User talk:David Eppstein/2009d

Trofimov & Smolensky
Since you seem to actually understand what their algorithm does, I'll ask you a question: is there any reason to think that its worst-case running time is any better than exponential? — Emil J. 13:47, 17 August 2009 (UTC)


 * No. But, like other similar algorithms, it would probably be very difficult to find examples where it actually does take exponential time. —David Eppstein (talk) 16:17, 17 August 2009 (UTC)


 * Thanks. — Emil J. 17:10, 17 August 2009 (UTC)


 * Sorry, but David Eppstein understood nothing :( Now I have some facts that GI is in P, but it is not printed yet ;)--Tim32 (talk) 18:35, 17 August 2009 (UTC)

Another nice graph
Since you've been adding articles on so many nice graphs lately: there's a 24-vertex cubic symmetric graph (the generalized Desargues graph GD(12,5)) that I think also deserves mentioning. In the absence of any better name, I called it the "Nauru graph" in the first of these five blog posts about it, which also includes some sources. I'd be happy to upload any of the images from those posts to Wikimedia commons so they can be used in an article, but given my prior involvement I wouldn't want to write an article here myself. —David Eppstein (talk) 15:54, 19 August 2009 (UTC)
 * Hello David. Since my PHD I am a very interested in cubic symmetric graph. That would be a pleasure writing the article if you upload the files. So you are 11011110 (0xDE) ? If I make a citation of your blog can I wrote David Eppstein as author name ?
 * PS : Is there any higher-order LCF notation for the Nauru graph ? I want to draw it showing a nice Hamiltonian cycle. Koko90 (talk) 16:07, 19 August 2009 (UTC)
 * The LCF notation is also in the first post of that series: [5,-9,7,-7,9,-5]4. Yes, I'm 0xDE (those are my initials), so you can write and link my author name as David Eppstein. —David Eppstein (talk) 16:22, 19 August 2009 (UTC)
 * I have created a basic article about the Nauru graph. Can you proofread it ? You are now free to add some more info and upload your pics. Koko90 (talk) 08:54, 20 August 2009 (UTC)

Question about permutations
David, I apologize if this turns out to be an elementary problem, but I was searching for information on iterated permutations and the lengths of their cycles and couldn't find it on Wikipedia. For instance, the permutation (2 1 9 8 7 3 6 10 5 4) when applied to itself (i.e., the new 3rd element is the old 9th element, the new 9th element is the old 5th element etc), it takes some 30 iterations before returning to itself. 30 turns out to be the longest such cycle-length for 10 elements, and there's a certain distribution of the cycle lengths that depends on the way the elements are partitioned into subcycles and their cycle lengths. An OEIS search for related entries wasn't helpful, and a search for work on longest cycles in the permutation graphs was too broad. Could you please point me to some keywords or OEIS entries so that I can add this information to Wikipedia? If it's already on here somewhere (I looked under permutation and derangement), please let me know. -- Brhaspati\talk/contribs 18:42, 19 August 2009 (UTC)
 * The "number of iterations" required to return to itself is exactly one more than the order of the permutation. The largest order of a permutation of n things is the value of Landau's function evaluated at n. JackSchmidt (talk) 18:57, 19 August 2009 (UTC)
 * Thank you! This was exactly what I was looking for, and couldn't find because I didn't know the term "order of a permutation", and I was looking at work in graph theory instead of group theory. I've added a sentence in the Landau's function article. On a related note, is there a named function for the number of permutations of n items whose order is a given value, like a generalized version of the inverse of Landau's function? (I apologize if these seem elementary -- I am a practitioner of combinatorial optimization and other operations research problems, but I'm not well-versed in combinatorics theory). -- Brhaspati\talk/contribs 19:45, 19 August 2009 (UTC)
 * Let me give two halves of the answer. The first half is theory, history, and nice algebra.  The second half is practical, easy combinatorics (the counting balls in urns kind).
 * To use group theory notation, Le(G) = { g in G : ge = 1 } is the set of elements of a group whose order *divides* a particular number e. This set is studied in the (multiply red-linked) article Frobenius conjecture and under the heading "equations in groups".  It is known that for any finite group the set has size a multiple of e (late 19th century, due to Frobenius), and if it has size exactly e then it is a subgroup (late 20th century).  There is a formula for the size:
 * $$\sum_{\chi\in\operatorname{Irr}(G)} \nu_e(\chi) \cdot \chi(1)$$
 * where νe(χ) is the eth Frobenius–Schur indicator of the irreducible character χ, but I think this is probably not too useful to you (the representation theory of the symmetric group is combinatorial, but probably you want something more practical).
 * More practically, you might find that it helps to divide the permutations into "cycle types" (a specific version of conjugacy classes). Your notation for a permutation is called "one-line notation".  Another common notation is cycle notation.  Your permutation in cycle notation is "(1,2)(3,9,5,7,6)(4,8,10)" and it means "1 goes to 2, 2 goes to 1;3 goes to 9, 9 goes to 5, 5 goes to 7, 7 goes to 6, 6 goes to 3; 4 goes to 8, 8 goes to 10, 10 goes to 4".  The "lengths" of the cycles are 2, 5, and 3.  Obviously these three numbers sum to 10, and in fact any (multi-)set of positive integers summing to 10 is the set of cycle lengths of a permutation of 10 things, that is, a partition of 10.  The order of a permutation is the least common multiple of the lengths of its cycles.  The only partition of 10 with lcm of 30 is 5+3+2, and so you need only count the number of permutations with that cycle type.  There are exactly 10!/5!/5 choices of the 5-cycle, and for each choice there are 5!/2!/3 choices for the 3-cycle, and 2!/1!/2=1 choice for the 2-cycle.  That is 10!/5!/5*5!/2!/3*2!/1!/2=120960 such permutations.  Be careful when there are multiple cycles of the same length, for instance there are 10!/5!/5 * 5!/1!/5 * (1/2!) = 72576 permutations of 10 things with two cycles of length 5.
 * In other words, I don't know of a short name for the numerical function you want, but it is a multiple of n, and the specific multiple can be calculated fairly quickly for permutations of a few hundred things using relatively simple concepts such "partitions", "lcm", and some basic counting (n things chosen k at a time where order matters, but (a,b,c) is the same as (b,c,a), and (a,b,c)(d,e,f) is the same as (d,e,f)(a,b,c)). If you wanted a table of values, I don't mind producing one for you.  I have no idea about asymptotics though. JackSchmidt (talk) 20:19, 19 August 2009 (UTC)
 * Thanks for taking the time to respond. I really appreciate it. No, I had already generated a table of values when working on a related graph-theoretic problem computationally (through an exhaustive search for up to n = 11) and had noticed the distribution well before then, but had no idea what the distribution of cycle lengths was named or what I should search under. Your example gives me a much better way to compute the cycle lengths and frequencies than actually generating them and counting them. A related question I'd had earlier was whether it was possible to generate all n! permutations using a single permutation operation recursively (at least for some values of n), but as Landau's function grows more slowly than n!, (the asymptotics show log(Landau's function) growing approximately like the square root of log(n!)), that means no such permutation exists, and that any Hamiltonian cycle of a permutation graph must necessarily involve several types of permutation operations. This is nice to know. -- Brhaspati\talk/contribs 21:26, 19 August 2009 (UTC)
 * Wow, thanks all for seemingly resolving all of this while I had a nice hike at Lake Louise... —David Eppstein (talk) 02:14, 20 August 2009 (UTC)

I have my own voice
Dear David! Tell what's happen - you've written such "interesting reason" for the last revised of Trofimov-Smolenskii paper... It looks like hurrasment! My relations is not your business: I have my own voice and have a right to tell my own point of view in Wiki. Are you against women' right? Can you explain such discrimination? And may be you can explain such unreasonable revised? --Mart071 (talk) 11:30, 23 August 2009 (UTC)

note at wikiversity:portal talk:Mathematics
Dear Mr. Eppstein, please see the note at wikiversity:portal talk:Mathematics. Do you now people wich might be interested in this topic? Best regards

‫·‏לערי ריינהארט‏·‏T‏·‏m‏:‏Th‏·‏T‏·‏email me‏·‏‬ 14:31, 23 August 2009 (UTC)

DYK Nomination for Dennis Baron

 * From AfD to DYK: Hi. I've nominated Dennis Baron, an article you worked on, for consideration to appear on the Main Page as part of Did you know. You can see the hook for the article here, where you can improve it if you see fit. Arxiloxos (talk) 00:17, 26 August 2009 (UTC)

Symmetric don't implies semi-symmetric
There is a problem with Template:Graph_families_defined_by_their_automorphisms. Symmetric does not implies semi-symmetric because a semi-symmetric can't be vertex transitive. Since you have created the template and you seem familiar with that odd syntax can you fix it? Koko90 (talk) 14:52, 27 August 2009 (UTC)

Golden ratio
I have worked directly with Professor Dragan at the University of Texas in Arlington. I presented my findings on the 4 node graph to him in 2003 during my graduate work there. That work as well as other work in topological properties of graphs have been documented. I hope that any edits you perform in the future at least come with discussion and a reason. Your credentials alone say that you can communicate with reason. —Preceding unsigned comment added by CWDURAND (talk • contribs) 21:56, 30 August 2009 (UTC)

DYK nomination of Martin Demaine
Hello! Your submission of Martin Demaine at the Did You Know nominations page has been reviewed, and there still are some issues that may need to be clarified. Please review the comment(s) underneath your nomination's entry and respond there as soon as possible. Thank you for contributing to Did You Know! Allen3 talk 07:54, 31 August 2009 (UTC)

Jacob M. Appel
Re: J.M. Appel. How was it decided that he was notable last time? It seems to me that he clearly isn't. I normally wouldn't have a problem with this, but there are a few articles that I seem to go back to where he is cited as some sort of authoritative source. Having a historical piece published in the Times does not make you a master bioethicist. Please advise.--24.200.159.33 (talk) 06:27, 1 September 2009 (UTC)


 * He looks notable for his fiction writing, to me. One doesn't have to be notable for each one of the listed accomplishments separately. —David Eppstein (talk) 06:59, 1 September 2009 (UTC)

Kielbasa, Historic Adobes of Los Angeles County
I notice that you deleted references to John Kielbasa's book, "Historic Adobes of Los Angeles County." Has there been a discussion somewhere about the validity of this source? If so, I'm not aware of it. Here is an example. From the research I've done, the Kielbasa book is the best researched work on the historic California adobes. It is my understanding that the work was originally published as a book, and permission was then given to include it on the "laokay" web site when it went out of print. Please clarify your objection to the work. Cbl62 (talk) 15:16, 8 September 2009 (UTC) Dorrance Publishing Co. is a vanity press. According to WP:SPS we can't use those as sources unless Kielbasa is established as an expert on the subject by some other evidence. Do we have any such evidence? —David Eppstein (talk) 16:19, 8 September 2009 (UTC)
 * Here is a citation to it's original publication as a book.   Published by Dorrance Publishing Co. in 1998, ISBN: 978-0-8059-4172-2. Cbl62 (talk) 15:20, 8 September 2009 (UTC)
 * Also,Kielbasa's book has been recognized as an authoritative source on the history of the local adobes by the Los Angeles Times. See . Cbl62 (talk) 15:21, 8 September 2009 (UTC)
 * The guideline you cite is not a prohibition on using sources published by firms like Dorrance. And the fact that the Los Angeles Times cites Kielbasa's book as a reliable, authoritative source should be sufficient. Cbl62 (talk) 16:35, 8 September 2009 (UTC)
 * What part of "self-published media...are largely not acceptable" do you think doesn't apply to this case? The L.A. Times article is certainly a reliable source but I don't see why that means Kielbasa is. —David Eppstein (talk) 17:34, 8 September 2009 (UTC)
 * I do not know whether you are correct that every work published by Dorrance Publishing should be regarded as "self-published", but will assume that to be the case for present purposes. The guideline on self-published works that you quote is not an inflexible prohibition. The word "largely" should be read as the operative word here.  If Joe Blow decides to waste his money paying a vanity press to publish his "memoirs," that doesn't turn Joe Blow or his memoirs into suitable content for Wikipedia.  However, if there is independent evidence that a book (even one published by a "vanity press") is authoritative, then it can and should be used as a source. As an active researcher and writer about Southern California history, I know that Kielbasa's book is very highly regarded in the local historical community.  Of course, my personal knowledge isn’t enough.  So, here is some further evidence that Kielbasa's book on the Historic Adobes has gained recognition as a reliable, and indeed authoritative, source on the subject:
 * 1.	The Los Angeles Times, one of the country's most respected newspapers, recognizes Kielbasa's book as a reliable, authoritative source on LA's historic adobes. In its Feb. 2009 article on the Centinela Adobe, the Times quoted from and cited to Kielbasa's book as its sole identified source for the history of the property.  The fact that the LA Times looks to the Kielbasa book as the authoritative source for information about the history of LA's adobes is strong evidence that the work has gained a level of respect and recognition as an authoritative work.
 * 2.	In a separate article published in 2006, the Los Angeles Times cited the Kielbasa book as its source for an article about the history of Baldwin Hills. See Here.
 * 3.	In a third article, the Los Angeles Times in March 2007 cited the Kielbasa book as a source for an article on the history of the westside community of Westchester. See Here
 * 4.	As an indication of the respect and recognition given to the book in historical circles, the Southern California Historical Society includes Kielbasa's book as one of about 60 works included on the Society's permanent "Recommended Reading" list.  See Here
 * 5.	Numerous major research libraries maintain Kielbasa's book in their collections. A search of the WorldCat database here shows that Kielbasa's book on the Historic Adobes of Los Angeles are maintained by the (i) Getty Research Library, (ii) UC-Irvine, (iii) UC-Berkeley, (iv) Claremont Colleges’ Library, (v) Cornell University, (vi) Indiana University, (vii) University of North Carolina, (viii) Los Angeles Public Library, (ix) New York Public Library, (x) Chicago Public Library, (xi) Cal State University Libraries at LA, Northridge, Fullerton, Fresno and San Bernardino, (xii) Marymount College, and (xiii) Library of Congress.  Typically, the country’s major research libraries do not expend scarce resources procuring and maintaining vanity books of no historical importance.  While the inclusion of the work in the collections of a couple scattered libraries may not be sufficient, the widespread inclusion of Kielbasa’s book in major research libraries is further evidence of the recognition it has received.
 * 6.	The Kielbasa book is used and relied upon by local government as a reliable and authoritative source in matters involving historic designation of properties. For example, in ruling on an application concerning the historic status of the Ygnacio Palomares Adobe, the LA County Board of Supervisors relied upon the historical accounts set forth in Kielbasa’s book.  See Here  See also use as a source by the LA County of  Department of Public Works in an Environmental Impact Report on the Santa Anita Dam, here.
 * 7.	As a further example of a local historian’s praise for Kielbasa’s book, see the comments of Dan Joseffini from Cal State University – Dominguez Hills. In making recommendations to others interested in the adobe period in LA history, Joseffini writes: "Two exceptional books on California adobes to purchase before starting your quest are: 'Historic Adobes of Los Angeles County,' by Mr. John R. Kielbasa … and "California Snapshot In Time 1850," by Janice Marschner ..."  See Here.
 * 8.	In an official publication for the Santa Susana State Park, prepared by the Historian of the California State Parks, the Kielbasa book is cited as a source of historical information about the park. See Here.
 * 9.	Kielbasa's book is cited as a source in a scholarly article published in The John Hopkins University Press journal, "American Quarterly." See Here.
 * 10.	The author of the book, "Earth Architecture," also cites Kielbasa’s book on the LA adobes. See here.
 * 11.	Though self-published the comments of another local historian are also indicative of the respect accorded to Kielbasa’s book: "I've gotta give a shout out to John R. Kielbasa for his book 'Historic Adobes of Los Angeles County,' which gives excellent background information for many of the historic homes of the Spanish period here in CA. Sadly, this book is out of print so I've been doing all my research via the online version … It's a must-read for adobe hunters!" See Here
 * In light of the foregoing evidence, I ask that you voluntarily revert your edits deleting all references on Wikipedia to the Kielbasa book. Also, before making such a wholesale deletion of a source from multiple articles, consider first opening up a discussion on the pertinent talk page(s). Cbl62 (talk) 21:06, 8 September 2009 (UTC)
 * I also find it a loss to Wikipedia to have these references removed. I have found the Kielbasa book to be extremely well researched and accurate. He has gone to the original documents, and there is no other source that comes anywhere close.  This is not a "vanity press" presenting some personal view point.  This is a unique and valuable resource.  I support reverting the edits.Emargie (talk) 00:33, 9 September 2009 (UTC)

Ok, that all looks like enough evidence of people taking Kielbasa seriously as a source for me to do so as well despite his vanity-press publisher. I'll try to get to it this evening — I don't just want to mass-undo the edits, though, as that would leave the same articles vulnerable to the same changes for the same reasons in future. So I'd rather take the time to work up a clean citation template that can be used in all of these articles together with a comment pointing to this discussion as a reason to ignore WP:SPS in this instance. —David Eppstein (talk) 00:50, 9 September 2009 (UTC)
 * Thanks for reconsidering, David. Cbl62 (talk) 00:52, 9 September 2009 (UTC)

✅ —David Eppstein (talk) 03:27, 9 September 2009 (UTC)

Talkback
Admrboltz (talk) 20:53, 13 September 2009 (UTC)

Riemann Hypothesis
As I pointed out over on Rodhullandemu's talk page here, Vasiliu Lucilius may have paranoid schizophrenia. All of the supporters of the online petition are at least alive, while Dr Riemann's support would require the use of a ouija board.-- ♦Ian Ma c M♦  (talk to me) 12:49, 23 September 2009 (UTC)

Parenthetical referencing
Thanks, David, for calling PR to my attention (in re four color problem). I've never seen it used before, and sailed right by the embedded references. The article is excellent, so I might have sensed there was something more subtle (and elegant) afoot. Cheers! Twang (talk) 23:32, 28 September 2009 (UTC)

Bill Sparkman and BLP violation
I'm the author of the deleted text in question and I would like to discuss it further. I started a section on the talk page where I've tried to explain myself and justify the deleted paragraph. I'm interested in your response. ——Rich jj (talk) 17:42, 30 September 2009 (UTC)


 * I suppose I should have specified to please respond on that talk page in case others may want to chime in. ——Rich jj (talk) 17:43, 30 September 2009 (UTC)

Your love of Applebaum
You are the one removing all mention of the authors articles. You are the one engaging in an edit war. You are the one pulling out every Wikipedia link and acronym you can find to justify removal. Nothing you've said is convincing and your arguments (what arguments?, you link incessantly). Did you want to pull out yet another WP:BlahBlah that doesn't apply Mr. 3RR?

Because of you and your ilk, the sentence I added grew to defend your nutty attacks. Now you attack the size. Pathetic. —Preceding unsigned comment added by 24.57.54.1 (talk) 02:13, 3 October 2009 (UTC)
 * Dude, I barely know who she is, and I'm certainly not on her side of the Polanski kerfuffle. But that doesn't mean that I think we should get rid of all our policies to make an example out of her for her bad judgement. Calm down and try to think of this as an encyclopedia and not as a place to showcase gaffes — that's for the blogs. And try to have a little faith in your fellow editors instead of making all these attacks. —David Eppstein (talk) 02:18, 3 October 2009 (UTC)
 * I agree with the IP. You come off as rabidly desperate. I wholly support the entry and might just join to lend more weight to the fight against YOUR attacks. It meets WP:BLP and nothing you've said so far (talk page) is useful. Leave the entry alone Mr. Edit war. 64.228.135.90 (talk) 02:26, 3 October 2009 (UTC)

Spherium
This new article coudl use some expert attention. ChildofMidnight (talk) 03:17, 3 October 2009 (UTC)
 * Thanks for the pointer, but quantum chemistry is really not my forté. —David Eppstein (talk) 04:49, 3 October 2009 (UTC)

Anne Applebaum RPP
It looks to me like your RPP ended up at the bottom of the page, with the already-acted-on requests, rather than at the top, with the pending requests. So I moved it. If this screws things up, be sure to point out that it was my fault. Hullaballoo Wolfowitz (talk) 03:38, 3 October 2009 (UTC)
 * It was my mistake, I think. Thanks for the fix. —David Eppstein (talk) 03:40, 3 October 2009 (UTC)

WikiProject Academic Journals/Deletion
Hi David, we seem currently to be the only two editors maintaining this page. However, given that these notifications are now automatically listed on WikiProject Academic Journals, I wonder whether it is still necessary. If you encounter an article prodded or taken to AfD, it suffices to tag it with the WPJournals template on its talk page to have it listed automatically on the project home page. What do you say? --Crusio (talk) 11:02, 4 October 2009 (UTC)
 * Yes, that looks like a better maintained listing than the manual one. For the same reason I don't deletion-sort mathematics articles because there is a bot that maintains WikiProject Mathematics/Current activity better. —David Eppstein (talk) 15:46, 4 October 2009 (UTC)

A Seddik
Hi, after deleting Ahmed Seddik, would you like to take care of A Seddik as well? Unfortunately there will be many potential ways of transliterating this name from Arabic -- Seddiq, Sediq, etc. -- but A Seddik appears to be the only one created by User:Kemetician for now. Nomoskedasticity (talk) 22:02, 4 October 2009 (UTC)


 * ✅ Deleted, salted, and blocked. —David Eppstein (talk) 22:09, 4 October 2009 (UTC)

Perspective
The explanatory comments at Articles for deletion/Joshua Greenberg were useful for me.

Pondering the array of views in this thread helped me to step back only slightly; but even small movements do evoke a changed perspective, a new appreciation of our focal point. --Tenmei (talk) 16:20, 6 October 2009 (UTC)


 * In my opinion, the AfD thread resulted in an improved article. Let me take this opportunity to acknowledge your contribution specifically.  Undoubtedly, your participation in this thread caused me to re-examine an imperfect understanding of what WP:notability requires.  Thank you. --Tenmei (talk) 18:16, 10 October 2009 (UTC)

Query complexity of subgraph isomorphism
When I wrote the article on the Aanderaa–Karp–Rosenberg conjecture, and added that Groger has shown a lowerbound for testing if the given graph G is isomorphic to a graph H, I hesitated to add that this is called the "subgraph isomorphism problem." (I noticed you added that line.) The reason I hesitated is that there are two subgraph isomorphism problems in my mind — one is when the graph to be checked, H, is fixed and independent of the input (for instance checking if G has a subgraph isomorphic to the path of length 4, or the clique of size 20) and the other is where the graph H can vary with n, like checking if G has a clique of size n/4. The first problem is in P for any fixed graph, whereas the second is NP-complete. I'm not sure which one of the two problems Groger proved the lowerbound for. If you know which is the case, I would be happy to know. --Robin (talk) 17:22, 6 October 2009 (UTC)
 * It looks like he handles the more general case when the subgraph can vary, but for some special cases of H (such as when it is an n-vertex cycle) he gets much tighter bounds. —David Eppstein (talk) 17:38, 6 October 2009 (UTC)
 * I see. Thanks! --Robin (talk) 17:44, 6 October 2009 (UTC)

P = NP page
It seems that the vandalism has shifted to the article after you protected the Talk page of this article. Perhaps the article should also be protected so IPs can't edit it. Also, since the page is move protected, could you help with the move request -- Talk:P_%3D_NP_problem? (I think the required waiting period of 7 days is over.) Thanks. --Robin (talk) 18:55, 24 October 2009 (UTC)

Human suit recreated as Human disguise
This is a notice to all who participated in the recent AfD of Human suit, here, that resulted in a consensus for delete. This article has been recreated as "Human disguise", and has been nominated for deletion: Articles for deletion/Human disguise. Thank you. Verbal chat  21:06, 29 October 2009 (UTC)