On two recent extensions of the Big Five of Reverse Mathematics

Fuente: arXiv
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Main Authors: Normann, Dag, Sanders, Sam
Format: Preprint
Published: 2024
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author Normann, Dag
Sanders, Sam
author_facet Normann, Dag
Sanders, Sam
contents The program Reverse Mathematics in the foundations of mathematics seeks to identify the minimal axioms required to prove theorems of ordinary mathematics. One always assumes the base theory, a logical system embodying computable mathematics. As it turns out, many (most?) theorems are either provable in said base theory, or equivalent to one of four logical systems, collectively called the Big Five. This paper provides an overview of two recent extensions of the Big Five, working in Kohlenbach's higher-order framework. On one hand, we obtain a large number of equivalences between the second-order Big Five and third-order theorems of real analysis dealing with possibly discontinuous functions. On the other hand, we identify four new 'Big' systems, i.e. boasting many equivalences over the base theory, namely the uncountability of the reals, the Jordan decomposition theorem, the Baire category theorem, and Tao's pigeon hole principle for the Lebesgue measure. We discuss a connection to hyperarithmetical analysis, completing the picture.
format Preprint
id arxiv_https___arxiv_org_abs_2406_10716
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle On two recent extensions of the Big Five of Reverse Mathematics
Normann, Dag
Sanders, Sam
Logic
03B30, 03F35
The program Reverse Mathematics in the foundations of mathematics seeks to identify the minimal axioms required to prove theorems of ordinary mathematics. One always assumes the base theory, a logical system embodying computable mathematics. As it turns out, many (most?) theorems are either provable in said base theory, or equivalent to one of four logical systems, collectively called the Big Five. This paper provides an overview of two recent extensions of the Big Five, working in Kohlenbach's higher-order framework. On one hand, we obtain a large number of equivalences between the second-order Big Five and third-order theorems of real analysis dealing with possibly discontinuous functions. On the other hand, we identify four new 'Big' systems, i.e. boasting many equivalences over the base theory, namely the uncountability of the reals, the Jordan decomposition theorem, the Baire category theorem, and Tao's pigeon hole principle for the Lebesgue measure. We discuss a connection to hyperarithmetical analysis, completing the picture.
title On two recent extensions of the Big Five of Reverse Mathematics
topic Logic
03B30, 03F35
url https://arxiv.org/abs/2406.10716