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COMPLEXITY OF INDEX SETS OF DESCRIPTIVE SET-THEORETIC NOTIONS

Published online by Cambridge University Press:  10 January 2022

REESE JOHNSTON
Affiliation:
DEPARTMENT OF MATHEMATICS UNIVERSITY OF WISCONSIN – MADISONMADISON, WI53715,USA Current address: ROBINSON CENTER FOR YOUNG SCHOLARS UNIVERSITY OF WASHINGTON 3950 BENTON LN NE, SEATTLE, WA98195, USAE-mail:[email protected]
DILIP RAGHAVAN
Affiliation:
DEPARTMENT OF MATHEMATICS NATIONAL UNIVERSITY OF SINGAPORE 21 LOWER KENT RIDGE ROAD, SINGAPOREE-mail:[email protected]

Abstract

Descriptive set theory and computability theory are closely-related fields of logic; both are oriented around a notion of descriptive complexity. However, the two fields typically consider objects of very different sizes; computability theory is principally concerned with subsets of the naturals, while descriptive set theory is interested primarily in subsets of the reals. In this paper, we apply a generalization of computability theory, admissible recursion theory, to consider the relative complexity of notions that are of interest in descriptive set theory. In particular, we examine the perfect set property, determinacy, the Baire property, and Lebesgue measurability. We demonstrate that there is a separation of descriptive complexity between the perfect set property and determinacy for analytic sets of reals; we also show that the Baire property and Lebesgue measurability are both equivalent in complexity to the property of simply being a Borel set, for $\boldsymbol {\Sigma ^{1}_{2}}$ sets of reals.

Type
Article
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of The Association for Symbolic Logic

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