The swap of integral and limit in constructive mathematics

✍ Scribed by Rudolf Taschner

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 108 KB
• Volume: 56
• Category: Article
• ISSN: 0044-3050
• DOI: 10.1002/malq.200910107

✦ Synopsis

Integration within constructive, especially intuitionistic mathematics in the sense of L. E. J. Brouwer, slightly differs from formal integration theories: Some classical results, especially Lebesgue's dominated convergence theorem, have to be substituted by appropriate alternatives. Although there exist sophisticated, but rather laborious proposals, e.g. by E. Bishop and D. S. Bridges (cf. [2]), the reference to partitions and the Riemann-integral, also with regard to the results obtained by R. Henstock and J. Kurzweil (cf. [9], [12]), seems to give a better direction. Especially, convergence theorems can be proved by introducing the concept of "equi-integrability".

The paper is strongly motivated by Brouwer's result that each function fully defined on a compact interval has necessarily to be uniformly continuous. Nevertheless, there are, with only one exception (a corollary of Theorem 4.2), no references to the fan-theorem or to bar-induction. Therefore, the whole paper can be read within the setting of Bishop's access to constructive mathematics. Nothing of genuine full-fledged Brouwerian intuitionism is used for the main results in this note.