User talk:Linas/Archive13

Spice Wars

You are correct, there is no specific article on the spice wars as such - but there is some material scattered through various geographical (ie places) and history articles concerning Indonesia - also under certain biographies. In fact, just last weekend, I was going through and created a page Timeline of Indonesian History in which i focused a lot on the 1500s and 1600s (check the wiki links there). I'd love to see this history developed further on wikipedia. Also see History of Indonesia info on this period i updated slightly. Also off the top of my head Ternate and Banda Islands. I've actually been travelling thru the so-called Spice Islands (ie, Maluku) so if you want to work on this area please keep me informed if you can. As i stumble across (and remember) other relevant articles I will let you know. regards --Merbabu 14:56, 16 February 2007 (UTC)

I've no plans to work in this area; not really expert or knowledgable in it. Its just that I saw a pop-culture ref to spice wars, and boggled at the idea that this was a red link, and not even a redirect to some existing article. Perhaps it might not be a bad idea to nuke what I wrote, and simply redirect to spice trade (maybe expanding that article a bit, to indicte that there was plenty of blodshed.). linas 01:05, 17 February 2007 (UTC)

WP:LITH

You might be interested in visiting WikiProject Lithuania. GL.--Lokyz 22:30, 16 February 2007 (UTC)

Missing topics about physics

Thanks for your help with the missing topics page - Skysmith 09:03, 21 February 2007 (UTC)

Your contribution to the page Complementary sequences

Thanks to your contribution but I must express my dissagreement with your See also items.

As much as I am aware Golay complementary sequences have no connection to Golay codes. Golay complementary sequences are pairs of sequences of lenghtt 2, 4, 8, 10, 16, 26, 32, ... with some special autocorrelation properties. Golay codes are perfect error correting codes of length 23. The only thing they have in common is the name of the autor.

So I propose to remove the section "See also" containing Golay codes and related links. This is similar to putting links to the Complementary DNA sequences in the "See also" section just because the word complementary appears in both terms.

I propose to put a link to "Maximum length sequences" (or m-sequences or PN-sequences) instead. I intend to do that after writing a section comparing Golay complementary sequences to PN sequences.

Budisin srdjan 19:25, 21 February 2007 (UTC)

The "see also" section of an article serves to list other topics that a reader might reasonably be interested in. Insofar as they are named after Golay, and concern sequences of binary digits, they seem related enough to be included in a see-also section. Adding complementary DNA sequences to the see-also list would be entirely appropriate, precisely because the phrase "complimentary sequence" appears in both of them. By contrast, phrases that appear directly in the article should not be placed in the see-also section. Thus, it would be wrong to put "maximum length sequence" in the see-also section. linas 03:49, 22 February 2007 (UTC)

I'm watching you!

Don't think you can creep up on me unoticed! Paul August ☎ 20:52, 5 March 2007 (UTC)

Dang. And here I was, rehersing the exact wording of the announcement that you've been dethroned! linas 23:50, 5 March 2007 (UTC)

Articles "Gravitational attraction" and "Gravitational force"

Dear Linas, if you have time, could you please help solve the problem with the articles Gravitational attraction and Gravitational force. Recently, User:JimJast has turned these articles from redirects to Gravity and Newton's law of universal gravitation, respectively, into pages with their own text. I'm sure you'll easily notice what the problem is :). See also Talk:Gravitational attraction. Thanks, Yevgeny Kats 13:17, 16 March 2007 (UTC)

Fraktalai

Hi, i've just started a page on fractals on lithuanian wiki. Your work on fractals is just amazing. Maybe you could contribute, put few lines on the subject. http://lt.wikipedia.org/wiki/Fraktalas Cheers Figuura 15:36, 16 March 2007 (GMT)

Aciu. Paziurejau, neaisku ka galiu daugiau prideti. Man idomiausias dalykas yra rysis su modular forms, sakykim Dedekind eta function arba j-invariant; jauciu kad svarbu pamyneti ta rysi. linas 04:05, 19 March 2007 (UTC)

na žiūrėk; šiaip būtų jėga, jei parašytum. žinai, kalbėjom apie lietuviškos vikipedijos reikalingumą (tarsi viskas randama angliškoj wiki), priėjom banalios išvados kad ne visi skaito angliškai, ...vadinasi reikia. Figuura 12:40, 19 March 2007 (GMT)

Zinoma; ne visi skaito ankiskai. Bet daznai nebekalbu lietuviskai, net maziau skaitau, tai rasyti butu sudetinga. Dar net neispellojau kaip isumsti zenklus. Bet galiu pabandyti. linas 16:14, 19 March 2007 (UTC)

WikiProject History of Science newsletter : Issue I - March 2007

The inaugural March 2007 issue of the WikiProject History of Science newsletter has been published. You're receiving this because you are a participant in the History of Science WikiProject. You may read the newsletter or unsubscribe from this notification by following the link. Yours in discourse--ragesoss 03:43, 24 March 2007 (UTC)

linas art galery

Hi Thx for great pages about fracatls. Can you give me some informations how to run your programs http://linas.org/art-gallery/src/

Adam Majewski

Hi, those are all old, stale and obsolete. They weren't realy meant for public use or consumption. linas 22:10, 30 March 2007 (UTC)

Extension of Heisenberg group

Hi Linas, in the discussion to Heisenberg group page you wrote:

I'm studying a group with the presentation M=(x,y| xz=zx) (...) Does this group M have a name?

If I understand correctly that you are interested in a discrete group, generated by x,y,z with a single relation xz=zx, then this is an example of a right-angled Artin group. I might write a short article in Wikipedia on them, but basically, you look at a group with n generators x(1),...x(n) and some relations of the form "x(i) and x(j) commute". Each such group can be encoded either by the graph with a n vertices and an edge for each commuting (i,j) pair, or by the Coxeter matrix (M) with m(i,j)=2 if the generators commute and infinity otherwise. The group that you are interested in a is a free product of the infinite cyclic group Z generated by y and the free abelian group Z2 of rank 2 generated by x and z. Arcfrk 18:56, 30 March 2007 (UTC)

In my case, the group M was the monodromy group of the polylogarithm. What you describe sounds just about right for what I've been able to deduce, but I'll have to think about it. I've found 3-4 papers that describe the monodromy of the polylogarithm. They're all mostly obtuse, they all make deep appeals to K-Theory (which I admit I don't understand), and given what I've found, I have the sneaking suspicion that some of them are wrong or at least confused. So I took the time to write up a simple, low-brow, from-first-principles derivation & analysis that should be widely accessible. I've posted it at arxiv.org/abs/math.CA/0702243. Unfortunately, the arxiv version has an error/confusion in discussing the monodromy, which won't be fixed until monday. So for now, grab a corrected copy here instead.

Never mind, I thought that you had asked "does this group have a name?", but I see that it was me...

I noticed the Heisenberg group had the braid-like relation xyyx=yxxy! So it seems now I can put a name on it. Err, I just tried, I can't quite squeeze xyyx=yxxy into one of the Artin group relations...

I agree that

$\langle x,y,z\vert xz=zx\rangle \simeq \mathbb {Z} *(\mathbb {Z} \oplus \mathbb {Z} )$

where * denotes the free product. That's almost what I want; except that I do have one additional relationship: $z=x^{-1}y^{-1}xy$, so its not quite that free. so my group was

$M=\langle x,y,z\vert xz=zx,z=x^{-1}y^{-1}xy\rangle$

which is not the same thing. linas 00:08, 31 March 2007 (UTC)

WikiProject History of Science newsletter : Issue II - May 2007

The May 2007 issue of the WikiProject History of Science newsletter has been published. You're receiving this because you are a participant in the History of Science WikiProject. You may read the newsletter or unsubscribe from this notification by following the link. Yours in discourse--ragesoss 05:48, 5 May 2007 (UTC)

Recherches Arithmétiques in Gauss-Kuzmin distribution

You added Recherches Arithmétiques as a reference to Gauss-Kuzmin distribution a couple of years back. I wondered where you found this. Unfortunately, I don't have access to the original, and I couldn't find it in skimming the Gauss' Collected Works (Werke Sammlung). I'd love to confirm the reference — for example, giving a page number — but I can't seem to, so I'm curious how you did. Thanks, Calbaer 15:50, 12 May 2007 (UTC)

Linas will hopefully be able to give a more complete reply. All I can tell you is that Recherches Arithmétiques is a translation in French of Disquisitiones Arithmeticae. [1] -- Jitse Niesen (talk) 03:31, 13 May 2007 (UTC)

I'm pretty sure that observation was not made in Disquisitiones Arithmeticae. According to Kuzmin's original paper, it was made in a letter to Laplace written after Disquisitiones Arithmeticae was published. According to Knuth (TAOCP v.2 ed.2 p.347), prior to that it was merely in his notebook. Kuzmin says that the letter is in volume 10 of the complete works, and, after poking around a fair bit, I found an entry in Gauss' "journal with explanations" on pp. 552-556 of Band 10, Abt 1 (of the edition linked above). The reference should be modified accordingly, unless there's also a mention of it in Disquisitiones Arithmeticae as well (which, again I doubt). Calbaer 05:40, 13 May 2007 (UTC)

Although I am fortunate in having access to a very good library (UT Austin), I would not be able to verify the reference i.e. come up with a page number, without going there, and spending half a day crawling through the thing. Which is not something I feel like doing just now. I no longer recall what prompted me to put the Recherches Arithmétiques reference in there, I must have been hasty. We should, however, move this conversation to the talk page of that article. linas 17:53, 13 May 2007 (UTC)

Out of curiosity, what prompts you to look at the Gauss-Kuzmin distribution? I notice you are a comp-sci person. I've recently been trying to write down the analogs of automorphic forms for finite state machines; things like the Gauss-Kuzmin distribution would be an example of a half-way point between these two worlds. Apparently, Philippe Flajolet has an entire chapter of a book, "Analytic Combinatorics", devoted to analytic functions defined on finite state machines, but I have not read it yet. linas 18:09, 13 May 2007 (UTC)

Braid group; presentation of modular group

Hello,

in your addition to Braid group you give a presentation of the modular group that doesn't look right to me. The presentation you give doesn't seem to admit any elements of finite order. Looking at the matrices, you have s⁴ = t⁶ = 1, but in the braid group that's not true. Also, (even though that doesn't mean much), the modular group article gives a different presentation. Cheers, AxelBoldt 19:05, 13 May 2007 (UTC)

I re-edited braid group so as to make the statement clear; your confusion was due to my fuzzy presentation of the topic. linas 20:46, 13 May 2007 (UTC)

Yes, now I get it. I was missing the 1 in the presentation I guess. Do we know that <c> is the center of B₃? I took that out for now. AxelBoldt 21:54, 13 May 2007 (UTC)

Yes, its in the center, and this is very easy to prove:

$\sigma _{1}c=\sigma _{1}(\sigma _{1}\sigma _{2}\sigma _{1})(\sigma _{1}\sigma _{2}\sigma _{1})$

$=\sigma _{1}(\sigma _{2}\sigma _{1}\sigma _{2})(\sigma _{1}\sigma _{2}\sigma _{1})$

$=\sigma _{1}\sigma _{2}\sigma _{1}(\sigma _{2}\sigma _{1}\sigma _{2})\sigma _{1}$

$=(\sigma _{1}\sigma _{2}\sigma _{1})(\sigma _{1}\sigma _{2}\sigma _{1})\sigma _{1}$

$=c\sigma _{1}$

and similarly easily, $\sigma _{2}c=c\sigma _{2}$; ergo c commutes with all elements.

Yes, but you used the fact that <c> is equal to the center, which isn't yet clear to me.AxelBoldt 16:10, 14 May 2007 (UTC)

BTW, v and p are sometimes common notations for the elements of order 2 and 3 in PSL(2,Z); its what Rankin uses. S and T are have several different conflicting conventions. linas 04:07, 14 May 2007 (UTC)

Ok, then we shouldn't use them for the elements in the braid group, which have infinite order. I'll switch the notation. AxelBoldt 16:10, 14 May 2007 (UTC)

Now I still have another question about the isomorphism Sn = Bn/Fn with Fn free. Is it clear that Fn is normal? Because we already know that Sn = Bn/Pn, where Pn is the pure braid group, which isn't free, and Fn is contained in Pn. It seems to me that Pn is the normal subgroup generated by Fn. AxelBoldt 22:05, 13 May 2007 (UTC)

I'll have to read the article more carefully. If something contains the free group as a subgroup, then, almost by definition, the free group will be a normal subgroup... how could it be otherwise? Right? (since you are "free" to tack on any elements to the left or right hand side, as you wish....) However, bedtime for me, I'll look tommorow, perhaps. linas 04:07, 14 May 2007 (UTC)

Well, B₃ contains for example the free group <σ₁> as a subgroup, but that isn't a normal subgroup. I'll take the Fn claim out for now. AxelBoldt 16:10, 14 May 2007 (UTC)

I copied this all over to the article talk page, where the conversation should be carried on. linas 18:50, 14 May 2007 (UTC)

Mathematics CotW

Hey Linas, I am writing you to let you know that the Mathematics Collaboration of the week(soon to "of the month") is getting an overhaul of sorts and I would encourage you to participate in whatever way you can, i.e. nominate an article, contribute to an article, or sign up to be part of the project. Any help would be greatly appreciated, thanks--Cronholm144 23:09, 13 May 2007 (UTC)