The Weihrauch lattice at the level of $\boldsymbolΠ_1^1\mathsf{-CA}_0$: the Cantor-Bendixson theorem

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Main Authors: Cipriani, Vittorio, Marcone, Alberto, Valenti, Manlio
Format: Preprint
Published: 2022
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author Cipriani, Vittorio
Marcone, Alberto
Valenti, Manlio
author_facet Cipriani, Vittorio
Marcone, Alberto
Valenti, Manlio
contents This paper continues the program connecting reverse mathematics and computable analysis via the framework of Weihrauch reducibility. In particular, we consider problems related to perfect subsets of Polish spaces, studying the perfect set theorem, the Cantor-Bendixson theorem and various problems arising from them. In the framework of reverse mathematics these theorems are equivalent respectively to $\mathsf{ATR}_0$ and $\boldsymbolΠ_1^1\mathsf{-CA}_0$, the two strongest subsystems of second order arithmetic among the so-called big five. As far as we know, this is the first systematic study of problems at the level of $\boldsymbolΠ_1^1\mathsf{-CA}_0$ in the Weihrauch lattice. We show that the strength of some of the problems we study depends on the topological properties of the Polish space under consideration, while others have the same strength once the space is rich enough.
format Preprint
id arxiv_https___arxiv_org_abs_2210_15556
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle The Weihrauch lattice at the level of $\boldsymbolΠ_1^1\mathsf{-CA}_0$: the Cantor-Bendixson theorem
Cipriani, Vittorio
Marcone, Alberto
Valenti, Manlio
Logic
03D78 (Primary) 03E15, 03B30, 03D30 (Secondary)
This paper continues the program connecting reverse mathematics and computable analysis via the framework of Weihrauch reducibility. In particular, we consider problems related to perfect subsets of Polish spaces, studying the perfect set theorem, the Cantor-Bendixson theorem and various problems arising from them. In the framework of reverse mathematics these theorems are equivalent respectively to $\mathsf{ATR}_0$ and $\boldsymbolΠ_1^1\mathsf{-CA}_0$, the two strongest subsystems of second order arithmetic among the so-called big five. As far as we know, this is the first systematic study of problems at the level of $\boldsymbolΠ_1^1\mathsf{-CA}_0$ in the Weihrauch lattice. We show that the strength of some of the problems we study depends on the topological properties of the Polish space under consideration, while others have the same strength once the space is rich enough.
title The Weihrauch lattice at the level of $\boldsymbolΠ_1^1\mathsf{-CA}_0$: the Cantor-Bendixson theorem
topic Logic
03D78 (Primary) 03E15, 03B30, 03D30 (Secondary)
url https://arxiv.org/abs/2210.15556