetism.

Five large and one small, or five total (four large and one small)? 72.75.125.22 (talk) 02:21, 25 January 2008 (UTC)

It is five total. I have fixed the article. Joshua Davis (talk) 17:54, 25 January 2008 (UTC)

Actually it is just doing General Relativity in 5 dimensions that one can show it can be decomposed into a 4 dimensional General Relativity together with an Electromagnetism. The large and small dimension thing just comes from an ad hoc attempt to account for the fact that we don't observe 5 dimensions.67.160.131.142 (talk) 04:30, 20 October 2008 (UTC)

Too much jargon?

Why is this article tagged? This article does NOT have too much jargon. I think that it was tagged by someone who didn't want to take time to read the whole article thoroughly. I am in the 7th grade, and I don't understand physics, but I understood THIS article enough to write a paper on the string theory! If you need an article that uses simple words and concepts, then use Simple English.--Princess Janay (talk) 17:58, 27 February 2008 (UTC)

I removed a {{Cleanup-jargon}} but it was restored with a comment that its removal was "vandalism". Are we going to dumb down this article by stripping it of its "jargon"? I have been working on the stack of prerequisites for this subject and created Template:Theory of everything. If you do not know the significance of, say, general relativity or Planck's constant, then you are not going to understand the significance of string theory. Are we going to dumb down this article the level of the three-hour show The Elegant Universe? Why not just face that if you do not have a good grasp of the math in quantum field theory, e.g. if you do not know what the Klein-Gordon equation means, then you are not going to be able to distinguish string theory from science fiction and you should either learn the math or go entertain yourself with the fiction.--Truthnlove (talk) 12:32, 2 March 2008 (UTC)

I think thats a pretty harsh reaction. Careful you don't hurt yourself dismounting your high horse, or do you just stay up there all the time. To be honest, if you didn't already know something about theoretical physics, you'd find most of the stuff in this article impenetrable. It does jump into very esoteric territory early on. Where is this template:theory of everything that people can read through first so they at least have some clue of what's going on? I think that would be very helpful.60.228.249.60 (talk) 13:33, 8 February 2009 (UTC)

Unified Field Theory

I couldn't see any section in the article discussion the relationship between the String Theory and the Unified Field Theory. Should we include such a section into the article?

--Mhsb (talk) 22:01, 28 February 2008 (UTC)

Opinion on "relative-ness" of extra dimensions?

In the Principia Newton defined time and space for physics:

I. Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration:

relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.

II. Absolute space, in its own nature, without relation to anything external, remains always similar and immovable.

Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies; and which is commonly taken for immovable space; such is the dimension of a subterraneous, an aerial, or celestial space, determined by its position in respect of the earth.

We all know that Einstein had something to say on this topic.

He writes in Relativity Chapter 9:

Now before the advent of the theory of relativity it had always tacitly been assumed in physics that the statement of time had an absolute significance, i.e. that it is independent of the state of motion of the body of reference. But we have just seen that this assumption is incompatible with the most natural definition of simultaneity; if we discard this assumption, then the conflict between the law of the propagation of light in vacuo and the principle of relativity (developed in Section VII) disappears."

The reason for the assumption could be Newton's description of absolute time being mathematical rather than relative time.

In Chapter 8, Einstein gives his working definition for time:

Under these conditions we understand by the 'time' of an event the reading (position of the hands) of that one of these clocks which is in the immediate vicinity (in space) of the event

Einstein is defining time in terms of the moving hands of a clock, which is nearly identical to how Newton defined relative time:

Relative, apparent, and common time, is some sensible and external (whether accurate or unequable) measure of duration by the means of motion, which is commonly used instead of true time; such as an hour, a day, a month, a year.

While I often hear some claim "Einstein has shown that time is relative", really, all that he has shown is that our present mathematics represent relative time, contrary to Newton's definition.

In fact, Einstein had made this point to Heisenberg, I think demonstrating how easily this subtle point is missed:

"But you don't seriously believe," Einstein protested, "that none but observable magnitudes must go into a physical theory?"

"Isn't that precisely what you have done with relativity?" I asked in some surprise. "After all, you did stress the fact that it is impermissible to speak of absolute time, simply because absolute time cannot be observed; that only clock readings, be it in the moving reference system or the system at rest, are relevant to the determination of time."

"Possibly I did use this kind of reasoning," Einstein admitted, "but it is nonsense all the same. Perhaps I could put it more diplomatically by saying that it may be heuristically useful to keep in mind what one has actually observed. But on principle, it is quite wrong to try founding a theory on observable magnitudes alone. In reality, the very opposite happens. It is the theory which decides what we can observe."

(In 'Physics and Beyond - Encounters and Conversations', Harper Torchbooks, 1972, p. 63.)

To summarize all that: in the eyes of both Newton and Einstein, while absolute space and time are "somewhere out there"; it is relative space and time that we measure..

Emphasis: RELATIVE SPACE AND TIME ARE MEASURED.

Now.

String theory.

There are visible dimensions of space and time, and there are hidden dimensions.

These hidden dimensions, cannot be measured.

Is there an opinion in the field regarding whether or not these extra dimensions are a "new" type of relative space?

Or is it absolute space? MobyDikc (talk) 06:34, 29 February 2008 (UTC)

Current/planned projects to find evidence of string theory section?

I am not an expert on string theory by any means, but i have a basic understanding, whist on the Primordial black holes wikipage i noted that it mentioned some work on trying to find black holes that are predicted by string theory which would be the "could be the first indirect evidence for primordial black holes and string theory.". Interested i came to the string theory wikipage to find out about any more projects aiming to do similar things but could not find any. A section dealing with these kind of experiments/projects/whatever that attempt to do this (even if its just links to other wikipages) could be quite useful and improve the article somewhat. gord (talk) 01:07, 21 March 2008 (UTC)

Description of an atom wrong

In the first line of 'Overveiw' it says: "Matter is composed of atoms, which in turn are made from quarks and electrons." Atoms are not made of quarks and electrons. this should say: "Matter is composed of atoms, which in turn are made of protons, neutrons, and electrons." Going on to state that protons and neutrons are made of quarks, leptons, and gluons should also be considered, but i don't think it's necessary. Oh no! I've messed up the discussion page. I'm sorry. I deleted the last post and replaced it with mine.

Minduser 01:22, 18 April 2008 (UTC)

History of String Theory (& SUSY)

The recent work to expand the history section is for the most part really good, but I worry about its uncited attribution of so much work to various individuals. I removed a claim that Ramond made "the first formulation of a supersymmetry outside the Soviet Union" in 1970. This contradicts my understanding, and the supersymmetry page, which says that Wess and Zumino invented SUSY (outside the USSR), but I don't know for sure. In general, we need to be very careful in writing history that we are fair to all who participated in it.PhysPhD (talk) 14:39, 22 April 2008 (UTC)

Hi-- you are right that attribution is necessary, but I wanted to cite the original articles. For the most part, these are collected in two good reprint volumes: "Dual models", and "superstrings", but I feel that only citing these is a cop out. for SUSY, Wess and Zumino cite Ramond, and motivate their construction by extending the two-dimensional supersymmetry discovered by Ramond to a four-dimensional supersymmetry which would be a space-time symmetry. Mathematically, Ramond did discover a true supersymmetry--- the two-dimensional super-conformal algebra which is a super-extension of the virasoro algebra. But this is not space-time supersymmetry, and when people say supersymmetry was discovered they usually mean space-time supersymmetry. In the soviet union, there were two groups which formulated space-time supersymmetry but were ignored in the west: Gol'fond and Likhtman(sp?) and Volkov and Akulov．The difference between them and Ramond is that Ramond is forced to do it to cancel ghosts, while they are doing it because it seems like a good thing to do.

It is hard to know exactly what to say about this. The mathematics of four-dimensional supersymmetry without superfields is more difficult than the mathematics of two-dimensional supersymmetry, and Ramond did not have a great geometrical picture for strings or supersymmetry--- he uses a one-dimensional string expansion, not a two-dimensional conformal field and his point of view is that the internal one-dimensional variable is a "time" variable, which is sort-of screwy but that's just the normal kinds of weird philosophies that flourish when something is new. Actually, I think he is sort-of formulating a "string" picture here, but his "string" is extended in time internally, but then again, mathematically all the Veneziano stuff with vertex operators has a string picture too implicitly, it's just not spelled out and given an action principle. There is no doubt though that the "F" operators he introduces to complement the "L" operators make a super-algebra, and for the first time. I think it might be most accurate to say "Ramond discovered two-dimensional world-sheet supersymmetry, the first use of supersymmetry outside the Soviet Union" and to say "Wess and Zumino, inspired by Ramond's two-dimensional algebra, constructed the first theory with a true space-time four-dimensional supersymmetry".Likebox (talk) 15:04, 22 April 2008 (UTC)

It's probably impossible to draw a clear line in this type of thing; In science, so many contribute incremental refinements, and who is to say which one step was key? I think erring on the side of mentioning more people is best, giving credit to all of the above.PhysPhD (talk) 20:01, 22 April 2008 (UTC)

I totally agree with that sentiment, and I think it is possible to be fair. Unfortunately, historical accounts are either written by busy professional physicists who rely on folklore history, or by popularizers glorifying certain figures. This case is particularly unfortunate, because Ramond was an unknown young guy at Syracuse.

Use of "SUSY": The main article has a section heading "SUSY", but no mention is made of SUSY in the section, or indeed anywhere else in the article. This is meaningless to the amateur reader. Fredsie (talk) 17:14, 24 January 2009 (UTC)

Ten vs. Eleven

While string perturbation theory suggested that spacetime was ten dimensional, string theory is just a limit of a non-perturbative theory which is fully eleven dimensional, and is only string-like when one of the dimensions is curled up. To say that string space-time is ten dimensional is so totally eighties.Likebox (talk) 01:02, 2 May 2008 (UTC)

Great Article!

You guys can remove this post if you like - it's not about editing, afterall. Just want to say that I'm also an artist with a wide field of interests, and this is one of the better articles I've read on any topic in WP. I suggested in "quantum gravity" that this could be a model for a deep article that's still readable. Good Job!!!

Compact dimensions : Structure vs Holonomy

I edited the section on compact dimensions to mention structure. The article said the compact dimensions must have holonomy of SU(3) or G2. This is wrong. They must have SU(3) or G2 structure which is basically including torsion. SU(3) holonomy assumes no torsion because it assumes the background NS-NS 3-form flux H3 is turned off. While this is true in the simplest cases, flux compactification is specifically making use of the non-zero H3 flux (along with things like the RR F terms and fluxs created by T duality from H3). Papers often assume SU(3) holonomy despite turning on H3, but again, it's an approximation. Considerable work is being done in the area of full SU(3) structure. See publications by Palti and de Carlos for the differential geometry approach and work by Wecht, Ihl and Shelton in terms of fluxs being turned on and their effect on orientifold model. While I'm not as up to speed for M theory models (non-geometric fluxs in IIB is my thing), a quick look through the thesis of Palti mentions G structure again, which is the M theory version of SU(3) structure. Hence I think it's important not to say "must have holonomy" and to mention the difference. If specific citations are needed, I can provide them AlphaNumeric (talk) 19:52, 20 June 2008 (UTC)

New image

Please comment on the new image on the progression from macroscopic objects to strings. Dhatfield (talk) 12:13, 27 June 2008 (UTC)

Loopholes and Implications

I noticed a few missing features after reading the Wikipedia article and watching the 3h instructional video, "The Elegant Universe" (see External Links on the article page), and am wondering about the following:

1. Rips in the time/space fabric, as proposed by Einstein; the video, The Elegant Universe, suggests that the paths left by the individual strings suck up the rips caused by the chaotic movements. However, later in the video they change their opinion about the formation of the strings; the are now severed in halves and attached to (I believe, off the top of my head,) the membrane, or some other semi-structural base. Now the strings are unable to move; so what happens to the tears now? Do we go back to our original belief that they simply don't exist? Or, more importantly, is it possible to create the "warp hole" Einstein proposed, now that there may be tears?

If this is valid as a question, there could be another part devoted to the string theories' stance on the above issue.

2. The fabric of time and space proposed by Einstein is, frankly, 2D. Although this doesn't fit entirely with only string theory, is it possible that there is a more 3D version of the fabric that isn't like a trampoline, but more like, say, weightless jell-o? Something that still captures the density of an object and weighs it accordingly... or would that deny the possibility of gravity by making the planets that revolve around the sun unable to move / the difference in density forcing the planets away from the Sun? But then again; in comparison to other stars and planets, etc. etc. the planets and the Sun aren't altogether far off in density (which opens up the possibility of another measurement for density).

Again, if this is valid, there could be a part devoted to the implications of string theory when weighed next to gravity.

3. Why must there be a "Big Bang", according to the video? There is a large, vast possibility that the Big Bang is simply that; a theory. If String Theory is correct, it would have amazing implications for religion, as well! It would finally tie together religion and science in an understandable way; combining faith with fact. The entire notion of string theory/M theory is entirely philosophical, and requires much faith. If it is correct, then there is finally room for a God in science, which would be highly dangerous but also very informative.

Perhaps there should be room for a religious aspect to the science of string theory?

Musicnotz (talk) 17:20, 29 July 2008 (UTC)

1. Gravitational strings are closed, they are not tied to a brane. As such, they can move unrestricted through space-time. Open strings have different properties to closed ones, since their ends define branes and thus are attached to them. So they don't change their minds, they go into more details.

2. Einstein's space-time is 4 dimensional. It's just that in order to get across basic concepts in relativity to people who don't do the maths simple analogies are used and since few people can think in 4d, lower dimensional examples are given on TV.

3. String theory is entirely seperate from religion. Don't be daft and try to subvert what is an entirely agnostic concept for the purposes of your religion. It makes you look desperate.

AlphaNumeric (talk) 14:40, 4 August 2008 (UTC)

On Terminology

The usage of "p-brane" and "D-brane" without stating that they are black holes in the classical limit makes them seem more mysterious than they are. They are not just surfaces, like topological domain walls in a field theory, they are gravitational objects. The metric for a p-brane is a higher dimensional charged black hole solution extended in the world-volume dimension, and sometimes with a long-ranged scalar field contribution. They are higher dimensional extremal charged black holes, and I believe they were originally defined this way in the supergravity literature (I didn't read the original p-brane papers--- someone who has please correct me).

D-branes are superficially different--- they are endpoints for strings--- but it was Polchinski's great insight that the D-brane should be identified with the p-brane at weak string coupling. In other words, the D-brane is just a p-brane, or what's left of it in limits where strings become perturbative. Unfortunately there is conflicting terminology. Some people call any extended object a "brane", using it as short for membrane, not restricting the usage to those objects which are an extended black hole solution in the classical limit. As far as I know, this is not the terminology that has become standard. If it's not a black hole, just an extended defect, most people (as far as I know) still call it a "domain sheet" or "domain wall" or "topological defect" or whatnot.

Howver in the literature on Randall Sundrum style models, the two concepts of "brane" and "sheet" are blurred. I believe that the reason is that the Randall Sundrum models are sometimes very phenomenological, and don't have to be completely precise about what the branes exactly are as fundamental string theory constructs. So the Randall Sundrum "branes" are not always branes. But I think that this article should stick to the terminology used here, because I think it makes things clearer. Just my 2c.Likebox (talk) 21:30, 2 September 2008 (UTC)

Weaseling

To avoid saying clearly, point blank, that D-branes are quantum versions of charged black holes makes it difficult for people to appreciate the logical coherence of string theory, and leads them to think that it is just guesswork. This is unfortunate, because it makes many people view the whole field with much more skepticism than it deserves. The string theory identification of matter and black-hole, resulting in a precise holographic description of both, is, in my opinion, the greatest achievement of science. But for some reason, people always tiptoe around saying this clearly. I tried to fix that here, but the weasel-words return.

For example--- D-branes are "extended objects which source a differential form vector potential" sounds much more mysterious than "D-branes are extended quantum-mechanical charged black holes". "D-branes are identified with black-hole like p-branes through AdS/CFT correspondence" sounds much more daunting than "when a bunch of D-branes are stacked up one on top of the other, they become classical charged black hole sheets, while the behavior of nearby objects is still described by a theory of the oscillations of the surface". Which is nearly the same statement.

To be fair, there are a few differences between the mental image conjured up by the words "black hole" and the mental image of D-branes. Black holes are classical, and the D-brane is quantum. Black holes are usually imagined to be neutral and thermal, while D-branes are extremal-charged and so non-thermal. Black holes are usually imagined as spherical in four dimensions, while branes are extended in higher dimensions. But that's the end of the list of differences. So to say "A D-brane is like a black hole" is too careful--- it's like saying "an electron in field theory resembles a negative point charge" or "an atom is similar to an electron orbiting a nucleus". We don't say those things anymore, we say "an electron is a point charge" and "and atom is an electron orbiting a nucleus", because the fact that they are quantum mechanical, so that the classical description is not completely correct, goes without saying. As far as authorities go, Witten said it in 1996, before AdS/CFT, and he's the most authoritative authority there is.Likebox (talk) 22:46, 7 September 2008 (UTC)

Simplified version?

M-theory has a simplified version. Why can't we have one for string theory? It would help quite a few people understand the concept better, which many would like.

Thank you for considering the idea.

Lunakeet 13:55, 18 October 2008 (UTC)

Nonsymmetric Tensor

I remember vaguely that Einstein at one point introduced a non-symmetric metric tensor for unification purposes. This is vaguely reminiscent of the way that you get a two form in string theory, it enters like an antisymmetric part of the metric tensor. Since this two form is fundamental--- it is the field of the charge carried by the string--- I thought it might be nice to make the connection, even though I think it is nearly certain that there was no historical connection between these two ideas.

On the other hand, I haven't read Einstein's unified field theory papers (very few people have) and I am not sure if the antisymmetric tensor he played around with is at all similar to the 2-form field. I was hoping somebody would know.Likebox (talk) 19:46, 9 November 2008 (UTC)

Tachyon has "imaginary" mass, or "negative" mass, or something else altogether?

The first line of the table under the String_theory#Dualities section says: "Only bosons, no fermions, meaning only forces, no matter, with both open and closed strings; major flaw: a particle with imaginary mass, called the tachyon, representing an instability in the theory."

So does the tachyon have an imaginary number value for mass under string theory, or is it some other interpretation of the word "imaginary"? I don't know enough about the subject, so I'll leave this change to somebody else. FFLaguna (talk) 06:43, 14 December 2008 (UTC)

• The tachyon mass is an imaginary number. But this is only formality, because there is no such thing as tachyon particle; rather, the tacyon represents an instability (see the article about tachyons). Dan Gluck (talk) 17:21, 28 February 2009 (UTC)

subatomic level

if the string frecuency is the diffrent between subatomic particle so in theory there is an infinet kinds of subatomic particles am i right?--אזרח תמים (talk) 11:22, 28 December 2008 (UTC)

Yes, there are, higher frequency vibrations make infinitely many higher mass particles. but the only subatomic particles we can see are the ones with zero mass, and there are only a finite number of those.Likebox (talk) 19:48, 28 December 2008 (UTC)