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May 1, 2013 at 16:52 comment added Martin Ziegler The degree of non-constructivity of Brouwer's fixed point theorem in various dimensions is explored in the following publication: link.springer.com/chapter/10.1007%2F978-3-642-30870-3_7 See in particular reference [12] to the paper by Orevkov in 1963!
Jun 4, 2012 at 21:10 comment added Felix Goldberg @Andrej Bauer: Not to put too fine a point on it, but the blog post first gave a link to the paper and then explained a toy example.
Jun 2, 2012 at 8:11 comment added Andrej Bauer @Michael: That's a different link. A blog post which mentions a toy example and then says "and there are other cool applications" is not a "serious application of Brouwer fixed point theorem". I never denied that there are such applications. Of course there are!
May 16, 2012 at 8:12 comment added Michael Greinecker @Andrej: You consider cowles.econ.yale.edu/P/cp/p00b/p0087.pdf to be popular math??
May 15, 2012 at 8:57 comment added Andrej Bauer The jstor paper referenced above is "constructive" in the sense that it is "explicit". The paper is written in classical logic, it seems.
May 15, 2012 at 5:12 comment added Andrej Bauer This worries me: jstor.org/stable/2156239. I will look at full version when I get to my office (stupid paywall), there must be an assumption that is not stated on the first page.
May 15, 2012 at 5:10 comment added Andrej Bauer @Igor: arxiv.org/abs/0804.3199
May 15, 2012 at 0:16 comment added Igor Rivin I was talking about the approximate version, you are right. Can you give a reference about what you mentioned (about the effective topos)?
May 14, 2012 at 21:01 comment added Andrej Bauer Thanks, but Brouwer Fixed point theorem fails in the effective topos, therefore it cannot have a constructive proof. Of course, the approximate version is constructive. The link pointed to in the answer is not a serious application, it is just popular math.
May 14, 2012 at 20:45 comment added Qiaochu Yuan @Andrej: en.wikipedia.org/wiki/Sperner's_lemma
May 14, 2012 at 20:40 comment added Andrej Bauer @Igor: Brouwer Fixed Point Theorem is not constructive. What are you referring to?
May 14, 2012 at 18:43 history made wiki Post Made Community Wiki by François G. Dorais
May 14, 2012 at 16:11 comment added Felix Goldberg Yes, you are right. I was thinking of the original proof...
May 14, 2012 at 16:06 comment added Igor Rivin The standard proof (using Sperner's lemma) is quite constructive, I think.
May 14, 2012 at 16:04 history answered Felix Goldberg CC BY-SA 3.0