User talk:Nbarth/Archive 2010

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Service awards proposal

Hello, Nbarth/Archive 2010! I noticed you display a service award, and would like to invite you to join the discussion over a proposed revamping of the awards. If you have any opinions on the proposal, please participate in the discussion. Thanks! — the Man in Question (in question) 04:43, 8 January 2010 (UTC)

Keynesian Revolution

Further information: Keynesian Revolution

Nice improvements! FeydHuxtable (talk) 15:31, 25 January 2010 (UTC)

Glad you enjoy them – thanks for your kind words!

—Nils von Barth (nbarth) (talk) 20:48, 25 January 2010 (UTC)

Coffee

Thanks for finding the Morris source for Coffee, it looks excellent. I hope you don't mind, but I've moved it to External links for the moment, as it's not yet used as a reference. I've also taken the liberty of adding it as an EL to Cappuccino, where I think it will be very useful. --RexxS (talk) 12:35, 23 February 2010 (UTC)

No problem at all – thanks!

I found the article and wanted to share, but haven’t gotten to integrating it into the page. I’ve also added it at Espresso, specifically in Espresso#History, where I have integrated it into the text, and hence listed it as a ref.

—Nils von Barth (nbarth) (talk) 21:50, 23 February 2010 (UTC)

CfD nomination of Category:Songs about travel

I have nominated Category:Songs about travel (edit | talk | history | links | watch | logs) for deletion. Your opinions on the matter are welcome; please participate in the discussion by adding your comments at the discussion page. Thank you. Ten Pound Hammer, his otters and a clue-bat • ^{(Many otters • One bat • One hammer)} 15:53, 25 February 2010 (UTC)

Cutco Article

Hey there. Wanted to ask exactly what was being cleaned up in the cutco article? Didn't leave much of an explination, and a lot of stuff has been cut out. Cutno (talk) 14:48, 28 February 2010 (UTC)

Hi Cutno,

Thanks for checking with me!

Apologizes for the terse explanation; on contentious articles I should take care to provide more detail.

In reference to this edit, I’ve added a more detailed explanation at the following edit (marked minor to indicate that comment is reference to previous edit; wording change so edit is non-empty and thus recorded).

In detail:

The diff is misleading, because I added paragraph breaks, which is shown as a red deletion, followed by an insertion in the next paragraph (lower down). The edit didn’t actually cut any material – the page went from 6,316 bytes (before) to 6,578 (after).

I linked (wikified!) tang, 440A steel, and serrated – and explained what a tang is (and what full-tang is as opposed to half-tang), and that the “Double-D doesn’t dull” is a property of serrated knives (because of the recessed edge, hence why they are commonly used in bread knives, though I didn’t say that).

I also added paragraph breaks, so each touted feature had a paragraph and the text is easier to parse, rather than running together.

Hope this helps (and that you like the edits!) – thanks for your careful patrolling.

—Nils von Barth (nbarth) (talk) 18:23, 28 February 2010 (UTC)

Thank you for the clarification. I think it looks much better now then it previously did. Trying to keep the Astroturf out of the article is quite hard. --Cutno (talk) 19:57, 28 February 2010 (UTC)

No problem, and thanks for your continued efforts!

—Nils von Barth (nbarth) (talk) 20:03, 28 February 2010 (UTC)

Slippery tigers

Hi, I noticed this edit of yours. I'm not sure I understand your reasoning here. Do you know any sources making the connection? Paradoctor (talk) 00:05, 4 March 2010 (UTC)

Hi Paradoctor,

The “three men make a tiger” story illustrates the little-by-little argument – if one man said that there was a tiger in the market, the king would not believe it, but if three said it, he would – on that basis I connected them.

I can’t find a reference making the connection (this story is unfamiliar to Western audiences), so you’re welcome to revert it if you wish.

(BTW, I was meaning to add the story of Sodom, which is a more strongly analogous situation and is so connected; I’ll add it, with reference.)

—Nils von Barth (nbarth) (talk) 01:15, 4 March 2010 (UTC)

BTW, thanks for checking with me!

—Nils von Barth (nbarth) (talk) 01:15, 4 March 2010 (UTC)

No problem, electrons are cheap. Where the tiger is concerned, I think the connection is rather tenous. The point of the analogy seems to be the inadmissibility of overriding logic by consensus. Please note that the report is improbable regardless of whether it's reported by one or many. It only becomes soritical when you presume that opinions reported by many are inherently more reliable than those reported by few. But since this concerns a See also section, my inclusionist delusions permit me to ignore that one. ;)

I'm panagnostic, so I don't know what you mean by the Sodom story, but if you can source it, nothing should stand in your way. Besides, I always love new dirt on old paradoxes. ;) Paradoctor (talk) 01:30, 4 March 2010 (UTC)

Electrons may be cheap, but βίος βραχὺς! (vita brevis).

Agreed that it’s at best an imperfect connection, and would be inappropriate to push it in the main text; hope that “kinda sorta similar idea” is ok in “See also” – thanks for your graciousness.

I’ve included the Sodom discussion in this edit – it would be interesting if there were some common near/middle eastern source for these (Babylon, most like), but I’m not going to speculate (quit snickering!).

I got a bit enthusiastic and added some references to the actual scholarly literature – someday we may be able to remove the “refimprove” tag!

—Nils von Barth (nbarth) (talk) 04:24, 4 March 2010 (UTC)

Βίος βραχὺς may be, but there is room for σκέψις. ;)

"near/middle eastern sources": If you could find them, that would be fantastic.

"actual scholarly literature": My kind of guy. :) This topic has a long history, almost none of which is covered. Anything you can add will be an improvement. Happy editing! Paradoctor (talk) 11:49, 4 March 2010 (UTC)

Re: Parnassus & Calvi

Yes, I saw the anon. message on the article talk page, and intended to respond, but simply forgot. Given the sources, and the fact that it comes straight from Gilliam's mouth, it should be restored. Thanks for your message. ---RepublicanJacobite_{The'FortyFive'} 15:52, 5 March 2010 (UTC)

No worries – I’ve restored it with the direct quote and ref; thanks for your care!

—Nils von Barth (nbarth) (talk) 21:37, 5 March 2010 (UTC)

Supply creates its own demand

Hi Nbarth, I saw you made that article. Are you sure it is coined by Keynes? That's written in the articles like Jean-Baptiste Say and Say's law, but when I see out of which area the first edits in that direction came (example), I am sceptical.

Afaik this sentence came from James Mill (who basically "invented" Say's law). See for example here based on "Thomas Sowell: Say's Law: An Historical Analysis". It's also stated in the second source of the Say's law wiki article [1] as a quote from Mill. It seems to me that it was a falsification and just part of an big pov wave by some people like Austroglide to bring the message "Say, Mill and the Neoclassicals are right, it were just Keynes and so on who doesn't understand it". Perhaps you fell into the fraud? If I am right, the article can contine to exist of course, but it should have Mill and his interpretation of Says law indeed as origin (other articles need an correction) and Keynes who reactivated it. --Larsenat (talk) 17:32, 8 March 2010 (UTC)

Hi Larsenat,

Thanks for the clarification!

I heard it attributed to Keynes and it’s certainly present in exactly that form in his text and popularized by him, and just as clearly echoes sentiments given by James Mill and J. S. Mill, though AFAICT, they did not use those exact words.

(does a little research, using Larsenat’s kind references as a starting point)

What James Mill wrote (in Commerce Defended, 1808, p. 81) is:

production of commodities creates, and is the one and universal cause which creates a market for the commodities produced

…which (substituting “supply” for “production”, “demand” for “market”, and making briefer) is the sentiment Keynes expressed, though not the exact words.

You’re quite right that the attribution to Keynes is generally emphasized by detractors (“Oh, that Keynes – his bastardization does not do justice to the full complexity of ideas expressed by the classical economists he so unfairly dismisses!”), though AFAICT, they are correct that he actually coined the phrase (whether the phrase is an accurate summary is rather more debatable).

The current article doesn’t emphasize enough the classical origins; I’ll have a stab at giving more history, and please feel free to do so yourself.

—Nils von Barth (nbarth) (talk) 00:22, 9 March 2010 (UTC)

Hi Larsenat,

I’ve finished researching and revising, with refs: there are other early statements of similar sentiments, and Keynes used the phrase earlier (1934), so it seems to have been an oral tradition, but he seems to have been the first person to have written it in publication. As such, I think it’s fair to attribute the phrase to him, though one should be careful that this not be a pretext to dismiss it (which some critics are wont to do) – it’s at the least a useful shorthand for how Keynes thought about it.

Thanks again for your careful and provocative attention!

—Nils von Barth (nbarth) (talk) 01:07, 9 March 2010 (UTC)

Thanks for the answer and the informative enquiries. I don't have much too add (just that Say didn't wrote about relative prices and unemployment in the law, it was a later interpretation, and he didn't emphasis everytime the word "free" before market like some of the wiki contributions :) , actualy he afaik always just writes about markets), but I will look in which other wiki-articles Say's law is mentioned and use your informations to clarify the case (Edit: I see you were already quite active in there with a link to the supply creates its own demand article). --Larsenat (talk) 16:37, 10 March 2010 (UTC)

No problem, and good luck editing – as you know, interpretations of Say’s law are hotly debated, and, as you indicate, more often to reject or justify government involvement in the economy than to study what Say and other classicals were actually saying.

—Nils von Barth (nbarth) (talk) 20:25, 10 March 2010 (UTC)

Coxeter-Dynkin diagram graphics

Hi, you appear to be a regular contributor to the Coxeter–Dynkin diagram article. Hoping that you feel able to contribute to the discussion over SVG vs PNG formatting for these diagrams. We are trying to establish a consensus to end a reversion war, and there are literally hundreds of instances to sort out. 83.104.46.71 (talk) 19:10, 11 March 2010 (UTC) (Alias?User:Steelpillow)

Hi 83-71 – thanks for bringing this to my attention and for your thoughtful note – I’ve given a detailed reply there.

—Nils von Barth (nbarth) (talk) 03:12, 12 March 2010 (UTC)

Font hinting is very interesting - thanks for linking on the talk page! Tom Ruen (talk) 10:06, 12 March 2010 (UTC)

No worries Tom, and thanks for your tireless work and patience; enjoy your wikibreak!

—Nils von Barth (nbarth) (talk) 11:50, 12 March 2010 (UTC)

Thanks for the barnstar! -- Cheers, Steelpillow (Talk) 20:51, 22 March 2010 (UTC)

No problem – you well deserved it!

—Nils von Barth (nbarth) (talk) 23:12, 22 March 2010 (UTC)

WikiProject Economics census

Hello there. Sorry to bother you, but you are (titularly at least) a member of WP:WikiProject Economics, as defined by this category. If you don't know me, I'm a Wikipedia administrator, but an unqualified economist. I enjoy writing about economics, but I'm not very good at it, which is why I would like to support in any way I can the strong body of economists here on Wikipedia. I'm only bothering you because you are probably one of them. Together, I'd like us to establish the future direction of WikiProject Economics, but first, we need to know who we've got to help.

Whatever your area of expertise or level of qualification, if you're interested in helping with the WikiProject (even if only as part of a larger commitment to this wonderful online encyclopedia of ours), would you mind adding your signature to this page? It only takes a second. Thank you.

Message delivered on behalf of User:Jarry1250 by LivingBot.

Generalized permutation matrix, the Dn group and demihypercubes

On the Generalized permutation matrix page in Nov 2009 you added a reference to Coxeter Dn groups being related to the demihypercubes. Can you help me with references to where this is defined?

I am trying to correlate Dn with the Simple Lie group article that D_r corresponds to the special orthogonal group, SO(2r).

The SO(2r) root systems are generated with (+/-1, +/-1,0,0,....) patterns, as in SO(8),SO(10), and part of the E6 (mathematics). It seems that this pattern is different than the demicube pattern of (+/-1, +/-1,...) with odd number of + signs.Jgmoxness (talk) 13:49, 13 April 2010 (UTC)

Hi Jgmoxness,

I’m not sure I understand your question – I’ll restate it and then answer it as best I see.

You’re asking for the connection between the Coxeter group D_n and the root system of the even special orthogonal group SO(2r),

specifically the connection between:

• the expression of the Coxeter group as signed permutation matrices with unit determinant, and
• the expression of the simple roots as $e_{i}-e_{i+1}$ and $e_{n-1}+e_{n}.$

The connection is that the Coxeter group is realized as matrices, while the roots are realized as vectors. Multiplying a vector by a matrix sends a root to a root, a simple root to a simple root, and a set of simple roots to a set of simple roots. Note that since the Coxeter group (properly here the Weyl group of the roots) does not preserve positive roots, it does not preserve any particular set of simple roots, but instead acts transitively on them.

In more detail:

Given a root system in $\mathbf {R} ^{n},$ the matrix form of their Weyl group is completely determined; for the root system D_n, the resulting matrices are the signed permutation matrices with unit determinant.

However, there are many possible choices for a system of simple roots; the +1, -1, (ending with +1 +1) pattern for D_n is simply a choice, and there are many others.

Though it is possible to collect the simple roots (vectors) in a square matrix (a change of basis matrix), I’m not sure that is terribly meaningful in this context.

Further, there is no reason to expect that the vectors of the roots should look anything like the matrices of the Weyl group, which I think is the source of your confusion.

Regarding references, the standard references include Coxeter (for geometric discussion of the groups), Humphreys (for formal algebraic treatment of the Lie algebras), and, most enjoyably, Griffiths and Harris. If you’re interested in Lie theory you owe it to yourself to read Griffiths and Harris – it’s one of the most enjoyable math books out there.

Does this address your question?

—Nils von Barth (nbarth) (talk) 23:07, 13 April 2010 (UTC)

Thanks for the prompt reply. This helps and is accurate but doesn't get to my point. Let me clarify. I have developed a tool to visualize the split real even E8 Lie Group (as 240 vectors). It takes these and projects them into 2D (or 3D) with animated projections using the dot product of 2 (or 3) basis vectors, etc. Quoting from the E8 article:

Explicitly, there are 112 roots with integer entries obtained from

$(\pm 1,\pm 1,0,0,0,0,0,0)\,$

by taking an arbitrary combination of signs and an arbitrary permutation of coordinates, and 128 roots with half-integer entries obtained from

$\left(\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}}\right)\,$

As you can see, the latter 128 vertices (vectors) are in fact the 7-cube vertices within an 8-cube. The 112 are essentially defined by the root system patterns of SO(2n)=Dn where n=8 (per other articles). Given these facts, my question is - where does the n-demicube pattern (which is a subset of the n-cube with vertices removed) come into play with respect to Dn (if it is clearly associated with $(\pm 1,\pm 1,0,0,0,0,0,0)\,$? It seems easy to understand n-demicube/n-hemicube patterns as subsets of Cn, but why Dn which is defined as related to SO(2n)? Jgmoxness (talk) 01:31, 14 April 2010 (UTC)

The 3-demicube.

Hi Jgmoxness – your visualization tool sounds very cool! (I’m very interested in visualization, and Lie algebras are at once challenging and rewarding to visualize.)

To your question, which I think I understand better, but which is still very vague to me – roughly, “what is the relation of $D_{n}$ & SO(8) to the root lattice of $E_{8}$”?

Here are some relations I can comment on.

Firstly, “why” the even signed permutations ($D_{r}$) correspond to the group SO(2r) is basically “because that’s how the algebra works”; I don’t have good geometric intuition for why these are related, though an expert on Lie theory might.

Careful that SO(8) corresponds to (has Dynkin diagram) $D_{4},$ not $D_{8},$ but that the Coxeter group $D_{8}$ naturally acts as orientation-preserving rigid motions of $\mathbf {R} ^{8}$ (I.e., $D_{8}<SO(8),$ but SO(8) has Dynkin diagram $D_{4}$.)

Secondly, in the E₈ context that is your interest, the demicube in question, or rather the two demicubes in question, is the polytope generated by the vertices

$\left(\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}}\right)\,$

where the number of negatives is even (the product is positive) – and the other demicube is where the number of negatives is odd (the product is negative). The even signed permutations acts transitively on each of these two sets, yielding two orbits of 64 vertices each. This yields two 8-demicubes given by the vertices.

The $D_{8}$ group then acts on the 112 vertices of the form

$(\pm 1,\pm 1,0,0,0,0,0,0)\,$

transitively (conveniently, 112 divides $8!\cdot 2^{8}/2$), which I think is what you were asking specifically. This is easy to see geometrically in low dimensions – for the 3-demicube (at right) these vertices are the centers of the 12 edges (${\binom {n}{2}}\cdot 2^{2}$ vertices).

Finally, I’m not sure how $D_{4}$ (rather than $D_{8}$) acts on the root system, seeing as $D_{4}<E_{8}$ – it has order 192, and thus presumably acts transitively on the 64 vertices of each of the 8-demicubes, while having 7 orbits on the 112 vertices (as the gcd of 192 and 112 is 16), which suggests a connection with imaginary octonions or $E_{7}$ or $G_{2}.$

So to summarize:

• There are two demicubes in the root system of $E_{8},$ on which the Coxeter group $D_{8}$ acts.
• I don’t know what the connection of the Weyl group $D_{4}$ (associated to SO(8)) is with the root system of $E_{8}.$

Hope this helps!

—Nils von Barth (nbarth) (talk) 04:35, 14 April 2010 (UTC)

Yes - thanks. Your analysis of the n-cubes and demicubes on the 128 vertices (vectors) generated by permutations of $\left(\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}},\pm {\tfrac {1}{2}}\right)\,$ is as I understand it and that pattern is n-cubic/n-demicubic. The inability to "easily" work the 112 vertices (vectors) is my issue. We agree that Dn=SO(2n) is correct (right?). Do we agree then that the 112 vertices generated by permutations of $(\pm 1,\pm 1,0,0,0,0,0,0)\,$ is D8=SO(16) related?

The root of my question relates to your and Ruen's entries in articles that suggest (per Ruen - from John Conway references) that Dn is related to the n-demicubes (as subsets of n-cubes). How is that, if we agree Dn=SO(2n)? How is the n-demicube as a series related to Dn (being permutations of all +/-1 (or factor thereof) and not $(\pm 1,\pm 1,0,0,...,0n)\,$ )? Bottom line - I think that Dn is not related to n-demicubes as referenced, but need to know more of why it is suggested to be related.
BTW - you can see the visualizations on the bottom of my talk page.

Jgmoxness (talk) 13:42, 14 April 2010 (UTC)

Ok, I think I see the confusion; when you say:

“How is Dn related to the n-demicubes (as subsets of n-cubes), if we agree Dn=SO(2n)?”

you’re confusing Coxeter groups and Weyl groups, and similarly the rank and dimension of a Lie algebra.

The Coxeter group aspects are straight-forward; the Weyl group aspects are rather more complicated. Thus, I would start with the simple proposition that $D_{n}$ is related to (is the symmetries of) the n-demicube, and only after try to understand how $D_{n}$ arises as a Weyl group of the Lie algebra ${\mathfrak {so}}_{2n}.$ See Coxeter group: Properties for context, and put root systems out of your mind for a minute.

Let’s carefully distinguish:

• The Coxeter group $D_{n}$ is an abstract group of order $2^{n}n!/2,$ presented by generators and relations.
• This abstract group has a natural faithful n-dimensional representation as a reflection group of symmetries of the n-demicube, represented by even signed permutation matrices – this is what we mean by “$D_{n}$ is related to the n-demicube”. In exactly the same way, BCn is the symmetries of the n-cube (as signed permutation matrices) and An is the symmetries of the n-simplex (as permutation matrices).
• This abstract group is the Weyl group of the Lie algebra $D_{n}={\mathfrak {so}}_{2n},$ which has rank n and dimension 2n.
  • Now, ${\mathfrak {so}}_{2n}$ is naturally represented as skew-symmetric matrices. This is a ${\binom {2n}{2}}$-dimensional algebra, acting on 2n-dimensional space, of rank n (it has Cartan algebra of dimension n, corresponding to rotations in n orthogonal 2-planes).

So for SO(8), it acts naturally on 8-dimensional space, but that is not what its Weyl group is – its Weyl group arises from the 4-dimensional Cartan subalgebra, corresponding to rotations in 4 orthogonal 2-planes.

Does this clarify matters?

—Nils von Barth (nbarth) (talk) 22:26, 14 April 2010 (UTC)

(BTW, your pictures are v. pretty; as I understand, you want them to show the symmetries of the high-dimensional structures, hence your interest in understanding them. —Nils von Barth (nbarth) (talk) 22:32, 14 April 2010 (UTC))

Thanks again - will digest it. Sounds like some syntactic overloading of symbology causing obfuscation.....Jgmoxness (talk) 01:19, 15 April 2010 (UTC)

Yeah, $D_{n}$ etc. are used for many objects (Coxeter group, reflection group, Weyl group, polytope, Coxeter diagram, Dynkin diagram, root system, Lie algebra, Lie group), which is very confusing. I’ve written up some at Dynkin diagram: Related classifications.

—Nils von Barth (nbarth) (talk) 02:42, 15 April 2010 (UTC)

Projective polyhedra

Hi, I just read the referenced paper by Arocha, Bracho & Montejano on the projective polyhedron article. They do not define a projective polyhedron as a tiling of the projective plane, but as something more general. Nor do I recall the term being used with this meaning by Hilbert & Cohn-Vossen (though I do not have a copy to hand). This worries me - how sure are you about your definition, and can you provide more credible references? If not, the article will have to be deleted or wholly rewritten, and there will be a lot of unpicking too do on other articles where you have recently introduced it. -- Cheers, Steelpillow (Talk) 01:24, 16 April 2010 (UTC)

Hello again Guy,

Thanks for your attention! (Someone who actually reads the references?)

Regarding the definition – I’ve added a ref for this definition, from Schulte & Weiss, 2006 (PDF), top of page 9; a regular projective polyhedron is also defined (as a regular tessallation of the projective plane) in McMullen and Schulte (Section 6C. Projective Regular Polytopes, pp. 162–165), which is pretty authoritative.

I’ve also added a clarification that this refers to globally projective polyhedra, in contrast to the locally projective polyhedra often studied in AP theory.

Schulte & Weiss use it analogously to (globally) spherical polyhedra and toroidal polyhedra, which on WP refer to globally spherical/toroidal, and so I named the page following the existing WP convention.

Apologies for not including better references earlier!

I was interested in making a category for (globally) projective polyhedra, to collate all the hemi-polyhedra – would Category:Projective polyhedra work? (Shall I also make a Category:Toroidal polyhedra, while we’re at it?)

—Nils von Barth (nbarth) (talk) 02:30, 16 April 2010 (UTC)

Sounds good to me. I suppose that the projective polyhedron article ought to explain, or at least link to, the two different usages of the term, although I am not going to push anyone into doing something I can't be bothered to do myself. -- Cheers, Steelpillow (Talk) 19:26, 16 April 2010 (UTC)

Cool, done!

—Nils von Barth (nbarth) (talk) 22:56, 16 April 2010 (UTC)

WPECON: Wikipedia:WikiProject_Economics/Reliable_sources_and_weight

Hey Nils. I see you put quite some time into the talkpage of the proposed guideline in late February and early March this year. Are you happy to go forward with it if the "census" approach to getting like-minded people together works? - Jarry1250 ^{[Humorous? Discuss.]} 13:29, 16 April 2010 (UTC)

Hi Jarry,

Yes, I’d be happy to organize and continue drafting guidelines (and incorporating various input), and hopefully find consensus. I’ve been a bit busy lately with other topics, but this is a high priority.

Thanks for organizing the census!

—Nils von Barth (nbarth) (talk) 21:23, 16 April 2010 (UTC)

Please, stop and correct your edits

Hi Nils,

Over a very short time you've made a large number of edits of questionable value and accuracy to many established mathematics articles. I've left a note at Talk:Triangle group, then checked your edit history and found mistakes, irrelevant or OR statements (and even sections) added to Triangle group, Dynkin diagram, Fundamental representation, Riemann–Hurwitz formula, Mathieu group, etc. I don't have time to look carefully at the polyhedral articles, and at the pace you are editing, I wonder if you have, either.

Other people have already pointed out similar problems to you. Please, slow down and review fundamental policies of Wikipedia: WP:OR, WP:Verifiability, WP:Undue weight (for example, you are adding a lot of inline references to the website of David Richter). Then, please, retrace your edit spree and address these issues. It will take a truly gargantuan effort on the part of qualified WPM members to verify your edits, and frankly, it may be more preferable to just blanket revert them if their quality cannot be assured. I am just giving you a heads-up, but I intend to follow up on this. Cheers, Arcfrk (talk) 19:24, 17 April 2010 (UTC)

Sorry about that – I somewhat over-enthusiastically drew a number of connections, some very legit (the 2,3,7 tiling is central to how one understands Hurwitz surfaces), some rather tenuous (Riemann–Hurwitz & Polytope density), while others were confusions on terminology (what’s the name for the reflection group in a Schwarz triangle with rational numbers, like (2 3/2 3)?)

Thanks for the heads-up; I’ll clean up and source, as it’s my responsibility to make my edits proper.

—Nils von Barth (nbarth) (talk) 20:29, 17 April 2010 (UTC)

Also, apologies for “undue weight” – I was mainly excited by tilings of the Klein quartic, and thus used the first reference I found. There are more references, which are quite informative (giving more details, formality, perspectives), and which I will place on relevant pages – see Klein quartic#References for now.

—Nils von Barth (nbarth) (talk) 21:26, 17 April 2010 (UTC)

Hi Arcfrk,

I’ve now finished (I believe) cleaning up all edits, which has included giving rather more balance, context, and references. (I’ve also made a few other edits in the intervening weeks.) I’ve checked over all the articles, and think I’ve cleaned up everything, though if you’ve any specific concerns I’d be happy to address them.

The additions are (understandably) rather more comprehensive, though of course it takes a while to fill everything in – hope you like it!

—Nils von Barth (nbarth) (talk) 00:16, 4 June 2010 (UTC)

CfD nomination of Category:Barefootedness

I have nominated Category:Barefootedness (edit | talk | history | links | watch | logs) for deletion. Your opinions on the matter are welcome; please participate in the discussion by adding your comments at the discussion page. Thank you. Shawn in Montreal (talk) 20:36, 28 April 2010 (UTC)

WikiProject Economics Newsletter (Issue I)

Positively Economics The Economics WikiProject Newsletter Issue I (May 2010)
Use the show/hide button to display or hide this newsletter. From the (self-appointed) editor Hello to all the economists who signed up on the census (covered in more detail below) and whom I have boldly signed up for this, the first in hopefully a long line of WikiProject Economics newsletters. The aim is simple: to distribute the project's news and developments in order that every member gets the opportunity to contribute to their fullest. It mirrors the ideals of any WikiProject: to support and assist. In creating this, on a whim, I have picked a name and stolen the layout of the Military History WikiProject's newsletter. If you have any comments or suggestions, feel free to leave them on the main newsletter talk page. The non-talk version of that page is also the place to unsubscribe yourself from the newsletter, which, for the moment, I anticipate will be monthly. Enjoy! - Jarry1250 [Humorous? Discuss.] 11:59, 25 April 2010 (UTC) Articles of note New featured articles: Economy of the Han Dynasty New featured lists: None New featured topics: None New good articles: Price elasticity of demand Production-possibility frontier Monetary Policy Committee Confederate war finance Redlinks to be squashed Skysmith has posted an updated list of missing economics topics. Most will need redirecting or new articles written to blueify them, so, if you can lend a hand with the effort, please do. There are some from virtually all areas of economics and hence to suit all tastes. Project news Census completed A big thank you to everyone who signed the census, an attempt to renew the project's membership list. Jarry1250 explained its purpose: "once we know how many active participants we have... we can make sure no interested parties get left out of discussions; ...to get everyone included. Not just to make them feel involved, but also to actively try to make them more involved [in the supportive atmosphere of the WikiProject]". Around forty editors, with a good range of specialisms and interests, have currently signed to show their activity, and it is still open for more. Project-wide discussions commence: A series of discussions have been commenced on the census talkpage about what, if anything, should be done to strengthen the Project. All comments are welcomed on a range of topics: the economic style guide, weight guidelines, notability and the creation of this newsletter. Other discussions, on categorisation, tagging and compiling an accurate list of unreferenced BLPs, are currently active. Your comments are invited in the following other ongoing project discussions: The normative economics of central banking. What article might this fall under? Does one exist already? Does it need a separate article? Inflation. Thoughts invited on the inflation article and how best to word the lead. 2010 European sovereign debt crisis - comments requested.
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CDS standardization

Hi Nbarth,

My name is Shirley Wang, I am a research assistant at the Federal Reserve. I came across the wiki page you edited regarding CDS standardizations and IMM dates. You mention that after 2002, CDS maturities roll on IMM dates. However, I am trying to figure out how CDS maturities were calculated previous to 2002. Was it the case that a 5-year CDS quoted on 5/17/2010 would mature on 5/17/2015 instead of 6/20/2015? If this is so, do you know exactly when this change occurred? Furthermore, do you know of any documentation regarding this change?

Thanks so much —Preceding unsigned comment added by 132.200.32.34 (talk) 15:01, 17 May 2010 (UTC)

Hi Shirley,

No CDS history expert I, but: I assume that prior to standardization in 2002, CDSs did not have standard dates, and were at discretion of the parties, as is currently still the case in interest rate swaps.

For example (to use proper historical dates), a “5-year” CDS quoted or traded on 5/17/2000 might have had an effective date of 5/17/2000 and a maturity date of 5/17/2005, or an effective date of 5/30/2000 and a maturity date of 5/30/2005, or whatever else the parties wanted – presumably being immediately effective for 5 years would have been most common.

Regarding exactly when the change occurred, I don’t know, but would guess that the standards were drafted in 2002, and became effective on the 3rd or 4th “IMM” date in 2002, i.e., all contracts executed on or after 9/20/2002 (or maybe 12/20/2002) would mature on one of the standard dates.

Regarding documentation, your best bet would be ISDA or Markit – the actual standardization was presumably at ISDA protocol promulgated in late 2002, while these organizations may have either public documents referring to this change or may have people better able to help.

Hope this helps, and good luck with your research!

—Nils von Barth (nbarth) (talk) 20:36, 17 May 2010 (UTC)

Hi Nils, thanks. I have one last question--where did you find the documentation that states CDS maturities were standardized in late 2002?

thanks again. —Preceding unsigned comment added by 132.200.32.34 (talk) 14:19, 24 May 2010 (UTC)

Hi Shirley, no problem.

The documentation was a webpage – "Creditflux: Names and Dates" (archive), which is now properly footnoted in IMM dates (current revision). No terribly official, but seems accurate (CDS market having expanded significantly in years up to 2002). Hope this helps!

—Nils von Barth (nbarth) (talk) 19:55, 24 May 2010 (UTC)

(typo —Nils von Barth (nbarth) (talk) 17:47, 2 June 2010 (UTC))

DYK for King Matt the First

The DYK project (nominate) 12:02, 23 May 2010 (UTC)

Talkback

Hello, Nbarth. You have new messages at Supertouch's talk page.
Message added 09:13, 24 May 2010 (UTC). You can remove this notice at any time by removing the {{Talkback}} or {{Tb}} template.

Supertouch (talk) 09:13, 24 May 2010 (UTC)

WikiProject Economics Newsletter (Issue II)

Positively Economics The Economics WikiProject Newsletter Issue II (June 2010)
Use the show/hide button to display or hide this newsletter. From the editor Sticking to my promise of sending these out monthly, it's time for the June edition of Positively Economics, covering the events of May, which has passed relatively quietly for the project. Nevertheless, Wikipedia is a wiki, and things can change quickly and often without much notice. All contributions can be, and often are, important, regardless of how trivial they may seem. I, for example, have been working on our new list of unsourced BLPs, having added a significant number of economists to the project earlier in the month. But more on that in the newsletter itself. - Jarry1250 [Humorous? Discuss.] 14:28, 27 May 2010 (UTC) Articles of note Note: this week's "new" FAs, and so forth, are ones that previously weren't included in the project but now are. New featured articles: Akhtar Hameed Khan New featured lists: None New featured topics: None New good articles: Abram Lincoln Harris George Lee (journalist) Stephen Harper Yulia Tymoshenko Redlinks to be squashed Skysmith has posted an updated list of missing economics topics. Most will need redirecting or new articles written to blueify them, so, if you can lend a hand with the effort, please do. There are some from virtually all areas of economics and hence to suit all tastes. Project news Unassessed articles: A whole swath of articles have been added to the WikiProject recently, mainly on notable economists. They are yet to be assessed on their talk pages; this also provides a good opportunity to check and improve some of our least monitored articles. Unsourced BLPs: Before the articles about economists were added, the project had very few unsourced biographies of living people; now there are a little over a hundred. If we can clear them, however, then it is unlikely that there will be many more. Again, they represent some of our least cared-for articles, and often present good targets for cleaning up. Your comments are invited in the following other ongoing project discussions and requests for help: Too big to fail Slowflation Jobless recovery Small Business Lending Index
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(Thank you)

Re: User talk:SteveWoolf#Barnstar, as per this revision —Nils von Barth (nbarth) (talk) 21:55, 5 June 2010 (UTC)

Thanks SteveWoolf (talk) 11:07, 5 June 2010 (UTC)

You are now a Reviewer

Hello. Your account has been granted the "reviewer" userright, allowing you to review other users' edits on certain flagged pages. Pending changes, also known as flagged protection, will be commencing a two-month trial at approximately 23:00, 2010 June 15 (UTC).

Reviewers can review edits made by users who are not autoconfirmed to articles placed under flagged protection. Flagged protection is applied to only a small number of articles, similarly to how semi-protection is applied but in a more controlled way for the trial.

When reviewing, edits should be accepted if they are not obvious vandalism or BLP violations, and not clearly problematic in light of the reason given for protection (see Wikipedia:Reviewing process). More detailed documentation and guidelines can be found here.

If you do not want this userright, you may ask any administrator to remove it for you at any time. Courcelles (talk) 00:41, 16 June 2010 (UTC)

Talkback

Hello, Nbarth. You have new messages at SchuminWeb's talk page.
Message added 01:39, 16 June 2010 (UTC). You can remove this notice at any time by removing the {{Talkback}} or {{Tb}} template.

projective linear group

Further information: Talk:Projective linear group § Projective linear group#Modular group

Hi Nils, Are you interested in making the necessary corrections there? Tkuvho (talk) 02:51, 16 June 2010 (UTC)

Oops! Thanks for catching, will fix!

—Nils von Barth (nbarth) (talk) 02:57, 16 June 2010 (UTC)

Fixed, in these edits!

—Nils von Barth (nbarth) (talk) 04:03, 16 June 2010 (UTC)

Misplaced main and see-also links

I've noticed you've added some {{main}} links to articles, but not in the way they are meant to be used. They are intended to link a summary section of an article to a main article, where an article or part of it consists of summaries of topics covered in full elsewhere, for example Six-dimensional space. Adding it at the top of an article as you have is simply confusing - in e.g. Charts on SO(3) it implies that if the reader really wants to learn about Charts on SO(3) they should consult Special orthogonal group, which is clearly wrong.

As the special orthogonal group is the first thing mentioned in the article there's no need to add another link. If there were a need - if it were a related topic but not mentioned in the article - then it should be added to the see also section. Or if the topics are so closely related that they really are the same thing they should maybe be merged. That section at the top of the article is for dab links, i.e. for links to articles with similar names in case the reader came to one article intending to find another, or to a DAB page when there are many articles with similar names. See e.g. WP:TMG for a summary of how and where the various links should be used.--JohnBlackburne^words_deeds 16:17, 1 July 2010 (UTC)

Oops! Sorry about that – I got confused about the use of {{details}} and {{main}}; I thought {{main}} was supposed to point up a hierarchy (from a detailed article to a context article), though, reading WP:SS: Subarticle navigation, I see that policy is to use a navigation box.

Main (sorry) reason for the confusion is that {main} and {details} appear to be redundant, so I assumed there was a distinction, and read it “The main article for this topic, of which this is a section, is (go up)”.

Thanks for clarifying – I’ve cleaned up the pages you mention and also others where I made the same mistake.

—Nils von Barth (nbarth) (talk) 20:23, 1 July 2010 (UTC)

WikiProject Economics Newsletter (Issue III)

Positively Economics The Economics WikiProject Newsletter Issue III (July 2010)
Use the show/hide button to display or hide this newsletter. From the editor Sticking to my promise of sending these out monthly, it's time for the July edition of Positively Economics, covering the events of June. It's been another constructive month for the project. Wikipedia remains, as ever, a very popular source of information about basic economic theory, as well as for biography and more specialised topics, and we shouldn't forget that contributions to these core articles remains our greatest strength. Onwards and upwards, as they say, for another month. - Jarry1250 [Humorous? Discuss.] 14:28, 27 May 2010 (UTC) Articles of note New featured articles: None New featured lists: None New featured topics: None New good articles: Brander–Spencer model Redlinks to be squashed Skysmith has posted an updated list of missing economics topics. Most will need redirecting or new articles written to blueify them, so, if you can lend a hand with the effort, please do. There are some from virtually all areas of economics and hence to suit all tastes. Project news Unassessed articles: A whole swath of articles have been added to the WikiProject recently, mainly on notable economists. They are yet to be assessed on their talk pages; this also provides a good opportunity to check and improve some of our least monitored articles. Unsourced BLPs: Before the articles about economists were added, the project had very few unsourced biographies of living people; now there are a little over a hundred. If we can clear them, however, then it is unlikely that there will be many more. Again, they represent some of our least cared-for articles, and often present good targets for cleaning up. Your comments are invited in the following other ongoing project discussions and requests for help: Featherbedding Herbert Hoover Intelligence-related citations
To start/stop receiving this newsletter, please add/remove your name from the list here. Thank you. This newletter was delivered to you by User:Jarry1250 at around 19:48, 1 July 2010 (UTC)

see: Aliasing folding image?

Further information: User talk:Bob K § Aliasing folding image?

See User talk:Bob K#Aliasing folding image? – e.g., this revision.

Abstract polytopes

You have previously contributed to the Abstract polytope article. If you feel able, please contribute to the discussion on Notation, where I am hoping to resolve a long-standing dispute. Many thanks in anticipation. — Cheers, Steelpillow (Talk) 14:45, 17 July 2010 (UTC)

Thanks for soliciting input Guy – I’ve given my 2¢ there!

—Nils von Barth (nbarth) (talk) 19:16, 17 July 2010 (UTC)

Your opinion is needed at Staright razor

Further information: Talk:Straight razor § Gallery, Images, & Captions

Hi Nbarth. Since you were the one who moved some of the captioned pictures into a gallery of examples in the article of Straight razor here, I would like to request your opinion regarding attempts at removal by Duchamps comb on the article talk page. Thank you. Dr.K. ^{λogosπraxis} 17:20, 22 July 2010 (UTC)

Redirect for logarithmic prior

I changed the redirect from logarithmic prior. It used to point to Jeffreys prior, but I find that connection insufficiently satisfactory. Yes, sometimes a comptued Jeffreys priors turns out to be the logarithmic prior, but there are many other ways to decide that a logarithmic prior will be a good prior probability for some situation. So I changed the redirect to be to prior probability. —Preceding unsigned comment added by Quantling (talk • contribs) 19:37, 3 August 2010 (UTC)

No problem – thanks for the edit, and for dropping a note!

I’ve edited it to point to the actual location of “logarithmic prior” on that article, and marked the redirect as “Redirect with possibilities”, since, as you indicated, this could stand an article (or at least section) of its own.

—Nils von Barth (nbarth) (talk) 07:16, 4 August 2010 (UTC)

WikiProject Economics Newsletter (Issue IV)

Positively Economics The Economics WikiProject Newsletter Issue IV (September 2010)
Use the show/hide button to display or hide this newsletter. From the editor After a brief intermission over the Northern hemisphere summer season and the Southern hemisphere's mid-winter, Positively Economics is back. In recent weeks it has been my privilege to work on countering systemic bias with a couple of articles on the economic history of Uganda. Projects like these help, little by little, to open up new areas on knowledge to Western audiences. Indeed, with English in the ascendancy when it comes to second languages, many other audiences too. Both of the new creations made the front page via the Did you know? section for newly-created or significantly expanded articles. I would encourage other editors, particularly those who like badges, to try to get more economics articles onto the front page through this and other sections. Those with a particularly competitive bent might also wish to consider signing up for the 2011 Wikicup (great for focussing the mind). - Jarry1250 [Humorous? Discuss.] 18:55, 1 September 2010 (UTC) Example chart New bot User:LivingBot has just been approved on Wikimedia Commons to compile and upload SVG graphs based on monthly time series of, for example, UK interest rates (illustrated). It will then revisit these on a monthly basis to update them with the latest information. If you would like to bot to create and update a graph for you, get in touch with its operator. Articles of note New featured articles: None New featured lists: None New featured topics: None New good articles: Jevons paradox Redlinks to be squashed Skysmith has posted an updated list of missing economics topics. Most will need redirecting or new articles written to blueify them, so, if you can lend a hand with the effort, please do. There are some from virtually all areas of economics and hence to suit all tastes. Project news Unassessed articles: A whole swath of articles have been added to the WikiProject recently, mainly on notable economists. They are yet to be assessed on their talk pages; this also provides a good opportunity to check and improve some of our least monitored articles. Unsourced BLPs: Before the articles about economists were added, the project had very few unsourced biographies of living people; now there are a little over a hundred. If we can clear them, however, then it is unlikely that there will be many more. Again, they represent some of our least cared-for articles, and often present good targets for cleaning up. Your comments are invited in the following other ongoing project discussions and requests for help: Vanderford-Riley well-being schedule New Economic Indicator for Infoboxes Beth Hayes
To start/stop receiving this newsletter, please add/remove your name from the list here. Thank you. This newletter was delivered to you by User:Jarry1250 at around 19:25, 1 September 2010 (UTC)

Categories for discussion nomination of Category:Military aircraft by war

Category:Military aircraft by war, which you created, has been nominated for deletion, merging, or renaming. If you would like to participate in the discussion, you are invited to add your comments at the category's entry on the Categories for discussion page. Thank you. Marcus Qwertyus 06:59, 7 December 2010 (UTC)

Venetian Pool

I re-edited the article Venetian Pool and removed the See also link to this outdoor pool from the article Lido which you added on 26 December. I didn't think any reference to the island Lido di Venezia was relevant to the article on the Venetian Pool, am I correct?--Lidos (talk) 15:37, 28 December 2010 (UTC)

Hi Lidos,

Thanks for your editing!

I added the link from Lido to Venetian Pool since they are both outdoor pools (the former a category, the latter a specific pool) from the same period with Venetian names, so they seem related concepts (i.e., so someone familiar with the British phenomenon can learn about the American one), hence of interest in linking.

I’ll defer to your judgment if you think this isn’t helpful, but perhaps you’d reconsider?

Thanks again!

—Nils von Barth (nbarth) (talk) 18:58, 28 December 2010 (UTC)

We prefer to add examples of lidos to the list in the appropriate category. The only ones included in the text of the article are a few of those which have the word 'lido' in their publicised title. So it's really a desciption of what a lido is, rather than specific examples, does that make sense?

I think the Venetian Pool is the only American example of a pool using the name Venetian, and I understand it refers to the lagoon not Lido di Venezia (the island), so I'd prefer not to mention it there. You will notice I added in the Category:Swimming venues in the United States. We have British categories for swimming pools in each county, but I couldn't one for Florida.--Lidos (talk) 15:14, 29 December 2010 (UTC)

Ok, understood – makes sense.

Sounds good, and thanks for explaining!

—Nils von Barth (nbarth) (talk) 18:26, 29 December 2010 (UTC)