User talk:David Eppstein/2011b

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Hey David, I always went by the UTC time... seems like a rather harmless joke for April Fool's day anyways. Any reason to not have it up for a day? Coffee // have a cup // essay // 01:38, 1 April 2011 (UTC)

I guess you must just have caught me in a humorless mood. If you try it again, I won't revert. —David Eppstein (talk) 02:13, 1 April 2011 (UTC)

To each according to his contribution ....

Hi David!

This is my first attempt to cite your SF-lemma image (for a non-hypertext linked document). Would you suggest any changes? Thanks again for your contributions! Best regards, Kiefer.Wolfowitz (talk) 02:41, 1 April 2011 (UTC)


  author = "Eppstein, David",
  title = "{Shapley--Folkman}~lemma ({File:Shapley--Folkman}~lemma.svg)",
  year = "2010",
  url = "",
  note = "\texttt{} [Online; accessed 1-April-2011]",
Looks pretty reasonable. The custom BibTeX styles I usually use would format that with two copies of the URL (once for the url= field and once for the note= field) but I guess the default styles don't use url=. It might be helpful to say "Wikimedia Commons" in there somewhere rather than letting people infer that from the URL. There are some model BibTeX entries (for Wikipedia, but Wikimedia should be similar) at Wikipedia:Citing Wikipedia#BibTeX entry. Oh, and you should probably be using \_ instead of ~ in the url. —David Eppstein (talk) 03:42, 1 April 2011 (UTC)
Thanks for the help.  Kiefer.Wolfowitz  (Discussion) 02:58, 5 April 2011 (UTC)
BTW, your zonotopic illustration reminds me of a thought from Wittgenstein:
"The beauty of a star-shaped figure — a hexagonal star, say — is impaired if we regard it as symmetrical relatively to a given axis." (Culture and Value or Zettel, 71e)

Daniel J. Shanefield

Nicely done! --joe deckertalk to me 22:18, 3 April 2011 (UTC)

Thanks! —David Eppstein (talk) 06:33, 6 April 2011 (UTC)

Lists of people

As you've also worked on cleaning up lists of people, this discussion may be of interest to you. Best.--Epeefleche (talk) 19:40, 5 April 2011 (UTC)

Thanks, I added my 2c there. —David Eppstein (talk) 06:34, 6 April 2011 (UTC)
Sure thing. Lots of different views there! Almost one per editor ... --Epeefleche (talk) 16:24, 6 April 2011 (UTC)

I think listing just one of Gleason's PhD students is misleading. Most readers don't know that you need a wikipedia entry of your own to be on a list of people - I didn't until I poked around here before complaining. I understand the policy. Can the label on the page say something like PhD students with wikipedia pages (ugly)? Or perhaps delete Spencer here but put a link in the entry to the math geneology page for all the PhD students. Ebolker (talk) 02:28, 7 June 2011 (UTC)

Nomination of Roger Walsh for deletion

A discussion is taking place as to whether the article Roger Walsh is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The article will be discussed at Wikipedia:Articles for deletion/Roger Walsh until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on good quality evidence, and our policies and guidelines.

Users may edit the article during the discussion, including to improve the article to address concerns raised in the discussion. However, do not remove the article-for-deletion template from the top of the article.   Will Beback  talk  06:12, 6 April 2011 (UTC)

Thanks for the notice, but given that he and I are at the same institution it may be better if I sit this one out. —David Eppstein (talk) 06:33, 6 April 2011 (UTC)

Minimal geodesics

This is in reference to the geodesic convexity page. I have never tried to communicate via wikipedia before, I apologize if this is not the best place to comment. I have seen geodesics been defined in metric spaces as minimal paths, however this is not how they are traditionally defined in Riemannian geometry (which is the context in question). Furthermore, the link to the wikipedia definition of geodesic defines them for general metric spaces, but as only locally minimal. Therefore, the term geodesic used in the context of convexity here must be qualified in some way. I see that this has already been discussed on the talk page. An example is given of a geodesic disk on the unit sphere whose radius exceeds . This should not be convex by any definition, however it is convex by the current definition: both great circle arcs between two points are geodesics as Wikipedia currently defines them.

Yasmar (talk) 08:41, 6 April 2011 (UTC)

Do you mean minimal or minimum? "Minimal", to me, means only that it is locally shortest. If you mean globally shortest you should use a different word. —David Eppstein (talk) 15:22, 6 April 2011 (UTC)

DYK for John R. Isbell

The DYK project (nominate) 00:03, 8 April 2011 (UTC)

More Smarandache stuff at AfD

Fuzzy matrix theory. Tijfo098 (talk) 19:56, 14 April 2011 (UTC)

Nomination of Gopala–Hemachandra number for deletion

A discussion is taking place as to whether the article Gopala–Hemachandra number is suitable for inclusion in Wikipedia according to Wikipedia's policies and guidelines or whether it should be deleted.

The article will be discussed at Wikipedia:Articles for deletion/Gopala–Hemachandra number until a consensus is reached, and anyone is welcome to contribute to the discussion. The nomination will explain the policies and guidelines which are of concern. The discussion focuses on good quality evidence, and our policies and guidelines.

Users may edit the article during the discussion, including to improve the article to address concerns raised in the discussion. However, do not remove the article-for-deletion template from the top of the article. —Mark Dominus (talk) 16:25, 15 April 2011 (UTC)

DYK for Ivar Ekeland

Hi David, would you consider the DYK nomination for Ivar Ekeland, please? Thanks,  Kiefer.Wolfowitz  (Discussion) 16:06, 17 April 2011 (UTC)

Thanks for your feedback. I made the corrections you suggested. Best regards,  Kiefer.Wolfowitz  (Discussion) 21:18, 17 April 2011 (UTC)
I added a digression about James Gleick as a political move to get a DYK for the article and for Tkuvho: The 8 April articles are now being added to the DYK prep area, so your approval of the hook as meeting all the concerns would be especially helpful. Best regards,  Kiefer.Wolfowitz  (Discussion) 21:25, 18 April 2011 (UTC)
Thanks for the comment and vetting of the DYK: Do you have a preference between the two hooks? Cheers,  Kiefer.Wolfowitz  (Discussion) 23:22, 18 April 2011 (UTC)
I prefer the Julia image to the bifurcation one. I guess either hook could go with either image though? —David Eppstein (talk) 23:47, 18 April 2011 (UTC)
There is some local optimization, because Ekeland doesn't discuss the Julia set, so a "like" is used. I'll link your preference (here) at the DYK page.  Kiefer.Wolfowitz  (Discussion) 00:06, 19 April 2011 (UTC)
The beautiful graphics were snubbed in favor of a Last Supper image, to attractive the fans of Dan Brown (shudder) more than the fans of Michael Crichton.
Cheers,  Kiefer.Wolfowitz  (Discussion) 17:59, 19 April 2011 (UTC)

DYK Medal

Dyk25CE.svg The 25 DYK Creation and Expansion Medal
Congratulations on your 48 high-quality DYKs!  Kiefer.Wolfowitz  (Discussion) 17:39, 22 April 2011 (UTC)

I counted 48 on your user page, but of course you should correct any error on my part.  Kiefer.Wolfowitz  (Discussion) 17:39, 22 April 2011 (UTC)

Thanks! I should have one more coming in just a few minutes... —David Eppstein (talk) 17:50, 22 April 2011 (UTC)

encyclopedia dramatica

sorry about the double post on the talk page. i was in the process of removing the first addition, but you beat me to it. the second addition also asked about the position of the section "Relaunch as Oh Internet", which somehow is before the "critical reception" section. shouldnt that be nearer to the end of the article? btw, sorry i couldnt fix that in time, wikipedia is being very slow and problematic this morning. Badmachine (talk) 16:30, 20 April 2011 (UTC)

That level of change probably requires building consensus on the talk page before requesting a protected edit. I agree, the software has been annoyingly slow this morning. —David Eppstein (talk) 16:33, 20 April 2011 (UTC)
thanks. Badmachine (talk) 16:42, 20 April 2011 (UTC)

DYK for Kawasaki's theorem

In this example, the alternating sum of angles (starting from the triangle in the bottom of the crease pattern) is 90 − 45 + 22.5 − 22.5 + 45 − 90 + 22.5 − 22.5 = 0. Since it adds to zero, the crease pattern may be flat-folded, as shown.

The DYK project (nominate) 18:02, 22 April 2011 (UTC)

That's a beautiful article.
With your WP work on mathematics, gracefully written, effortlessly accurate, and sumptuously illustrated, you may be the Martin Gardner of our generation.  Kiefer.Wolfowitz  (Discussion) 18:12, 22 April 2011 (UTC)


Can you please answer Purplepox01's question in regards to this personal attack? I'm not in the mood to play games with this person, and I'm not amused by the fact that Purplepox01 proposed one of my articles for deletion in retaliation. --Michaeldsuarez (talk) 18:15, 25 April 2011 (UTC)


I was mimicking other articles that I had seen which used Π (capital Pi) for DEFAULTSORT. I don't care which way is chosen, but there should be some consistency. CRGreathouse (t | c) 19:04, 28 April 2011 (UTC)

We want π to sort within the range for "p", not after z, right? So to achieve that we need to spell it out. I think the wording in WP:MCSTJR about spelling out accented characters is also suggestive that we should spell out pi in this context. —David Eppstein (talk) 20:05, 28 April 2011 (UTC)
I don't get that from MCSTJR. (I'm not sure how you read that into the guidelines there -- are you calling pi an "accented character"?) But I also don't mind spelling it out in DEFAULTSORT. CRGreathouse (t | c) 22:13, 28 April 2011 (UTC)
Obviously MCSTJR doesn't say anything explicit about π. But it's about spelling out other non-ASCII characters in ASCII and by extension the same principle applies to π. I don't think it makes much difference in this case, anyway, since the π is at the end of the article title and there don't seem to be other articles whose titles compare the same up to that point. —David Eppstein (talk) 22:14, 28 April 2011 (UTC)

DYK for Widest path problem

Gatoclass (talk) 12:02, 3 May 2011 (UTC)

DYKs at Math Portal

Hi David!

The Mathematics Portal had a shortage of DYKs, including a few blank years, so I added your mathematics DYKs.

Let me know if you'd like them deleted. Best regards,  Kiefer.Wolfowitz 14:57, 3 May 2011 (UTC)

I would have done this myself if I'd remembered, so thanks. —David Eppstein (talk) 15:01, 3 May 2011 (UTC)

Sally Oey

Hi. You removed the alternate name in this article with the comment "since she goes by Sally professionally, let's just keep it that way unless we have sources for the other name". As I had already pointed out on the talk page, the AAS page announcing her prize, which is the first reference in the article as it stands, and presumably therefore a reliable source, uses the alternate form of the name that you changed. Old Crobuzon (talk) 05:44, 6 May 2011 (UTC)

Help request

Hi David, I'm asking for help since I'm in contact with a new user who may need the assistance of an administrator. We've been having a discussion, both at User talk:Slawekb#Deletion of Fractal Space Map and at User talk:Gervasecb. The user wants to have his article Fractal space map restored, which was deleted following this discussion. I've gone over the various options with him to the best of my abilities—I'm not really very knowledgeable of the procedure for article re-creation. I've also tried to discourage him from continuing to work on the article, since he has a clear conflict of interests in the subject, but I have been very gentle about it (perhaps too much so). I'm also very busy in real life at the moment. I would appreciate it if you could look into this and see if you think it's a good idea to restore a copy into Gervase's user space. If not, could you please have a word with him? (Disclaimer: He asked me to contact an administrator on his behalf.) Thanks, Sławomir Biały (talk) 11:41, 6 May 2011 (UTC)

Philip Harper for TotW

Hi, I noticed that you have done some editing on Philip_Harper_(sake_brewer). Just to let you know, I've nominated this article to be Translation of the Week here. Thanks for improving an article about nihonshu. Gotanda (talk) 06:09, 7 May 2011 (UTC)

Fractal space map article

Hi David, Thank you for the quick response. Please do go ahead with the userfication. If you could do the same with the images the article references that would be great: Fractal Map of Global Equity Markets.png, Fractal Map labelling.png, Fractal Map with Various Degrees.gif and Fractal Map with Degree 3.gif. I believe I will be able to upgrade the references in a satisfactory manner. Many thanks, 08:57, 10 May 2011 (UTC) —Preceding unsigned comment added by Gervasecb (talkcontribs)

 Done I've restored the text of the article to User:Gervasecb/Fractal space map. But the images were labeled as being deleted because they did not have the appropriate copyright, so I am uncomfortable restoring them. If you think the article can be improved to a level where it can be put back into Wikipedia (and as I've said before, I find this doubtful myself: I think what you need is not more work on the article, but more evidence that other people outside Wikipedia are paying attention to this research) then one of the improvements you should make is to find or make images that satisfy Wikipedia's image licensing requirements. —David Eppstein (talk) 01:14, 11 May 2011 (UTC)

Response to your edits of my biography

David, this is Ogi Ogas. I'm not sure how you can allow a number of unverifiable and libelous criticisms of me on my discussion page (e.g., Boston University never reprimanded me or asked me to stop claiming I was affiliated with BU), and allow our book to be called "pop psychology" when it has been endorsed by a number of prominent scientists who all publicly have stated the book is valuable science, not pop psychology. Then you remove the references to this, but leave the criticism--which is sourced by anonymous blogs!

I believe an 8-part series of articles by an established sex therapist in Psychology Today describing the utility of our book for sex therapy both gives a more accurate portrait of how the book has been received by clinicians and scientists than a bunch of fan fiction blogs. As does the opinion of Steven Pinker, David Buss, and Donald Symons, all luminaries in the behavioral sciences. If you're going to take out mainstream coverage and mainstream opinion of our book, how can you leave in criticism that consists of anonymous blogs and comments by non-scientists? 6inthePocket (talk) 18:24, 10 May 2011 (UTC)

You removed much of the criticism of your book, violating WP:NPOV. In addition, per WP:COI, you should not be editing the article of your own book. The appropriate action is to leave a message on the talk page (as you did) and let less-biased editors handle the judgement issue of whether your desired edits are appropriate. —David Eppstein (talk) 18:25, 10 May 2011 (UTC)

I certainly did not remove "much of the criticism." I removed exactly one piece of criticism, the false one: that Boston University asked us to stop claiming affiliation. The policy on the biography of living persons states: "Contentious material about living persons that is unsourced or poorly sourced must be removed immediately, especially if potentially libellous." The material I removed is poorly sourced, false, and libelous, since it suggests some kind of negative institutional attitude by Boston University towards myself, my colleague, and our book, when in fact Boston University faculty and administrators have been supportive. —Preceding unsigned comment added by (talk) 18:41, 10 May 2011 (UTC)

According to this report the claim that Boston University asked you to stop claiming affiliation is factual. But sadly, that's not usable as a source here, and I can't find a better source, so it should probably be removed. As for whether your work is pop psychology or academic science, I think you're not in the best position to judge accurately, but your publisher is a popular press publisher, not an academic publisher. Additionally, per WP:LEGAL, please be careful using words such as "libelous" here. If you feel you are getting inadequate response on the talk page of the article, you might also try WP:OTRS. —David Eppstein (talk) 18:52, 10 May 2011 (UTC)

I feel that you are being unfair to me.

I am trying to help fix a bad situation by pointing the way to a solution. Please help me to do this. Making personal attacks is only going to be counterproductive. Cheers! bd2412 T 01:00, 11 May 2011 (UTC)

As far as I can tell, the "bad situation" exists only as an overly legalistic interpretation of rules within your mind. The status quo has been working well for the rest of us who actually use these lists regularly to keep up on changes to Wikipedia's mathematics coverage. —David Eppstein (talk) 01:02, 11 May 2011 (UTC)
David, I'm not even the first person to bring up this issue. This is a serious issue, and as the disambiguation project clears the brush and gets down to core problems, it is one that will come up over and over again until a resolution is achieved. Would you be frustrated if you invested a great deal of time in cleaning up a bunch of errors only to have those errors mindlessly and needlessly restored by a bot. bd2412 T 01:46, 11 May 2011 (UTC)

Enda Marren

Hi David, you edited a profile on my father Enda Marren by deleting most of his biography on March 11, 2010. Can you tell me why did you do this? —Preceding unsigned comment added by (talk) 08:13, 19 May 2011 (UTC)

Because the parts I deleted neither had reliable sources listed nor could I find sources when I searched for them. Everything in Wikipedia must be verifiable and those parts weren't. —David Eppstein (talk) 14:50, 19 May 2011 (UTC)

Dedekind–MacNeille completion

Well that was quick! :-) Thanks! Melchoir (talk) 07:45, 22 May 2011 (UTC)

You're welcome! By coincidence I happen to be working on a paper in which the Dedekind–MacNeille completion plays a central role, so I had those references handy. —David Eppstein (talk) 07:48, 22 May 2011 (UTC)
That's great! So, do you plan to put the article on DYK? I think it only needs a couple more paragraphs to qualify as a 5x expansion (the original split probably isn't eligible).
I think by now it may be big enough. The more important issue, to me, is that it's still pretty technical: I'm having a difficult time thinking of a hook that would not immediately baffle most Wikipedia readers. —David Eppstein (talk) 00:42, 25 May 2011 (UTC)
Good point. Maybe something about filling in the gaps between decimal coordinates in a plane? I guess that's kind of contrived... Melchoir (talk) 01:28, 25 May 2011 (UTC)
The easy/powerful theorem that positive linear operators are continuous uses a hypothesis that the Banach lattice(s?) is Dedekind complete.  Kiefer.Wolfowitz 06:38, 27 May 2011 (UTC)
In other news, I started another stub: CC system. I'm not sure whether you've written about these structures, but I figure you might be interested. Melchoir (talk) 21:55, 24 May 2011 (UTC)
I misplaced my copy of Axioms and Hulls, so I can't quickly look this up: are these things the same as rank-three oriented matroids? —David Eppstein (talk) 23:12, 24 May 2011 (UTC)
"Oriented matroids" was the magic phrase of the day:
Springer-Verlag has an on-line edition, to which your library may have a subscription. I quote from D. E. Knuth (title page, although "Donald E. Knuth" is on the LoC info page): "Section 10 demonstrates a two-to-one correspondence between pre-CC systems and uniform oriented matroids of rank 3" (page 2).  Kiefer.Wolfowitz 23:29, 24 May 2011 (UTC)
Page 40: "CC systems turn out to be equivalent to ... 'uniform acyclic oriented matroids of rank 3.' More precisely, there is a two-to-one correspondence between CC systems on a set of labeled points and all such oriented matroids defined on the same set. The two CC systems with the same image under this correspondence are obtained from each other by negating the value of every triple pqr."  Kiefer.Wolfowitz 23:43, 24 May 2011 (UTC)
David's work with Bern et alia (published in Goodman Pollack DIMACS volume) is discussed on pages 96 and 100.  Kiefer.Wolfowitz 23:45, 24 May 2011 (UTC)

Hurwitz quaternion order

Hi David, thanks for your critical comments. Hope my recent edits make the relative roles of the various authors clearer. Tkuvho (talk) 10:41, 24 May 2011 (UTC)

Yes, much better thanks. —David Eppstein (talk) 13:49, 24 May 2011 (UTC)

google scholar

Hi David, Is it appropriate to cite google scholar statistics in the bibliography of an article? There is a budding edit war over this unfortunately. Tkuvho (talk) 04:46, 27 May 2011 (UTC)

My feeling is generally not. It's a very indirect and not very reliable measure of someone's impact. It's not really information about the subject of the article, and to my mind it's not really well-defined and reliable enough to even be thought of as data about the subject. It can be a helpful indicator to editors about which papers on or by some subject are the important ones, but that's not the same as putting it into the article. —David Eppstein (talk) 04:50, 27 May 2011 (UTC)
I see. I think that when an article or a book get 1000 hits there, it is difficult to argue that this is not an indication of notability, but no matter. What about MathSciNet statistics, do you think it's reasonable to include this in a bibliography as indication of influence? Tkuvho (talk) 07:38, 27 May 2011 (UTC)
I am referring to the mathscinet tool that calculates the number of papers that cited a given paper. Tkuvho (talk) 07:39, 27 May 2011 (UTC)
Oh, I think a paper with 1000 hits is a big indication of notability too, where "notability" means "merits a Wikipedia article". And a big indication of actual impact. I'd definitely mention those things in an AfD for an article, and I'd take them into account when choosing selected publications. I just don't think that it's an indication that should go into the article itself. —David Eppstein (talk) 15:32, 27 May 2011 (UTC)
OK, I guess that one's a nonstarter :) Tkuvho (talk) 20:16, 28 May 2011 (UTC)

Template:Citation example doesn't explain zbl

Template:Citation has mr, zbl, and jfm as the last three parameters, but they're not present or explained in the example. (See Template talk:Citation#Explain mr, zbl, jfm.) Would you please add them, and appropriate descriptions? (At least for zbl; I don't know who wrote the others in.) TIA. --Thnidu (talk) 16:07, 28 May 2011 (UTC)

Why me? I didn't set up those parameters and I don't actually know what jfm is. —David Eppstein (talk) 16:17, 28 May 2011 (UTC)
I'm sorry. What I see now when I look there doesn't match what I seem to remember, and I thought I'd seen your name on a comment on one of them. It's probably a sign from above that I shouldn't do this when I'm so tired. --Thnidu (talk) 03:33, 11 June 2011 (UTC)

Logarithm FAC

Hi, you commented at Wikipedia:Featured_article_candidates/Logarithm/archive1, but did not declare whether you support or oppose the nomination. SandyGeorgia, FAC delegate suggested that I ask you, if you want to do so now. (If you don't want to declare either way, simply disregard this message.) Thanks, Jakob.scholbach (talk) 15:12, 29 May 2011 (UTC)

List of people by Erdős number

Thanks a lot ! (I was not able to be so quick and efficient). What a pity, (I had no great hopes but) I liked the idea of Master Karoubi being n°2. By the way, any idea about this and that ? Anne Bauval (talk) 19:04, 31 May 2011 (UTC)

You're welcome. I've replied to your comment about the Riemann redirect at the talk page. Sorry, I have no special information on Sato–Tate. —David Eppstein (talk) 20:06, 31 May 2011 (UTC)

G space

Can you perhaps have a look at this article? It looks fine, just that it cites a huge amount of publications from what seems to be the article creator. Perhaps justified, perhaps a bit of self-promotion, I don't know enough about this to judge. --Crusio (talk) 14:33, 5 June 2011 (UTC)

Please report this to the WP:WikiProject Mathematics (and perhaps additionally to the WP:WikiProject Computer Science), because it may have possible COI or self-promotion issues. Kiefer.Wolfowitz 15:23, 5 June 2011 (UTC)
Thanks, yes, please do take this report to those places. It does smell of self-promotion to me but it's enough not my area that I'm not really sure about it, and "G space" gets quite a few hits in Google scholar but whether they're really for the same subject is less clear to me. —David Eppstein (talk) 18:01, 5 June 2011 (UTC)

Jason W. Fleischer

I've just closed this keep, it was clear the turning point in the AfD was your improvements, stubby as they might be, to the article. Well done! --joe deckertalk to me 18:24, 5 June 2011 (UTC)

Ref suggestion

I reviewed your triangle entry, seems good to go, but see my comment about using a different ref style there. --Piotr Konieczny aka Prokonsul Piotrus| talk 01:06, 10 June 2011 (UTC)

I deleted your comments on a talk page

Hi, David. I saw a new section at Talk:Four color theorem where some guy proposed a method of extending the theorem to higher dimensions. I went ahead and deleted the section, citing WP:OR (see [1]), but not before you replied to it. So I accidentally deleted your comments too. I probably wouldn't have deleted the section if I had realized you had already replied, but I'm not sure that it's worth it to undo my deletion now that it's done. If you think it's meaningful or proper to put that section back, please feel free to do so. Sorry about that. —Bkell (talk) 05:10, 14 June 2011 (UTC)

I'm fine with it being deleted; as you say the comment to which I replied was OR. —David Eppstein (talk) 13:46, 14 June 2011 (UTC)

DYK for Malfatti circles

Materialscientist (talk) 18:03, 16 June 2011 (UTC)