User talk:Sławomir Biały

Untitled post

Hi, and welcome to Wikipedia!

I have noticed your recent edits to the article functional determinant, and I must disagree with what you assert. You say it is possible to compute the functional determinant without "infinite constant", but that one can compute it using regularization. All very well, but regularization is just one way to avoid infinite constants. Sweeping them under the rug does not mean they are not there! Also you say zeta function regularization is "the most popular". I'd like to see a reference for that (as you requested for the rest of the article in your second edit). The only way I have ever seen functional determinants be regularized is by taking the quotient of two of them, making the infinite constants cancel. (That's how it's done in the example calculation.)

Greets, MuDavid 08:11, 24 March 2009 (UTC)

Red link restored

I undid this edit. Generally, one should not delete a link merely because the article doesn't exist. See WP:Red link. Michael Hardy (talk) 21:53, 24 March 2009 (UTC)

not maintaining a watchlist?

Hi Slawomir, I noticed on your user page that you don't maintain a watchlist. I do not think other people can be expected to go to the trouble of leaving notes on your talk page for every edit of yours they revert. Editing messages go on article talk pages, for obvious reasons (other editors will come along and want to follow the discussion). I believe people will find it too much hassle to copy to your talk page every time. However, as a courtesy, I advise you that I may have to revert some or all of your edits to the articles on the Frechet and Gateaux derivatives, since I'm not confident you've understood these things correctly. I would advise you at least to visit those pages for a while if you are concerned. It's been emotional (talk) 15:15, 1 May 2009 (UTC)

Rethinking your reference edits

I'm fascinated that you do not maintain a watch list. You ask a lot of other editors without giving much yourself, no?

Nevertheless, I've responded to your concerns User_talk:TedPavlic#Restoring_some_references_sections. I've also added Wikipedia_talk:Citing_sources#References.2C_Inline_references.2C_and_further_reading for discussion.

Thanks for your time. I don't have enough time to undo all of the edits you just did; I think it's unfortunate that you made so many changes so quickly without any discussion. Those changes were certainly not urgent, and they certainly deserved a little more discussion. Please ask before making these edits. There's being WP:BOLD and then there's just being obnoxious. —TedPavlic (talk) 15:53, 31 May 2009 (UTC)

Ping (please see User_talk:TedPavlic#Restoring_some_references_sections). In short, all journals that I've submitted to in both engineering (I'm not sure why you made reference to software engineering; I'm not a software engineer), biology, and psychology have a note to authors like "All listed references must be cited in the text." Anything else is lazy, sloppy, ambiguous, and possibly misleading. —TedPavlic (talk) 12:45, 1 June 2009 (UTC)

Ping. The following is pasted from User_talk:TedPavlic#Restoring_some_references_sections. Wikipedia:Footnotes states that additional explicitly numbered references under a <references/> tag are mistakes that should be converted to "ref" tags (or moved). I'm suggesting that your convention encourages people to mix "ref" tags and explicit references, which is clearly not encouraged by WPMOS. Your convention lacks consistency. —TedPavlic (talk) 13:48, 1 June 2009 (UTC)

Ping. I've posted an example of the problem at User_talk:TedPavlic#Restoring_some_references_sections. —TedPavlic (talk) 14:34, 1 June 2009 (UTC)

Generalizations of derivatives

Do you intend this category only for liner generalizations of derivative? What about geometric derivative and bigeometric derivative [1] ?--MathFacts (talk) 10:00, 9 June 2009 (UTC)

Linear operators in calculus

What is this category intended for? Why gradient is included but rotation is not? And shouldn't generalizations of derivative be a subcategory of this one?--MathFacts (talk) 07:38, 10 June 2009 (UTC)

Integral

Hi, I recently made a change to the lead at the Integral page, since you don't keep a watch list (kudo's to you!) I wanted to call your attention to the edit to your attention and find out what you thought. Thanks, Thenub314 (talk) 11:00, 12 June 2009 (UTC)

RE: "See also" in radon transform and tomographic reconstruction

Thanks, that was a good fix at sinogram. The word doesn't appear in the CT article, but that's probably a shortcoming of that article. I mentioned this at Talk:Computed_tomography#sinogram.3F for them to sort out, and I'm going to remove all these pages from my watchlist now. Thanks for your help. Agradman (talk) 18:30, 15 June 2009 (UTC)

Poisson summation formula

Hi, I made some changes over at this page I thought you'd like me to explain. Here they are roughly in order.

• I added an assumption that f is continuous and integrable, following Stein& Weiss and Grafakos, to get rid of annoying issues about modifying the set on a measure zero and destroying the equality on that set.
• I made more explicit that the continuity of the periodization φ_T doesn't follow simply from the continuity of ƒ but also from the decay assumption on ƒ. (This follows from Katznelson's example where the function you construct is uniformly continuous, but the continuity of φ_T fails.)
• I removed the phrase (which I previously added) "without summability methods" because summability methods do not effect that example, because the sums involved are absolutely convergent.
• Finally I removed the phrase implying that the continuity of φ_T is implied but the absolute summability of its Fourier series. Again, this is contradicted by Katznelson's example.

Also, thanks for finding the Córdoba reference! A very nice addition. Thenub314 (talk) 09:59, 4 July 2009 (UTC)

Hi, I left a reply to you over at my talk page. Thenub314 (talk) 05:45, 5 July 2009 (UTC)

smooth functor

Thank you very much for your additions to this page. What you're saying looks correct, but do you know of any references we could use for the material? —Anonymous Dissident^Talk 02:00, 17 July 2009 (UTC)

Thanks for clarifying that. Can I ask – what did you mean when you said that the TeX for the common smooth functors doesn't look good "inline"? I find the non-TeX formatting hard to read and more messy. As an aside, is the math output directory failing for you as well? —Anonymous Dissident^Talk 03:13, 17 July 2009 (UTC)

Are you sure that Vect is the category of all finite-dimensional real vector spaces with linear isomorphisms? —Anonymous Dissident^Talk 03:42, 17 July 2009 (UTC)

So, why does Lee 2002 define smooth functors differently? Is he wrong? —Anonymous Dissident^Talk 03:49, 17 July 2009 (UTC)

Spaced em dashes are generally discouraged. Since you kept using spaced em dashes, I decided it was simpler (and, indeed, more to my aesthetic preference) to convert to en rather than remove the spaces. —Anonymous Dissident^Talk 04:02, 17 July 2009 (UTC)

2F0

Hello again, I am using exactly the same notation as in these references: http://mathworld.wolfram.com/ConfluentHypergeometricFunctionoftheSecondKind.html,

http://www.math.sfu.ca/~cbm/aands/page_504.htm

I don't understand why you constantly delete this - correctly quoted - statement and others. "=" is completely clear in formal power series; read, for example Ken Ono's famous identity in this entry: Basic hypergeometric series. 14:27, 21 July 2009 (UTC) —Preceding unsigned comment added by A. Pichler (talk • contribs)

Because, as I have repeatedly pointed out, the identity in question makes no sense "as a formal power series identity". I am willing to entertain the possibility that you may know what it in fact is supposed to mean. If that is the case, you are certainly invited to explain rather than accuse me of deleting things, as you say, simply because I don't understand them. If you are truly interested in building an encyclopedia, then it is clearly not too much to ask that your edits should be understandable to an expert, let alone someone who might want to use the encyclopedia for reference purposes. Sławomir Biały (talk) 15:50, 21 July 2009 (UTC)

Citation style

WRT: You might be interested to know about WP:CITE and the variety of {{citation}}: Empty citation (help) templates that Wikipedia has made available for the formatting of academic citations. In particular, it is much better to have full publication information, including the names of authors, the title of the work, and the name of the journal in which the paper was published, rather than just a link. Also, generally google books links are discouraged because they typically expire after a short period of time. A citation including the title and page number of a book, on the other hand, can be verified indefinitely. Also, there is no requirement that references need to be weblinks. Books (or "dead tree" references as we call them) are still perfectly acceptable

Often wondered about link expirations without much concern, its a good point without much priority. Weblinks have the advantage of immediate and convenient verification. There's a nice little tool for citations in google scholar http://toolserver.org that i am trying to use more often, if you don't already know about it, i think you'll like it. It is good that you took time to make contact. By the way, good job with editions to Cheng's eigenvalue comparison theorem. There is one thing, however. The pipe to normal coordinates from geodesic balls is an oversimplification of the definition for use in context with the intention of the sentence (tubular domains). In this context, geodesic balls are specifically used to approximate curvature, a much more specific use than just normal coordinates. It would have been better to have left the link red. But not a big deal because in the very near future i will create a geodesic balls article (unless you want to do it). Cheers. Henry Delforn (talk) 18:35, 21 July 2009 (UTC)

Got your message. Thank you Sławomir Biały. We will talk again soon. Henry Delforn (talk) 19:13, 21 July 2009 (UTC)

Kondrakov theorem

Dear Sławomir,

I believe there is a small problem in the Sobolev article, about compactness of the Sobolev embedding in the $\mathbf {R} ^{n}$ case, problem that was there before you edited it recently. If you take a smooth compactly supported function and consider a sequence of translates of that function, with size of the translation tending to infinity, there is no chance to extract a convergent subsequence in the target space, as the norm is translation-invariant. Since you seem to care about this article, you might have a look at this. Thanks! --Bdmy (talk) 14:18, 23 July 2009 (UTC)

I realized now that you changed the setting from compact manifold to $\mathbf {R} ^{n}$ which causes this problem. --Bdmy (talk) 14:24, 23 July 2009 (UTC)

Thanks for your message, and for the correction. Another point: in the embedding theorem, if I just take $k=\ell =0$  then I have Lebesgue spaces and I can't have any embedding between $L^{p}$ spaces on $\mathbf {R} ^{n}$ unless p=q. Here I don't know what the correct answer is. I remember that the Sobolev embedding with critical exponent is bounded on $\mathbf {R} ^{n}$ so one may need an equality in the Sobolev condition, otherwise it should be just a local statement? With best regards, --Bdmy (talk) 14:47, 23 July 2009 (UTC)

You may have changed it already, but

${\frac {1}{p}}={\frac {1}{q}}-{\frac {k-l}{n}}.$

is wrong! (perhaps exchange p and q?) --Bdmy (talk) 15:07, 23 July 2009 (UTC)

Derivative of a vector-valued function

Hi Sławomir,

I have some reservations about your bold move of the derivative of a vector-valued function section. I believe that section is limited in scope to Euclidean 3-vectors, primarily as a kinematical quantity. Its applicability to the more general mathematical concept of vector-valued functions is suspect.

Additionally I think the article on Euclidean vectors deserves a more thorough treatment of the topic in its own right. One of the most common uses of Euclidean vectors is kinematics and geometry, which involve the heavy use of differentiation and integration. The article already contains quite a few equations describing geometrical relationships between vectors and the algebraic operations you can perform on them. Why should calculus be excluded? MarcusMaximus (talk) 00:55, 4 August 2009 (UTC)

(pasting your response from my page)

I'm afraid I don't understand your objection to my move. If by "vector-valued function" one understands the usual notion as one might encounter in, say, an undergraduate calculus or physics course—a Euclidean vector that depends on a time parameter—then the content is clearly more suited to an article dedicated to the notion of a vector that varies in time than to an article whose subject is vectors in themselves. One only needs to look at the article vector-valued function to see that it is indeed germane.

As for arguing that large portions of text in the Euclidean vector article should be devoted to the discussion of vector-valued functions, probably a little more could be said than at the present, but we should try to observe WP:Summary style, and just convey the essential information. Volumes of text could also be brought in on vector fields, and for that matter, a detailed treatment of vector calculus could also be presented. However, these other topics are rightly treated in their own separate articles, as I think should detailed treatments of the calculus of vectors. Sławomir Biały (talk) 02:12, 4 August 2009 (UTC)

Yes, I suppose my pride of authorship is getting in the way. I guess the vector-valued function article just needs a lot of spiffing up. MarcusMaximus (talk) 02:59, 4 August 2009 (UTC)

Nakayama's lemma

Hi Slawomir,

Recently, User:Plclark has noted that the original sources of Nakayama's lemma (including the paper published by Nakayama himself) give equal importance to both the commutative and non-commutative case. Therefore, if this is correct, the article should not put undue weight on the commutative case, and should rather treat both cases equally. Could you please have a look at Talk:Nakayama lemma? --PST 04:59, 9 August 2009 (UTC)

Finsler geometry related articles

Thank you for your welcoming message. You seem to share interest in Finsler geometry related topics. It is not clear to me what should be the correct forum to discuss a bundle of new (and old) articles related to it. There are plenty of articles (Torsion,Covariant derivative,Geodesic,Jacobi field,Conjugate points) which turn a blind eye for the (semi)spray structures and nonlinear connections on TM \0, which are indispensable in Finsler geometry. On the other hand, spray (mathematics) redirects to Jet bundle.

Lapasotka (talk) 15:29, 19 August 2009 (UTC)

Differential of a function

Hi, let's talk on the Differential of a function Talk page, just so that we understand our reasons for the edits, and don't end up reverting each other so quickly. WardenWalk (talk) 18:55, 21 August 2009 (UTC)

What does "the principal part of the increment of a function" mean? It doesn't seem to make sense in context, but maybe I am misunderstanding your intention. WardenWalk (talk) 22:11, 22 August 2009 (UTC)

Semigroups

If you feel like working on that article, go ahead. It gets very little love, just like semigroups don't get that much attention in algebra at large. Don't get hanged-up on what's already written, the focus is generally wrong in the 2nd part of the article (structure theorems). The structure results considered important by mathematicians are usually different from Khron-Rhodes; see inverse semigroups for example. So, if you have the time to invest in it, be WP:BOLD. Pcap ping 17:49, 22 August 2009 (UTC)

Edit summary

I noticed the comment in your edit summary -"trimming down rubbish". This struck me as rude and unnecessary. Even if it were true (and remember, in mathematics articles there is always an element of WP:MTAA in the lead which raises controversy), a simple comment of "trimming down unnecessary elements of the lead" would do. Since this is not the first time you have made a comment of this nature, I politely request that you stop doing so. --PST 06:04, 24 August 2009 (UTC)

I do not deny the fact that I have used "rubbish" in my edit summaries six months ago. However, I have learnt that this is inappropriate and have not repeated that. In effect, I am saying that you can only learn that the word you have used is inappropriate - I cannot expect you to instantaneously stop it if you really feel that way about the content. Nevertheless, experience has helped me to understand that what I wrote a while ago was unnecessary and hence I have informed you so that you do not make the same mistake.

Secondly, edit summaries serve the purpose of explaining one's edit. They do not serve to attack previous revisions. Although to most people that edit summary may not be inappropriate, it is inappropriate to the person who wrote the "rubbish" (I think I may have written a part of that at some point). Everyone in Wikipedia plays a role in improving articles and therefore, I do not think that it is wise to attack other editor's work - WP:AGF. I should repeat that I have done so, but I do not do it any longer (if someone else jumps of a cliff, it is certainly not justification that you can do it as well). Please only consider this as a friendly outside remark. --PST 04:00, 25 August 2009 (UTC)

Look over?

Hello,

I remember that you helped me with Smooth functor. Your oversight there was much appreciated and advanced the article significantly. I'm only an amateur, so I'd appreciate it if you'd have a look over my most recent article, Eutactic star. Any input or improvement would be great. Thanks for your time. —Anonymous Dissident^Talk 11:42, 28 August 2009 (UTC)

Thanks for your help. I have a question: do you think there could be an image we could use or create for the article? It might improve the readership's comprehension. —Anonymous Dissident^Talk 01:34, 29 August 2009 (UTC)

I had the same though. It would be nice to cook up an illustration, which I would happily do, but my graphical skills are rather limited. Perhaps a pro like User:Salix alba might be a better choice. Sławomir Biały (talk) 01:36, 29 August 2009 (UTC)

Those images are great. Thanks once again. Though it's quite an obscure and minority topic, I've nominated the article to be featured in "Did You Know?" on the main page. Too few mathematical articles are displayed on DYK, and we have an image (two images!) to make things interesting. I've mentioned that you should also be credited for the nomination. —Anonymous Dissident^Talk 15:16, 29 August 2009 (UTC)

One other thing: I see that s<->n, but is it best to use them in a seemingly arbitrary manner in the Definition section? For example, "the n-dimensional space B = ±b₁, ... , ±b_s" is likely to confuse the readership – the subscript of the final b seems to disagree with "n-dimensional". I think we should adopt a standard – either s or n – and run with that, only using the other when absolutely necessary. Things become confused otherwise. If not, we should at least more clearly state that s<->n at a pertinent point. —Anonymous Dissident^Talk 15:28, 29 August 2009 (UTC)

I swapped s and n for consistency with the Coxeter reference. I'm not sure what you mean about these being used in an arbitrary manner: s vectors in n dimensions form a star, that is eutactic if they are the orthogonal projections of s vectors in s dimensions. At no point does the article change from one convention to the other. Sławomir Biały (talk) 15:44, 29 August 2009 (UTC)

Tensor Rewrite

If you look at the talk page, you can see the article has been complained about many times. It's poorly written (tell me you honestly think you could explain to someone what tensor rank is from reading the section on it). It's full of weasel words. It acts on the defensive, stating that there are conflicting definitions from field to field instead of assuming a main definition and redirecting people looking for the usage in fluid mechanics to the tensor field article. If you're still on the fence, compare the sections that have already been rewritten to the original article's versions. LokiClock (talk) 01:30, 3 September 2009 (UTC)

I take your point that the Tensor article could benefit from copyediting. But I would still like you to explain a specific plan for the article. In many ways, the current treatment of tensors on Wikipedia is far from ideal: a fragmented bunch of articles that no one was ever able to organize into anything coherent. It would be better if someone could manage to pull these together into something unified and encyclopedic.

I have one specific point to make, that I think is interesting that you brought up. The section on tensor rank is incoherent both in the article and the rewrite, so I don't share your opinion that the new one is superior. Both versions suffer from the same problem of having no appropriate context: what is V? What is a tensor product? How is a tensor related to a tensor product? The article either needs to commit to defining these things, and thus duplicating most of the article Tensor (intrinsic definition), or the section should be moved to an appropriate subarticle. Sławomir Biały (talk) 02:28, 3 September 2009 (UTC)

I thought it was fairly clear that it meant a vector space, but I could note that as well. It took me a long time to find out that V* was supposed to mean the dual space. Obviously there are some prerequisites to understanding tensor rank, but I worked to explain a lot more than the existing section did. As you moved the Tensor Rank section from the article, I'm going to replace it with the rewritten Rank section. It's obviously a long work in progress, but I still think it's a better starting point. Please keep the criticism coming as the articles evolve. LokiClock (talk) 01:35, 4 September 2009 (UTC)

The point is, of course, that it isn't just any vector space. In order for the section to make any sense at all, the article must define a tensor (over V) to be an element of the tensor product $V\otimes V\otimes \cdots \otimes V\otimes V^{*}\otimes \cdots \otimes V^{*}$. That is to say, if we are going to include this section in the main tensor article, then we must also include the entire contents of the article tensor (intrinsic definition). Is that what you are saying? Sławomir Biały (talk) 01:39, 4 September 2009 (UTC)

See, I wouldn't know that. My main motivation in trying to actively contribute in this case is because I was trying to learn what tensors were and was absolutely stunned by the incoherence of the article. So I've just been trying to track down definitions and bizarre references made by the original author. And actually most of my work on that section HAS been through small, incremental changes, besides some overhauls of the wording. Also, how does the rewrite's summary work for you? LokiClock (talk) 02:08, 4 September 2009 (UTC)

I misunderstood. I now see that you had in mind pasting in the new section to tensor (intrinsic definition). I don't think the new version is all that much better than the old version. I will edit it. Sławomir Biały (talk) 01:41, 4 September 2009 (UTC)

DYK for Eutactic star

On September 5, 2009, Did you know? was updated with a fact from the article Eutactic star, which you created or substantially expanded. You are welcome to check how many hits your article got while on the front page (here's how) and add it to DYKSTATS if it got over 5,000. If you know of another interesting fact from a recently created article, then please suggest it on the Did you know? talk page.

NW (Talk) 17:21, 5 September 2009 (UTC)

Envelope (mathematics)

Thank you for you recent edits to this article. I have reversed them because they make the article less attractive and less readable. You quoted wp:MOSMATH in you edit history. I would be interested to see the actual section to which you refer. Who would say that your revised version is better looking and easier to read than the original version? (Not to mention the errors that you added, e.g. f^t(x,y) in place of the correct f_t(x,y)). ~~ Dr Dec (Talk) ~~ 20:06, 19 September 2009 (UTC)

Don't you think that you should have left the article as the original editor, i.e. me, had written it and opened a thread on the talk page to gain consensus? The manual of style says that "Having LaTeX-based formulae in-line which render as PNG under the default user settings... is generally discouraged." That doesn't mean that it should never be done! (Please see fourth pillar of Wikipedia) ~~ Dr Dec (Talk) ~~ 09:59, 20 September 2009 (UTC)

I've re-written the first paragraph of this section to include a regularity condition. After that I've removed Whitney's theorem and any other information covered in the regularity condition. I would appreciate it if you contacted me, or left a note on the talk page if you made any changes. ~~ Dr Dec (Talk) ~~ 10:37, 20 September 2009 (UTC)

As per your last comment on my talk page, this is exactly how Wikipedia should work. I quite often post proposed changes onto the talk page and wait a couple of days to see if there's any feedback. If not then I go ahead and make the changes. You're right in as much that too much discussion and not enough editing would lead to nothing ever being done, but it's a fine balance: if we don't seek consensus then Wikipedia's pages would be a total mess. ~~ Dr Dec (Talk) ~~ 12:05, 20 September 2009 (UTC)

I've made a couple of suggestions on the talk page. ~~ Dr Dec (Talk) ~~ 09:03, 21 September 2009 (UTC)

Okay, I've added a subsection on ODEs. Any thoughts? ~~ Dr Dec (Talk) ~~ 10:08, 21 September 2009 (UTC)

1. Why do you keep removing the i.e.? Did you not read my edit summary? It reads much better with i.e. included than without. I.e. can mean that is to say or which is. In that case "the envelope..., which is the parabola,..." reads much better than simply "the envelope..., is the parabola,..." Is English your first language? I can't understand how you would think that the second reads better than the first. The second is disjoint and doesn't read as smoothly as the first. ~~ Dr Dec (Talk) ~~ 14:45, 21 September 2009 (UTC)
2. I've made this change. Please don't use phrases like "cut out", they are highly non-standard. I've been working in singularity theory, e.g. discriminants and bifurcations, for seven years and until today had never seen the phrase used once. Secondly, the way you had re-written it made it harder to understand. You threw the generating function at the reader and expect them to see what it has to do with families of curves. It's better to introduce the notation and ideas step-by-step, as it was before. ~~ Dr Dec (Talk) ~~ 14:57, 21 September 2009 (UTC)

Again, you seem to be making quite considerable changes without any decent edit summary or talk page note. None of your edit summaries even suggested a change like the second one. I stumbled across it by chance. It's becoming very frustrating: we've both spent a lot of time over the last couple of days working on this article. While I take the time to suggest changes to you, and then explain changes, you just undo my work without any warning, let alone explanation. Please be more considerate. ~~ Dr Dec (Talk) ~~ 14:57, 21 September 2009 (UTC)

Mathematical symbols

Could you point me towards a list of symbols like ∈ and ⊂ please? ~~ Dr Dec (Talk) ~~ 12:54, 20 September 2009 (UTC)

Thanks

for your kind notice. Redheylin (talk) 01:28, 26 September 2009 (UTC)

?

I'm coming over here and I discover that you have retired :-( ...I hope you'll be back some day! cheers, --pma (talk) 23:26, 27 September 2009 (UTC)

!

welcome back! --pma (talk) 11:11, 15 November 2009 (UTC)

I guess you could not keep away from the project, Slawomir? Great to see you editing again! --PST 13:20, 15 November 2009 (UTC)

Regarding your recent edits on Fourier Transform:

For #310, I see you added the range from 0 to 1. What is the situation with 1/x^a, where a is fractional (say, 5/3 or 7/3) and greater than 1? Any clues? Is it convergent? Is it known? Can you post that if it is known?

Also, rather than remove it entirely, I recommend that you restore the original 310 for integer 1/x^n, somewhere else in the tables, even if that is not suitable for the distributions section.

Retrieved from "http://en.wikipedia.org/wiki/Talk:Fourier_transform" —Preceding unsigned comment added by 74.70.96.16 (talk) 00:29, 21 November 2009 (UTC)

Request for advice

I understand that you're RETIRED of Wikipedia drama, but I wonder if you could fill in some details on your recommendations concerning the RfC at Celestial spheres. This has been going on for over three years now and I'm at a loss as to where to go next; your incomplete suggestion, which I read as a suggestion to move on to a straight up RfC/U, made some sense.

Thanks for your insights. --SteveMcCluskey (talk) 01:17, 26 November 2009 (UTC)

Actually, I was referring only to the RfC at Celestial spheres. A user conduct RfC may also be a good idea, but they tend to die on the vine quite easily from insufficient interest. I see that already happened to one RfC on Logicus: Wikipedia:Requests for comment/Logicus. I think it is going to be very difficult to convince uninvolved parties that Logicus deserves to be topic banned from editing history of science articles, although that seems to be the optimal outcome. Wikipedia:Civil POV pushing is possibly relevant here. I will gladly comment as a semi-involved party if you will start the RfC. Sławomir Biały (talk) 14:18, 26 November 2009 (UTC)

Thanks for the insights; some of the same points are made at WP:DE#How disruptive editors evade detection, which has the advantage of being a Guideline, not just an Essay.

Do you think any route other than an RfC/U would be feasible? I wrote the last RfC that died on the vine through lack of interest and I don't know want to go that route again. --SteveMcCluskey (talk) 18:24, 26 November 2009 (UTC)

I'm not really a great expert on dealing with problematic editors. I see that Logicus has had some recent interactions with User:Dave souza, who might be able to offer more options. Sławomir Biały (talk) 14:49, 27 November 2009 (UTC)

I understand; Dispute Resolution is really a bureaucratic maze. I've started drafting an RfC but the conflict has been going on for so many years that the RfC is really a chore. I may ask other involved editors for help and advice, Dave souza being one of them.

BTW, love the little icon on your edit page. --SteveMcCluskey (talk) 15:56, 27 November 2009 (UTC)

Talk:Radial function

Hello. An interesting article; surprised it hadn't been written. I've asked a question on the talk page, just for my own interest. I thought I'd let you know, since you don't maintain a watchlist. Any help is appreciated. —Anonymous Dissident^Talk 14:43, 30 November 2009 (UTC)

Jordan decomposition

Thank you for expanding a Jordan decomposition part in semisimple Lie algebra. (The article probably needs an example to show how things could go wrong in the non-semisimple (or non-reducible?) case, though). Anyway, I have something else I want to ask. Do you think we should have a linear Lie algebra article? (I don't know why no one has crated.) Since finite-dim Linear algebras are basically linear, maybe there is not much to discussion. On the other hand, there is some ambiguity issue (like Jordan decomp in abstract sense v.s. in concrete sense), which might be better discussed in such an article. (I was just wondering. Maybe I should ask in the WikiProject math.) -- Taku (talk) 00:54, 2 December 2009 (UTC)

I think there is definitely enough material for such an article. Bourbaki devotes a section to discussing decomposable linear Lie algebras: decomposable here means that the Lie algebra contains the Jordan decompositions of each of its elements. Every semisimple Lie algebra is decomposable, but the converse is not true, even over an algebraically closed field. Sławomir Biały (talk) 13:25, 2 December 2009 (UTC)

Ok. Thank you for the advice. -- Taku (talk) 12:49, 3 December 2009 (UTC)

Total variation

Should we have a separate article for the notion of total variation in probability theory and measure theory? I don't like the current arrangement where the material on probability theory has been forked off from the material on measure theory, even though they are essentially the same thing. What seems better to me is to have an article total variation in measure theory and probability theory that deals with both of these notions. Sławomir Biały (talk) 12:15, 9 December 2009 (UTC) (Retrieved from "http://en.wikipedia.org/wiki/User_talk:Melcombe")

I made the change to the redirect of "total variation distance" because the (or some) articles using this link require an emphasis on the "distance" component of the name rather than "total variation". There is now a group of articles in Category:F-divergences under Category:Statistical distance measures: "total variation distance" is a special case of an "F-divergence". Thus the majority of the stuff under "total variation" covers variation within a single function or measure, rather than the distance between two functions or measures ... in fact I don't think the article had anything about applying "total variation" to measure the difference between functions or measures (it might have been implicit in allow a measure to have a negative component). Thus I am not particularly looking for a split betweeen probability theory and measure theory, but rather for a good/accessible place to find information about "total variation distance" as a distance ...hopefully without having to read the whole of a long article to find definitions used within a subsection that might be pointed to by a redirect. Melcombe (talk) 12:42, 9 December 2009 (UTC)

Thank you for explaining. The total variation often is used to define a norm on the space of signed measures, and thus a fortiori a distance between measures. So the stuff about distance between probability measures is just the restriction of this metric to the set of probability measures. I would rather keep the related material together, and would instead keep the treatment of signed measures together with that of probability measures. It thus makes more sense (to me) to create a more inclusive article total variation (measure theory) or the like, in which the norm can be discussed along with the induced distance function on the space of probability measures since they are exactly the same construction. Sławomir Biały (talk) 11:33, 10 December 2009 (UTC)

you changes to asymptote

Please discuss article changes at Talk:Asymptote, not my talk page.
The following discussion has been closed. Please do not modify it.
OK, now you are doing wrong. Why do you also removed the etymological part. It addresses the topic about intersecting the asymptote. A huge amount of discussion, in the talk page is devoted to that point. It is important to be said in the article. Besides it is supported by references both the literal etymology an the use in old books. That deletion was unnecessary and decreases the value of the content of the article.  franklin  14:20, 13 December 2009 (UTC) But the etymology is still there. Sławomir Biały (talk) 14:22, 13 December 2009 (UTC) Never mind. You were moving around things.  franklin  14:22, 13 December 2009 (UTC) OK, now about the quantitative information stuff? I don't see that one move but removed.  franklin  14:25, 13 December 2009 (UTC) Yes. Removed. See explanations on talk. Sławomir Biały (talk) 14:28, 13 December 2009 (UTC) Saw it already and there is an answer to that also. Meanwhile the topic is resolved is better if the information stays in the page as it is in the very least referenced.  franklin  14:40, 13 December 2009 (UTC) You have said many times that you would prefer it if editors would "fix" the article rather than discuss it on the talk page. That is what I am trying to do. Sławomir Biały (talk) 14:42, 13 December 2009 (UTC) Definitely, do it. But I also will look for the relevant information to be preserved.  franklin  14:44, 13 December 2009 (UTC) OK now you are getting unreasonable. The paragraph comes from an idea expressed in a book. Please don't remove information change it if you don't like the wording.  franklin  14:46, 13 December 2009 (UTC) You see? I am happy now. It would be good to also add further down in the article more detain on how that quantitative info is used and is different from the other several notions of limiting behaviors.  franklin  15:05, 13 December 2009 (UTC) Please look at what you do. I don't have strong feeling about mentioning the classification in the intro, but in your revert you put qualitative again instead of quantitative. And there is a big difference. Difference which is the main point of that sentence.  franklin  15:42, 13 December 2009 (UTC) Also now the part after the etymology only talk about the use of asymptotes as tangents at infinity but not about intersecting (they are different things and both should be addressed since both lead to a lot of discussion and confusion in the talk page and in the history of the article)  franklin  15:47, 13 December 2009 (UTC) solved. good. better wording needed (since looks like an isolated phrase, a forgotten thing said at the end of a conversation) but that can be fixed.  franklin  15:53, 13 December 2009 (UTC) The sections on horizontal, vertical and oblique should be subsections and should have some intro. There are notation and approach not properly introduced. That was the reason for putting the classification thing there. But it was more important to preserve the pride of having that in the intro than to make the text consistently written.  franklin  15:53, 13 December 2009 (UTC)

paragraph order

It is funny. the new paragraph order turns out to be the same in my first big edition of the article. Isn't that peculiar?  franklin  16:16, 13 December 2009 (UTC)

Lipschitz maps and cones

As to the picture in the Lipschitz maps article, I agree with you talking about Lipschitz maps Rⁿ→R. But note that for a Lipschitz curve R→Rⁿ the "literal" or "traditional" cone is the green area, and not the white. For a Lipschitz map from a normed space to a normed space (both of dimension larger than 1), of course, neither the white nor the green is a literal cone. Do you understand my point? If you really want the generality, then you have to abandon the idea of a traditional cone, and use {(x,y): ||y||≤C||x||} instead. The fact that the latter has not a specific name is not essential (e.g., on Mars they have a specific word for it). Moreover, if we look more at the ideas and less at the language, "belonging to the green set" is quite more natural than "being disjoint from the white set", for the same reason that one defines Lipschitz maps saying "for all x,y ||f(x)-f(y)||≤C||x-y||" and not "for no x,y ||f(x)-f(y)||>C||x-y||". Anyway, I just meant to recall you these facts, then you will decide what you like more. --pma (talk) 23:00, 13 December 2009 (UTC)

Yes, I do see your point. Maybe the issue can be settled with a more thorough discusion in the text. Thanks, Sławomir Biały (talk) 23:17, 13 December 2009 (UTC)

Hello, Sławomir Biały. You have new messages at Moonriddengirl's talk page.
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Another potential approach

Hi. A contributor to the clean-up at the CCI (and thank you for your help there!) asks whether material can be presumptively deleted. It can, in accordance with policy. There's more about this at Wikipedia talk:WikiProject Mathematics#Copyright concerns related to your project, including a template that may prove helpful should you wish to take this approach. --Moonriddengirl ^(talk) 18:16, 21 December 2009 (UTC)

Thank you. I will look into that. I have not been especially agressive in tagging the articles for deletion. But I may up the ante on some of those that I have blanked for CP. Sławomir Biały (talk) 18:37, 21 December 2009 (UTC)

Message

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Tensor rank

Okay, we both know that tensors have rank, and that tensor rank, like many terms regarding tensors, is a generalization of the concept in matrices. As such, it may seem that the paragraph is a confusion of the two. If you recall, this is the remaining section from the rewrite, which you edited down (I'm a fan of brevity) to about that level. I decided to make it a summary paragraph for the main article linked to at the top of the section. Then I asked you how you felt about it and you failed to respond. If you felt a section on tensor rank was unnecessary, or you felt that particular summary was inadequate, that was your opportunity to say so. If the section gives you impression of confusion with matrix rank, disambiguating statements are the way to improve the section, not removal. If you're not willing to make those changes yourself, leave a message on the talk page. LokiClock (talk) 17:29, 27 December 2009 (UTC)

Well, the section was dead wrong. If it is possible to present a correct idea of tensor rank at this naive level, and with some care to source it to reliable sources, then perhaps we can discuss it. But totally incorrect/incoherent material should not be permitted. If you want a good source on tensor rank, then Chapter III of Bourbaki's Algebra is an excellent place to begin. The old section on tensor rank has been moved to tensor (intrinsic definition), since it had no context in the main tensor article. Incidentally, tensor rank (in this sense) is not of critical importance in a main article on the topic. Given the three-tiered structure of our tensor treatment, it is currently in the right place. Also, I don't recall ever being asked about this section on a talk page, but my response then would have been the same. Sławomir Biały (talk) 20:57, 27 December 2009 (UTC)

The article shouldn't be in a three-tiered system to begin with. If you base all your future edits on the present state it will never get fixed, because it will take more and more work as the content builds up around that structure. If you question the content's validity, mark it with a citation template. You don't delete brand new content because you consider it dubious, at least not if you can't justify that decision. Give the author the time to work on the content. Sometimes it takes more than a little while to work on that content. Give other editors the time to investigate the issue of the content's validity, which they will not if it isn't raised to their attention that it needs to be investigated by another editor such as yourself. Yes, content needs to be sourced. Yes, it can wait a little while. No, you should not delete content without due editorial process. This includes, at the very least, a contradicting source or concurrence with another editor. As a courtesy, a public notice (citation template). LokiClock (talk) 05:17, 28 December 2009 (UTC)

We don't mark things we know to be untrue with citation templates. We remove them, especially if they were just added (refer to WP:BRD). Also, the proposed revision of the rank section had started with a correct version, and gradually degraded over a period of months to a version that is completely incorrect. So obviously in this case giving "the author time to work on that content" did not have the beneficial effect you seem to believe it should have. Instead the content should have been left alone from the beginning. If you want contradicting sources, please obtain a book on tensor analysis or multilinear algebra (e.g., the aforementioned Bourbaki). Read and learn. Finally, I agree that our tensor analysis articles should be more unified, but that is a separate discussion independent of this particular edit which I would not mind having if somehow wider input can be brought in. If there is to be a unified treatment, then the old section on tensor rank should be restored (the one sourced to reliable sources, not the new one that is dead wrong). Sławomir Biały (talk) 11:45, 28 December 2009 (UTC)

Correct, possibly, but completely opaque and poorly written. I was trying to clarify it. I didn't destroy any information, merely defined terms used in the article. Looking at my edits, I overdid it on linear combination and didn't end up doing much else. I could give it another shot, in its present location, and would do it completely differently than I did the first time. I could even avoid adding any information, merely working on the language. That's why the rewrite was called for to begin with, and that's why I felt I could do it even without being versed in the subject.

Other problems with the original version included understanding how rank generalizes from matrices to tensors. That's why I wrote clarifying statements such as, "Just as a linear combination of vectors multiplies each by a scalar coefficient and then sums them, a linear combination of tensors multiplies tensors of the same order by scalar coefficients and sums the results.(Owlnet reference)" Linear combination of vectors is everywhere. Linear combination of tensors is not, and the section relied and relies on it to define rank. Maybe you don't see eye to eye with me, that doesn't mean I learned to write in a bag. What I'm trying to communicate is that when you restored the old version of the section when it was moved to Tensor (intrinsic definition) you destroyed information indiscriminately. Don't Etch-a-Sketch others' work. Cut out the parts that aren't useful, copy and paste parts from the old version. Just because one part of one version isn't good does not make the whole draft bad. LokiClock (talk) 22:13, 28 December 2009 (UTC)

I think you may not have correctly understood the way in which tensor rank is a generalization of matrix rank. See my post about outer products below. Sławomir Biały (talk) 00:36, 29 December 2009 (UTC)

Another thought: the notion of tensor rank (in our sense) pretty much only makes sense in relation to the intrinsic definition of tensors. So, while I'm all for having a more unified treatment, having a section on tensor rank in the main article here will only be possible if it is preceded by a proper intrinsic treatment of tensors using the tensor product. Sławomir Biały (talk) 12:28, 28 December 2009 (UTC)

It can make as much sense as establishing prerequisites to the reader. Full understanding surely not, but you're not going to get that the first read anyway. You'll have to read the foundation articles and come back to it. I did notice that problem when trying to understand and work on the section, though. Obviously references to V* make no sense with the section in the main article. LokiClock (talk) 22:13, 28 December 2009 (UTC)

Look, tensors don't have "rows" and "columns". So the following text is patently nonsensical:

The rank of the tensor is the dimension of its column space. It is by this token that rank defines the number of components that contribute to a tensor's degree of freedom. If a tensor has a row rank of three, but four rows, then one of the rows can be represented through linear combination of the other three rows. That is, by scaling them in some mixture and adding them. If the rows are vectors, this is a change of magnitude, but not direction. If a tensor has full rank, then all of it's components affect the tensor's degree of freedom and none of them can be produced through a combination of the others. A basis of a vector space is a 2nd order tensor of full rank.

To say nothing of the fact that a basis is a list of vectors, not a tensor. Sławomir Biały (talk) 23:50, 28 December 2009 (UTC)

I fully apologize for those mistakes. I should have said that I was referring specifically to a 2nd-order tensor. Also, I failed to notice that column space only refers to vectors. I thought to check on that later but forgot, not that it mattered with the section being deleted shortly after. I was under the impression that any collection of vectors could be treated as an object with vectors as components, i.e. a 2nd+-order tensor. I often fail to recognize the distinction of such things like that; if you could represent the same thing two different ways, both representations are equivalent in my head, so because you can represent a vector basis as a 2nd-order tensor, I'll think it might as well be one. LokiClock (talk) 21:27, 29 December 2009 (UTC)

I don't see how a basis is in any way something that could be represented as a tensor. It is a list of vectors. While each vector obeys a contravariant transformation law, the list itself is fixed. Also, I wonder why you are so insistent on including this section at the very top of the formulations section, above even tensor valence (which is probably the most important thing about a tensor). There are entire books on tensor analysis that do not even mention tensor rank (in our sense). This is one reason that I would like you to try to find references: it will help to give the notion context. Sławomir Biały (talk) 23:10, 29 December 2009 (UTC)

Also, I should add that it doesn't even approach the matrix rank in a manner that is easily generalized to tensors. Rather than thinking about rows and relations, you should think of writing the matrix as a sum combination of outer products, like

$A=v_{1}w_{1}^{T}+\cdots +v_{k}w_{k}^{T}.$

A matrix has rank one if and only if it is an outer product of two nonzero vectors. In general, the rank of a matrix is the minimum number of outer products needed to determine the matrix. Sławomir Biały (talk) 00:02, 29 December 2009 (UTC)

First of all, that's not in the section now, and why not? Second of all, while that provides one, comprehensive way of looking at it, a big picture is not the whole picture. You need multiple perspectives from which to get a big picture, and also you need examples by which to understand what the meaning of rank is, the purpose of understanding it. If you understand why it's important in a case you can quantify, then you can understand why it's important in general, not the least reason for which is the relationship with degree of freedom. My example had plenty of mistakes, as you pointed out above, but one can see where I'm going with it (I hope), enough that it can be corrected. LokiClock (talk) 21:27, 29 December 2009 (UTC)

I'm not sure what you mean. This is pretty much what the section in tensor (intrinsic definition) says. A rank one tensor is a tensor product of vectors. In general the rank of a tensor is the minimal number of rank one tensors needed to express it. Anyway, I have included more of a discussion of the rank of a matrix, although I still feel that we should expect a target audience to have at least a decent course of linear algebra in order to understand tensors.

I do think that our discussion would benefit greatly if you would put some effort into finding sources about the rank. There are limits (under policies like WP:OR and WP:V) to what we are allowed to say. We must make every effort not to oversimplify to the point where we say something incorrect, and having good sources helps. I do like the idea of saying something about degrees of freedom in the text, but I don't see a way to do it that will be correct and yet any simpler than what's already there. So, while I'm all for "big picture", I am afraid that the big picture must also be sourced: if no author has ever put the big picture in writing before, then Wikipedia should not be the first to do so. Sławomir Biały (talk) 23:50, 29 December 2009 (UTC)

Compactness vs Konigs lemma

There are numerous problems that can both be solved with compactness and Konigs lemma.

Example, to extend the four color theorem from finite graphs to infinite graphs, you can use compactness or you can use Konigs lemma (you need to set up a new graph correctly, not the original map). But I admit, I know compactness from some books about logic and not from topology. So, I have to study that. —Preceding unsigned comment added by Lkruijsw (talk • contribs) 01:52, 30 December 2009 (UTC)

Compactness is a general notion that touches all areas of mathematics, so including links to each topic that uses compactness in some way is not appropriate. (Indeed, most of the mathematics articles would then be included.) Sławomir Biały (talk) 02:03, 30 December 2009 (UTC)

Merry Christmas to you, too

Hi Slawomir. Thanks for your kind message on my talk page. I have to admit that when I saw the "new message" notification at the top of the page when I logged in, I cringed. I was relieved to find a pleasant message. Cheers, Doctormatt (talk) 03:21, 30 December 2009 (UTC)

Radon transform

You have again removed the Herman reference stating; "Don't care what the citation index is. This source is neither cited nor was it used to write any part of the article. Please don't dump references." I think that this reference is appropriate for this entry. Please consider the following and either restore the reference or respond to my points.

1. You may not care about the citation index, but it is an indicator of the influence of the book on scientific development. The 1983 book by Deans has less than half the citations of the 1980 first edition of the Herman book. Why do you list the former, but refuse to list the latter?

2. You say that the Herman book is not cited in the article, but neither are the books by Deans, Helgason (2008,1999), and Natterer. Clearly, not being cited in the article is not a relevant reason (in this article) for not being listed under References.

3. The 2009 edition of the Herman book gives coverage of up-to-date developments relevant to the Radon transform; for example 83 of its references have been published 2005. The readers of the Wikipedia should not be denied pointers to recent developments in the topic of an article. —Preceding unsigned comment added by Klar sagen (talk • contribs) 14:20, 2 January 2010 (UTC)

1. I see no evidence of your claim that the Herman textbook is cited more often than the Helgason text. On Google scholar, Helgason's "Groups and geometric analysis" and Deans "The Radon transform and some of its applications" each have over 1000 citations. The first Natterer reference has over 1500 citations on Google scholar. Compare that to the Herman reference, which gets only 21 references (apparently). So, if Google scholar is any indicator of the comparative influence of these texts, by your same argument the Herman textbook should not be referenced. 2. I said that the Herman book was not cited, nor used as a reference when preparing the article. Some of the other general references were added by editors who made nontrivial contributions to the content (not just dumping references in). I am therefore reluctant to remove them, but I do feel that there are already too many of them. I added the additional Helgason references because I intended to expand the article along those lines, but have not yet gotten around to it. 3. I dispute the claim that this book somehow represents the cutting edge of knowledge about the Radon transform. It fails to mention any connection with the Penrose transform, or with the general group-theoretic Radon transform. It does not discuss plane wave decompositions, and it fails to reference both Fritz John and Sigurdur Helgason (mathematician) in connection with the Radon transform. It might be better suited as a reference for tomographic reconstruction (if you can manage to work in a citation), but it should not be in the Radon transform article. Also, I would ask that you please stop adding this reference indiscriminantly to related articles: it seems like unwarranted promotion of a reference, often a red flag that you have a conflict of interests in the subject (which you should disclose if so). Sławomir Biały (talk) 15:06, 2 January 2010 (UTC)

I just went to Google Scholar. The first entry for GT Herman is "Image Reconstruction from Projections" and it has 1968 citations. However, Google scholar screwed up (as it often does, which is why I use Web of Science) and instead referring to the first edition of the Herman book, which is what is being cited in the overwhelming majority of those citations) it refers to an obscure paper by Herman, which according to Web of Science has only 12 citations, as opposed to the first edition of the Herman book that has well over 1350 Web of Science citations. Comparing like with like, on Web of Science, the first Natterer book has about 1000, the Helgason book has about 800 and the Deans book has about 600 citations. In order to see evidence you have to look! I agree with you that the Herman book does not cover the topics that you list, but in the the article it is stated that "The Radon transform is useful in computed axial tomography (CAT scan), electron microscopy of macromolecular assemblies like viruses and protein complexes" and the Herman book is definitely cutting edge in the former and deals with the latter and it carefully derives the methodology for these applications from the Radon transform and its inversion. I maintain that the usefulness of the Radon transform entry is diminished by not having a reference to such material. —Preceding unsigned comment added by Klar sagen (talk • contribs) 17:30, 2 January 2010 (UTC)

I wasn't able to find anything in Web of Science, but I am not used to that database (I tend to use MathSciNet, which only indexes mathematics articles.) The reason the current article states applications is mostly to provide links to other articles where applications would be covered concretely in more detail. At least, that is why I wrote this paragraph of the lead. A better place for this sort of thing would seem to be tomographic reconstruction (as I suggest above). The Springer Encyclopedia of Mathematics keeps separate entries for the Radon transform and tomographic reconstruction as well, likely because the applications to tomographic reconstruction comprise an entire area of research unto itself which is quite distinct from pure research on the Radon transform. That said, I think our discussion might be further advanced by having a third opinion on the matter. I have contacted User:Billlion, who I believe added some of the earlier references to the article, in addition to making more substantial additions. Sławomir Biały (talk) 18:44, 2 January 2010 (UTC)

Article for Deletion that I had nothing to do with

Hexateronic numbers? Such a stupid name. I would never edit this! And I never have! The source of the cosmos... 18:50, 3 January 2010 (UTC)