M-theory is the remarkable physical theory in eleven dimensions whose existence was conjectured by Edward Witten in 1995. Witten's discovery ignited the second superstring revolution and led to a number of important developments in theoretical physics and pure mathematics. This year is the 20th anniversary of Witten's announcement, so I thought it would be cool to bring this article to featured status. Polytope24 (talk) 03:42, 4 February 2015 (UTC)Reply[reply]
Comments
Roughly speaking, bosons are the constituents of radiation, while fermions are the constituents of matter.
I associate bosons more with mediating forces than radiation.
Such objects had been considered as early as 1962 by Paul Dirac, and they were reconsidered by a small but enthusiastic group of physicists in the 1980s.
A reference to a Dirac publication would be nice.
Branes are dynamical objects which can propagate through spacetime according to the rules of quantum mechanics. They have mass and can have other attributes such as charge.
Do all branes have mass?
There is a small amount of inline LaTeX. As always, it looks awfulAWFUL when using PNG rendering on a large screen.
Suggestion: Use the math templates like in xy ≠ yx and 1/g or 1⁄g.
Thanks for these comments, YohanN7. I just finished making changes to the article. Please let me know if I have adequately addressed your concerns. Polytope24 (talk) 05:38, 6 February 2015 (UTC)Reply[reply]
Yes, every single one. I'll actually read that Dirac paper. His papers are usually very clearly presented. YohanN7 (talk) 06:14, 6 February 2015 (UTC)Reply[reply]
Support I was early on in favor, but undecided because I cannot really trust my extremely limited knowledge in string theory (cursory acquaintance with the first few chapters of Zweibach) and wanted to await comments from people with a more firm knowledge. Nice article. YohanN7 (talk) 12:24, 12 March 2015 (UTC)Reply[reply]
Support All my issues have been dealt with, I hope my comments are ultimately useful to the audience. Maury Markowitz (talk) 21:17, 13 February 2015 (UTC)Reply[reply]
Oppose: To start with, I'm actually surprised how well this article is put together. I especially like the lede's summation of the theory's (theories) applicability to math vs. physics, which is often overlooked in more glowing articles (well, in the past at least, perhaps the bloom is off the rose). Most of the wiki's math articles are absolutely atrocious collections of jargon, but this one is presented in easily readable prose with actual explanations. Most of what follows is minor, but there is one big issue I'd like to see addressed, lacking which I think the article is incomplete and inherently misleading. So, onward...
*Notes
This section mixes notes and citations. I'd strongly recommend removing the notes, like item 1, should be in their own section. If you're OK with that, I can quickly implement that with efn if you'd like.
*"In everyday life, there are three familiar dimensions of space (up/down, left/right, and forward/backward), and there is one dimension of time (later/earlier). Thus, in the language of modern physics, one says that spacetime is four-dimensional."
I don't think it's reasonable to state that 4d spacetime is a part of "everyday life". More broadly, I think it's worth another couple of sentences in this para to explain where 4d "is". Conceptually, GR is quite simple (IMHO) and I think we should make an attempt to explain that here, otherwise what follows is sort of floating about on it's own. Perhaps something along the lines of...
In everyday life we are familiar with the three dimensions of space, up/down, left/right, and forward/backward. In physics, however, general relativity introduces the concept that time itself is a similar dimension, giving rise to the modern concept of spacetime, a four-dimensional universe. We do not directly observe the 4th dimension in the same way we do the other three, we do not see it as a physical construct. Many everyday effects, like gravity, are a side-effect of this unseen "direction"; under general relativity, you are held to the surface of the Earth not because something is pulling you down, but because that is the shortest distance between today and tomorrow in a direction you cannot see.
I apologize for the prose of that last sentence, but you get where I'm going here. Some explanation of the geometric basis for gravity seems appropriate at this spot.
*"Despite the obvious relevance of four-dimensional spacetime for describing the physical world"
Again, I don't consider this "obvious". Perhaps something discussing the success of these theories, as opposed to their obviousness, would be more appropriate here.
*"History and development"
Here's where I see an actual problem. Higher-dimensional solutions to physics have been around since GR. It was not long after that we had Kaluza–Klein theory and Einstein's own efforts. I consider these to be the forerunners of M-theory in every fashion. That they failed in their quest is not surprising given the difficulty of applying GR generally, and it is equally unsurprising that supergravity became "a thing" shortly after the golden age of GR began. I really think that this article should mention the development of the precursors, and the "battle" between these and QM's development through the same era. In that historical context, attempts to "dimensionize" physics were failures, QM was offering more progress and those other efforts dropped by the wayside. They briefly re-emerged in the 70s, and I think the article does a fine job from that point on.
I think this is a serious problem. In this historiography, M theory is the latest salvo in a 100-year battle between the two great physics. It's the way it potentially sits above either that makes it such a hot topic. Currently the article doesn't talk this at all, and I think that is a serious oversight.
That's all I have for now, I'm about 2/3rds through it. Maury Markowitz (talk) 16:41, 11 February 2015 (UTC)Reply[reply]
Hi Maury, thanks for these comments. I actually think all of these points are fairly easy to address, including the issue with the history section. I'll start working on it as soon as possible. In the mean time, if you want to make changes to the notes/citations, you're certainly welcome to do that. Polytope24 (talk) 18:58, 11 February 2015 (UTC)Reply[reply]
@Polytope24, check out my User:Maury Markowitz/sandbox and see if you think that would be a useful first section in the history area. I wrote it to lead directly into the existing section. If you like it, I can ref it up. Maury Markowitz (talk) 21:08, 11 February 2015 (UTC)Reply[reply]
Thanks for these suggestions. I just added a short subsection explaining the prehistory of higher dimensional models of spacetime and Kaluza-Klein theory. This is all based on the material you posted in your sandbox, but I changed a bunch of things in order to ensure that writing was accurately reflected in the citations.
I also decided to leave out the parts explaining Newton's laws and the history of general relativity. The purpose of of this section is to give a concise history of M-theory, not to explain the whole history of physics starting with the work of Newton. On the other hand, I am sympathetic to your concern that the article did not sufficiently emphasize the prehistory of the subject and the role of Kaluza-Klein theory. Hopefully the changes I've made will address your concerns. If not, please let me know, and we can talk about it.
You'll also notice that I added a few sentences elaborating on the notion of four-dimensional spacetime. This should help emphasize the point you've been making, namely that the idea of extra dimensions was implicit in a lot of the thinking leading up to the discovery of M-theory.
Please let me know if there's anything else I need to change. Thanks. Polytope24 (talk) 01:49, 12 February 2015 (UTC)Reply[reply]
Excellent work! My only remaining suggestion in the history section is to mention the 1960s rebirth of GR as a leadup to supergravity. Maury Markowitz (talk) 02:31, 12 February 2015 (UTC)Reply[reply]
Okay, I added a sentence on this. Please let me know if that's what you wanted. Polytope24 (talk) 03:01, 12 February 2015 (UTC)Reply[reply]
I have moved the sentence into the appropriate section, expanded it slightly and cited it. I extracted notes into a separate section, and re-sectionized the references. See what you think. Maury Markowitz (talk) 13:18, 12 February 2015 (UTC)Reply[reply]
Looks good. I made a few changes to maintain a consistent citation style. Polytope24 (talk) 01:39, 13 February 2015 (UTC)Reply[reply]
All of the issues above have been dealt with. I just finished the section on AdS/CFT correspondence and think I actually understand it now. This is precisely the sort of clear explanation that many of the math and science articles lack, and I'm calling it out for attention on how to do this right. Ok, just a few more...
*"One property of this boundary is that, locally around any point,"
So does this mean "at any arbitrary point on the boundary"? I'm a bit confused about this passage. Do we live in the middle of the disk, or on it's edge?
*"(2,0)-theory"
I can't find an explanation of what "(2,0)" means, either here or the linked article. The 6D is explained, as is AsD7, but not this term. Maybe a return directly after this to separate the para and then a single sentence on this?
*A couple of cites need buffing, Randall, Wald and Zee have harv tags with nothing pointing to them. Would you like me to fix these?Maury Markowitz (talk) 11:54, 13 February 2015 (UTC)Reply[reply]
I made some very subtle changes in the section on AdS/CFT to emphasize that "locally around a point" refers to a region restricted to the boundary surface, and not intersecting the interior at all. The point of the AdS/CFT correspondence is that you have two separate theories. For one of them, "spacetime" is the bulk anti-de Sitter space, and for the other, it's the two-dimensional surface at the boundary. Please let me know if the revised version is more understandable.
I also added a sentence explaining the meaning of (2,0). This is a pretty technical bit of jargon that's not really relevant for understanding what this theory is all about, so I mentioned only very briefly.
Finally, I went ahead and removed those harv tags. They were originally being used to create citations within the explanatory footnotes. However, I was bothered by the fact that these citations showed up as hyperlinks and none of the others did. I also didn't like the idea of having footnotes within footnotes. Feel free to make further changes to the references if you like. Polytope24 (talk) 16:47, 13 February 2015 (UTC)Reply[reply]
Comment. I'm coming in late to this, but I would like to remind editors that WikiProject Mathematicsstrongly discourages use of ((frac)) in mathematical formulas. I see that hasn't been done. I would not be at all surprised if ((math|((frac|1|''g'')))) would fail at some point. I did make one change, which I hope meets with approval. I changed ((math))10<sup>-30</sup>)) to ((nowrap|10<sup>−30</sup>)), changing "math" no "nowrap" and changing the hyphen to a mathematical minus. I don't think wrapping numbers, by themselves, in ((math)), serves any purpose. — Arthur Rubin(talk) 19:30, 12 February 2015 (UTC)Reply[reply]
Thanks Arthur Rubin. I don't know much about typesetting math on Wikipedia, so I appreciate your help with this. Do you have any recommendations for typesetting fractions? Polytope24 (talk) 20:08, 12 February 2015 (UTC)Reply[reply]
(({math|((sfrac|1|''g'')))) 1/g is considered acceptable, but formulas involving complex fractions have many of the same problems using <math>...</math> and ((math)). ((frac|1|2|3)) (1+2⁄3) uses superscript and subscript and thinspaces to simulate pre-computer typesetter's fraction notation; there is a version of that in LaTeX, but it's (wisely) not available within our math tags. I used to have a template ((tfrac)) which used the same parameters as ((frac)) and ((sfrac)), but just used the inline version (with, I think, some thin spaces). It was deleted as unnecessary. — Arthur Rubin(talk) 20:29, 12 February 2015 (UTC)Reply[reply]
I just learned about ((frac)) and have been going through my articles looking for places to use it. ((frac)) is my new god. And they don't like it? <moviesound>Noooooooo!</moviesound> Maury Markowitz (talk) 11:54, 13 February 2015 (UTC)Reply[reply]
My knowledge of the topic is that of an interested layman with a maths background, so some of these questions may reveal my ignorance more than they point up issues in the article.
"One of the vibrational states of a string gives rise to the graviton": I don't think you say clearly that there is only one type of string, which may have different vibrational states, and that these states correspond to the various fundamental particles -- that is, that there are no particles left over by this approach. For a reader unfamiliar with the topic I think this would be worth stating directly. Perhaps even enumerate a couple more well-known particles beyond the graviton to make it clearer this approach models all particles.
"the type I theory includes ..., while the type II theories include ...": why singular "theory" for "type I" but plural for type II?
D'oh. I see you fixed this, but I just realized the answer, and it really didn't need to be changed. Oh, well, it works the way you have it now. Mike Christie (talk - contribs - library) 00:49, 27 February 2015 (UTC)Reply[reply]
I'm not sure that this needs to be in the article, but I found myself wondering to what extent the dualities are transitive. The description you give: "If two theories are related by a duality, it means that one theory can be transformed in some way so that it ends up looking just like the other theory" is pretty strong; wouldn't that imply that all five of these theories can be transformed into any of the others?
I'm a bit confused by the appearance of M-theory in the duality diagram. It's been described up to this point as a superset of all the string theories; the five named theories are limit points of it. So in what sense can it be specified to the point where it is dual to some of the five theories but not others?
You give two (apparently) different informal characterizations of "supergravity theory". In the supersymmetry section you say a theory in which supersymmetry is imposed as a local symmetry is a supergravity theory; later you say "fresh work on higher-dimensional concepts combining general relativity with recent developments in particle physics, under the general name supergravity". Are these slightly different informal terms for the same underlying theories, or was the term used slightly differently in the 1960s?
In a couple of places you have "work of" rather than "the work of"; if you don't want to use "the" I think "work by" would read more naturally.
"One of the problems was that the laws of physics appear to distinguish between clockwise and counterclockwise, a phenomenon known as chirality. As emphasized by Edward Witten and others, this chirality property cannot be readily derived by compactifying from eleven dimensions." The start of the second sentence seems a bit clumsy to me. How about "...a phenomenon known as chirality: Edward Witten and others have emphasized that this chirality property cannot be readily derived by compactifying from eleven dimensions"?
"Indeed, by the 1990s, physicists had identified five consistent supersymmetric versions of the theory": does this mean they'd identified five, and there are possibly more still to be identified? I'm not clear what "indeed" is adding here.
The change you made is an improvement, but I'm still not quite clear if the implication is that there were exactly five to be found, and they were found; or if five had been found by the 1990s, with possibly more remaining to be discovered. The use of "determined" makes the former seem likely but I wanted to check. In the context of the rest of the article it seems as though there should in fact be many more theories, inside the grey "M-theory" shape in the schematic diagram, but perhaps only five of them qualify as purely supersymmetric theories, with only ten dimensions. Mike Christie (talk - contribs - library) 00:49, 27 February 2015 (UTC)Reply[reply]
The general belief is that there are exactly five supersymmetric string theories in ten dimensions, but I'm not comfortable writing this in the article. An expert on perturbative string theory could probably give you arguments why this is the case, but the statement that there are only five string theories is not a theorem. It's certainly possible that theorists will eventually discover a new string theory; see here, for example. Let me know if you think there's a better way to express this state of affairs in the article. Polytope24 (talk) 03:57, 27 February 2015 (UTC)Reply[reply]
I think if we just weaken "determined" to something like "identified" it will fix the issue -- "identified" would be neutral about whether there are five or more than five theories. Mike Christie (talk - contribs - library) 04:37, 27 February 2015 (UTC)Reply[reply]
Damn. I just noticed that that's the exact word you originally had, and when I first read it I took it as not neutral. Sorry for being so unhelpful on this one; let me think about it and see if I can come up with a phrase that works. Mike Christie (talk - contribs - library) 04:48, 27 February 2015 (UTC)Reply[reply]
Currently the article has "In string theory, the possibilities are much more constrained, and there are only a few consistent formulations of the theory. By the 1990s, physicists had determined that there were five consistent supersymmetric versions of the theory." Could we say something like "In string theory, the possibilities are much more constrained: by the 1990s, physicists had identified five consistent supersymmetric versions of the theory, and it is possible that there are no more to be found"? That would let the reader know that it isn't definitely the case that there are only five. The phrase I cut seems redundant with the second half of the sentence, which makes it clear by example that there are only a few consistent formulations. Mike Christie (talk - contribs - library) 22:57, 27 February 2015 (UTC)Reply[reply]
I don't think it's necessary to explicitly mention the possibility of a new string theory. That would give undue weight to a very speculative possibility. Take a look at my edit to the article and let me know what you think. Polytope24 (talk) 01:55, 28 February 2015 (UTC)Reply[reply]
"Ashoke Sen studied the heterotic theory compactified down to four dimensions": should this be "theories" rather than "theory", since there are two heterotic theories?
Your change addresses my concern, but now I wonder why this is here. Presumably his work was significant, but you don't actually say so -- I imagine he's not the only theorist who has studied heterotic strings in four dimensions. Can we say why his work is worth mentioning? Mike Christie (talk - contribs - library) 00:49, 27 February 2015 (UTC)Reply[reply]
The section "Relationships between string theories" is written as if no mention of the two dualities had been made earlier in the article. I think the level of detail is about right, but I think it would read more naturally to acknowledge the fact that these have already been mentioned and diagrammed and the reader can be presumed to recall some of that information. Alternatively, you might be able to move the information on dualities (and probably also on branes) down to the subsection of the history and development section where those concepts come up. I think either approach can work.
"These calculations led them to conjecture that the BFSS matrix model is exactly equivalent to M-theory. It can therefore be used to describe M-theory and investigate its properties in a relatively simple setting": assuming that their conjecture is not yet proven, would it be more accurate to say "It might therefore be used"? As it stands the sentence makes it seem that the usefulness is not contingent on the truth of the conjecture.
Sorry, the change you made doesn't really address what I was trying to say. The last sentence starts "It can therefore be used", which is unconditional. Is the BFSS matrix model now known to be exactly equivalent to M-theory, as proposed? Or is the equivalence still conjectural? Mike Christie (talk - contribs - library) 00:49, 27 February 2015 (UTC)Reply[reply]
The problem with saying that matrix theory is equivalent to M-theory is that the latter isn't really well defined. The very existence of M-theory is a conjecture, whereas matrix theory is a well defined construction that theorists can study mathematically. Therefore it doesn't really make precise sense to "conjecture" an equivalence.
Instead, what's going on here is the following. The BFSS paper showed that matrix theory has certain properties that are expected to hold in any correct formulation of M-theory. It therefore proposed matrix theory as a possible definition of M-theory, and this proposal now has wide support. It is in this sense that matrix theory may be used to investigate the properties of M-theory.
I realize that this is potentially a very confusing issue, so I went ahead and changed the language in the article. Polytope24 (talk) 04:02, 27 February 2015 (UTC)Reply[reply]
"In 1999, Nathan Seiberg and Edward Witten described further relations between string theory and noncommutative geometry": this is quite a bland statement. No doubt the technical details wouldn't be helpful but is the point here that their work tightened or strengthened the links mentioned in the previous sentence? If so, perhaps we could say that.
Thanks for the comments, Mike Christie. You've asked a couple of really excellent questions that I'm not sure how to address within the article. I'll try to explain the answers here, and perhaps you can recommend changes to the article that would clarify things.
I found myself wondering to what extent the dualities are transitive… wouldn't that imply that all five of these theories can be transformed into any of the others?
That is correct. A duality, by definition, is an exact (and very nontrivial) equivalence of two physical theories. The conjecture is that all of the five superstring theories are equivalent by these dualities and in addition that they are all equivalent to M-theory in eleven dimensions. In certain contexts, it may be useful to work in one theory or another, but in principle it should be possible to map any calculation in one theory to an equivalent calculation in any of the other theories.
It's been described up to this point as a superset of all the string theories; the five named theories are limit points of it. So in what sense can it be specified to the point where it is dual to some of the five theories but not others?
M-theory is meant to describe some physical phenomena in eleven dimensions. If you take one of the dimensions to be shaped like a circle, the physics is still that of M-theory: two- and five-dimensional branes. If you take the circle to be very small, then there's an alternative description of the physics in terms of type IIA strings in ten-dimensions, but fundamentally we're talking about the same physics as before, so these theories must be equivalent. Since we're talking about a very special physical regime in which spacetime has a very special geometry, we label this theory at one of the cusps in the M-theory diagram. Polytope24 (talk) 06:00, 26 February 2015 (UTC)Reply[reply]
It sounds as though the grey area in the M-theory schematic diagram in the article could be regarded as a parameter space, and the five superstring theories represent different points in that parameter space. Is that more or less right? Then the dualities are equivalence relations within the parameter space. So are there multiple equivalence classes within M-theory? Or are all possible "parameterizations" (if that's the word I'm looking for) of M-theory essentially equivalent? Mike Christie (talk - contribs - library) 00:58, 27 February 2015 (UTC)Reply[reply]
The gray region in the diagram is similar to a parameter space. The different points represent different physical situations that are possible in M-theory. In certain parts of the diagram, it is natural to describe the physics in terms of one of the five string theories, but the relationship between M-theory and these five string theories is valid more generally. In principle, you could consider a physical scenario corresponding to any point in the diagram and describe it in any of the string theories. Polytope24 (talk) 04:04, 27 February 2015 (UTC)Reply[reply]
That's helpful; thanks. I don't think that that's stated as clearly in the article as you just put it; perhaps something to that effect could be added? I think that might be enough to resolve my concern, but I'm finding it difficult to articulate exactly what my concern is. I'd like to sleep on it and take another look at the article tomorrow. Mike Christie (talk - contribs - library) 04:37, 27 February 2015 (UTC)Reply[reply]
I'm still not clear how the dualities diagram can work with the description of M-theory you give. Perhaps the right question is: if any point in the diagram can be described, in principle, in any of the five theories, why does the diagram show only two of the five with a duality connecting them to M-theory? To put it another way: the duality between Type I and SO (32) heterotic connects two different points on the gray shape; the duality "converts" one point into the other. For the duality between Type IIA and M-theory, what is the other point -- the non-Type IIA point? Mike Christie (talk - contribs - library) 23:17, 27 February 2015 (UTC)Reply[reply]
I think you're asking two questions here, so let me answer them separately.
why does the diagram show only two of the five with a duality connecting them to M-theory?
As you pointed out in an earlier comment, these dualities are transitive, so we can compose them to get a duality of any of the five string theories with M-theory. The diagram of string dualities has the lines color coded to indicate which ones are S-duality and which ones are T-duality. However, if we compose an S-duality with a T-duality, the result will not be of either type; it'll be a combination of the two. That's why there are only two lines in the diagram connecting M-theory to the string theories.
For the duality between Type IIA and M-theory, what is the other point -- the non-Type IIA point?
Let's say we're at some point in the diagram near the cusp labelled IIA. Then we're describing a physical system consisting of strings interacting in ten dimensions. If we deform the situation by slowly moving this point away from the cusp, then the strings will start to interact more strongly. If we keep moving the point, we'll eventually end up somewhere in the bulk of the diagram. The strings are now interacting very strongly, and type IIA string theory ceases to provide a useful description of the physics because we don't know how to do calculations in this regime. It is therefore more natural to switch to a different description where we're talking about M-theory in an eleven-dimensional world in which one of the dimensions looks like a circle of finite size.
Conversely, suppose we start at a point in the center of the diagram corresponding to an eleven dimensional world with one dimension shaped like a circle. If we slowly move this point in the diagram, bringing it closer and closer to the cusp labeled IIA, then the circular dimension begins to shrink. It gets smaller and smaller as we approach the cusp, and eventually, when it's sufficiently small, the corresponding description in type IIA string theory becomes mathematically tractable. It's then convenient to view the system as a collection of weakly interacting strings in ten-dimensions.
One can play a similar game with the theories labeled at the boundary of the diagram. For example, we can choose a point near the type I cusp. The corresponding physical system has a nice description as a system of open and closed strings in ten dimensions. We can deform the situation by dragging this point along a path connecting the type I and SO(32) heterotic cusps. As we move along this path, the strings interact more strongly. Eventually, the description becomes intractable, so we apply S-duality to view the system as a collection of weakly interacting heterotic strings.
Note that at any point in the diagram, we can apply dualities to describe the physics using the M-theory description or any of the five string theory descriptions. These are all equivalent, but in a particular part of the diagram, it may be convenient to use one description rather than another. Polytope24 (talk) 02:00, 28 February 2015 (UTC)Reply[reply]
That answers my question; I think I now understand this as well as I'm going to, and I can see why the diagrams are the way they are. Could we add a couple of sentences, near to one or the other of the two diagrams, that explain this? Your last paragraph above is very concise and seems to me to summarize the situation very well. Mike Christie (talk - contribs - library) 12:45, 28 February 2015 (UTC)Reply[reply]
I think I understand what was confusing in the article. I've expanded both of the captions to make things more understandable. Polytope24 (talk) 17:11, 28 February 2015 (UTC)Reply[reply]
Perfect. Thanks for sticking with me through these questions; I think that really helps. Mike Christie (talk - contribs - library) 17:20, 28 February 2015 (UTC)Reply[reply]
I just made a bunch of changes to the article to address your other points. Let me know what you think. Polytope24 (talk) 20:57, 26 February 2015 (UTC)Reply[reply]
I've struck most and responded to a couple above; feel free to reply indented at the appropriate points in my bullet list -- sometimes that's easier to follow. I'll try to come up with sensible answers to your first two replies in a moment. Mike Christie (talk - contribs - library) 00:49, 27 February 2015 (UTC)Reply[reply]
Support. All my concerns have been addressed. This seems to me to strike the right balance between technical and simplistic. The prose is clear and the article is well-organized. Mike Christie (talk - contribs - library) 17:20, 28 February 2015 (UTC)Reply[reply]
Thanks for all your help, Mike Christie! You've given some very thoughtful comments, and I think it's helped clarify some very subtle points in the article. Polytope24 (talk) 17:47, 28 February 2015 (UTC)Reply[reply]
These comments are for the scientific content of the article. I don't feel particularly qualified to judge the more generic FA criteria, but I will say that I don't see any glaring deficits relative to FA criteria. I'm a physicist who is familiar with the basics of string theory, but who has not worked in the field.
Overall, this article looks great. I had a hard time providing constructive criticism, because it all seems well-written and explains most concepts about as simply as possible.
Here is one seeming omission:
There is no mention of , e.g., brane cosmology in the article. Are there no cosmological predictions from M-theory? This article by Tom Banks suggests there might be some general predictions.
Here are some minor points:
In this article supergravity is called a gravitational theory in the lead. In the supergravity article, it is called a field theory. I tend to think of it more as a field theory, but reasonable people can disagree.
In the quantum gravity and strings introductory section, the last sentence on the second para says "One of the vibrational states of a string gives rise to the graviton, a quantum mechanical particle that mediates gravitational interactions." Mediates gravitational interactions is a grad-level physics expression; maybe something like provides the gravitational force.
First para of the dualities section: what "strongly vs weakly interacting" means is not provided. In physics it has to do with the applicability of perturbation theory, or perhaps the energy of the interacting field relative to the particles. One might just gloss over those technical points and say it refers to the relative strength of the forces between particles.
Calling ABJM superconformal field theory a main article (in the ABJM superconformal field theory section) is a stretch, as the paragraph in this article provides more detail than said article. Probably better just to link to it, rather than call it a main article.
Noncommutative quantum field theory is linked to as a main article in the Noncommutative geometry section, but field theory isn't really mentioned in the prose of that section.
Great comments as usual, Mark viking! I made changes to the article to address each of your points. Let me know if there's anything else that needs to be changed. Polytope24 (talk) 17:48, 28 February 2015 (UTC)Reply[reply]
Support All my comments have been addressed. The additional short paragraph on brane cosmology looks good and IMO is of due weight relative to the whole topic. Hence, I support this article for feature article status. Excellent work, Polytope24! --Mark viking (talk) 20:06, 28 February 2015 (UTC)Reply[reply]
I'm really concerned about the image used in ((String theory)), File:Calabi-Yau-alternate.png. First of all, because the image itself is linked, it's very difficult for the average reader to find out copyright details for the image. I had to edit the template code to even find the name of the image. To me, that's a problem. Secondly—and most importantly—I don't think the source (and details about it from the description) are correct. It claims to be from the cover of the November 2007 issue of Scientific American. Not only does the image not appear on the cover of that issue (or any other back to at least 1997), but there are no articles in that issue pertaining to string theory. Furthermore, Scientific American copyrights all of its graphics, per its terms of use. In short, this image may need to go. And even if it can stay, it would be best to convert it into an SVG file.
I know this is an archive of a long-ago conversation, but I do want to make several important clarifications.
Yes, the File:Calabi-Yau-alternate.png did in fact appear on the cover of the November 2007 issue of Scientific American. The link above even shows as much. It's in the upper right-hand corner. I sent a letter to the editor about it because it was used without attribution. The editor wrote a kind letter back acknowledging the use, and a correction was printed a couple of months later.
If anyone is interested in having an SVG version of the image, I believe I still have the code I used to generate the image. However, it was over 10 years ago now, and would take some time and effort to dig up.
Please fix up the description and source of File:Compactification on a circle.png. The description should describe the contents of the image, and the source should point back to the SVG from which it is derived. On Commons, a good template for this is "Derived from". Also, a source for the original visualization is needed.
File:Dualities of string and M-theory.jpg (and most other images in this article) should be recreated in SVG format. (Inkscape is a good open source software package for doing this.) Also, a source for the content should be provided.
File:MichaelDuff.JPG is flagged to be moved to Commons. Issues like these need to be resolved before bringing the article to FAC. Also, the image should probably be cropped.
File:Uniform tiling 433-t0.png has not been reviewed since being moved to Commons, and probably should be converted to SVG. And once again, what's the source for this visualization?
Oppose – It's clear that the images and their licensing have not been given anything more than a cursory glance, even at GAN. Many issues need to be resolved here. – Maky« talk » 19:57, 2 March 2015 (UTC)Reply[reply]
Thanks for the image audit. Regarding your first point, I agree that there are problems here. There is a picture of a Calabi-Yau manifold on the cover of the November 2003 SciAm, but it is not the same as this one. The image is an alternate of File:Calabi yau.jpg and in the description of that image, it says the image was generated by Lunch, based on algorithms created by A. J. Hanson. Looking at Hanson's website, there is an image that looks a lot like this image here and similar software was used to generate the SciAm image, probably the source of the confusion. The algorithms were based on this paper. We could fix the description of File:Calabi-Yau-alternate.png to reflect that of File:Calabi yau.jpg--is that the sort of thing you are looking for? Regarding PNG to SVG, Lunch has not edited since 2011, so source code is unavailable. Conversion using autotracers such as potrace, etc., are unlikely to produce better looking results. What do you suggest? --Mark viking (talk) 21:41, 2 March 2015 (UTC)Reply[reply]
Hi Maky, I appreciate your comments here, but there are some things I don't understand.
1. I fixed the description of File:Compactification on a circle.png. You say that a source for the original image is needed, but I see that the source is already given as "own work". Is this a problem?
2. Would it be okay if I simply uploaded a new cropped version of File:MichaelDuff.JPG to commons even though the current version is flagged?
5. I modified the description of File:Knot table-blank unknot.svg by copying a bunch of links from the description of the source image. Is this what you wanted?
6. In general, why is there such a strong preference for SVG format?
@Mark viking: Yes, the description fixes you hinted at should suffice. I suggest making sure all related images are cleaned up so there is no confusion in the future. Regarding an SVG conversion, it is not required for an image this complex, but you could request help at Wikipedia:Graphics Lab.
@Polytope24: For files like File:Limits of M-theory.png and File:AdS3 (new).png, where did this sort of visualization come from? For the types of articles I write, I create range maps for species by highlighting where they are found on a map. I can't just create a map and say "Own work" and leave it at that. People want to know where I got my data, or in other types of illustrations, where I got the inspiration and data for the illustration. And the reference doesn't have to be in the "Source" per se—as long as the description notes what it's based on. (Here are two examples: [2] & [3]) For files like File:Compactification on a circle.png, it's a little trickier. If this illustration was inspired by similar illustrations in the literature, it's worth citing those. But if no one else has made similar illustrations, then "Own work" would probably suffice. I'm open to second opinions on this. As for File:MichaelDuff.JPG, I'd just move it to Commons and then crop it there (replacing the original, but keeping it in the history). For File:Uniform tiling 433-t0.png, click the links in the box about reviewing and do it yourself. "Own work" might be fine in this case, but consider what I said above. File:Knot table-blank unknot.svg looks good now. As for SVG, for geometric shapes, it is much more scalable because it is a vector graphic format. As I've learned, the way MediaWiki downsamples PNG, it makes JPEG better for articles, and JPEG (as a raster graphic format) losses quality with scaling. Again, Wikipedia:Graphics Lab can help if you don't know how to create SVG files. – Maky« talk » 08:49, 3 March 2015 (UTC)Reply[reply]
Thanks for the reply. I wanted to let everyone know that my computer/internet access is somewhat limited over the next few days. I'll definitely be able to fix some of these issues this weekend, but in the mean time, please feel free to edit the images in the article.
As for the Calabi-Yau image in the string theory template, why don't we just replace it with this one? Polytope24 (talk) 01:01, 4 March 2015 (UTC)Reply[reply]
Okay, Maky, everything should now be taken care of, except for File:Compactification on a circle.png, which you have kindly offered to replace. I think the conversion to SVG format has slightly compromised the quality of some of the images, especially those with text. If this is a problem, please let me know and I'll switch them back to their original formats. Thanks. Polytope24 (talk) 23:19, 7 March 2015 (UTC)Reply[reply]
Thanks for working on this stuff. I've just recreated a bunch of your SVG files as true vector graphics (not just SVGs with embedded raster graphics). Let me know what you think. Unfortunately, all this image work means that someone else will have to do the image review as I am now too involved in the article's image content. Regardless, I will try to find time within the next day to review and strike any comments that have been resolved. – Maky« talk » 10:22, 9 March 2015 (UTC)Reply[reply]
Thanks for all your hard work, Maky! I'm sorry if I was unhelpful in addressing these issues; you obviously know much more about images than I do. I'll try to find someone to complete the image review. In the mean time, are you still opposed to seeing the article promoted to featured status? Polytope24 (talk) 15:26, 9 March 2015 (UTC)Reply[reply]
Upon reviewing the changes, at this point I would still have to oppose. Though things have come a long, long way, there are still lingering issues. I just made a bunch of fixes for you on Commons. In regards to File:MichaelDuff.jpg, I advised that you follow the steps at WP:MTC, yet you simply cropped the existing image and uploaded it to Commons. I'm not an admin on Commons, so I can't really help fix it. Maybe it's fine, but that will take a second opinion. I feel you should have followed the proper procedure and then cropped the image after it had been moved. I think I've managed to fix most of the other images with sources and formatting (if you hadn't), but File:Knot table-blank unknot.svg still lacks source information. As for File:Calabi yau formatted.svg, I believe this SVG is sufficient, but I'm not skilled enough to judge it. On a positive note, the article's images are much, much closer to being appropriate for a FA. – Maky« talk » 08:26, 10 March 2015 (UTC)Reply[reply]
Hi Maky, I'm sorry for the lingering issues. For some reason I completely overlooked your instructions on how to deal with File:MichaelDuff.jpg. As a first step to resolving the issue, I put in a request to delete the cropped image at Commons. After that request goes through (and that might take up to a week), I'll go through the process you described for moving the original file to Commons.
Honestly though, I was having some doubts about whether it was really appropriate to include the picture of Michael Duff in this article. There were many other physicists involved in the development of M-theory (most notably Ashoke Sen, Chris Hull, and Paul Townsend), and I cannot get pictures of all these people. I have therefore concluded that it's best to just remove the picture of Duff from the article. I'll still make sure the image gets properly moved to Commons, but at least now it's no longer a concern for this article.
Hoste, Jim; Thistlethwaite, Morwen; Weeks, Jeffrey (1998), "The First 1,701,935 Knots", Math. Intelligencer (Springer) 20 (4): 33–48
which contains a similar table and is most likely the source on which the image was based. Please let me know if this resolves your concern. Thanks. Polytope24 (talk) 18:35, 10 March 2015 (UTC)Reply[reply]
I think you made the right choice regarding the photo of Michael Duff. With the citation you added for the last image, I think all of my concerns have been addressed. Again, I can't judge File:Calabi yau formatted.svg, and I've become too involved in the images in this article to give my support. But great work so far. In the future, please clean up and check all images in your FAC nominations, especially if the GAN reviewer didn't even give them much of a glance. As noted above, there are plenty of resources to help create and clean up illustrations, plus you now have examples of how to make the description and licensing sections look. – Maky« talk » 19:13, 10 March 2015 (UTC)Reply[reply]
Thanks for all your help with this, Maky. Polytope24 (talk) 20:44, 10 March 2015 (UTC)Reply[reply]
Note regarding image review: An independent review of the article's images is needed. All material should be good, but as noted above, I have become too involved in the creation and clean-up of these files. – Maky« talk » 19:13, 10 March 2015 (UTC)Reply[reply]
(head spinning) Alright, I'm not a physicist, nor anything near one, but the situation of these images looks alright. File:Calabi yau formatted.svg is fine as an SVG; we have many considerably more complex illustrations in that format. Images look okay. — Crisco 1492 (talk) 23:48, 10 March 2015 (UTC)Reply[reply]
Comments. As always, feel free to revert my copyediting. - Dank (push to talk)
I changed "the" [string theory conference at the University of Southern California in the summer of 1995] to "a", because of the shift from a specialist readership (all of whom know which conference you mean) to a general readership. (At the second mention of the conference, "the" is fine.)
"toy model": I don't know what that means.
Support on prose per standard disclaimer. These are my edits. The article was surprisingly readable and engaging, given the content. - Dank (push to talk) 20:48, 9 March 2015 (UTC)Reply[reply]
Thanks, Dank, for your support and for taking the time to read and comment on the article. I went ahead and translated the term "toy model" to the more familiar words "semi-realistic simplified model". Polytope24 (talk) 21:20, 9 March 2015 (UTC)Reply[reply]
Coord note -- I didn't spot a source review above, you can list a request at the top of WT:FAC. Cheers, Ian Rose (talk) 12:53, 12 March 2015 (UTC)Reply[reply]
Comment There are no citations in the lead. In my opinion, there should be approximately one per paragraph in this case. On the other hand, since the article
is well-referenced as a whole, the lack of references in the lead may be "by design" (e.g. it may be that it is hard to fairly single out a particular reference in each particular paragraph), in which case I have no strong objection. YohanN7 (talk) 13:18, 12 March 2015 (UTC)Reply[reply]
Rule of thumb for the body of the article is at least one citation per paragraph (assuming all the information in that para can be found in that source) but the lead generally only requires citations for quotes or for information that for whatever reason does not appear (and is therefore not sourced) in the main body. Cheers, Ian Rose (talk) 13:24, 12 March 2015 (UTC)Reply[reply]
I agree with Ian. The relevant style guide is WP:CITELEAD. As a summary of the the article, the lead content usually doesn't need much sourcing. But there are exceptions. If I was to assert in the lead the BLP tidbit "M stands for Magic Marker, the preferred writing instrument of Ed Witten", that would need a a citation and reliable source. --Mark viking (talk) 17:37, 12 March 2015 (UTC)Reply[reply]
I would say though that the "According to Witten" statement in the lead should include a citation. Nikkimaria (talk) 16:25, 20 March 2015 (UTC)Reply[reply]
I don't know if you noticed, but an almost identical statement appears in the body of the article, and is supported by citation 41. Let me know if you still think we need a citation in the lead. Polytope24 (talk) 18:29, 20 March 2015 (UTC)Reply[reply]
I did notice, but I feel this statement would still warrant citing under WP:LEADCITE. Nikkimaria (talk) 18:52, 20 March 2015 (UTC)Reply[reply]
First paragraphs of Background have explanatory footnotes but not citations - are they meant to be supported by the sources mentioned in those footnotes?
FN4: page?
Be consistent in whether you abbreviate page ranges
Nakrasov or Nekrasov?
Compare FNs 55 and 56 for formatting
I'm a bit confused by Moore 2012 - the link seems to be a different publication than that suggested by the given bibliographic details
All the books except Woit do not include location - should be consistent
Don't repeat entries between References and Further reading or External links. Nikkimaria (talk) 16:25, 20 March 2015 (UTC)Reply[reply]
Thanks for helping out with the source review! I made a bunch of small corrections to the article to address your points. All of the information in the first few paragraphs of the Background section is supported by the sources cited in the footnotes. All of this material is well known and easy to verify, so I wanted to direct the reader to some of the standard literature on the subject. Polytope24 (talk) 18:29, 20 March 2015 (UTC)Reply[reply]
Comment..was first conjectured by Edward Witten at a string theory conference at the University of Southern California in the spring of 1995.
Is the place of conference, and that it was spring, really that important that it should be mentioned in the lead? --Siddhant (talk) 21:38, 20 March 2015 (UTC)Reply[reply]
I don't know… It was a pretty historic event, so I thought it was best to say precisely where and when it happened. If you think this is too much information, I can take it out. Polytope24 (talk) 01:19, 21 March 2015 (UTC)Reply[reply]
Closing note: This candidate has been promoted, but there may be a delay in bot processing of the close. Please see WP:FAC/ar, and leave the ((featured article candidates)) template in place on the talk page until the bot goes through. Ian Rose (talk) 02:38, 26 March 2015 (UTC)Reply[reply]
The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.
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