Computable counter-examples to the Brouwer fixed-point theorem
General Mathematics
2008-04-22 v1
Abstract
This paper is an overview of results that show the Brouwer fixed-point theorem (BFPT) to be essentially non-constructive and non-computable. The main results, the counter-examples of Orevkov and Baigger, imply that there is no procedure for finding the fixed point in general by giving an example of a computable function which does not fix any computable point. Research in reverse mathematics has shown the BFPT to be equivalent to the weak K\"onig lemma in RCA (the system of recursive comprehension) and this result is illustrated by relating the weak K\"onig lemma directly to the Baigger example.
Keywords
Cite
@article{arxiv.0804.3199,
title = {Computable counter-examples to the Brouwer fixed-point theorem},
author = {Petrus H. Potgieter},
journal= {arXiv preprint arXiv:0804.3199},
year = {2008}
}
Comments
10 pages; to appear in local proceedings of Computability in Europe 2008: Logic and Theory of Algorithms