Borel and Baire reducibility

Tom 164 / 2000

Harvey M. Friedman Fundamenta Mathematicae 164 (2000), 61-69 DOI: 10.4064/fm-164-1-61-69

Streszczenie

We prove that a Borel equivalence relation is classifiable by countable structures if and only if it is Borel reducible to a countable level of the hereditarily countable sets. We also prove the following result which was originally claimed in [FS89]: the zero density ideal of sets of natural numbers is not classifiable by countable structures.

Autorzy

  • Harvey M. Friedman

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