Talk:Non-Borel set

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 Definition A constructive example of a set of real numbers that is not a Borel set. [d] [e]
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WP article "Non-Borel set", version of 23 Aug 2008, was used. I am its sole author.
Boris Tsirelson

Suggestion: Create "Related Articles" subpage

Hi, Boris. The only suggestion I have is that you should create the "Related Articles" subpage:

  • When you click on the "Related Articles" tab just above, you will see the instructions on how to do it.

Other than that, you seem to have learned the CZ style quite well. Milton Beychok 23:55, 20 June 2009 (UTC)

A question. The related articles are already linked from the article. Should they be linked again from "Related Articles"? And if you answer "yes" then I have another question: some of these are for now non-existent articles; should they also be included into "Related Articles"?
By the way, I am astonished to see "Elementary function" a subtopic of "Logarithm". Indeed, the logarithm is just one of the elementary functions; why "subtopic"? Boris Tsirelson 05:35, 21 June 2009 (UTC)
I don't think that Logarithm/Related Articles is a good example. I am also quite new here, so I am not yet sure what the expected practice is, and the choice of related articles (and links in the article) will always be to some extent a subjective matter.
But I think that the list should be selective to be of use. It should only contain topics which can be recommended if one wants to learn more. For instance, I would hesitate to add Lusin or Borel because reading their biographies does not help when one wants information on (non-)Borel sets. On the other hand, there should be a link to Lusin (and in the article on Borel sets to Borel).
By the way: Do you have the original source of this example? If so, I would add it to the bibliography.
Peter Schmitt 15:26, 21 June 2009 (UTC)
Unfortunately, not. I only see that Kechris attributes it to Lusin. And I am not an expert in descriptive set theory; I only have some idea of it. Boris Tsirelson 17:37, 21 June 2009 (UTC)
In fact, the book by Kechris contains exactly one ref to Lusin:
N.N. Lusin [1972] Lecons sur les Ensembles Anatytiques, 2nd edition, Chelsea, New York.
On page 209 Kechris writes:
(27.2) Exercise. (Lusin) Consider the space...
Thus, there is a chance that the book by Lusin is the original source; but maybe not. Boris Tsirelson 20:40, 22 June 2009 (UTC)

Some remarks

I think it would be better to merge this with Borel set (which is not more than a stub). An article about Borel sets should also tell about non-Borel sets.

In my opinion (I do not know if this is a general opinion) this article does not need a link to "simple" topics like divisor, etc. It necessarily addresses readers who should know this.

The "Advanced" subpage only contains one sentence and a reference -- that could/should be moved to the article.

Peter Schmitt 00:11, 21 June 2009 (UTC)

About merge: in principle I agree, but for now the "Borel set" article is even shorter than this short one; the merge will create a ridiculous dis-balance.
About simple links: OK, I'll remove some.
About "Advanced": I guess that only a small fraction of readers acquainted with Borel sets are also acquainted with analytic sets and their completeness. Maybe it is better not to frighten them? Boris Tsirelson 05:46, 21 June 2009 (UTC)
merge: sure -- but on the other hand, it could be an incentive to expand that article, and it could make it easier. But there is no hurry, of course.
advanced: To show what I mean, I have added a paragraph and the data to the bibliography. I think that it does not hurt if a reader does not understand it, if it is clear that it is not meant to be "elementary". On the other hand, it shows that mathematics is not all about fiddling with numbers. Peter Schmitt 15:27, 21 June 2009 (UTC)

Student level subpage

It seems that "Student level" is meant for simpler material. Therefore that page should be moved. From the existing subpages /Advanced seems to be the best choice. (Since I already have included the reference on this page into the main page and the /Bibliography , no information will be lost. Peter Schmitt 00:10, 1 July 2009 (UTC)

Some information IS lost. The book by Kechris is long and complicated; it is hardly possible to just find this claim there. My reference was specific (items, pages). Boris Tsirelson 05:58, 1 July 2009 (UTC)
Sorry, I thought that I already moved the complete citation to the bibliography. I have done it now. (However, your information is still present in the early versions of /Advanced.) Peter Schmitt 08:46, 1 July 2009 (UTC)